GIFT OF MICHAEL REESE HEATING AND VENTILATING BUILDINGS.' A MANUAL FOR -HEATING ENGINEERS AND ARCHITECTS. BY ROLLA C. CARPENTER, M.S., C.E., M.M.E., PROFESSOR EXPERIMENTAL ENGINEERING, CORNELL UNIVERSITY. fast President American Society Heating: and Ventilating Engineers; Member American Society Mechanical Engineers. THIRD EDITION, REVISED. FIRST THOUSAND, NEW YORK: JOHN WILEY & SONS. LONDON: CHAPMAN & HALL LIMITED. 1898 * Copyright, 189^, BY ROLLA C. CARPENTER 2% fchAUNWORTH, MUNN A. BARBER, PRINTERS AND BOOKBINDERS, NEW YORK. PREFACE. THE subject of heating and ventilating buildings relates to a branch of engineering devoted to a -practical application of the general physical laws of heat to the construction of heating and ventilating apparatus. A general discussion of this subject was given in treatises by Thomas Tredgold, in 1836, and by Charles Hood in 1855, in England, and by E. Peclet in 1850, in France, in which the condition of the art of heating and ventilating as it existed at that time was described. Since those early periods no treatise has been produced relating to the general principles and methods of construction in vogue, although many excellent works have been written relating to special systems or methods of heating, and one very complete and full treatise on ventilation has been published, to which reference is made in various places in the work. The object of the present book is to present to the reader in as concise a form as possible a general idea of the principles which apply, and of the methods of construction which are in use at the present time in various systems of heating and ventilating. In writing the book the aim has been to present first the general principles which are well established, and later the methods of application to erection of systems of heating and ventilating. It has been the desire to render the reader familiar with general methods and important details of con- struction, also with methods of designing and estimating costs of apparatus. A full description of the various systems in use at the present time is given so that the reader may obtain an intelligent idea of the relative merits of different methods and the classes of buildings to which each is best adapted. In preparing the present book, which is an elementary treatise on the subject, the writer has endeavored to present in as clear and concise a manner as possible, first, a statement of IV PREFA CE. the general principles and laws of pure science which apply ; second, a collection of important tests which give data and figures showing the relation of theoretical principles to prac- tical construction ; third, a description of the various practical methods which are in use in heating and ventilating buildings ; fourth, a description of the methods of designing various sys- tems of heating and ventilating ; fifth, a collection of tables which will be useful in the practical application of the princi- ples stated. The writer has endeavored to arrange the matter so that it can be understood by any person possessing a practical knowl- edge of English and arithmetic. Algebraic demonstrations, when introduced, are printed in smaller type, and any con- clusion deduced is stated in the form of a rule or general principle. Many valuable suggestions and much material aid have been given by J. J. Blackmore, J. G. Dudley, and W. S. Higgins, members of the Committee of Publication of the National Association of Manufacturers of Heating Apparatus, in adapting the book for practical use. It has been the desire of the writer to arrange the work in a scientific manner, and to give no methods or rules of practice which were not based on the results of good, sound reasoning, modified by such coefficients as have been obtained by actual tests or experience. In the case of most systems of heating this has been possible, and it is believed in this respect that the book will be quite different from anything which has pre- ceded it. A great part of the. material employed in writing the book has been used in a course of lectures on the subject of heating to the students in architecture in Cornell University, and one of the objects in preparing the work was to make it useful to the architect as giving a statement of principles and methods of practice applying to this branch of his profession. Professor Charles Babcock and C. F. Osborne of the Department of Architecture, Cornell University, have given material aid and service by suggesting the nature of the information needed in connection with building design. The book generally presents such information as the writer has found in an extensive practice in the erection and opera- PREFA CE. V tion of heating apparatus to be that which is required by con- tractors and by mechanics who have charge of erection of plants. The limited size of the book does not permit any extensive illustration of plants actually constructed, but a few examples are presented, selected from work done by our most noted engineers in this line. For the literary part of the work obligation is due to nearly every writer who has preceded ; in nearly every case special credit has been given ; but in the back part of the book will be found a complete list of references. The writer has had the cordial assistance of many noted heating engineers, many manufacturers of heating apparatus, and all the publishers of current literature devoted to this subject. The principal portion ojf the practical part of the book is devoted to construction of gravity heating systems with steam and hot water, but systems of heating with hot air, with or without a blower, with exhaust steam and with electricity, are considered, and practical directions for construction are given. The general character of the contents will be best seen by con- sulting the appended table. ITHACA, N. Y., October i, 1895 TABLE OF CONTENTS. CHAPTER I. NATURE AND PROPERTIES OF HEAT. TICLE PAGP 1. Demand for Artificial Heat i 2. Magnitude of the Industry of Manufacturing and Installing Heating Apparatus i 3. Nature of Heat 2 4. Measure of Heat Heat-unit 4 5. Relation to Mechanical and to Electrical Units 4 6. Temperature Absolute Zero 6 7. Thermometer Scales 7 8. Special Forms of Thermometers 9 9. Pyrometers and Thermometers for High Temperatures 11 Maxima and Minima Thermometers 12 Use of Thermometers 13 Specific Heat 14 Latent Heat 15 Radiation 15 Reflection and Transmission of Radiant Heat 16 Diffusion of Heat 17 Conduction of Heat .... 17 xl8. Convection, or Heating by Contact 19 19. Systems of Warming 20 CHAPTER II. PRINCIPLES OF VENTILATION. 20. Relation of Ventilation to Heating 21 21. Composition and Pressure of the Atmosphere 21 22. Diffusion of Gases 24 23. Oxygen 24 24. Carbonic Acid or Carbon Dioxide, CO 2 , and Carbonic Oxide. CO.... ... 2 vi ii ABLE OF CONTENTS ARTICLE TA36. 25. Nitrogen Argon 27 26. Analysis of Air 27 27. Determination of Humidity of the Air 29 28. Amount of Air Required for Ventilation 31 29. Influence of the Size of the Room on Ventilation 34 30. Force for Moving the Air 35 31. Measurements of the Velocity of Air 37 32. The Flow of Air and Gases 40 33. The Effect of Heat in Producing Motion of Air 43 34. The Inlet for Air 44 35. The Outlet for Air 48 36. Ventilation-flues 49 37. Summary of Problems of Ventilation 50 38. Dimensions of Registers and Flues , 52 CHAPTER III. AMOUNT OF HEAT REQUIRED FOR WARMING. 39. Loss of Heat from Buildings 54 40. Loss of Heat from Windows 54 41. Loss of Heat from Walls of Buildings 55 42. Heat Required for Purposes of Ventilation Total Heat Re- quired 59 CHAPTER IV. HEAT GIVEN OFF FROM RADIATING SURFACES. 43. The Heat Supplied by Radiating Surfaces 60 44. Heat Emitted by Radiation 61 45. Heat Removed by Convection (Indirect Heating) 63 46. Total Heat Emitted 64 47. Material of Radiators 67 48. Methods of Testing Radiators 69 49. Measurement of Radiating Surface... 73 50. Effect of Painting Radiating Surfaces 74 51. Results of Tests of Radiating Surface. r 75 52. Tests of Indirect Heating Surfaces 79 53. Conclusions from Radiator Tests 83 54. Probable Efficiency of Indirect Radiators 84 55. Temperature Produced in a Room by a given Amount of Sur- face when Outside Temperature is High 84 TABLE OF CONTENTS. IX CHAPTER V. PIPE AND FITTINGS USED IN STEAM AND HOT-WATER HEATING. \RTICLE PAGE 56. General Remarks 87 57. Cast-iron Pipes and Fittings 87 58. Wrought-iron Pipe 89 59. Pipe Fittings 92 60. Valves and Cocks 98 61. Air-valves 102 62. Expansion Joints 105 CHAPTER VI. RADIATORS AND HEATING SURFACES. 63. Introduction 107 64. Radiating Surface of Pipe 107 65. Vertical Pipe Steam Radiators 109 66. Cast-iron Steam Radiator 1 10 67. Hot-water Radiator 112 68. Direct Indirect Radiator 116 69. Indirect Radiators 1 16 70. Proportion of Parts of a Radiator 119 CHAPTER VII. STEAM-HEATING BOILERS AND HOT-WATER HEATERS. 71. General Properties of Steam Explanation of Steam Tables... 120 General Requisites of Steam Boilers 121 73. Boiler Horse-power 122 74. Relative Proportions of Heating to Grate Surface 123 75. Water Surface in Boiler Steam and Water Space . 126 76. Requisites for Perfect Steam-boiler 127 77. Classification of Boilers 1 28 78. Horizontal Tubular Boiler 130 79. Locomotive and Marine Boilers 131 79^7. Vertical Boilers 132 8p. Water-tube Boilers 133 X8i. Hot-water Heaters 133 82. Classes of Heating-boilers and Heaters 1 36 83. Heating-boilers with Magazines 141 84. Heating-boilers for Soft Coal 142 TABLE OF CONTENTS. CHAPTER VIII. SETTINGS AND APPLIANCES, METHODS OF OPERATING. .ARTICLE PAGE 85. Brick Settings for Boilers 143 86. Setting of Heating-boilers 147 87. The Safety-valve , 149 88. Appliances for Showing the Level of the Water in Boiler 152 89. Methods of Measuring Pressure ... 153 90. Thermometers 1 56 91 . Damper Regulators 1 56 92. Blow-off Cocks or Valves 157 93. Expansion Tank 158 94. Form of Chimneys ibo 95. Size of Chimneys 161 96. Chimney-tops 1 62 97. Grates 163 98. Traps 1 64 99. Return Traps 1 67 -loo. General Directions for the Care of Steam-heating Boilers 169 101. Care of Hot-water Heaters 171 J02. Boiler Explosions 171 103. Explosions of Hot-water Heaters 176 104. Prevention of Boiler Explosions 176 CHAPTER IX. VARIOUS SYSTEMS OF PIPING. 105. Systems Employed in Steam-heating 176 106. Definitions of Terms Used 176 107. Systems of Piping 180 108. Systems of Piping Used in Hot- water Heating 185 109. Combination Systems of Heating 1 88 1 10. Pipe Connections, Steam-heating Systems ., 191 in. Pipe Connections, Hot-water Heating Systems 193 112. Position of Valves in Pipes 195 113. Piping for Indirect Heaters 196 114. Comparisons of Pipe Systems 1 97 115. Systems 9f Piping where Steam does not return to the Boiler. 197 116. Protection of Main Pipe from Loss of Heat 198 CHAPTER X. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 117. General Principles . 201 118. Amount of Heat and Radiating Surface Required for Warm- ing 202 TABLE OF CONTENTS. XI ARTICLE PAGE 1 19. The Amount of Surface Required for Indirect Heating 209 ^ f2O. Summary of Approximate Rules for Estimating Radiating Surface 215 21. Flow of Water and Steam 217 22. Size of Pipes to Supply Radiating Surfaces 222 23. Size of Return Pipes, Steam Heating 227 24. Size of Pipes for Hot-water Radiators 228 25. Size of Ducts and Ventilating Flue for Conveying Air 232 126. Dimensions of Registers 235 127. Summary of Various Methods of Computing Quantities Re- quired for Heating 236 1 28. Heating of Greenhouses 236 129. Heating of Workshops and Factories 245 CHAPTER XI. HEATING WITH EXHAUST STEAM. NON-GRAVITY RETURN SYSTEMS. 1 30. General Remarks 247 131. Systems of Exhaust Heating 247 132. Proportions of Radiating Surface and Main Pipes Required in Exhaust Heating 249 133. Systems of Exhaust Heating with Less than Atmospheric Pres- sure 251 134. Combined High- and Low-pressure Heating Systems 255 135. Pump Governors -256 136. The Steam Loop 257 137. Reducing Valves 258 1 38. Transmission of Steam Long Distances 260 CHAPTER XII. HEATING WITH HOT AIR. 1 39. General Principles 268 140. General Form of a Furnace 270 141. Proportions Required for Furnace Heating 272 I 142. Air-supply for the Furnace 275 143. Pipes for Heated Air 276 144. The Areas of Registers or Openings into Various Rooms 278 145. Circulating Systems of Hot Air 280 146. Combination Heaters. 281 147. Heating with Stoves and Fireplaces 281 148. General Directions for Operating a Furnace. . . 282 xii TABLE OF CONTENTS. CHAPTER XIII. FORCED-BLAST SYSTEMS OF HEATING AND VENTILATING. ARTICLE yAGE 149. General Remarks .... ...................................... 283 150. Form of Steam-heated Surface .................. ............ 283 151. Ducts or Flues Registers ....... . 284 j 52. Blowers or Fans ..................................... ...... 289 1 53. Heating Surface Required ..... ................ 291 1 54. Size of Boiler Required ............... ...... 292 155. Practical Construction of Hot-blast System of Heating ....... 292 1 56. Systems of Ventilation without Heating ..................... 298 157. Heating with Refrigerating Machines ........................ 299 158. Cooling of Rooms ........................................... 300 CHAPTER XIV. HEATING WITH ELECTRICITY. 159. Equivalents of Electrical and Heat Energy ................... 301 160. Expense of Heating by Electricity ........................... 301 161. Formulae and General Considerations ....................... 304 162. Construction of Electrical Heaters ........................... 306 163. Connections for Electrical Heaters .......................... 309 CHAPTER XV. TEMPERATURE REGULATORS. 164. General Remarks ........................................... 310 165. Regulators Acting by Change of Pressure .................... 31 1 166. Regulators Operated by Direct Expansion ................... 315 167. Regulators Operated with Motor General Types ............. 316 168. Pneumatic Motor System ................................... 318 169. Saving Due to Temperature Regulation ...................... 320 CHAPTER XVI. SPECIFICATION PROPOSALS AND BUSINESS SUGGESTIONS. 170. General Business Methods ................................... 322 171. General Requirements ................................... ... 323 172. Form Proposed by the National Association of Manufacturers of Heating Apparatus ................................. 326 173. Form of Uniform Contract ................... . ............. 336 TABLE OF CONTENTS. Xlll ARTICLE PAGE 174. Specifications for Plain Tabular and Water-tube Boilers 340 175. Protection from Fire Hot Air and Steam Heating 344 1 76. Duty of the Architect 347 177. Methods of Estimating Cost of Construction 347 1 78. Suggestions for Pipe-fitting 348 APPENDIX. LITERATURE AND REFERENCES 353 EXPLANATIONS OF TABLES 356 TABLES 359 INDEX 401 A TREATISE ON HEATING AND VENTILATING BUILDINGS. CHAPTER I. INTRODUCTION. NATURE AND PROPERTIES OF HEAT. 1. Demand for Artificial Heat. The necessity for artifi- cial heat depends to a great extent upon the climate, but to a certain extent on the customs or habits of the people. In all the colder regions of the earth artificial heat is necessary for the preservation of life, yet there will be found a great difference in the temperature required by people of different nations or races living under the same circumstances. On the continent of Europe,. 1 5 degrees centigrade, corresponding to about 59 degrees F., is considered a comfortable temperature ; in America it is the general practice and custom to maintain a temper- ature of 70 degrees in dwellings, offices, stores, and most work- shops, and a heating apparatus is considered inadequate which will not maintain this temperature under all conditions of weather. 2. Magnitude of the Industry of Manufacturing and In- stalling Heating Apparatus. The industry connected with the manufacture and installation of the various systems for warming is a great one and gives employment to many thou- sand workmen. The manufacture of heating apparatus is not only of great magnitude, but it is varied in its nature ; all kinds of apparatus for heating as, for instance, the open fireplace built at the base of a brick chimney, the cast-iron stove with its unsightly piping, the furnace and appliances for warming 2 HEATING AND VENTILATING BUILDINGS. air, apparatus for heating by steam and also by hot water can be readily bought on the market in almost every form, from that of the simplest to that of the most complicated design. The exact amount of capital invested in this industry could not be ascertained by the author, but in twenty cities, selected in alphabetical order from a list of one hundred and sixty-five cities of the United States containing over twenty thousand inhabitants, the total amount invested in the business of erect- ing and installing heating apparatus as given in the Census Report by the U. S. Government for 1890 was $12,910,250, and the yearly receipts for 1890 from this business in the same cities was $5,592,148. The aggregate population of these cities was 1,573,508 people. This would indicate an invest- ment of $8.20 and a yearly expenditure of $3.52 for each inhabitant. Reckoning on the same basis for the cities of the United States which contain over 25,000 inhabitants each, we should have an invested capital of over $106,000,000 and a yearly expenditure of over $46,000,000. These numbers are probably less than the amount actually invested, but they serve to give an idea of the magnitude of the industry connected with the supply of apparatus for artificial warming. 3. Nature of Heat Before consideration of the methods of utilizing heat in warming buildings a short discussion of the nature and scientific properties of heat seems necessary. Heat is recognized by a bodily sensation, that of feeling, by means of which we are able to determine roughly by com- parison that one body is warmer or colder than another. From a scientific standpoint heat is a peculiar form of energy, similar in many respects to electricity or light, and is capable, under favorable conditions, of being reduced into either of the above or into mechanical work. We shall have little to do with the theoretical discussion of its nature, but, as it is well to have a distinct understanding of its various forms and equivalents, we will consider briefly some of its important properties. Heat was at one time considered a material substance which might enter into or depart from a body by some kind of con- duction, and the terms which are in use to-day were largely founded on that early idea of its material existence. The theory that heat is a form of energy and is capable of INTRODUCTION. 3 transformation into work or electricity is thoroughly established by fact and experiment. It probably produces a molecular motion among the particles of bodies into which it enters, the rate of such motion being proportional to the intensity of the heat. Heat has two qualities which correspond in a general way to intensity on the one hand and quantity on the other. The intensity of heat is termed temperature this can be measured by a thermometer ; but, except in scientific discussion, no name has been applied to designate the unit-quantity of heat,* and there is no method of measuring it directly, although it is of as much importance as temperature. It is a fact which will appear from later statements that the amount of heat contained in two bodies of different kinds, but of the same weight and temperature, may be essentially different. A familiar analogy might perhaps be seen in the case of the dimensions and weight of men. The weight would depend on the general dimensions, height, breadth, etc., and it would probably be the case that two men having equal heights would have quite different weights. In a similar manner the amount of heat depends upon the temperature and also upon the property of the body to absorb heat without showing any effects which may be measured on a thermometer. This latter property in itself depends upon the nature of the body and also upon that peculiar quality of heat to which reference has been made. Under every condition heat must be quite differ- ent in nature from temperature. Note that heat is equivalent, not to mechanical force, but to mechanical work. Work, defined scientifically, is the applica- tion of force in overcoming some resistance; it is the result of a force acting through a certain distance ; the distance moved through having as much effect on the result as the force acting. The work done is proportional to the product of the force exerted, multiplied by the space passed through. In English measures the unit of this product is a foot-pound, which signifies one pound raised to a height equal to one foot ; it is itself a complex quantity resembling heat in this respect. Heat can be transformed into work. *The term entropy is now applied in scientific discussions to this property. 4 HEATING AND VENTILATING BUILDINGS. 4. Measure of Heat Heat-unit. As explained heat can- not be measured by the thermometer; it can, however, be measured by the amount that some standard is raised in tem- perature. The standard adopted is water, and heat is univers- ally measured by its power to raise the temperature of a given weight of water. In English-speaking countries the heat-unit is that required to raise one pound of water from a temperature of 62 to 63 degrees, and this quantity is termed a British thermal unit ; this will be referred to in this work, by its initial letters B. T. U., or simply as a heat-unit. The amount of heat re- quired to change the temperature of one pound of water one degree is not the same at all temperatures ; the variation, how- ever, is slight and for practical purposes can be entirely disre- garded. The unit of heat used by the French and Germans, and for scientific purposes generally, is called the calorie ; it is equal to one kilogramme (2.20 pounds) of water raised one degree centigrade (1.8 degrees Fahrenheit) and is equal to 3.9672 B. T. U. The calorie is referred to water at a temper- ature of 15-16 Centigrade (60 degrees Fahrenheit). 5. Relation to Mechanical Work and to Electrical Units. The relation of heat to mechanical work was accu- rately measured by Joule in 1838 by noting the heating effects produced in revolving a paddle-wheel immersed in water. The wheel being revolved by a weight falling a given distance, the mechanical work was known ; this compared with the rise in temperature of the water enabled him to determine that the value of one heat-unit estimated from 39 to 40 F. was equiv- alent to 772 foot-pounds. Later investigation has slightly in- creased this result, so that when reduced to a temperature of 62 degrees F., and for this latitude, it is 6 foot-pounds greater, so that at present the work equivalent of one heat-unit is generally regarded as 778 foot-pounds. This signifies that the work of raising I Ib. 778 feet is equivalent to the energy re- quired to change the temperature of I Ib. of water, at 62 F. in temperature, I degree. The equivalent value of heat and mechanical work is now thoroughly established, and under favorable conditions the one can always be transformed into the other. As illustrations of the transformation of heat into work we have only to consider INTROD UCT1ON. 5 the numerous forms of steam-engines, gas-engines, and the like. A transformation from mechanical work into heat is shown in the rise of temperature accompanying friction in the use of machines of all classes. The heat produced in the perform- ance of any mechanical work is exactly equivalent to the work accomplished, 778 foot-pounds of mechanical work being per- formed in order to produce a heating effect equivalent to rais- ing i Ib. of water i Fahr. The term horse-power has been used as the measure of the amount of work. It has been fixed as 33,000 foot-pounds per minute. This is equivalent to 42.42 B. T. U. per minute, or to 746 watts in electrical measures. For the work done in one second the above numbers should be divided by 60 ; for that done in one hour they should be multiplied by 60. In all English-speaking countries the capacity of engines and ma- chinery in general is expressed in horse-power, so that it is necessary to become familiar with this term audits equivalents in heat and electrical units. The electrical units are all based on French measures, the centi- metre (0.3937 inch) being the standard of length, the gramme (15.432 grains) the standard of mass, and the second the unit of time; the system being "generally denominated the C. G. S. system. In this system the unit of force, the dyne, is i gramme moved so as to acquire a velocity of one centimetre per second. As the force of gravity in lati- tude of Paris is 32.2 feet = 981 cm., the dyne is equal to the weight moved, expressed in grammes divided by 981, for latitude of Paris. The unit of work and of energy is called an erg and is equal to the force of one dyne acting through one centimetre, or to a gramme-centi- metre divided by 981. One million ergs is equal to 0.0738 foot-pound. One watt is equal to 10 million ergs per second, or 738 foot-pounds per second. One calorie is 42,000 million ergs, one minor calorie 42 million ergs. One B. T. U. is 10,550 million ergs. Expressed in work we have the following equivalents : One horse-power = 746 watts =550 foot-pounds per second = 0.707 B. T. U. per second. = 0.1767 calories per second = 176.7 minor calories per second = 7460 millions of ergs per second. (See full table of equivalents in back of book.) 6 HEATING AND VENTILATING BUILDINGS. 6. Temperature Absolute Zero. One of the properties of heat is called temperature ; this property can be measured by a thermometer and is proportional to the intensity of the heat. All our knowledge of heat, as obtained by the sensation of feeling, deals only with the temperature, and the terms in common use by means of which bodies are compared and denominated hot, hotter, hottest, have reference, not to the heat actually in the different bodies, but to the temperature. There is always a tendency for heat to flow through inter- vening mediums from a hotter to a colder body, and there is no tendency for heat to flow from a cold to a hot body, although the relative amounts of heat in the two bodies might be different from that indicated by the thermometer. Thus, as an illustration, a pound of water requires about eight times as much heat to raise it one degree in temperature as a pound of iron, and hence when equal weights of both of these materials are at the same temperature the water contains eight times as much heat as the iron, although in common parlance the two bodies would be equally hot. The tendency for the hotter body to cool off and give up its heat to surrounding objects is characteristic of all materials, and if no other heat were supplied all bodies would come sooner or later to one common temperature. This temperature, when finally reached by all bodies in the universe, will represent the ultimate limit of all cooling and almost the entire absence of heat. It will be near absolute zero for all thermometric scales, and no greater cold will be possible or even conceivable. The inter-planetary space is believed by many to be very nearly at this limit, at the present time. Scientific men have made very careful determinations to ascertain what such a temperature must be, compared with the ordinary thermometric scales. A perfect gas which remains under constant pressure will contract in volume an amount directly proportional to the change of temperature when reckoned from the point of great- est cold, which point is known as the absolute zero. By experi- ment it is found that when air is at a temperature of 32 degrees its volume is reduced one part in 492 each time that the tem- perature is lowered one degree. From this fact it has been concluded that the absolute zero is 492 degrees on the Fahren- IN TROD. UCTION. heit scale or 273 degrees on the Centigrade scale, below the freezing-point of water. Strictly speaking there is no perfect gas, yet the results obtained with different gases by different ob- servers are so nearly in accord that there is no question but that the results as given above are for all practical purposes correct. 7. Thermometer Scales. The thermometer is an instru- ment used to measure temperature. The effect of heat is to expand or to increase the volume of most bodies. For perfect gases the amount of this expansion is strictly proportional to the change of temperature ; for liquids and solids the expansion, while not exactly proportional to the increase of temperature, is very nearly proportional to it, and these bodies can be used for an approximate and even a close measure of difference of temperature. In nearly all thermometers the temperature is measured by the expansion of some body, mercury, alcohol, or air being commonly used as the thermometric substance. The first thermometer was probably made by Galileo before 1597. It consisted of a glass bulb containing air, terminated below in a long glass tube which dipped into a vessel containing a colored fluid. The variations of volume of the enclose'd air caused the fluid to rise or fall in the tube, the temperature being read by an arbitrary scale. Alcohol thermometers were in use as early as 1647, being made by connecting a spherical bulb with a long glass stem, on which graduations were made by beads of blue enamel placed in positions correspond- ing to one thousandths of the volume. Fahrenheit, a German merchant, in 1721 was the first to make a mercurial thermometer, and the instru- ment which he designed, with certain modifications, has been retained in use by the English-speaking people up to the present time. Fahrenheit took as fixed points the temperature of the human body, which he called 24 degrees, and a mixture of salt and sal-ammoniac, which he supposed the greatest cold possible, as zero. On this scale the freezing-point is 8 degrees. These degrees were afterwards divided into quarters, and later these subdivisions themselves, termed degrees. On this modified scale the freezing-point of water becomes 32 ORDINARY FORM OF MERCURI- AL THER- MOMETER. 8 HEATING AND VENTILATING BUILDINGS. degrees, blood-heat 96* degrees, and the point of boiling water at atmospheric pressure 212 degrees. Unscientific as this thermometer is, it has been retained by two of the principal nations of the world, the English and the American ; it is awkward to use, it was borrowed from a foreign nation which had itself adopted a more scientific instrument, and except for the fact that it has been long in use it has not a single feature to recommend it. In 1724 Delisle introduced a scale in which the boiling- point of water was called zero and the temperature of a cellar in the Paris Observatory was called 100 degrees. This ther- mometer was used for many years in Russia, but is now obso- lete. In 1730 Reaumur made alcohol thermometers in which the boiling-point of water was marked 80 degrees. This thermometer is still in use in Russia. Celsius adopted a centesimal scale in 1742 on which the boiling-point was marked zero and the freezing-point of water 100 degrees. This instrument is not now in use, although the centigrade scale is often called after Celsius. The botanist Linnaeus introduced the centigrade thermometer, in which the freezing-point of water is marked zero and the boiling- point of water 100 degrees. This themometer is now adopted for ordinary use by the nations of continential Europe and for scientific use by every nation in the world. The relative values of the degrees on the different ther- mometers used by various nations are given in the following table : THERMOMETRIC SCALES. Fahren- heit. Centigrade. Reau- mur. Celsius. Degrees between freezing and boiling.. Temperature at freezing-point I So 00 IOO So Q IOO IOO Temperature at boiling-point 212 TOO So o Comparative length of degree j o/c 0/A Q/- Countries where used 5/9 V/3 9/4 5/4 W 3 I and America and Germany * As determined later, this should be 98. INTRODUCTION. 9 In all thermometric scales as given above, fixed points are determined by reference to the freezing and boiling points of water, with barometer at 29.92 inches, and all thermometers are constructed by marking these two points and then subdi- viding into the required number of degrees. The boiling- point of water changes with the atmospheric pressure and with the purity of the water. The greater the pressure the higher the boiling-temperature. A table in the Appendix of this book shows the relation between the barometer* pressure and the temperature of boiling water at atmospheric pressure. Mer- cury, alcohol, liquids and solids generally do not expand uniformly for each degree of temperature, or, in other words, they are not perfect thermometric substances. The error, however, is slight and is of more scientific than practical im- portance. Any perfect gas, however, does expand uniformly and is a perfect thermometric substance, but gas varies in volume with slight change in barometric pressure, and, while of great value as material for a scientific thermometer, is too bulky and awkward for ordinary use. It is at the present time considered doubtful if there is any perfect gas in exist- ence, or one which cannot be liquefied by intense cold or great pressure. Air, hydrogen, and nitrogen act like perfect gases at ordinary temperatures; the same is true in a slightly less degree of oxygen. Yet oxygen is a liquid whose boiling- point is 119 degrees centigrade (182 degrees Fahrenheit) below zero. Nitrogen and air are liquids boiling at a temper- ature of 193 degrees centigrade (315 degrees Fahrenheit) below zero. Pictet and Cailletet have reduced the temper- ature to 200 degrees C. below zero, finding air at that tempera- ture to be a liquid as limpid as water and, like water, having a decided blue tint when seen by transmitted light. 8. Special Forms of Thermometers. Tr\e mercurial ther- mometers, as ordinarily constructed (Fig. i), consist of a bulb of glass joined to a capillary glass tube filled so as to leave a vacuum in the upper part of the glass stem, above the mer- cury ; they cannot be used for any temperature higher than that of the boiling-point of mercury, which is about 575 F. More recently these thermometers have been filled with nitro- gen or carbonic dioxide in the upper part of the glass stem, 10 HEATING AND VENTILATING BUILDINGS. which by pressure prevents the mercury boiling. Thermom- eters constructed in this way can be used safely in temperatures as high as the melting-point of -ordinary glass, say to 1000 F. Mercurial thermometers are made in various ways ; the cheaper ones have graduations on an attached frame of wood or metal, Fig. i, but the more accurate and better grades have the graduations cut directly on to the glass stem, Fig. 2. It has been found that the glass from which these thermometers are made changes volume slowly for many months after construction, so that it is necessary to fill the thermometer with mercury a long time before graduation. In the better grade of thermometers the graduations are obtained by comparing point by point with an accurate standard ; in the cheaper ones by sim- ply subdividing into equal parts between freezing and boiling points. At very low temperatures (38 F.) mer- cury solidifies and its rate of expansion changes ; alcohol or spirits of similar nature are not so affected, and hence are better suited for use in thermometers for measuring o extremely low temperatures. Air thermometers, while rather difficult to use and of somewhat clumsy construc- FIG. 2 tion, are accurate through any range of temperature. These are made either by confining the air in a constant vol- ume and measuring the increase in pressure (Fig. 3), or else by maintaining the pressure constant and noting the increase in volume. If the volume be maintained constant, the pressure will increase directly propor- tional to the increase in absolute tem- perature. In the air thermometer (Fig. 3) the volume is kept constant and the increase in pressure is measured by the rise of mercury in the tube OC above the line AB. That is, in passing from the freezing to the boil- ing point of water, the barometer being FIG. 3. AIR at 29.92, the pressure will increase 180/492, as expressed on the Fahr. scale, or 100/273 on the Cen. scale. -t -r B TER - OF THE UNIVERSITY IN TROD UCTION. II The determination of temperature with the air thermometer, even if the instrument is calibrated to read in degrees, needs a correction for barometer-reading, since the height to which the mercury will rise in the tube will depend on the pressure of the air. The directions for using the instrument would be: ist. Find the constant of the instrument by putting the bulb in melting ice, and dividing the absolute temperature, 492, by the sum of barometer- read ing and reading of tube of the ther- mometer; 2d. To find any temperature, multiply the constant as found above by the sum of barometer-reading and reading of thermometer, and subtract from this product 460. NOTE. In using the instrument always keep the mercury at or near point A, so as to keep volume of air constant. 9. Pyrometers and Thermometers for High Temper- atures. Most metals have rates of expansion which differ sensibly from each other, and this fact has been utilized in the construction of thermometers. Metallic thermometers are frequently used for high temperatures and have often been called pyrometers. If two bars of metal with unequal rates of expansion be fastened together at one end and heated, the difference of extension of the two ends can be utilized in moving a hand over a dial graduated to show change of temperature (Fig. 4). The metal may also be bent into the form of a helix, in which case the heating will tend to change the curvature and thus move a hand which can be used to measure the temperature. A thermometer consisting of an iron bulb and a dial, very much like the metallic pyrometer in appearance, is made by filling the bulb with ether or hydro- carbon vapor, and constructing it on the same principle as gauges used to register pressure on boilers. The vapor has a temperature corresponding to a given pressure, so that the dial can be calibrated to read in degrees of temperature instead FlG of pounds of pressure. METALLIC PYROMETER. 12 HEATING AND VENTILATING BUILDINGS. These instruments are extremely convenient and answer admirably for temperatures not exceeding 1000 F. Calorimetric Pyrometers. The principle of operation used in determining specific heat, Art. 13, can, if the specific heat is known, be employed to ascertain the temperature of any hot body. Temperature by the Color of Incandescent Bodies and by Melt- ing-points. Pouillet, as the result of a large number of experi- ments, concluded that all incandescent bodies have a definite and fixed color corresponding to each temperature. This color and temperature scale was given as follows : Color. Temp. C. Temp. F. Faint red Z2Z Q7T Dark red 7OO I 2Q^ Faint cherry 800 16^2 Cherry QOO l6^2 Bright cherry IOOO 1932 Dark orange . . / . . , 1160 1850 Bright orange I2OO 2192 White heat 1300 2372 Bright white 1400 2552 Dazzling white 1500 2732 This scale applies only to bodies that shine by incandescent light and not from actual combustion. A pyrometer making practical application of this scale has been invented by Noel, and consists of a telescope with polarizing attachment and a scale so fixed as to read the angle through which a part of the instrument turns while a sudden transition of color takes place. Temperature by the Melting-points of Bodies. The melting- points of bodies often provide an excellent means of deter- mining temperature. The temperature is obtained by using metallic alloys having known melting-points, it being higher than those which have melted, but lower than those which remain unmelted. A table of temperature of melting-points is given in the Appendix. In Germany a carefully prepared set of alloys can be purchased for temperature determinations in this manner. 10. Maxima and Minima Thermometers. The ordinary method of making a thermometer for recording the highest temperature is by introducing a small piece of steel wire about IN TROD UCTION. half an inch in length and finer than the bore of the thermom- eter into the tube above the mercury, in a mercurial thermom- eter. The thermometer is placed with its stem in a horizontal position, and the steel index is brought into contact with the extremity of the column of mercury. Now when the heat increases and the mercury expands the steel wire will be thrust forward ; but when the temperature falls and the mercury contracts the index will be left behind, showing the maximum temperature. For showing minimum temperature a spirit thermometer prepared in a similar manner is used, as the spirits in contracting draw the index with the alcohol because of the capillary adhesion be- tween the alcohol and the glass ; but when the alcohol expands it passes by the index, without displacing it, so that its position shows the lowest temperature to which the in- strument has been subjected. 11. Use of Thermom- eters. In the use of ther- mometers for determining the temperature of the air, they should be exposed to unob- structed circulation in a dry place and in the shade. Any FIG. 5. STEAM- THERMOMETER. FIG. 6. THER- MOMETER-CUP. drops of moisture on the bulb of the thermometer tend to evaporate and lower the tem- perature. For determining the temperature of steam or water under pressure thermometers are set into a brass frame so that they will screw directly into the liquid (Fig. 5) without per- mitting leakage. In other cases the thermometer can be in- serted into a cup made as shown in Fig. 6. Cylinder-oil or mercury is put into the cup, and the reading of the thermom- eter will then indicate the temperature of the surrounding 14 HEATING AND VENTILATING BUILDINGS. fluid. When the thermometer is inserted into a cup somt time will be required to obtain the correct temperature. The temperature of steam-pipes or hot-water pipes cannot be obtained accurately by any system of applying the thermometers externally to the pipes, and in case ther- mometers are used they should be set deep info the current of flowing steam or water, not placed in a pocket where air can gather. 12. Specific Heat. The capacity which bodies have of absorbing heat when changing temperature varies greatly ; for instance, the same amount of heat which would raise one pound of water one degree in temperature would raise about 8 pounds of iron I degree in temperature or would raise I pound 8 degrees in temperature. The term used to express this property of bodies is specific heat, which is defined as follows: Specific heat is the quantity of heat required to raise the temperature of a body one degree, expressed in percent- age of that required to raise the same amount of water one degree, or in other words with water considered as one. Specific heat can always be found by heating the body to a given temperature, cooling it in water, and noting the increase in temperature of water. Thus if I pound of iron in cooling 8 degrees heats one pound of water one degree, its specific heat is -J = 0.125. A table of specific heats of the principal materials is given in the back of the book, from which it will be seen that the specific heat of water is greater than that of any other known substance. A knowledge of the specific heat of various materials is of considerable importance in the design of heating apparatus, since it indicates the capacity for absorbing heat without in- crease of temperature. The heat which is absorbed in raising the temperature of a body is all given out when the body cools, so that although there is a difference in the amount absorbed, there is no difference in the final result due to heating and cooling. The total heat which a body contains is equivalent to the product obtained by multiplying difference of temperature, specific heat and weight. The results will be expressed in heat-units or in capacity of heating one pound of water. INTRO D UCTION. I 5 The specific heat of bodies 4n general increases slightly with the temperature, the values in the table being true from 32 to 212. 13. Latent Heat. When heat is applied to any liquid the temperature will rise until the boiling-point is reached, after which heat will be absorbed ; but the temperature will not change until the entire process of evaporation is complete, or until the liquid is all converted into vapor. The heat ab- sorbed during evaporation has been termed latent, since it does not change the temperature and its effects cannot be measured by a thermometer. In the evaporation of water about five and one-half times as much heat is required to evap- orate the water when at 212 degrees, into steam at the same temperature, as to heat the water from the freezing to the boiling point. Heat stored during evaporation is given out when the vapor condenses, so that there is no loss or gain in the total operation of evaporating and condensing. A similar storage of heat takes place when bodies pass from the solid to the liquid state, but in a less degree. Although similar in some respects, latent heat differs in nature from specific heat. In both cases, heat not measured by the ther- mometer is stored ; when the temperature is lowered the stored heat is given up in both cases: in the first it represents a change in the physical condition, as from a solid to a liquid or a liquid to a gas ; in the second the condition remains unchanged. 14. Radiation. Heat passes from a warmer body to a colder by three general methods, each of which is of consider- able importance in connection with the methods of heating. These methods are radiation, conduction, and convection. The heat which leaves a body by radiation travels directly and in a straight line until it is intercepted or absorbed by some other body. Radiant heat obeys the same laws as light, its amount varying inversely as the square of the distance, and with the sine of the angle of inclination. The amount of radiant heat which is emitted or which is absorbed depends largely, if not altogether, upon the character of the surface of the hot and cold body ; it is found by experiment that the power of ab- sorbing radiant he.at is exactly the same as that of emitting 1 6 HEATING AND VENTILATING BUILDINGS. it. The relative amount of heat emitted or absorbed by different surfaces is given in the following table. RELATIVE EMISSIVE POWERS AT THE BOILING TEMPERATURE. Lamp-black 100 White-lead 100 Paper 9 8 Glass 9 India ink 8 5 Shellac 7* Steel , I? Platinum 17 Polished brass 7 Copper 7 Polished gold 3 Polished silver 3 Radiant heat passes through gases without affecting their temperature or being absorbed to any appreciable extent. It is probably true that a very large body of air, especially air containing watery vapor, does absorb radiant heat, for it is known that the earth's atmosphere intercepts a sen- sible proportion of the heat radiated from the sun. 15. Reflection and Transmis- sion of Radiant Heat. Radiant heat, like light, may be reflected and FIG. 7. REFLECTION OF HEAT. sent j n various directions by materials of various kinds. Thus in Fig. 7 heat radiated from K is re- flected to L, and vice versa. The following table shows the proportion of radiant heat which would be reflected by various substances : REFLECTING POWER. Silver-plate 97 Gold 95 Brass 93 Speculum-metal 86 Tin 85 Polished platinum 80 Steel 83 Zinc 81 Iron 77 Radiant heat also possesses the property of passing through certain substances in very much the same manner that light will pass through glass. This property is called diathermancy. The following table gives the diathermanous value of various substances, the heat being obtained from a lamp. The trans- mission power varies with the source of heat. IN TROD UCTION. PER CENT OF HEAT TRANSMITTED THROUGH SUBSTANCES. DIFFERENT WHEN RECEIVED FROM AN ARGAND LAMP (DESCHAUD's PHYSICS). SOLIDS. Colorless Glass \.$>&.mm. thick. Flint-glass from 67 to 64% Plate-glass 62 to 59 Crown-glass (French) 58 Crown-glass (English) 49 Window-glass 54 to 50 Colored Glass 1.85 mm. thick. Deep violet 53 Pale violet 45 Very deep blue. 19 Deep blue 33 Light blue 42 Mineral-green. ... 23 Apple-green 26 Deep yellow 40 Orange 44 Yellowish red 53 Crimson 51 LIQUIDS 9.21 MM. THICK. Colorless Liquids. DistHled water n Absolute alcohol 15 Sulphuric ether 21 Sulphide of carbon 63 Spirits of turpentine. 31 Pure sulphuric acid 17 Pure nitric acid 15 Solution of sea-salt 12 Solution of alum 12 Solution of sugar 12 Solution of potash 13 Solution of ammonia 15 Colored Liquids. Nut-oil (yellow) . . 31 Colza-oil (yellow) 30 Olive-oil (greenish yellow) 30 Oil-carnations (yellowish) 26 Chloride sulphur (reddish brown).. 63 Pyroligneous acid (brown) 12 White of egg (slightly yellow) n CRYSTALLIZED BODIES 63.62 MM. THICK. COLORLESS. Rock-salt 92$ Iceland spar 12 Rock-crystal 57 Brazilian topaz 54 Carbonate of lead 52 Borate of soda 28 Sulphate of lime 20 Citric acid 15 Rock-alum... . 12 COLORED. Smoky quartz (brown) 57 Aqua-marina (light blue) 29 Yellow agate 29 Green tourmaline 27 Sulphate of copper (blue) o 16. Diffusion of Heat. Various materials possess the property of reflecting the radiant heat in such a manner as to diffuse it in all directions, instead of concentrating the heat in any one direction. If the heat were all returned, the tempera- ture of the body would not rise, but would remain constant. The diffusive power as determined by Laprovostaye and Desains was found to be as follows for the following substances, the heat received being 100 : White-lead 82 Powdered silver 76 Chromate of lead . . .66 18 HEATING AND VENTILATING BUILDINGS. 17. Conduction of Heat When heat is applied to one end of a bar of metal it is propagated through the substance of the bar, producing a rise of temperature which gradually travels to the remote portions. This transmission of heat is called conduction. It differs from radiation, first, in being gradual instead of instantaneous ; second, in exhibiting no preference for travelling in straight lines, the propagation being as rapid through a crooked as a straight bar. In heating a body the heat is at first largely absorbed by the body with- out changing its temperature, then for a time it is applied in raising the temperature ; the time required for this operation will depend upon its specific heat. After a certain time the temperature of the body will remain constant, the heat being removed as rapidly as it reaches a given position, and in this case we have an illustration of the transmission of heat by conduction. The amount of heat which passes is directly pro- portional to the area of cross-section, to the difference of temperature divided by the thickness, and to a coefficient which depends upon the character of the material. The coeffi- cient is the quantity of heat which flows, in unit time, through a cross-section of unit area, when the thickness of the plate is unity and the difference of temperature is one degree.* The conducting power of materials varies greatly. The metals are in general good conductors of heat, but differ greatly among themselves. The following table gives the relative values of the conducting powers for different metals : RELATIVE CONDUCTING POWERS. Silver 100 Copper 77.6 Gold 53-2 Brass 33 Zinc !9-9 Tin 14.5 Steel .......................... 12 Iron ......................... 17 Lead .......................... 8.5 Platinum ....................... 8.2 Palladium ..................... 6.3 Bismuth i . 9 Rocks and earthy materials have very much less power of conducting heat than the metals. Table XIV in the back part * This can be expressed in a formula as follows : in which Q = quantity of heat, k = coefficient, A = area, x = thickness, / 2 r= difference of temperature on the two sides of the plate. IN TROD UCTION. 1 9 of the book gives the value of " the coefficient of various mate- rials in terms of the absolute amount of heat conveyed. The relative conductive powers of stone is about 4 per cent of that of iron and f of one per cent of that of copper. The conduct- ing power of woods does not differ greatly from that of water, and is about I per cent of that of iron. The conduct- ing power of the air and gases is very small, and for practical purposes may be considered as zero. As compared with iron the conducting power is about as I to 3500. A knowledge of the conductive powers of bodies is of very great importance in connection with the loss of heat in buildings of various classes. The bodily sensation of heat or cold is affected to a great extent by the conducting power of the material with which the body comes in contact. Thus if the hand were placed upon a metal plate at a temperature of 40 degrees, or plunged into mercury of the same temperature, a very marked sensation of cold is experienced. This sensation is less intense with a plate of marble of the same temperature, and still less with a piece of wood. The reason is that the heat is more rapidly con- ducted away in the case of the metals, and this causes a more marked sensation of cold. Where heat is applied to one surface of a metallic body, it passes through the body by conduction and is given off on the opposite side, usually to the air or to bodies in the surrounding room, by radiation and convection. It will be found that the rate of conduction through the metallic body is many times greater than the rate of passage of the heat from the metallic substance. The knowledge of the conductive power is of little practical importance, as regards heating surface, because of this fact, but it is of great value in the selection of materials which will prevent the escape of heat from dwellings. This subject will be taken up in Chapter III, and applications given show- ing the loss of heat from different constructions of building. 18. Convection or Heating by Contact. When bodies are in motion there is more or less rubbing contact of their particles with each other and against stationary objects. When the particles rub against hot bodies they will themselves be- come warm ; it is only by such motion that liquids or gases 20 HEATING AND VENTILATING BUILDINGS. can be heated any appreciable amount. The heating of the air of a room is practically.all accomplished- by currents, which brings the particles into contact with radiators, heated pipes, or even the walls of a room. If the air enters a room at a higher temperature, then by the reverse process the heat is given up to the colder objects, and the air is lowered in tem- perature. The heating of water in steam-boilers is largely due to a circulation which brings the particles of water in direct contact with highly heated surfaces, so that the heating in that case is -accomplished largely by convection. 19. Systems of Warming.- Any general consideration of a system of warming must include, first, the -combustion of fuel which may take place in a fireplace, stove, steam or hot- water boiler ; second, a system of transmission by means of which the heat shall be conveyed with as little loss as possible to the position where it can be utilized for heating ; third, a system of diffusion of heat so that it shall be conveyed from any reservoir, radiator, etc., which is heated to objects, persons, or to the air of a room,. in the most economical way possible. Jn case stoves are used the heat is directly applied by radiation and convection to heating the objects and air in the room in which the stove is placed. There is in this case no special system for the transmission of heat. In the case of hot- air heating, the air is drawn over a heated surface and then transmitted by pipes while at a high temperature to the rooms where heat is required. In the case of steam-heating, steam is formed in a boiler, transmitted through pipes to radiators which are placed either directly in the room or in passages leading to the rooms, and the condensed steam is returned either directly or by means of a pump to the boiler. In the case of hot-water heating the general system is much the same water instead of steam circulates from the heater to the rooms where heat is required and back to the heater ; the motive force which produces the circulation being the differ- ence in weight between the hot and cold water. CHAPTER II. PRINCIPLES OF VENTILATION. 20. Relation of Ventilation to Heating. Intimately connected with the subject of heating is the problem of main- taining air of a certain standard of purity in the various build- ings occupied. The introduction of pure air can only be done properly in connection with the system of heating, and any system of heating is incomplete and imperfect which does not provide a proper supply of air. The general principles relating to ventilation are con- sidered in this chapter, but the practical methods of securing ventilation are considered in connection with systems of in- direct heating. The subject of ventilation often receives very little con- sideration in connection with the erection' of apparatus for heating. 21. Composition and Pressure of the Atmosphere. Atmospheric air is not a simple substance, but consists of a mechanical mixture of nitrogen and oxygen, together with more or less vapor of water, and almost always a little carbonic acid and a peculiarly active form of oxygen, known as ozone. The nitrogen and oxygen are combined in the ratio of 79.1 to 20.9 by volume, and these proportions are generally the same in all parts of the globe, and at all accessible elevations above the earth's surface. The amount of carbonic acid in the air varies in the open country from 4 to 6 parts in 10,000 by volume. The amount of moisture in the atmosphere sometimes forms 4 per cent of its entire weight, and sometimes is less than one.tenth of one per cent. The weight of the atmosphere is measured by the height in inches at which it will maintain a column of mercury in an in- strument called a barometer. The pressure of the atmosphere is less as the distance from the centre of the earth becomes 21 22 HEATING AND VENTILATING BUILDINGS. greater. For that reason points of different elevation give different average readings of the barometer. The normal reading of the barometer at sea-level, which corresponds to a boiling-point for pure water of 212 F., is 29.905 inches. The weight of the atmosphere, even at the same place, is constantly fluctuating with various conditions of the weather. The variation in barometer-reading from the mean may be 1.5 inches in either direction. The fall of the barometer due to different elevations from the sea-level would be approximately as follows : At 917 feet the barometer sinks i inch. " 1860 " " " 2 inches. " 2830 " " " 3 " " 3830 " " " 4 " " 4861 " " 5 " The atmospheric pressure has great effect upon the boiling- temperature of water; thus pure water will boil ^.t the tem- peratures corresponding to the various barometric pressures, as shown in the following table :* Boiling-temperature F. Barometer, Inches Boiling-temperature F Barometer, Inches. 212 29.905 205 25.990 211 29- 33' 204 25-465 210 28.751 203 24.949 209 28.180 2O2 24.442 203 27.618 201 23-943 207 27.066 200 23-453 206 26.523 The weight of a cubic foot of air is inversely proportional to the absolute temperature ; if freed from aqueous vapor and under a pressure of 30 inches of mercury, it weighs, according to Regnault, 536.29 grains or 0.076613 pound, The rate of expansion in volume or decrease in density is > . for each degree Fahrenheit, t being temperature above 32. Table VIII in the Appendix gives the weights of air for different temperatures. For the temperature of 60 air is * Encyc. Brit., vol. in. p. 387. PRINCIPLES OF VENTILATION. 2$ 813.67 times lighter than water. Various other units are sometimes used to measure the head or pressure, and for con- venience of reference these equivalents can be arranged as follows : 30 inches of mercury = 14.7304 Ibs. = 407.07 in. water == 33.92 ft, water = 1 1985.4 ft. air at 60 Fahr. I inch water = 0.57902 oz. Air contains more or less impurities which are to be found only in places where the ventilation is not perfect. These impurities consist of carbon monoxide, CO, ammoniacal com- pounds, sulphuretted hydrogen, and sulphuric and sulphurous and nitric and nitrous acids. It also contains some ozone, which is a peculiarly active form of oxygen, and is believed by many to have an important influence in the preservation of the purity of the atmosphere. Authorities, however, differ very widely as to its distribution and action. Lately a new con- stituent called argon has been discovered. Air contains more or less solid matter in the form of minute particles of dust. The dust particles are thought to bear an important part in the propagation and distribution of the bac- teria of various diseases, and also in the production of storms. Air contains microbe organisms, or bacteria, in greater or less numbers. The number of bacteria may be determined by slowly passing* a given volume of the air through a glass tube coated inside with beef jelly ; the germs are deposited on the nutrient jelly, and each becomes in a few days the centre of a very visible colony. In outside air the number of microbe organisms varies greatly, being often less than one per litre (61 cubic inches) ; in well-ventilated rooms they vary from r to 20, while in close schoolrooms as many as 600 per litre have been found. Carnelley, Haldane, and Anderson found in their researches in mechanically ventilated schoolrooms an average number of \j microbe organisms per litre. The results of stopping the mechanical ventilation was to increase the car- bonic acid without changing the number of microbe organisms. * Encyc. Britannica, article "Ventilation." 24 HEATING AND VENTILATING BUILDINGS. 22. Diffusion of Gases. Gases which have no chemical action on each other will, regardless of weights or densities, mingle with each other so as to form a perfectly uniform mix- ture. This peculiar property is called diffusion, and is of great importance in connection with ventilation, since it indicates the impossibility of separating gases of different densities. Liquids of different densities do not make uniform mixtures, unless they have a special affinity for each other ; the heavier invariably settles to the bottom. Perfect diffusion is a process which requires some time, so that the composition of samples from the same room may in some instances be sensibly different. The time required for the diffusion of gases is inversely proportional to the density, and directly proportional to the square root of the absolute temperature. Diffusion is a molecular . action, and can be calculated from the kinetic theory of gases. One computation of this character indicates that the time required for the equal diffusion of carbonic acid throughout the atmosphere was 2,220,000 years. Dr. Angus Smith found the following percentages of oxygen present in the air, in samples collected in various places, which serve to show the variation which may exist under different conditions : * Seashore of Scotland, on the Atlantic 20.99$ Top of Scottish hills : 20.98 Sitting-room, feeling close, but not excessively so. 20.89 Backs of houses and closets 20.70 Under shafts in metal mines 20.424 When candles go out 18.50 When difficult to remain in air many minutes 17.20 The variation in amount of carbonic acid is equally great, the quantity being as follows : London parks 0.0301$ In workshops 0.3$ On the Thames o 0343 In theatres 0.32 London streets 0.0380 Cornwall mines. .... 2.5 Manchester fogs 0.0679 23. Oxygen, Oxygen is one of the most important ele- ments of the atmosphere, so far as both heating and ventilation * Encyc. Brit., vol. xvi. p. 617 ; also vol. n. p. 35. PRINCIPLES OF VENTILATION. 2$ is concerned. It is the active element in the chemical process of combustion, and also of a somewhat similar physiological process which takes place in. the respiration of human beings. It exists in a free state mixed with about four parts of nitrogen in the air, and is essential not only for the support of any com- bustion, but for the support of life. It is not to be considered as having any properties as a food, but is rather the necessary element which makes it possible to assimilate and utilize the food. Taken into the lungs it acts upon the excess of carbon of the blood, and possibly also upon other ingredients, forming chemical compounds which are thrown off in the act of respiration. The chemical action of oxygen with the other elements can generally be considered as a sanitary one. In many respects the process of respiration resembles that of combustion ; for in both cases oxygen is derived from the air, carbon or other impurities are oxidized, and the products of this oxidization are rejected. In both cases heat is given off as the result of this process. Its weight is sixteen times that of hydrogen. It is sometim'es found in a peculiarly active form called ozone. 24. Carbonic Acid or Carbon Dioxide, CO,, and Car- bonic Oxide, CO. The first is a product resulting from the perfect combustion o-f carbon ; it is always found in small quan- tities, 3 to 5 parts in 10,000 in the atmosphere of the country. This gas, although very heavy as compared with that of pure air (22 times that of hydrogen), will, if sufficient time be given, mix uniformly with the air. It is npj^ppjsonous gas, although in an atmosphere containing large quantities of car- bonic dioxide a person might die from suffocation- or for want of oxygen. While carbonic dioxide is not of itself injurious, yet as it is a product of combustion and respiration, and is usually accom- -panied with other injurious products, it is regarded as an index of the quality of the air, and the amount of it present in the air is taken as the standard by which we can judge of the ven- tilation.* In such a case pure air, containing 4 parts of car- * }. S. Billings, in his work on Ventilation and Heating, cites an experi- ment by Carneiley and Mackie, showing that the ordinary theory of increase 26 HEATING AND VENTILATING BUILDINGS. bonic dioxide in io,OOO would be the standard of absolute purity. Authorities differ as to the greatest atnount of car- bon dioxide which might be permitted. It is quite certain that any unpleasant sensation is not experienced until the amount is increased to 10 or 12 parts in 10,000; yet authorities are gen- erally agreed that the maximum amount should not exceed 10 parts in 10,000, at least for sleeping-rooms. The standard of good ventilation usually adopted at present would permit about 8 parts in 10,000 in the air. There has been a tendency to make the standard of ventilation higher and higher during the last few years, thus requiring the introduction of greater quantities of air. Carbonic acid is continually increased by the processes of combustion and respiration, yet for the past thirty years the amount in the air has not sensibly changed. Plant-growth and vegetable life assimilate carbonic acid and give off oxygen.* There exists in the air about 28 tons of carbonic acid to each acre of ground, yet an acre of beech- forest annually absorbs about one ton, according to Chevandier ; and no doubt the total vegetation growing is sufficient to absorb the excess due to combustion and respiration, so that the total does not experience much change. Carbonic Oxide, CO. This compound is not found in the air except under unusual circumstances. It is distinctly a poJspj^, and has a characteristic reaction on the blood. Hem- pel, t the German chemist, experimented on its poisonous of organic matter wiih mcrease of carbon dioxide is a reasonable on results of the experiment were as follows : The Proportion of Organic Matter. Oxygen required to Oxidize 1,000,000 Average Carbonic Acid in 10.000 Volumes Number of Trials. Volumes. of Air. o to 2.5 2.8 2O 2.5 to 9.5 3 o 20 4.5 to i.o 3-2 2O 7.0 to 15.8 3-7 20 " How Crops Feed," by Johnson, page 47. f Hempel's Gas Analysis. Macmillan & Co. PRINCIPLES OF VENTILATION. 2/ effects with a mouse. No symptoms of poisoning were de- tected until there were 6 parts CO in io;ooo of air, in which case after 3 hours' time respiration was difficult ; in another case the mouse could scarcely breathe in 47 minutes. With 12 parts in IO,OOO the mouse showed symptoms of poisoning in 7 minutes; with 29 parts in 10,000 the mouse died in convul- sions in about two minutes. 25. Nitrogen Argon. -The principal bulk of the earth's atmosphere is nitrogen, which exists uniformly diffused with oxygen and carbonic acid. This element is practically inert in all the processes of combustion or respiration. It is not affected in composition either by passing through a furnace during combustion or in passing through the lungs in process of respiration. Its action is to render the oxygen less active, and to absorb some part of the heat produced by the process of oxidation. It is an element very difficult to measure directly, as it can be made to enter into combination with only a few other elements, and then under peculiarly favorable circumstances. A very small amount of ammonia, which is a compound of nitrogen and hydrogen, is found in the atmosphere. Argon. A constituent of the atmosphere recently dis- covered, which amounts to about one per cent of the total, was announced at the meeting of the Royal Society, January 31, 1895. This element is very soluble in water, and liquefies at a temperature 232 below zero F., under a pressure of 50.6 atmospheres. It is even more inert in action than nitrogen, and practically may be considered the same. 26. Analysis of Air. The accurate analysis of air requires the determination of aqueous vapor, carbon dioxide, carbon monoxide, oxygen and ozone, but for sanitary purposes the determination of carbon dioxide and water is the most fre- quently called for. For a complete discussion of these various methods the reader is referred to Hempel's Gas Analysis, trans- lated by Dennis and published by Macmillan & Co. The nitrogen of the atmosphere cannot be determined by any known method of analysis ; it is obtained by deducting the sum of all the other elements from the total. The approxi- mate determination of the oxygen is done very readily by 28 HEATING AND VENTILATING BUILDINGS. drawing a certain volume of the air into a measuring-vessel and then passing it over a mixture of pyrogallic acid and caustic potash ; the oxygen is absorbed, reducing the volume in amount proportional to the quantity of oxygen. This pro- cess is, however, not of extreme accuracy, and for minute quantities very much more complicated methods must be re- sorted to. Method of Finding Carbon Dioxide (CO^). The amount of this material present in the atmosphere is so small that the most delicate methods are required in order to measure it. The writer gives here the only simple method which can be rapidly applied, and which is said to be accurate to one part in one hundred thousand. This system of finding CO 2 was devised by Otto Pettersson and A. Palmqvist, two European chemists. The instrument used for this determination is shown in Fie. 8, o and can be had from any dealer in physical apparatus. It con- sists of a measuring-vessel, A, connected with a U-shaped bu- rette B, from which communica- tion can be made by a small stop-cock, b', a manometer, fg 9 containing a graduated scale nearly horizontal ; and two stop- cocks, f and g, by means of which communication can be made with the air. One side of this manometer,/, is in com- munication with the closed ves- sel C\ the other side can be put in communication with the measuring-vessel A. The burette B contains a saturated solution of caustic potash (KOH). The flask E contains mercury, and by raising it, when the stop-cock c is open, the mercury will rise in the flask A^ and the air will be driven out. If the flask E be lowered the mercury will flow from the measuring-tube, and the amount of air entering A can be measured by the gradua- FIG. 8 PETTKRSSON'S APPARATUS FOR DETERMINING CO 2 IN AIR. PRINCIPLES OF VENTILATION. 29 tions. When the measuring-tube A is full of air, the stop-cocks c, b,f, and g being open, the position of the drop of liquid in the horizontal tube of the manometer is accurately read. The stop-cocks c, a,f, and^are then closed, that at opened, and the vessel E raised, driving the air out of the measuring-tube A into the absorption burette B. This operation of raising and lowering the flask E is repeated several times ; it is then lowered, and the air is drawn over into the measuring burette ; the cock a is then opened and the vessel E manipulated until the reading of the manometer on the horizontal scale agrees with that in the beginning of the test. The reading of the graduated tube A gives directly the amount of CO 2 . The determinations are made with air of ordinary humidity, and there is a very slight correction due to this fact, which is not likely to equal, in any case, one part of CO 3 in one million parts of air.* 27. Determination of Humidity of the Air. The hu- midity of the air is determined by gradually cooling a body and observing at what temperature the vapor of the air con- denses on the body as dew. When dew is deposited the air is saturated for the given temperature, and if the temperature of the air be known, at which dew will be deposited, and also the temperature of the air in its normal condition, we can com- pute the amount of moisture contained in the air. The in- strument generally employed for this purpose consists of two thermometers, the bulb of one of which is exposed in its ordi- nary condition to the air ; the bulb of the other is kept con- stantly wet by means of a bit of cloth extending to a vessel filled with water. If the air were saturated with moisture these two thermometers would give the same reading, but if the air is not saturated the readings will differ an amount de- pending upon the humidity. The table following, and a more complete one in the Appendix, give the amount of moisture expressed as percentage of saturation for different readings of the wet and dry bulb thermometer. * For approximate methods of determining the purity of air see Appendix to book. HEATING AND VENTILATING BUILDINGS. MOISTURE IN GRAINS PER CUBIC PER CENT OF SATURATION FOR DIF- FOOT ABSORBED BY SATURATED FERENCE IN READINGS, WET AND AIR. DRY BULB THERMOMETER. Temp, Air, degs. Grains per cu. ft. Temp. Air, degs. Grains percu. ft. Difference in Reading. . . _, , Temp. Air, 32 F. Temp. Air, 70 F. Temp. Air, 95 F. 2O 1-56 70 7-94 r o 100 100 100 32 2-35 Bo 10.73 I 96 97 97 40 3.06 90 t4.38 2 92 93 94 50 4.24 100 IQ. 12 3 88 QO 9i 60 5.82 no 25-5 5 81 84 86 7-5 72 77 79 10 65 7i 73 15 52 59 62 20 41 49 53 The first table gives the weight of moisture contained in one cubic foot of saturated air; the second shows the per- centage of saturation for any difference in reading of the wet and dry bulb thermometer. The weight of moisture is the product of the results. Thus, saturated air at 70 F. contains 7.94 grdns per cubic foot, and if at the same time the differ- ence between the wet and dry bulb thermometers was 10, this air would be 71 per cent saturated, and would contain 71 per cent of 7.94 grains, or 5.62 grains. Since there are 7000 grains in one pound, this weight may, if desired, be re- duced to pounds. Moisture in air can also be determined approximately, but with sufficient accuracy for practical purposes, by the hair hygrometer. This instrument is illustrated in Fig. 9. It is con- structed by fastening a hair, from which the oil has been re- moved, in the top part of a suitable frame, and winding the lower part on a cylinder which is free to revolve, and which carries a balanced pointer. The hair increases or diminishes in length, quite exactly, in proportion to the amount of moisture in the air, and this acquired property seems to be a permanent one. A scale graduated by comparison with determinations made with a wet and dry bulb thermometer serves to show the amount of moisture present, as a percentage of saturated air. The degree of moisture in the air has an important in- PRINCIPLES OF VENTILATION. fluence on ventilation. When^ air is saturated with moisture water is deposited on all bodies which conduct heat readily and have a lower temperature than the air. On the other hand, if the air is entirely deprived of watery vapor it evap- orates moisture from the body, and thus causes an unpleasant sensation. It also takes up a great deal of heat. When the air is saturated no evaporation can take place from the body. When the air is very dry, very rapid evap- oration will take place. A mean condition between these two ex- tremes is required in every case. The air should be from 50 to 70 per cent saturated in order to feel pleasant, and be of the most value for ventilating purposes. 28. Amount of Air required for Ventilation. The amount of air required in order to maintain the standard of purity below a cer- tain given amount can be very readily determined, provided weknow the amount of carbon dioxide which is given off in the process of respiration. It is estimated that at each respiration of an adult person 20 cubic inches of air on the average are required, and that 16 to 24 respirations take place per minute ; so that from 320 to 480 cubic inches, or about one fourth of a cubic foot, are required per minute.* The air ejected from the lungs is delivered at a temperature from 70 to 90 degrees, and very nearly saturated with watery vapor ; hence it is about 2. 3 per cent lighter than pure air. The following table shows the approximate effect of respiration on the composition of air:f FIG. 9. THE HAIR HYGROM- ETER * This is estimated by Box as Soo cubic inches, but is given by recent phys- iologists as above. See works of Dalton, Dr. Carpenter, Art. Respiration in Ency. Brit., etc. This is increased by violent exercise, and to make the allow- ance liberal 576 cubic inches or \ cubic foot is taken as the amount to be supplied. f Ency. Britannica, Art. Respiration. HEATING AND VENTILATING BUILDINGS. Entering Respired Air. Gases. Oxygen, per cent of volume 20.26 16 Nitrogen, " " " " . 78.00 75 Watery vapor" " " 1.70 5 Carbonic acid " " " 0.04 4 If we take the carbon dioxide as an index of the character of ventilation, and consider that each person uses one third cubic foot of gas per minute, and that the respired gas contains 400 parts in 10,000 of carbonic acid, while the entering air con- tains but 4, we can calculate the amount of air which must be provided to maintain any standard of purity desired. The formula for this operation would be as follows : If a = the number of parts of CO 3 in 10,000, thrown out in respiration or other impurities ; if b = the cubic feet of air used per minute ; if n = the standard of purity to be preserved, expressed as the number of units of CO 2 permissible in 10,000, and C = the number of cubic feet of air required, we shall have C = ab/(n 4). For the condition we have just considered, for each adult person a = 400, b = -J, so that the formula becomes C= I33/ (n 4), By taking n as 8, C = 33, and n as 10, C = 22. The following table shows the amount of air which must be introduced for each person in order to maintain various standards of purity : AMOUNT OF AIR REQUIRED PER PERSON FOR VARIOUS STAND- ARDS OF PURITY. Standard Parts of CO 2 in 10,000 of Air in the Room. Cubic Feet of Air required per Person. Per Minute. Per Hour. 5 133-3 8 ooo 6 6 7 4000 7 44 2667 8 33 2000 9 27 16OO 10 22 1333 ii '9 H5I 12 17 I OOO 13 15 889 14 13 800 15 12 727 16 II 667 18 9-5 571 20 8-3 500 PRINCIPLES OF VENTILATION. 33 The combustion of one cubic foot of gas per hour contam- inates about the same amount of air as one person, so that an allowance, equivalent to that required for four or five people, should be made for each gas-burner. Authorities differ greatly as to the amount of air to be provided per person, but at the present time they seem well united in considering the admission of 30 cubic feet of air per minute for each person as giving good ventilation, and this amount is required by law for school buildings in Massa- chusetts.* Some authorities insist that a higher standard should be required, but there is little doubt that present conditions would be very much improved could the above amount be obtained in every case. The amount advised by various authorities has been as follows : Parkes advises 2000 cubic feet of air per hour for persons in health and 3000 to 4000 for sick persons. The English Barracks Improvement Commissioners require that the supply be not less than 1200 cubic feet per man per hour. Pettenkofer recommends 2100 cubic feet; and Morin considers that the following allowances are not too high:t Hospitals (ordinary) 2000 to 2400 cubic feet per hour. " (epidemic) 5 Workshops (ordinary) 2000 (unhealthy trades) 3500 Prisons 1700 Theatres 1400101700 Meeting-halls 1000 ' ' 2000 Schools (per child 400" 500 " (per adult) 800 " 1000 Tredgold :f in 1836 considered 4 cubic feet of air per minute as good ventilation for healthy people, and 6 cubic feet per minute for the sick in hospitals. * Dr. Billings states that this amount could be increased 25 to 50 per cent, with good results. Ventilation and Heating. t Etudes sur la Ventilation. \ Warming and Ventilating Buildings; third edition. 34 HEATING AND VENTILATING BUILDINGS. 29. Influence of the Size of the Room on Ventilation. The purity of the air of a room depends to some extent on the proportion of its cubic capacity to the number of inmates. This influence is often overestimated, and even in a large room if no fresh air be supplied the atmosphere will quickly fall below the standard of purity. It must be considered that no room is hermetically sealed. Ventilation takes place through every crack and cranny, and even by diffusion through the walls of the room. Such ventilation is generally, however, uncertain and inadequate. Large rooms have the advantage over small ones that they act as reservoirs of air, and also be- cause there is chance for intermittent ventilation such as occurs when doors or windows are opened, and for the casual ventila- tion which takes place through the walls and around the win- dows. They are also advantageous, because a larger volume of air may be introduced with less danger of producing dis- agreeable air-currents or draughts. The following table, taken in part from article " Ventilation," Encyc. Britannica, gives a general idea of the cubic capacity per person usually allowed in certain cases, and the time which would be required to reduce the air inclosed to the lowest admissible standard of purity (12 parts of CO 2 in 10,000 of air), provided no fresh air was admitted. Class of Building. Cubic Contents. Time required for contaminating the Air. Hospitals 1200 Cl 1000 600 500 130 300 240 212 1. f t. ai id abc >ve 70 m 59 35 29 8 18 14 13 in. Barracks . . Good secondary schools Workhouse dormitories London lodging-houses It is seen from the above table that in the ordinary grade of middle-class houses it would require about one hour to render the air unfit for breathing, while for the lowest grade of houses the time required would be only 13 minutes. It may PRINCIPLES OF VENTILATION. 35 be said, however, respecting the cheaper grade of houses, that while the amount of space allowed per person is small, the character of construction is such that air can usually enter or leave the room without very great retardation, and conse- quently this table does not fairly represent the character of ventilation actually secured. Pettenkofer found that, by diffusion through the walls, the air of a room in his house containing 2650 cubic feet was changed once every hour when the difference of exterior and in- terior temperatures was 34 degrees. With the same difference of temperature, but with the addition of a good fire in a stove, the change rose to 3320 cubic feet per hour. With all the crevices and openings about doors and windows pasted up air tight the change amounted to 1060 cubic feet per hour ; with a difference of 40 degrees the ventilation through the walls amounted to 7 cubic feet per hour for each square yard of wall surface. The effect of diffusion in changing the air of a room should generally be neglected in practical ventilation, because it is very uncertain in amount and character. 30. Force for Moving the Air. No ventilation can be secured unless provision is made for (i) power for moving the air, (2) passages and inlet for admitting the air, (3) passages and outlet for escape of air. Air is moved for ventilating purposes in two ways: first, by expansion due to heating; and second, by mechanical means. The effect of heat on the air is to increase its volume and lessen its density directly in proportion to the increase in absolute temperature. The lighter air simply because of its less density (tends to 'rise, 'and is replaced by the colder air below. The head which induces the flow is a column of air corresponding in weight to the difference in heights of columns of equal weight of cold and heated air. The velocity can be computed, since theoretically it will be equal to the square root of twice the force of gravity into this difference of height. The result so computed will apply only when there is un- restricted openings at both ends. It is scarcely ever appli- cable to chimneys, for the reason that the flow of air is retarded by passing through the fuel. 36 HEATING AND VENTILATING BUILDINGS. The amount of air which may be made to pass through a ventilating flue of ordinary construction and of different heights is given in a table on page 45. The available force for moving the air which is obtained by heating is very feeble, and quite likely to be overcome by the wind or external causes. Thus to produce the slight pressure equivalent to one tenth inch of water in a flue 50 feet in height would require a difference in temperature of 50 degrees. In a flue of the same height a difference of temperature of 150 degrees would produce the same velocity as that caused by a pressure of 0.5 inch of water. To produce the same velocity as that due to a pressure sufficient to balance o.i inch of water will require that the product of height of chimney and difference of temperature should be 1760. It will in general be found that the heat used for produc- ing velocity, when transformed into work in a steam-engine is considerably in excess of that required to produce draught by mechanical means. In a rough way, an increase in temperature of one degree increases the head producing the velocity only about one part in 500. Ventilation by Mechanical Means is performed either by pres- sure or by suction. In the first case the air is increased in dens- ity and discharged by mechanical force into the flue, the flow being produced by an excess of pressure over that of the atmos- phere, so that the air tends to move in the direction of least resistance, which is outward to the atmosphere. In the second case, pressure in the flue is less than that of the atmosphere, and the velocity is produced by the flowing in of the outside air. By both processes of mechanical ventilation the air is supposed to be moved without change in temperature, and the force for moving it must be sufficient to overcome effects of wind or change of temperature, otherwise the intro- duction of air will not be positive and certain. The velocity in feet per second for various differences of pressure is com- puted as explained in Article 32, and tables are given on pages 42 and 45 for use in computing the amount dis- charged per square foot of the area of the cross-section of the flue. PRINCIPLES OF VENTILATION. 37 31. Measurements of the Velocity of Air. The velocity of air or other gases is measured directly by an instrument FIG. io. BIRAM'S PORTABLE ANEMOMETER. called an anemometer, or it is measured indirectly by differ- ence of pressure. The anemometer which is ordinarily em- ployed for this purpose con- sists of a series of flat vanes attached to an axis and a series of dials. The revolu- tion of the axis causes mo- tion of the hands in pro- portion to the velocity of the air. In the forms shown in Figs, io and n the dial mechanism can be started or stopped by a trip arranged conveniently to the operator. In some instances the dial mechanism is operated by an electric current, in which case FIG. n PORTABLE ANEMOMETER. OF THF UNIVERSITY HEATING AND VENTILATING BUILDINGS. it can be located at a distance from the vanes. For measur- ing the velocity of the wind an anemometer, which consists of hemispherical cups mounted on a vertical axis, is much used. The anemometers are all calibrated by moving them in still air at a constant velocity and noting the readings of the dials. This is usually done by mounting the anemom- eter rigidly on a long horizontal arm which can be rotated about a vertical axis at a constant speed. When the pressure is light it can be measured by using a U-tube partly filled with water. Such an instrument is shown in Fig. 12, attached to a flue. There being less than atmospheric pressure in the flue K, the water rises in the leg FE and sinks in the leg DE. The difference of level in the two legs is ab, which is usually measured in inches. If the flue is under press- ure the water will stand higher in the leg DE than in FE, but the method of use is essentially the same in all cases. In case the pressure and velocity are great, considerable error will be made by using the open tube as above, and for such a case a Pitot's tube arranged as shown in Fig. 13 should be used. This tube consists of two parts, one of which is straight and enters at right angles to the current dB\ the other is curved so as to face the current at right angles, cA. These are connected to a U-shaped manometer containing water or some light liquid. The pressure in the two tubes will be the same except for the velocity of the current. This will tend to make the liquid stand higher in the arm fm than in the arm en. The difference in elevations of these two arms will be the velocity-head producing the flow. Call this difference in height h, and the ratio of specific gravity of the liquid in the tube and of the gas in the flue r; then will v V 2ghr. That is, the velocity is equal to 8.03 multiplied by the square root of the difference in height multiplied by ratio of weight. in case water is used in the manometer and the gas is air FIG. 12. U-SHAPED WATER GAUGE. PRINCIPLES OF VENTILATION. 39 at a temperature of 60 degrees, V will equal 813. Hence v will equal 228 Vh, in which k is in feet, and will equal 65.7 Vh when // is in inches of water. For any other temperature than 60 degrees this quantity must be multiplied by the square root of 460 + the temperature, and then divided by ^5 20. Practically for air the velocity will equal 228 times the square root of the difference in the heights of the columns. The velocity of air may also be computed by the heating effects, provided the amount of heat is accurately measured FIG. 13. SKETCH OF PITOT'S TUBE FOR GREAT PRESSURES. and the increase in temperature of the air be known. The specific heat of air is 0.238, hence the heat sufficient to warm one pound of water would heat (17.238) = 4.2 pounds of air. This at 60 degrees would correspond to about 231 cubic feet. By consulting Table VIII the volume heated I degree by I heat-unit at any other temperature can be found. The total number of cubic feet of air heated would be equal to the total number of heat-units absorbed divided by the number of degrees the air is heated, and this result multiplied by the volume of one pound divided by the specific 40 HEATING AND VENTILATING BUILDINGS. heat (the latter number can be taken directly from Table VIII). Having the total amount of air in a given time, the velocity can be obtained by dividing by the area of the passage. NOTE. In the shape of a formula these results are as follows : Let T equal temperature of discharged air, / that of entering air; H equal the total number of heat-units given off per unit of time; V equal the number of cubic feet of air heated I degree by i heat-unit (see Table VIII) ; A equal area of passage in square feet; v equal velocity for the same time that the total number of heat-units are taken. Then we shall have HV C = Total amount of air in cu. ft. = ; 32. The Flow of ir and Gases. The flow of air obeys the same general laws as those which apply to liquids. The gases are, however, compressible, and the volume is affected very much by 'change of temperature, so that the actual re- sults differ considerably from those obtained for liquids. These laws can only be expressed in mathematical formulae, from which, however, practical tables are derived. The flow of air from an orifice takes place under the same general conditions as those of liquids, and we have the general formula v = \/2gh as applicable. In this case h is the head which is equal to the height of a column of air of sufficient weight to produce the pressure. Air under a barometric pressure of 30 inches and at 60 degrees in temperature is 813 times lighter than water. The pressure of air is usually meas- ured by its capacity of balancing a column of water in a U- shaped tube (see Article 31), and this pressure is expressed in inches of water. One inch of water-pressure is equivalent to 65.7 feet of air at 60, and increases -g-f^ part for each degree of increase in temperature. The above formula is only ap- proximate, and does not account for the change in temper- atures and of pressures due to expansion, although sufficiently accurate for the designing of ventilating apparatus. Prof. Unwin gives in the article " Hydromechanics," Encyc. Brit., PRINCIPLES OF VENTILATION. 4! the following formula for computing the velocity of flow of air: T = absolute temperature ; P l = absolute pressure in vessel from which flow takes place ; P t = absolute pressure in surrounding space. To find the volume discharged the velocity must be multi- plied by the area and that result by a coefficient which Prof. Unwin gives as follows: Conoidal mouthpieces of the form of the con- c = tracted vein, with effective pressures of .23 to I . i atmosphere 097 to 0.99 Circular sharp-edged orifices , 0.563 " 0.788 Short cylindrical mouthpieces 0.81 " 0.84 The same, rounded at the inner end. . . . 0.92 " 0.93 Conical converging mouthpieces 0.90 " 0.99 In the flow of air or gases through pipes the same con- siderations hold that have been stated for water. There is the same condition respecting the head which produces press- ure and that which produces velocity, and in addition we have those changes due to the compressible nature of the fluid moved. Taking into account all these conditions, Prof. Unwin gives as a formula for the flow of air in a circular pipe p* in which u = velocity in feet per second ; c = 53.15; / = absolute temperature; g =32.16; d diameter in feet ; HEATING AND VENTILATING BUILDINGS. I length in feet ; = coefficient of friction = 0.005(1 4- p = greatest absolute pressure ; pi least absolute pressure. For a velocity of 100 feet per second C varies from 0.00484 to 0.01212 for a diameter varying from 1.64 ft. to 0.164 ft- For a temperature of 60 F. and for a pipe one foot in diameter and 100 feet long, C = 0.006. For barometer reading of 30 inches, pressure being expressed in inches of water, p 6 = 407, we have from which the third column of the following table is calculated. VOLUME OF AIR DISCHARGED AT VARIOUS PRESSURES. Difference of Pressure. Velocity in Feet pe.' Second. Inches of Water. Ounces per Square Inch. By Accurate Formula Pipe i Ft. in Diam , ioo Ft. Long. By Approximate Formula. (Coefficient 0.7.) O.OI O.OO6 4-3 4-6 0.05 0.030 9.6 9-5 O.I 0.058 14-5 14-5 O.2 O. Il6 19.4 20.5 0-3 0.174 23.6 25.1 0.4 0.232 27.4 29.1 0.5 0.289 30-5 32.5 0.6 0-347 34-0 35.2 0.7 0.405 36.0 38.3 0.8 0.463 39-2 40.7 0.9 o. 512 41.0 43-7 I.O 0-579 43-0 45-7 2.0 1.158 6I..I 65.2 3.0 1-303 78.0 78.2 4.0 2.316 85.3 91.1 5.0 2.895 86.2 103.3 6.0 3.474 104.0 II3-3 7-0 4.053 114.0 122. 1 8.0 4.622 121 .O I3O.6 9.0 5.221 128.0 138.8 10. 5-790 136.0 145.7 II .0 6.369 I42.O 153-0 12.0 6.948 148.0 159.6 The preceding table gives the velocity of air in feet per second as calculated from the accurate formula of Prof. Unwin, PRINCIPLES OF VENTILATION. 43 and also from the approximate formula v = V2gh, using a co- efficient of 0.7. The table is calculated for a barometric press- ure of 30 inches and for a temperature of 60 F. For any other temperature the results must be multiplied by factors which are calculated as explained below. For the discharge at any other temperature divide the above results by the square root of 520 multiplied by 460 plus the temperature. For temperature of 32 degrees multiply by .972, 40 degrees .981, 50 degrees .987, 70 degrees i.oi, 80 degrees 1.018, 90 degrees 1.03, IOO degrees 1.04, 1 10 degrees 1.05, 1 20 degrees 1.06, 130 degrees 1.07. 33. The Effect of Heat in producing- Motion of Air. The effect of heat is to expand air in proportion to its abso- lute temperature for each degree of increase. If a column of air be heated it will expand and occupy more space. In other words, a given bulk will have less weight as its tempera- ture is increased ; which has the effect of producing lack of equilibrium, and the warmer air will be replaced by colder air, causing a velocity which is in proportion to the change in tem- perature. The case is analogous to the action of two fluids in the branches of a U-tube, Fig. 14, DABC, the heavier fluid in DA and the lighter fluid in BC. The action of gravity causes the heavier fluid to flow downward and displace the lighter fluid, causing an upward motion in BC. If a volume of the lighter fluid with height greater than BC balances the weight of the heavier fluid DA, the FlG J 4- flow which is produced will take place with a head equal to the difference in height of AD, and an equal weight of the lighter fluid. The flow will take place in the same manner whether the heavier fluid be confined in a tube arranged as in the dotted lines, Fig. 14, or whether it be drawn from a large vessel, or from the surrounding air. Let the head which produced the draught be equal to //', the height of the flue BC as // ; let / be the temperature of the outside air or heavier fluid and /' that of the lighter fluid ; and let a be the coefficient of ex- pansion, which for one degree of temperature of air will be 44 HEATING AND VENTILATING BUILDINGS. . Since the expansion is directly proportional to the in- crease in temperature, we shall have in general : h h + K . ,, ha(t' -f) - = , from which ft = - . i + at i + at' i + at By substituting for a its value ^fo, we shall have the following for the head producing the flow in case air is the moving fluid : V - k(t> ~ *> = h( ? ~ t} -460(1 + 4 -ioO 460 + /' 460 + 1 is the absolute temperature of the air. The velocity is equal to the square root of twice the force of gravity, 32.16, into the head which produces the flow, as follows: The velocities given above, multiplied by 60 and by the area of cross- section, will give the discharge in cubic feet per minute. Mr. Alfred R. Wolff takes the actual discharge as 0.5 of that given by the formula, so that the actual discharge in cubic feet per minute would be, with 50 per cent allowance for friction, 460 + / in which F equals the area of cross-section of the flue in square feet. The table on next page gives the discharge per square foot of area of flue for various temperatures and heights computed from the formula. The above formulae are for the discharge of air from a flue. The volume, and consequently the velocity, for the entering air will be pro- portional to its absolute temperature ; and hence to obtain the quantity of air entering when T' is the temperature at entering and T that at dis- 460 + T 1 charging multiply the preceding formula by -- . ^.oo -f~ J. 34. The Inlet for Air. The air for ventilation is usually warmed and a portion or all of the heat required for warming is introduced at the same time. PRINCIPLES OF VENTILATION. 45 TABLE SHOWING THE QUANTITY OF AIR, IN CUBIC FEET, DISCHARGED PER MINUTE THROUGH A FLUE, OF WHICH THE CROSS-SECTIONAL AREA IS ONE SQUARE FOOT. (EXTERNAL TEMPERATURE OF THE AIR, 32 FAHR ; ALLOWANCE FOR FRIC- TION, 50 PER CENT.) Height of Flue in Feet. Excess of Temperature of Air in Flue above that of External Air. 5 10 15 20 25 30 50 100 150 I 24 34 42 43 54 59 76 1 08 133 5 55 76 94 109 121 134 167 242 2 9 8 10 77 1 08 133 153 171 188 242 342 419 15 94 133 162 188 210 230 297 419 5U 20 108 153 188 217 242 265 342 484 593 25 121 171 210 242 271 297 383 541 663 30 133 1 88 23O 265 297 325 419 593 726 35 143 203 2 4 8 286 32O 351 453 640 784 40 153 217 265 306 342 375 484 684 838 45 162 230 282 325 363 398 5M 724 889 50 171 242 2Q7 342 333 419 54i 765 937 60 188 264 325 373 42O 461 594 835 1006 70 203 286 351 405 465 497 643 900 IH5 80 217 306 375 453 485 530 688 965 1185 9 220 324 393 460 516 564 727 1027 1225 100 243 342 420 485 534 594 768 1080 1325 125 273 383 468 542 604 662 855 I2IO 1480 150 298 420 515 596 665 730 942 1330 1630 It is found from experience that if the velocity of the enter- ing air is very great it produces a disagreeable current, which is generally known as a draught, and is more or less dangerous to health. The following table from Loomis' Meteorology gives the relation between the velocity and force of air: RELATION BETWEEN VELOCITY AND FORCE OF AIR. Sensation. Velocity. Pressure, Lbs. per Sq. Foot. Miles per Hour. Feet per Second. 2 4 12.5 25 35 45 60 70 So IOO 2.92 5.85 IS. 3 36.6 5L5 66 -88 -105 H7 1146 O.O2 0.08 0.750 3-0 6 IO 18 24 3i 49 Gently pleasant . . . Pleasant brisk Very brisk High wind . Verv high wind * Violent gale . . Hurricane ... Most violent hurricane.. 46 HEATING AND VENTILATING BUILDINGS. It is quite generally agreed that the velocity of the entering air should not exceed four to six feet per second unless it can be introduced in such a position as to make an insensible cur- rent. The table which has just been given, while only approxi- mately correct, gives a very fair idea of the sensations produced by air-currents of different velocities and pressures, and is use- ful in fixing limiting values. The most effective location for the air-inlet is probably in or near the ceiling of a room, although authorities differ much in this respect. The advantages of introducing warm air at or near the top of the room are : first, the warmer air tends to rise and hence spreads uniformly under the ceiling; second, it gradually displaces other air, and the room becomes filled with pure air without sensible currents or draughts ; third, the cooler air sinks to the bottom and can be taken off by a ventilating, shaft. So far as the system introduces air at the top of a room it is a forced distribution, and produces better results than other methods. When the inlet is placed in the floor or near the bottom part of the walls it is a receptacle for dust from the room, and a lodging- and breeding-place for microbe organisms. In the ventilation of large buildings the inlets can usually be located in the ceiling, especially if the lighting be done by electricity or in some manner not affected by air-currents. Some experiments were made by Mr. Warren R. Briggs, of Bridgeport, Conn., on the subject of the proper method of introducing pure air into rooms and the best location for the inlet and outlet. The experiments were conducted with a model having about one sixth of the capacity of a schoolroom to which the perfected system was to be applied. The move- ments of the air in the model of the building were made visi- ble by mingling the inflowing air stream with smoke, which rendered all the changes undergone by it in its passage appar- ent to the eye. The results of the experiments are shown graphically in the six sketches. Figs. 15 to 20. In each case the distribution of the fresh air is indicated by the curved lines of shading. A study of these sketches is very suggestive, as it indicates the best results when the inlet is on the side near the top, and the outlet is in the bottom and near the centre of the room. The PRINCIPLES OF VENTILATION. 47 tendency of the entering air to form air-currents or draughts, which in some instances tend to pass out without perfect dif- fusion, is well shown. This tendency is less as the velocity of the entering air is reduced, and we probably get nearly per- fect diffusion in every case where the outlet is well below that of the inlet, provided the velocity of the entering air is small less than 4 feet per second. FIG. 15. AIR INTRODUCED AT BOTTOM, DISCHARGED AT TOP. FIG. 16. AIR INTRODUCED ON SIDE, DISCHARGED AT TOP. FIG. 17. AIR INTRODUCED ON SIDE, DISCHARGED ON OPPOSITE SIDE. 48 HEATING AND VENTILATING BUILDINGS. FIG. 18. AIR ADMITTED ON SIDE, DISCHARGED NEAR BOTTOM. FIG. 19. AIR ADMITTED AT BOTTOM, DISCHARGED NEAR BOTTOM. FIG. 20. INLET NEAR TOP, DISCHARGE NEAR BOTTOM. 35. The Outlet for Air. The outlet for air should be as near the bottom of a room as possible, and it should be con- nected with a flue of ample size maintained at a temperature higher than that of the surrounding air, unless forced circula- PRINCIPLES OF VENTILATION. 49 tion is in use, in which case the excess of pressure in a room will produce the required circulation. If the temperature in a room is higher than that of the surrounding air, and if the flue leading to the outside air can be kept from cooling and is of ample size and well proportioned, the amount of air which will be discharged will be given quite accurately by the tables referred to. These conditions should lead us to locate vent- flues on the inside walls of a house or building, and where they will be kept as warm as possible by the surrounding bodies. If for any reason the temperature in the flue becomes lower than that of the surrounding air the current will move in a re- verse direction, and the ventilation system will be obstructed. The conditions as to size of the outlet register are the same as those for the inlet ; the register should be of ample size, the opening should be gradually contracted into the flue, and every precaution should be taken to prevent friction losses. 36. Ventilation-flues. The size of ventilation-flue will depend to a great extent upon the character of system adopted, but will in all cases be computed as previously explained. A prac- tical system of ventilation gener- ally is intimately connected with a system of heating, and the vari- ous problems relating to the size and construction of ventilating ducts will be considered later. In general the ducts should be of such an area as not to require a high velocity, since friction and eddies are to a great extent due to this cause. The size of the ventilating duct can be computed, knowing its rise, length, and the differ- ence of temperature by dividing the total amount to be discharged FIG. 21. VENTILATION-FLUE. by the amount flowing through one square foot of area of the flue under the same conditions. 5O HEATING AND VENTILATING BUILDINGS. In introducing heated air into a room, it is very much bet- ter to bring in a large volume heated but slightly above the required temperature of the room rather than a small volume at an excessively high temperature. If the temperature of the air be brought in 25 degrees above that of the air in the room, the discharge in a flue one square foot in area would be in cubic feet per minute, 171 for a height of 10 feet, 271 for a height of 25 feet, 342 for a height of 40 feet. By referring to the table, Article 33, the discharge for any condition can be readily determined. As the difference of temperature of the air in the room and outside may usually be taken as 20, the velocity in feet per minute for heights corresponding to the distance of floor to roof in a building of 3 stories would be about as follows : ist floor, 306 ; 2d floor, 242 ; attic or top floor, 188, or about 5, 4, and 3 feet per second. For air discharged, the order of the velocities would be reversed on the particular floors. The area of the flue would be found by dividing the total air re- quired per second by these numbers. The general arrangement for heating the air and introduc- ing it into a room is shown in Fig. 21. In this case the cold air is drawn in at D and delivered into the chamber C, whence it passes through the heater, thence into the flue, entering the room at the register B. The vitiated air enters the ventilating flue at E. 37. Summary of Problems of Ventilation. From the foregoing considerations it is to be noted that the practical prob- lems of ventilation require the introduction, first, of thirty or more cubic feet of air per minute for each occupant of the room, and in addition sufficient air to provide perfect combus- tion for gas-jets, candles, etc., which are discharging the prod- ucts of combustion directly into the room. Second, the prob- lem requires the fresh air to be introduced in such a manner as to make no sensible air-currents, and to be in such quanti- ties as to keep the standard of contamination below a certain amount. This problem can be solved by either, first, moving the air by heat, in which case the motive force is very feeble and likely to be counteracted by winds and adverse conditions ; second, by moving the air by fans or blowers, in which case PRINCIPLES OF VENTILATION. 51 the circulation is more positive, and less influenced by other conditions. The methods for meeting these conditions will be given under appropriate heads in later articles. It will generally be found much more convenient to esti- mate the air required, not in cubic feet per minute for each person, but by the number of times the air in the room will need to be changed per hour. If the number of people who occupy a room be known, and each one requires 30 cubic feet of air per minute or 1800 cubic feet per hour, one can easily compute the number of times the air in a room must be changed to meet this requirement. Thus a room containing 1800 cubic feet, in which five people might be expected to stay, would need to have the air changed five times per hour in order to supply the required amount for ventilation purposes. By consulting the table Properties of Air, No. VIII, it will be seen that one heat-unit contains sufficient heat to warm 55 cubic feet of air, at average pressures and temperatures, one degree ; so that practically to find the number of heat-units re- quired for warming the air one degree we must simply divide by 55 the number of cubic feet to be supplied,. If the cubic contents of the room is to be changed from five to ten times per hour, we can very readily make the necessary computations by knowing the volume of the room. Even in the case of direct heating, where no air is purposely supplied for ventilation, there will be a change by diffusion of the air in a room which the writer has found-practically met by an allowance equal to one to three changes in the cubic contents per hour, which serves to supply heat for ventilation purposes in addition to that transmitted by the walls. The number of times that air will need to be changed per minute in a given room will depend upon its size as com- pared with the number of occupants. If we take the smallest size of rooms, in which we allow only 400 cubic feet of space per occupant, a supply of 30 cubic feet per minute would change the air in this space in 13^ minutes, or at the rate of 4^ times per hour. If 600 cubic feet are supplied per occupant, the air of the room would be changed once in 20 minutes, or at the rate of 3 times per hour. The following table may be HEATING AND VENTILATING BUILDINGS. of practical value, as it shows the number of changes per hour required to supply each person with 30 cubic feet per minute when the space supplied is as given in the table : Space to each Person. Cubic Feet. IOO. 200, 300. 400. 500, 6OO. 700. 800 90O Number of Times Air to be Changed per Hour. 18 9 6 4-5 3-6 3 2.6 2.25 2 38. Dimensions of Registers and Flues. The approxi- mate dimensions of registers and flues can be computed from considerations of the limiting velocity of entering air. For residence heating the velocity in flues is likely to be as follows, in feet per second : . Warm-air Duct. Ventilating Duct. Entering Air at Register. Discharge Air at Register. First story 2 C to 4. 6 a 4 Second story e c 3 4 Third story 6 4 3 3 Attic floor 7 3 a 2i The velocity per hour is 3600 times that per second. The area of the duct can be found by dividing the cubic feet of air needed per hour by 3600 times that in the above columns. If the air required is taken as a certain number of times the cubic contents of the room the following method is applicable: If we denote the cubic contents of a room by C, the num- ber of times the air is to be changed per hour by , the velocity in feet per second by V, then will the area in square c A H C T r. n C feet A = - . In square inches a = - . 3600 V 2$V The following table gives the net area in square inches for PRINCIPLES OF VENTILATION. 53 each 1000 cubic feet of space, of either the hot air or ventilat- ing register, for any required velocity of the air. The net area is about 0.7 the nominal area. (See Table of Registers, Article 144.) AREA IN SQUARE INCHES FOR EACH 1UOO CUBIC FEET OF SPACE. Velocity, Feet per Second. Number of Times Air changed per Hour. 2 i 4 5 6 8 10 I 40 2O 13-3 1O 8 6.7 5 4 2.7 2 1.6 1-3 80 40 26 20 16 13 4 8 5-3 4 3-4 2-7 120 60 40 30 24 2O 15 12 8 6 4-8 4 1 60 80 53 40 34 27 20 I? " 3 8-5 6.8 5-7 200 100 67 50 40 33 25 20 13-3 TO 8 6-7 .240 120 80 60 48 40 30 24 16 12 9 .6 8 320 1 60 107 80 64 53 20 32 21 16 12.8 10.5 400 2OO 133 100 80 67 50 40 26.6 20 16 13.3 2 a 5. 6 8 10 je. . 2O 2e OQ. . CHAPTER III. AMOUNT OF HEAT REQUIRED FOR WARMING. 39. Loss of Heat from Buildings. Heat is required to warm the air of a room to a given temperature, to supply the loss due to the radiation and conduction of heat from windows and walls, and to supply the heat for the air re- quired for ventilation. The amount of heat required for these various purposes will depend largely upon the construction of the building and the supply needed for ventilation purposes. This question was investigated experimentally by Peclet^ and it also received attention by Tredgold at about the same time, and has been more recently investigated by the German Government. Peclet's investigations were carried out with extreme care, and reduced to general laws. He divides the loss into two parts : first, that from the windows ; second, that lost by conduction through the walls. He considers the loss in each case from the exterior of the wall as due in part to radiation and in part to convection. 40. Loss of Heat from Windows. The values which Peclet found for glass, reduced to English measures, were as follows :* LOSS PER SQUARE FOOT PER DEGREE DIFFERENCE OF TEM- PERATURE FAHR. PER HOUR FOR WINDOWS. Height of Window. 3 ft. 3 in. ! 6 ft. 7 in. 10 ft. 13 ft. 3 in. 16 ft. 3 in. Loss in B. T. U. per) square foot per degree ! difference of tempera- j ture, j 0.98 O.Q45 i o-93 0.92 0.91 * The general formula which Peclet gives as expressing this loss is as fol- lows : M\(T )(K-\-K'), in which T equals temperature of the room, 6 = temperature of the air, K = coefficient loss for radiation, JC'= coefficient loss for convection. A" varies with; the height. A' is constant, and in all cases equal to 291 when the temperature is measured by a centigrade thermometer. The values of the coefficients A' and K 1 were determined by experiment. 54 AMOUNT OF HEAT REQUIRED FOR WARMING. $5 For multiple glass the above numbers are to be multiplied by the following coefficients : 21 2 Double , Triple -, Quadruple -, n layers 3 2- 5' ,+ The coefficients given above do not differ greatly from unity for each square foot of single glass and two thirds as- much for each square foot of double glass per degree differ- ence of temperature. Tredgold, in his work on " Warming and Ventilation," states that one square foot of glass will cool 90 cubic feet of air one degree per hour. This is about equivalent to 1.7 B. T. U. per degree difference of temperature per hour. This number was used in computation by both Tredgold and Hood, neglecting the cooling effect of the walls. Hood, in his work "Warming of Buildings," third edition, page 213, gives various other experiments of the same nature. Mr. Alfred R. Wolff, M.E., in a recent pamphlet gives co- efficients adopted by the German Government, as follows : Heat transmission in B. T. U. per square foot per hour, per degree difference of temperature : Single window, 1.09; single skylight, 1.118: double window, 0.518; double skylight, 0.621. These coefficients are to be increased, as explained in the next article, for exposed buildings. 41. Loss of Heat from Walls of Buildings. The loss of heat depends upon the material used, its thickness, the num- ber of layers, the difference of temperature between outside and inside surfaces, and air exposure. The problem is one very difficult of theoretical solution, and we depend principally for our knowledge on the results of experiments. The following tables were computed from formulae given by Peclet and reduced to English measures by the writer:* * M = CQ( T - 9) -r- (2(7+ Q_e\ in which Q - K + K' , e = thickness, and C coefficient of conduction. See Table XlV. Other values as on page 54- HEATING AND VENTILATING BUILDINGS. AMOUNT OF HEAT IN BRITISH THERMAL UNITS PASSING THROUGH WALLS PER SQUARE FOOT OF AREA PER DEGREE DIFFERENCE OF TEMPERATURE PER HOUR. Single Wall. Wall with Air-space. Thickness, inches. Brick or Stone. Wood.* Brick or Stone. 4 0-43 O. 12 0.36 8 0-37 0.065 0.30 12 0.32 0.045 0.25 16 0.28 0.033 0.21 18 0.26 0.031 O.IQ 20 0.25 0.03 0.18 24 0.24 O.O2Q 0.17 28 0.22 O.O27 0.15 32 O.2I 0.025 0.13 36 0.20 O.O2O 0.12 40 0.18 O.OlS O. IO Mr. Alfred R. Wolff, in a lecture before the Franklin In- stitute,! gives coefficients for loss of heat from walls of various thicknesses, which he translated from and transformed into American units from tables prescribed by the German Govern- ment as follows : FOR EACH SQUARE FOOT OF BRICK WALL. Thickness of wall = 4" 8" 12" 16" 20" 24" 28" 32" 36" 40" Loss of heat per square foot per hour per degree difference of temperature .... o 68 o 46 O ^2 o 26 O 21 O 2O O I Id. O I ^ o 1 29 o 115 I square foot, wooden beam, planked j as flooring. . . . K = 0.083 over or ceiled, { as ceiling K = o. 104 i square foot, fireproof construction, j as flooring. ... K = o. 124 floored over, \ as ceiling K =0.145 i square foot, single window K 1 .09 i square foot, single skylight K i . 1 1 5 i square foot, double window ... K = 0.518 i square foot, double skylight K = 0.621 I square foot, door K =0.414 * This experiment applies to solid wood ; it is evidently of little use when applied to wooden buildings, since these buildings generally present so many opportunities for loss of heat through crevices. f Lecture on Heating of Large Buildings, published in pamphlet form. AMOUNT OF HEAT REQUIRED FOR WARMING. 57 These coefficients are to be increased respectively as fol- lows : Ten per cent where the exposure is a northerly one and the winds are to be counted on as important factors. Ten per cent when the building is heated during the daytime only, and the location of the building is not an exposed one. Thirty per cent when the building is heated during the daytime only, and the location of the building is exposed. Fifty per cent when the building is heated during the winter months intermittently, with long intervals (say days or weeks) of non-heating. Mr. Wolff has arranged the results in a graphical form (Fig. 22), so that the values for heat losses can be obtained by in- spection. .10 20 &> 40 60 CO 70 _ __ FIG. 22. WOLFF'S DIAGRAM OF Loss OF HEAT FROM WALLS In this diagram distance in horizontal direction is the re- quired difference in temperature between that of the room and the outside air ; the various diagonal lines correspond to the different radiating surfaces of the building, floors, ceiling, doors, windows, etc. The heat transmitted per square foot of sur face per hour is given by the numbers in the vertical column. 58 HEATING AND VENTILATING BUILDINGS, The German Government require computations to be made on the following assumed lowest temperatures :* External temperature 4 Fahr. Assumed lowest temperature of non-heated cellar and other portions of building permanently non- heated 3 2 Vestibules, corridors, etc., non-heated, and at fre- quent intervals in direct contact with external air 23 ( Metal and slate roofs. . . 14' Air-spaces between roof j Denser methods of roof- and ceiling of rooms, j ing, such as brick, con- [ crete, etc 23 As the temperature to be attained in rooms of various kinds, the German Government prescribes for Stores and dwellings 68 Fahr. Halls, auditoriums, etc 64 Corridors, staircase-halls, etc 54 Prisons, occupied by day and night 64 In making calculations for heat losses for buildings in America the minimum external temperature is usually assumed as zero Fahr., and the required temperature in stores and dwell- ings as 70 degrees. In many portions of the country the cor- ridors, staircase, halls, etc., are required to be from 65 to 68; while in other portions of the country the halls are required to be as warm as the living-rooms. In the preceding computa- tions no allowance has been made for the heat carried off in the process of ventilation, nor for that supplied from the bodies of people in the room, gas, electric lights, etc. The loss of heat from walls and glass surfaces has also been considered by Leicester Allen, Metal Worker, October, 1892 ; and by John J. Hogan. Mr. Hogan gives the cooling power of one square foot of glass as 1.57 heat-units, and that of a brick wall 4 inches thick as .231 results which are somewhat different from those given by Mr. Wolff. 42. Heat required for Purposes of Ventilation. In ad- dition to the loss of heat through walls of buildings, more or less heat will be carried off by the air which escapes from various cracks and crevices. By consulting Table VIII it will be seen that, for ordinary * Lecture by Alfred Wolff before Franklin Institute. AMOUNT OF HEAT REQUIRED FOR WARMING. 59 temperatures and pressures, 55 cubic * feet of air will absorb one heat-unit in being warmed one degree F., and hence can be considered the equivalent of one pound of water. The heat-units required for ventilation can then be found by multiplying the number of cubic feet of air by the differ- ence of temperature between warm and outside air, and divid- ing by 55-t Total Heat Required. By referring to the values for heat losses given by Wolff and Peclet, it will be noted that a fair average value would be I heat-unit for glass and 0.25 heat- unit for walls per degree difference of temperature per square foot per hour. Usually we can neglect all inside walls, floors, and ceilings, and consider only the exposed or outside walls with sufficient accuracy. For direct heating of residences it seems necessary to con- sider the air of halls changed 3 times per hour, that of rooms on first floor 2 times per hour, and that of rooms on the upper floors once per hour, to account for changes taking place by diffusion. If C represent cubic contents of room, W the area of ex- posed wall surface, G the area of glass, n the number of times air is changed per hour, / the difference of temperature be- tween air in room and outside, we have, as a general formula for heat required, in heat-units per hour, Very elaborate methods of computing the loss of heat through the walls of a building are given by Box in his Treatise on Heat as a translation from the experiments by P^clet.J These methods have in some instances been employed by amateurs in this art in computing the loss of heat through the walls. It seems necessary to remark here that the coefficients obtained by Peclet are accurate only under the conditions gov- * This quantity varies somewhat with barometric pressure and temperature. f If C cubic contents of room, n the number of times air is changed, /the difference of temperature, // the heat-units for ventilation, h = /. J Traite de la Chaleur, Paris. HEATING AND VENTILATING BUILDINGS. erning his experiments, and there is little or no proof that the loss of heat from the walls of a building was ever actually measured by him. Recent writers* on heat have found that Peclet made an error in the position of the decimal point in reporting the coefficient of conductivity, and that his values in consequence were ten times too small at least for metals of high conductibility and were probably in error for all cases. Not only are the coefficients given by Peclet doubtful, but his method or rule for computing the heat lost through the walls is erroneous. For computing the loss of heat he employs formulae of the same general nature as those given on page 63 for loss of heat from a heated body in still air. For such cases there is a decrease in the loss of heat per unit of area with in- crease in height, but different conditions apply to the the side of a building freely exposed to air-currents. Actually there is in many cases an. increase in heat transmission, due to stronger air-currents near the top of a building. The application of the formulae quoted by Box f shows that the loss of heat from a building with one side exposed is greater per unit of area than from a building with all sides exposed, which is rarely ever true. The principal objection to the methods referred to lies in the fact that, while the loss of heat through the walls is computed with great elaborateness of detail, no consideration is given to the heat required to warm the air, which in spite of all precau- tions will constantly enter and leave an apartment and for which considerable heat is in all cases required. Practically there is little or no difference in the amount of heat required to warm a wooden or a brick building, which is due to the fact that air-spaces lined with heavy building-paper make the heat losses in the one practically as small as in the other. There is, however, a great difference in the amount of heat transmitted through the walls of different buildings, due to good or bad construction or to use of inferior or superior materials ; this fact renders any elaborate formula for this pur- pose abortive. The best that can be expected of any rule is agreement with the average condition. * Theory of Heat, Preston, London, f A Practical Treat/se on Heat, p. 218. AMOUNT OF HEAT REQUIRED FOR WARMING. 59^ The author in two cases measured the loss of heat, witli the following results :* In the first case a room on the second floor with exposed side and end had 246 sq. ft. of wall surface and 96 sq. ft. of window surface. When the air in the room was 28 degrees above that outside the loss was 4247 B. T. U. per hour, and when 27 degrees above, was 4240 B. T. U. per hour. To supply loss of heat by the rule stated would re- quire respectively 4410 and 4253 B. T. U. per hour, the error varying from a fraction of one per cent to nearly five per cent. In the second case a test was made in the N. Y. State Veterinary College ; this showed that to maintain the room 31 degrees warmer than the outside air 16,000 B. T. U. were required per minute, of which 39 per cent escaped in the ventilation-flues, and 61 per cent passed by conduction through the walls and windows. The building was exposed on all sides, was 3 stories in height, had 9281 sq. ft. of glass and 31,644 sq. ft. of exposed wall surface. By the rule quoted the building loss should be 532,952 B. T. U. per hour. The actual loss by experiment was 9120 B. T. U. per minute or 547,200 B. T. U. per hour, which is within two per cent of that called for by the rule. In this case the building was of brick, the thickness of walls varied from 24 to 16 inches, the windows had single glass. The above experiments, which were made on a large scale and en actual buildings, indicate the substantial accuracy of the rule quoted. Data regarding the number of changes of air which take place per hour under different conditions of direct heating in buildings are still very deficient. The following seems to be reliable : Number of Changes of Air per Hour. Residence heating Halls, 3 ; sitting-room, etc., 2 ; sleeping-rooms, i. Stores First floor, 2 to 3 ; second floor, \\ to 2. Offices 4 . First floor, 2 to 2$; second floor, i \ to 2. Churches and public assembly-rooms, 2 to 2\. * Transactions of American Society of Heating and Veniiiatiog Enguicexs, vols. in. and IV. CHAPTER IV. HEAT GIVEN OFF FROM RADIATING SURFACES. 43. The Heat Supplied by Radiating Surfaces. The heat used in warming is obtained either by directly placing a heated surface in the apartment, in which case the heat is said to be obtained by direct radiation, or else by heating the air which is to be used for ventilating purposes while on passage to the room, in which case the heating is said to be by indu rect radiation. As air is not heated appreciably by radiant heat, this latter term is very clearly one which is used in a wrong sense. In this treatise we shall use the terms direct heating or radiation and indirect Jicating. Direct heating is performed by locating the heated surface directly in the apartment : this surface may be heated by fire directly, as is the case with stoves and fireplaces; or it may receive its heat from steam or from hot water warmed in some other portion of the premises and conveyed in pipes. The general principles of warming are the same in all cases, but for the case of stoves the temperature is greatly in excess of that for steam or hot-water heating surfaces. The heat is carried away from the heated surface partly by radiation, in which case the heat passes directly in straight lines and is absorbed by people, furniture, and objects in the room, without warming up the intervening air directly, and also by particles of air coming in contact with the heated surface, which may be the radiating surface, or the people and objects in the room which have been warmed by radiant heat. The sensation caused by radiant and convected heat is quite different: the radiant heat has the effect of intensely heating a person on the side towards the source of heat, and of producing no warming effect whatever on the opposite side. The heat which has passed off by convection is first utilized in warming the air, and the sensation produced on any person is that of loyver temperature-heat equably distributed. Radiant and con- Co HEAT GIVEN OFF FROM RADIATING SURFACES. 6 1 vected heat are essentially of theVsame nature: in the one case it is received by the person directly from the source of heat, and at a high temperature ; in the other case it is received from the air, which is at a comparatively low temperature. The heat in passing through any metallic surface raises its temperature an amount which depends upon the facility with which heat is conducted by the body and discharged from the outer surface. The phenomena of the flow of heat through any metallic substance can be i E I L illustrated by the sketch in Fig. 23. A If E represents the source of heat, and ABCD a section of a metallic wall sur- rounding, the flow of heat takes place FIG. 23. into the metallic surface, then through the solid metal, and finally through the outer surface. It is noted that the heat meets with three distinct classes of resistances: first, that due to the inner surface; second, that due to the thickness of the material; and third, that due to the outer surface. The first and third resistances are due to change of media, and when the material under consideration is a good conductor, constitute the principal portion of the resistance to the passage of heat. If the resistance on the inner surface AB is small and that on the outer surface CD is great, the temperature of the metal- lic body will approach that of the source of heat, for the reason that the heat will be delivered to the surface CD faster than it is discharged. In this case the thickness of the material is of little or no importance, and the rate at which heat will pass will depend entirely upon the rapidity with which it can be discharged from the outer surface. 44. Heat Emitted by Radiation. Heat emitted by radia- tion, per unit of surface and per unit of time, is independent of the form and extent of the heated body, provided there are no re-entrant surfaces which intercept the rays of radiant heat. The amount of heat projected from a surface of such form as to radiate heat equally in all directions, depends only on the nature of its surface, the excess of its temperature over that of the surrounding air, and the absolute value of its tem- perature. ^2 HEATING AND VENTILATING BUILDINGS. Radiation of heat was stated by Sir Isaac Newton to be in exact proportion to the difference of temperature of the heated surface and the surrounding media, but this law was found to be inaccurate by Dulong and Petit. They found that the radiation increased at a greater rate than the difference in tem- perature, and for high temperature, was much in excess of that given by the law of Newton. From a large number of experi- ments on the cooling of bodies they were able to determine the following law : " The rate of cooling due to radiation is the same for all bodies, but its absolute value varies with the nature of the surface." It is represented by the formula I), in which m represents a number depending on the nature of the surface of the body, a represents a constant number, which for the centigrade thermometer is equal to 1.0077 and for the Fahrenheit above 32 to 1.00196, 6 the temperature of the sur- rounding air, and t the excess of temperature of the body over that of the surrounding space. Pclet found that if the radiant heat be received by a dull surface the value of m becomes equal to a constant 124.72 mul- tiplied by K, a coefficient which depends on the nature of the surface. A table giving the rapidity of cooling for different values of difference of temperature in both Fahrenheit and metric units is given on page 64, and the value of the coeffi- cient K for different surfaces, which is to be multiplied by the numbers which express the relative rates of cooling, is given in a subsequent table. The results of the experiments by Peclet accord very well with recent experiments made in testing radiators for steam and hot-water heating. For these cases either wrought or cast iron is used, and the difference in radiating power is im- material. The construction of the ordinary form of radiator is such as to present very little free radiating surface, as all the heat which impinges from one tube on another is reradiated back, and consequently not of use in heating the apartment. The greater portion of the heat removed is no doubt absorbed HEAT Gll'EN OFF FROM RADIATING SURFACES. 63 by the air which comes in contact with the radiator, or, in other words, it is removed by convection. 45. Heat Removed by Convection (Indirect Heating). The heat removed by convection is independent of the nature of the surface of the body and of the surrounding absolute tem- perature. It depends on the velocity of the moving air, and is thought to vary with the square root of the velocity. It also depends on the form and dimensions of the body and of the ex- cess of temperature over that of the surrounding air. We are indebted to Peclet for exact experiments giving us the value of the loss from this cause. Peclet's experiments were, however, made in ordinary still air, and if the velocity is increased should be multiplied by factors which will be given later. The formulae which Peclet found as applying to bodies of different form were as follows, the results below being given in heat-units per square foot per hour. The general formula for loss by convection is, in metric units, A = o.^2K't l 2 33. The values of K' depend upon the form and surface of the body and are as follows : For a sphere, radius r, K'= 1.778 + 0.13/7-. For a vertical cylinder, circular base, radius r, height //, K' = (0.726 + 0.0345 / v7)(2.43 + 0.8758 t'//). For horizontal cylinder, radius r, K' 2.058 + 0.0382/7-. For vertical planes, height //, K' = 1.764 + 0.636/4^. Numerical values of these various quantities are given in tables, Art. 46. 6 4 HEATING AND VENTILATING BUILDINGS. 46. Total Heat Emitted. The amount of heat given off by radiation and convection for various differences of tempera- HEAT-UNITS PER HOUR. RADIATION. CONVECTION. Excess of Temperature. Total Radiation. Per Degree Differ- ence. Total. Per Degree Dif- ference. Deg. Cent. Deg. Fahr. Calories per Sq. Metre. B. T. U. per Sq. Ft. Calories per Sq. Metre. B. T. U. per Sq. Ft. Calories per Sq. Metre B.T.U. per Sq. Ft. Calories per Sq. Metre. B.T.U. per Sq. Ft. 10 18 II. 2 /If 4.1 AT .12 AT .228/T 9-4 K' 3.4 K' 0.94 K' .189 K' 20 36 23.2 8.6 " .16 " .239 " 22.2 8.2 " .11 ' .228 " 3 54 36.1 13.2 " .20 " 243 " 36.6 13-5 " .22 ' .025 " 40 72 50.1 18.5 2 5 " 257 52. 2 t { 19.2 30 ' -265 " 5 9 65.3 24.2 3* " .269 " 68.6 25-3 " 37 ' .284 " 60 108 8l. 7 30.2 -36 " .281 " 86.0 31-8 " 43 2 95 " 70 126 99-3 36.6 .42 " .291 " 104.0 38-4 " 49 ' -306 " 80 144 118.5 43-7 .48 " 304 " 122.6 45-o " 53 " 3" 90 162 138.7 51.2 -54 " 317 141.7 52.2 57 ' 32 ' 100 180 161.3 59.5 .6l " -33 " 161.5 59-5 " .61 " 33 ' no 198 185-3 68.5 .69 " 035 " I8l.5 67.0 -64 " 334 ' 120 216 211. 3 78.0 .76 " .361 " 202. 75-5 " .68 " 345 I 3 234 239.3 88.3 8 3 ' 377 " 22 3 . 82.2 " .72 ' 35 ' I 4 252 269.5 99-o .92 ' 395 '' 244. 90.0 " 74 ' 355 ISO 270 302.1 112 .01 ' .416 " 266. 98.0 " .76 ' 36 " 160 288 339-0 125 . 12 ' 435 288. 106 " 79 ' .365 " 170 306 37'-4 T 39 .22 ' 454 310. 115 " .82 ' 372 1 80 324 418.5 155 32 " .478 ' 333- 123 " -85 ' 38 " 190 342 463.2 172 43 J* 503 ' 356. 132 " .87 ' .384 " 200 360 5"- 2 188 523 379- 140 ' .89 ' 39 ' 210 378 563-1 208 .68 " 553 402.9 149 ' .01 394 220 396 619.0 229 .81 " 573 " 426.7 57 " 93 ' .40 ' 2 3 414 679-5' 255 95 " .617 " 450.4 166 " 95 43 ' 240 432 744.8 275 3.10 " -665 " 475-o J 75 ' 97 .406 " 2 5 450 848.7 3M 3-39 " .700 " 498.6 184 " 99 " .408 " FACTOR TO DETERMINE RADIATION LOSS FROM VARIOUS SURFACES. VALUE OF COEFFICIENT K. Polished silver ... . O 43 Powdered wood . 3 ^"3 " charcoal . 3.42 . o.2<;8 . q.62 Gilded paper .... O 2"? a 71 Red copper ... o 16 Paper . 3.71 Zinc Soot 4.OI Tin o 215 Building stone . 3 6O Polished sheet iron O 4^ Plaster . . . . 3.60 Sheet lead Wood 3 . 60 Calico 3.65 Rusty sheet iron 1 16 Woollens q.68 Cast iron, new . ^17 Silk . 3.71 Rusty cast iron . l.lb Water 5.31 Glass Oil . 7.24 Powdered chalk NOTE. To find the total heat emitted by radiation, multiply the value of K as given in the above table by the numbers corresponding to radiation due to difference of temperature as in the preceding table. HEAT GIVEN OFF FROM RADIATING SURFACES. 65 ture and from any surface when K or K' is unity is given in the first table on p. 64, as computed from Peclet's experiments. The total heat emitted by any surface will be obtained by multiplying the results given in the first table by the factor of radiation and convection for the required conditions. This table is exact for the surrounding air at 15 Centigrade or 59 Fahrenheit. FACTOR TO DETERMINE CONVECTION LOSS FROM BODIES OF VARIOUS DIMENSIONS. VALUE OF COEFFICIENT K'. Diameter. o. C/3 Horizontal Cylinder. Vertical Cylinder, Height in Metres and Feet. Metres. Indies. 0.5 m. 1.64 ft. i m. 3.28 ft. h 2 m. 6.56 ft. k 3 m. 9.84 It. h 4 m. 13. I2ft. h 5 m. 16.4 ft. h 10 m. 32.8 ft. O.O25 0.05 0.10 O.2O 0.40 0.60 0.8 O. IO 0.16 0.984 1.968 3-94 7 -.88 '5-74 23.62 31.50 39.38 63.0 5.114 6-9 4.33 3-o8 2-43 2.IO 3-59 2.82 2.44 2.25 2.18 2.15 3-55 3-22 3-05 2-93 2.88 2.85 2.83 3-2 2-9 2-75 2.65 2.60 2-57 2-55 2.95 2.68 2.54 2-45 2.40 2.37 2.36 2.8 4 2.57 2.44 2.35 2.31 2.28 2.26 2.79 2.52 2-39 2.30 2.26 2.23 2.22 2.73 2.48 2-35 2.26 2.22 2.20 2.18 2.62 2.38 2.26 2.17 2.13 2. II 2.O9 1.94 ratio d 20 20 20 15 i3i 12.5 20 The table on p. 66 gives the total loss from various forms of direct radiating surfaces in still air, calculated by Peclet's coefficients, slightly modified by recent experiments. The loss of effective surface due to rays of radiant heat im- pinging on hot surfaces can be calculated as follows : FIG. 24. D () () () FIG. 25. 66 HEATING AND VENTILATING BUILDINGS. Thus in Fig. 24, supposing pipes equally hot, occupying the relative positions of C and B, the effective radiating sur- FIG. 26. face of C will be diminished by that portion of the circumfer- ence intercepted by the lines CD and CE. The angle DCB HEAT-UNITS EMITTED PER HOUR PER SQUARE FOOT FROM VARIOUS SURFACES, DIRECT RADIATION, STILL AIR. Coefficient or Amount per Degree Difference of Temperature. Total per Square Foot per Hour.* Differ- Horizontal Pipe, Diameter. Horizontal Pipe, Diameter. of 6 in. 4 in. 2 in. i in. 6 in. 4 in. 2 in. J in. Tempera- ture. Radiator, Height. Radiator, Height. Deg. F. 40 in. Massed Surface. 40 in. Thin. 24 in. Massed. 12 in. Thin. 40 in. Massed Surface. 40 in. Thin. 24 in. Massed. 12 in. Thin. 10 0-55 O.62 0.66 0.85 5.50 6-7 6.6 8-5 2O .11 25 32 1.72 20.2 24.9 26.4 34-4 30 .18 34 .42 1.84 35 39-7 42.7 55-2 40 .24 .40 . .48 1.92 49.6 56.2 59- 77 50 .29 .46 54 2. or 64.5 73 o 77 100 60 33 50 58 2.06 79.8 90 95 124 70 36 54 63 2. 12 95.2 1 08 148 80 .40 58 67 2.18 112 127 133 90 43 .63 .72 2.24 128 147 153 199 100 47 .66 76 2.28 147 167 175 228 IIO .51 .71 .80 2-34 1 66 1 88 198 257 120 54 1.74 84 2-39 184 208 219 287 130 57 1.78 .88 2-44 203 230 242 I4O .61 1.81 .91 2. 4 8 223 2=12 266 346 150 .64 1.84 94 2-53 244 276 291 378 160 .66 1.87 97 2-57 265 300 316 410 170 .69 1.91 2. 02 2.62 286 324 341 443 i So 72 1.94 2.05 2.65 307 348 367 475 190 75 1.98 2.09 2.71 330 375 393 512 200 .78 2.OI 2. 12 2.76 356 403 415 552 225 87 2.12 2.24 2.91 420 477 500 650 250 97 2.2 3 2-35 3.06 493 557 587 762 275 2.07 2-34 2-47 3-22 563 637 670 872 300 2.17 2-45 2.58 3-37 654 742 780 IO2O 325 2.27 2-55 2 70 3.50 740 840 882 II5O 350 2-37 2.6 7 2.82 3.66 835 945 995 1295 * Results divided by loco give approximate weight of steam condensed per hour. HEAT GIVEN OFF FROM RADIATING SURFACES. 67 has for its sine DB/BC. DB is the external radius of the pipes, BC the distance between the centres, which is usually not far from two diameters. In Figs. 25, 26, and 27 the shaded FIG. 27. areas show the position of surface, by which the radiant heat coming from a single pipe or a single section is intercepted and reradiated to its source. Supposing the distance apart to be as given above, the fol- lowing table gives the percentage of reduction in amount of heat transmitted due to this cause : Number of Rows of Tubes. Amount of Surface from which no Radi- ation takes place. Probable Reduc- tion in Heat transmitted. Per cent. Per cent. I 16 8 2 42.7 21.3 3 4 6 55 66 73 79 27-5 33 36.5 39-5 47. Material of Radiators.* As bearing directly upon the above subjects, the writer planned a series of experiments which were conducted by E. T. Adams and M. H. Gerry in Sibley College during the winter of 1893-4. The results of these experiments show that the amount of heat transmitted does not depend so much upon the kind of metal as upon the * Transactions of American Society Heating and Ventilating Engineers, vol. i. 68 HEATING AND VENTILATING BUILDINGS. media in contact with the metal on both sides. The experi- ments performed were quite elaborate ones, and every precaution was taken to secure accuracy. The heat measurements were made with an apparatus arranged as in Fig. 28. The box A was fitted so that plates of cast or wrought iron of vari- ous thickness could be used as a bot- tom. The box B directly beneath the box A was so constructed that steam, air, oil, or water of a given tempera- ture could be supplied, and would transmit its heat upward through the bottom of the box A. The heat thus transmitted was measured by its effect on the temperature of the water in box A. The results were reduced to thermal units passing through one square foot of metal per hour, for each degree difference in temperature in box B and box A. We see from the table that when steam and water are in contact with the plates considerable difference in the results were obtained by varying the thickness of the plate in the bot- tom of the vessel A. But when air is on one side, the results are little affected by varying the nature and thickness of the plate. The experiments were made with a clean cast-iron plate, also with a wrought-iron plate, and then with each of these plates covered with a thick layer of boiler-scale, neatly fitted. In the latter case the heat had to pass through both the scale and the plate. Tne table (page 69) is of interest, since it shows that with the same material for heat transmission, and with the same dif- ference of temperature, there is a great difference in the results. These depend more upon the material which receives or takes up heat than upon the material which conducts it. It can be readily seen, however, that such would not -have been the case with poor conductors. Thus the heat transmission through iron, from steam to water, varies from 25 to 75 times as much as that transmitted through the same plate from air to water. When the heat was passing from steam to water there was a sensible differ. HEAT GIVEN OFF FROM RADIATING SURFACES. 69 cnce, due to the material and thickness of the plates used, but when passing from air to water this difference wholly dis- appeared. In passing from steam to water the rate of trans- mission increased very rapidly with increase in difference of temperature. HEAT TRANSMITTED IN THERMAL UNITS FOR EACH SQUARE FOOT PER HOUR AND PER DEGREE DIFFERENCE OF TEM- PERATURE. Difference Steam to Water. Lard Oil to Water. Air to Water. ol Tem~ perature of the Two Sides of the Plate, Deg Fahr. Clean Wrought Iron T 5 B inch thick. Clean Cast Iron T T B inch thick. Wrought- iron Plate and Scale iJ4 inches thick. Cast-iron Plate and Scale ,9fi inches thick. Clean Cast- iron Plate h inch thick. Cast- iron Plate and Scale. Clean Cast Iron /.inch thick. Cast- iron Plate and Scale. 25 28.8 21 2.7 1.8 6.5 4 1.2 0.15 50 6o.O 48 5-5 3-6 13 8 2-5 0-3 75 96.0 84 8.2 5-4 19.5 12 3-7 o.45 100 150.0 127 II 7-3 26 16 5 0.6 125 228 185 13.7 9.1 3L5 20 6.2 o.75 150 348 255 16.5 10.9 39 24 7-5 0.9 175 19.2 12.7 45-5 28 8.7 1.05 2OO 22 14.6 52 32 10 1.2 300 33 21.9 78 48 15 2.8 400 44 36.2 20 2.4 500 25 3.0 600 3-6 48. Methods of Testing Radiators. So far as the writer knows, no standard method has been adopted for use in the testing of radiators, and while numerous tests have been made by different engineers and experimenters, they are often not concordant either as to the method of testing or as to the re- sults obtained. The results in the testing of radiators are greatly affected by small variations in temperature, by irregu- lar air-currents, and by the amount of moisture contained originally in the steam. Obscure conditions of little apparent importance and often disregarded greatly influence the results. The heat emitted _by the radiator is in all cases to be computed by taking the difference between that received and that dis- charged. This result is accurate, and easily obtained. This heat is utilized in warming the air and objects in the room, and to supply losses from various causes, which take place constantly, and is diffused so rapidly, and used in so many 70 HEATING AND VENTILATING BUILDINGS. ways, that it is practically impossible to measure it, although it is, of course, equal to that which passes through the radiator. The radiating surface is almost invariably heated either by steam or by hot water. In the case of a steam radiator the heat received may be determined, by ascertaining the number of pounds of dry steam condensed in a given time, multiplying this by the heat contained in one pound of steam, and deduct- ing from this product the weight of condensed water, multi- plied by its temperature. To make a test of this kind with accuracy requires, first, a knowledge of the amount of moisture contained in the original steam ; second, the pressure of the steam or its temperature; third, an arrangement for permitting FIG. 29. RADIATORS ARRANGED FOR TESTING. water of condensation to escape from the radiator without the loss of steam, and means of accurately weighing this water, and also of determining its temperature. The radiator can be located in any desired position in the room; on the floor, or slightly elevated therefrom. The temperature of the room during the test should be maintained as nearly constant as possible, and no test should be less than from 3 to 5 hours in length. The method adopted by Mr. George H. Barrus in making a radiator test is shown in Fig. 29. The one adopted by the author, in many respects similar, is shown in Fig. 30. In some recent tests of steam radiators made at Sibley College * the author adopted the following plan of operation * See Transactions vol. i., American Society Heating and Ventilating En gineers. (^ HEAT GIVEN OFF FROM RADIATING SURFACES. Jl for measurement of the heat discharged and for operating the radiators : First, the steam supplied to the radiator to be passed through a separator and a reducing-valve to remove entrained water and maintains a constant pressure during any given run. Second, the amount of moisture in the steam to be measured by a calorimeter, and corrections made to the result for the entrained water. Third, the pressure and temperature of the steam in the radiator to be measured by accurate gauges and thermometers. Fourth, the amount of heat passing through the radiator to be obtained by weighing the condensed FIG. 30. RADIATOR ARRANGED FOR TESTING. :eam, measuring its temperature, and computing by this leans the heat discharged. Fifth, the air from the radiator to be effectually removed, irge errors are caused by leaving varying amounts of air in :he radiator. The ordinary air-valve is often very unsatisfac- tory for this purpose ; if used, it must be closely watched, or the results may be seriously affected. The heat supplied was computed by knowing the weight, percentage of moisture, and the heat contained in one pound of steam. Various methods were tried for drawing off the condensed water : in some tests a trap was used, but better results were obtained by employing a water-column with gauge- glass and drawing off the water of condensation by hand, at HEATING AND VENTILATING BUILDINGS. such a rate as to maintain a constant level in the glass. To prevent loss by evaporation, this water needs to be received either into a vessel containing some cold water, or else into one with a tight cover, the latter being generally preferred. Methods of Testing Indirect Steam Radiators. For this case the general methods of testing should be the same as those previously described, and in addition the volume of air which passes over the radiator should be measured ; also, its temperature before and after passing the radiator. For meas- uring the velocity of air the most accurate instrument at present known is the anemometer, which has been described and illustrated in Article 30, page 37. In measuring the veloc- ity the anemometer should be moved successively to all parts in the section of the flue, and the average of these results should be used. The velocity in feet per minute multiplied by the area of section in square feet should give the number of cubic feet. The number of cubic feet of air heated can also be computed, as ex- plained in Article 30, page 40, by dividing the heat emitted by the radiator by the prod- uct of specific heat of air and increase in temperature. The heat which is ab- sorbed by the air can be com- puted by multiplying that required to raise one cubic foot one degree, as given in Table VIII, by the total num- ber of cubic feet warmed mul- p APPARATUS. tipl ; ed by thg ; ncrease Jn tgm _ perature. Fig. 31 shows an arrangement adopted by the author in testing indirect radiators, the air-supply being measured by an anemometer not shown. Testing Hot-water Radiators. The amount of heat trans- mitted through the surfaces of a hot-water radiator can be determined in either of two ways : first, by maintaining circula- OF THE ^ XJNIVEBSITY HEAT GIVEN OFF FROM RADIATING SURFACES. 73 tion at about the usual rate, measuring the temperature of the water before entering and after leaving the radiator; also, measuring or weighing the water transmitted. The heat trans- mitted would be equal in every case to the product of the weight of water, multiplied by the loss of temperature. In making these tests the same precautions as to removing the air from the radiator must be adopted as in testing steam radiators. These radiators can also be tested by filling with water at any desired temperature and noting the time required for the water to cool one or more degrees. In this case the iron which composes the radiator would cool the same amount, and a correction must be added. The easier way to correct for the metal composing a radiator is to consider the weight as that of the water increased by that of the iron multiplied by its specific heat. The specific heat of wrought iron is, practically, I di- vided by 9 ; that of cast iron, I divided by 8 ; hence for a cast- iron radiator the effect would be the same as though we had an additional amount of water equal to -J of the weight of the radiator. In the practical operation of this test the water in the radiator must be kept thoroughly agitated by some sort of stirring device. 49. Measurement of Radiating Surface. The amount of radiating surface is usually expressed in square feet, and the total surface is that which is exposed to the air, and includes all irregularities, metallic ornaments, etc., of the surface. Where the surface is smooth and rectangular or cylindrical it is easily measured, but where it is covered with irregular projections the measurement is a matter of some difficulty and uncertainty. The only practical method of measuring irregu- lar surface seems to be that of dividing it up into small areas and measuring each one of these areas separately by using a thick sheet of paper or a bit of cord, and carefully pressing it into every portion of the surface. The sum of all the small areas is equivalent to the total area. This method is at best only approximate, and even when exercising the utmost care different observers are likely to differ three or four per cent in their results. The writer has tried several other methods of measuring surface, but so far without 74 HEATING AND VENTILATING BUILDINGS. marked success. One method, which promised good results, was to cover the whole surface with a thin paint and compare the weights with that required for covering one square foot of plain surface. This method proved even more approximate than the other, and had to be abandoned, as the paint was not of equal depths on all portions of the surface. The total contents of the radiator in cubic feet can be easily determined by filling it with a weighed amount of water of a known temperature and dividing the result by the weight of one: cubic foot. The volume displaced by the whole radiator can be determined by immersing it in a tank whose cubic contents, can readily be measured. The difference between the cubic contents when the radiator is in the tank and when taken out is the volume of the radiator. For this test the openings in; the radiator must be tightly stopped. The same method applied with the radiator immersed ini both cases ; but in one case with the radiator filled with air and the other with water would give as a result the water displaced' by the metal actually used in the construction, or, in other words, the cubic volume of the metal. This could no doubt be more accurately obtained by dividing the weight of the metal by the weight of one cubic inch or cubic foot. These methods give accurate means of measuring the total external and internal volume of the radiator, but not the surface. 50. Effect of Painting Radiating Surfaces. In the ex- periments of Peclet which have been given in Article 46 the effect of different surfaces has been fully considered. From these experiments it would appear in a general way that the char- acter of the surface affects the heat given off by radiation only, and not that given off by convection. In ordinary cases of direct radiation, because the surfaces are closely massed to- gether, the radiant heat does not probably exceed on an aver- age 40$ of the total emitted, and is nothing in indirect heating. From the experiments quoted, on page 64, it would appear that if we consider the radiant heat given off as 100 from a new sur--j face of cast iron, that from wrought iron would be 87, from a surface coated with soot or lampblack 125, from a surface with a lustre like new sheet lead 20^, from a polished silver surface ! 13^. These results make very much less difference, when ap- HEAT GIVEN OFF FROM RADIATING SURFACES. 75 plied to total heat emitted, since the total radiant heat is only a small portion of the whole heat given off. Calling the radiant heat as 40$ of the total, we should have the following numbers as representing the heat emitted from various surfaces : Cast iron, new 100 Rusty surface 102 Wrought iron. ....... 93 Bright iron surface 72 Dull lampblack 106 White lead, dull 106 The writer had some experiments made in Sibley College, the results of which showed that the effect of painting was to increase the amount of heat given off. It was found that two coats of black asphaltum paint increased the amount 6$, two coats of white lead 9%. Rough bronzing gave about the same results as black paint. On the other hand a coat of glossy white paint reduced the amount of heat emitted about io#. 51. Results of Tests of Radiating Surface. The results of the experiments of Peclet have been given quite fully, and they will be found to agree well with best modern tests when the conditions are similar. The radiating surface ordinarily employed for steam or hot-water heating consists of a number of pipes closely grouped together so as to occupy as little space as possible. In some instances long coils or series of parallel rows of pipe are employed arranged horizontally, but ordinarily the pipes are vertical, and grouped together in two to four rows. The usual height of radiator is 36 to 40 inches with the bottom placed about 3 inches from the floor, making the actual height of radiating surface about 3 feet. In some instances radiators are lower, in which case the results per unit of surface are considerably increased. The value of a radiator in which the surface is grouped so as to prevent the free escape of radiant heat will depend largely upon the effectiveness with which the air-currents strike the heating surfaces. There is a tendency for heated air to move in a vertical current in contact with the radiator surface, and thus to keep the upper portion in a very hot atmosphere, which has the effect of materially lessening its efficiency. The prac- tical effect of these restrictions is to reduce the heating power of radiators which are composed of a large amount of surface HEATING AND VENTILATING BUILDINGS. closely grouped. The following summary of a series of radi- ator tests made by J. H. Mills shows that with very small radiators the results are in practical accordance with those of Peclet's experiments, but as the radiators increase in size they fall off about in proportion to the loss of effective radiat- ing surface. B. T. U. per Sq. Ft. per Hour per Degree Difference of Temperature. Sq. Ft. of Radiating Surface. Difference of Temperature. Peclet's Formula. Actu-il 10 155 .66 2. JO 20 150 .84 2.08 30 I 5 8 .87 2.06 40 175 .92 1-75 50 155 .86 1-73 60 165 1.89 1.67 The following experiments were made by Tredgold * for the time of cooling of water in vessels of various kinds. The writer has reduced the results to heat-units given off per square foot of surface per hour. SUMMARY OF TREDGOLD'S EXPERIMENTS. "o 'o o o Heat-units Emitted per Sq. 3-0* 3 Ft. per Hour. tLjr , j *-* o y h Cooling. Material of Radiator. i- |f 1* Total Per By J* 1* i Q Heat- units. Deg. Diff . Temp. Pe'clet's Formula. Hot water... Tinned iron cylinder. . . . 180 55-5 124.5 255 -43 1.17 Hot water.. . Glass 1 80 56.5 426 2.37. 2 ^6 Wrought-iron block Rusty wrought iron 1 80 180 57 57 123 123 434 486 2.41 2.70 2-5 Prof. C. L. Norton, Boston, Mass., reported in Transactions of American Society of Mechanical Engineers, 1898, that the heat transmitted from a body of hot oil was proportional to the following numbers : tfew pipe 100 Painted dull white 115 Coated with cylin- Fair condition . . 115 Painted glossy " 1004 der oil 1 16 Rusty and black .... 1 18 Cleaned with caustic Cleaned with pot- ash US Painted dull black 120.5 Painted glossy '* 101 potash 118 * Tredgold's Warming and Ventilating of Buildings, second edition, pages 56 to 60. HEAT GIVEN OFF FROM RADIATING SURFACES. J? The following table is abstracted from one published in " Warming and Ventilation of Buildings," by J. H. Mills: jiy PUB mea^s ma aaoSaa _#*3- S^SS.^2^ 'S^S S'Kvg^ ?JcS S\RI?#S8 J3Q S?IUn-JB9H UH Jad -jj 'bs jad pasuapuo3 fc ;;H jt^l^Hs? WCI MO^^OSfOO* lAO*^ O^*O m Iv M x O">OM\O M\O * H M K M M H Si (i) |9) J31BM jo -sqT *8 p5-5-5- 5- 5- 5- 5- 5- 5- 5- 5- S.'iS.vS S #3 ^^'S.^^-vS 1 5;^ S^-5, 5gJ[ -i "~ 1 -1 s * URRR RRg.RRg.Rg. RR3vSv f:R?.R^^SRKRR H e N *i2 S, S,^ ^'iS "2 'S ^2 & 1 e. NN .88SSSS8 *30BUnC &88 <-R83Rr&8 888888888888888888 jo Wji aasnbs - 6 * ~ (1) M M * $ N : : : :^ : . . ... i 1 1 :3 : : ': 1 i i i ". i ;- '.'.. '.'.'. : : : : a : : 6 u : : : jn>o 10 o N oo^ o t^oo^ in o^ o^oo vo^ O^ O ^> ! fl i ;- is 9 ffi 11 : :M : 2 ' : : -5 o "S -a : :u- -rt S ::::::: fc s :&::::; i i : i : i i a : i i i i i : : 2*^ :r :::::: Description of heating surface Plain wrought-iron pipe, i", 100' in a single horizontal lir Plain cast-iron pipe 3'' diameter outside, 5' long " 3" " 5' " but thinne Ribbed cast-iron pipe, S. Williams; core 3" in diam., 5' cylinders, i" cylinders ' Ribbed cast-iron pipe, No. i, J. Nason & Co., 3" outside. . RibSed 38 - ir n ^ J " Na ' n * C " ' } Placed ide bv 8ideC Curved rib cast-iron radiator, Morris, Tasker & Co Box-radiator, cast iron, with straight vertical ribs k Vertical cast-iron ringed-pipe radiator, 7 Sec. " Clogston ' Cast-iron pipe 3" diam., in single line. Steel pipe 4" diam., in single line Brass i" horizontal pipe ; 4-branch circulation Wrought-iron, i" horizontal pipe, 4-branch circulation .. Plain brass vertical tube-radiator " diam., 2x4 Corrugated brass vertical tube-radiator |" diam., 2 x 16.. Vertical wrouglit-iron tube-radiator, Walworth, i row of a " " Union " radiator, cast iron, 6 sec., 29" high "Triumph" r.idiator, A. A. Griffing Iron Co., cast-iron, i Peirce Excelsior " cast-iron radiator, 10 sections " Art M radiator, cast iron, 6 panels 4 xa " double Detroit Radiator Exeter Machine Co., cast-iron, 8 loops.. Single bar of Gold's Pin Indirect Radiator, 3" x 6" x 3!'. . . Howard Oxbow Radiator, 2 loops, cast iron. Date 1866.. 2931 'UOSBN *H 'f 888 'SUFW 'H 'f HEATING AND VENTILATING BUILDINGS. The following table gives the abstract of a large number of radiator tests made under the supervision of the author: * Name or Kind of Radiator. Dimensions. Tests of Kelsey & Jackson. Tests of Camp & Woodward. Tests of Dunn & Mack. a V 1 & *45 288 M9 313 158 255 i. 5 8 i. 4 8 1.28 1.42 1.42 '43 1. 60 1.61 1.71 C. B. Richards, j Novelty.. .. 1873-4. lG. Whittier [Pipe coil W. J. Baldwin, J Gold's pin 1885. 1 Compound coil. . . W. Warner, 1880, Gold's pin J H Mills j Walworth. 1879. j Mills 100 Cubic Feet of Air per Foot per Hour, Average. 126 231 197 214 214 212 2I 4 214 308 37 343 3>9 320 3'9 323 354 390 379 336 1.50 1.81 i. 80 2.66 2-53 1.94 2.03 2.13 2.02 2.15 2.91 3-68 3-46 2.48 2. 51 3.36 3-52 3-52 2.96 10 4 19 20 21 22 23 24 25 Dr. Gray, 1875. Gold's pin J. R. Reed, 1875, whittier f Gold's pin. C. B. Richards, J Novelty 1873-4. 1 G. Whittier [Pipe coil 9o 68 20 3 i i i 259 222 215 215 215 33 45 o o 125 129 139 132 102 106 c 139 132 T02 106 226 177 215 215 215 25 6-54 5-09 9-15 8.70 6.66 6.98 400 572 544 416 436 200 Cubic Feet of Air per Foot per Hour, Average. 449 344 366 495 701 744 533 540 531 5 10 T r> T> A (Whittier... 68 68 58 60 3 3 3 i i i 10 5 5 222 222 222 21. S 215 215 215 239 227 227 52 52 52 o o 81 82 82 no 114 127 129 121 8 7 89 159 152 75 129 121 8 7 80 78 68 70 170 170 170 215 215 215 215 158 145 145 5-50 5.86 7.92 12.65 ii .90 8-53 8.64 8-49 8.16 8.16 J. R Reed J G Whiuier 18751 (Gold's pin f Gold's pin C. B. Richards, j Novelty T 873-4 I G Whittier 1 Pipe coil . J. H. Mills, 1876. Gold's pin W J Baldwin j Gold's pin Nov., 1885. '1 Compound coil.. . 300 Cubic Feet of Air per Foot per Hour, Average. 53 6 at 11 29 30 3' 32 J. H Mills 1876 Gold's pin.. .. 76^ 60 60 10 5 5 i i i i 239 22 7 227 215 215 215 215 90 70 70 o o I 5 8 135 1" 3 1 % "3 77 76 148 158 215 215 215 215 8.91 8-93 8.40 15.92 14.86 10.14 10.02 433 433 420 428 428 428 428 557 558 525 995 929 634 626 3-76 3-55 3-34 4-63 4.32 2-95 2.91 W. J. Baldwin, j Gold's pin 1885. /Compound coil., f Gold's pin C. B. Richards, J Novelty 1873-4. j G. Whittier [Pipe coil 400 Cubic Feet of Air per Foot per Hour, Average. 428 689 3-64 3 ? J H Mills, j Gold's pin . & 6 6 2 3 230 88 88 158 142 70 54 142 142 10.04 8.88 467 534 628 555 59 2 4.42 3-9* 1876 1 Walworth 35 3 r 500 Cubic Feet of Air per Foot per Hour, Average. 4-17 J H. Mills, j Walworth 85 76* 20 20 259 259 90 160 166 70 76 169 169 13.69 15.16 636 649 856 948 5.06 5 61 1876 \ Gold's pin 600 Cubic Feet of Air per Foot per Hour, Average. 643 902 5-34 i J. H. Mills, j Walworth . 7^ 3 3 222 222 90 90 142 145 52 55 132 132 ii. 61 12.54 726 734 726 784 755 5-5 5-94 5-72 1876. | Gold's pin 700 Cubic Feet of Air per Foot per Hour. Average. 39 40 J. H. Mills, I Gold's pin 77 85 7* 22 7 233 94 79 M5 56 133 154 15-30 855 888 8 3 9 956 6.31 6.21 1876. ") Nason . . 800 Cubic Feet of Air per Foot per Hour, Average. 872 898 6.26 * From John H. Mills' work on Heat, by permission. 82 HEATING AND VENTILATING BUILDINGS. Q Z S i EN " J O < S Oi . % Q ~ Z -5 H CL < D U Units of Heat per Sq. Ft. .sa $% S 3 Qc/1 cd : v^ Radiators with Water Circulation. . t'imf^tii IS t T^ ^ ? o ~ 00 t^ ^S Q" m o moo vo 4 OO Ov 10 t^ io "5- pi 10 [^ w ro t^ i- vo Pi vo O\ 6 PI M Difference of Temperature. 3-d uiV p[03 pUB OOO OOPioOioOPlw-* -^- 10 o o> t^oo M - oo r^ t-^ CO *&**&* 22 si^fc jiy jo mesas SlffS'R'BSS^JSUI ,, t>. 10 N O- Pi OO -4-03 -o o SS5S.S Temperatures. Air to be Warmed. d 1 * WaW $iwBtf , VO f--vo Pi vo O t^ t~~ *4- ^t rovo vo t^ io 10 St %SffiS e cfl V a o U 10 1000 ITOO 00 OO 00 * ro in O OOOOOOO P) VO PI S l^VO PI vo *i ' Water or Steam. Return. \o io N N \o -^-co o io in ro VO 1 00 Ov O 00 P) O * O oo ONOO oo io r~ Comparison o: 1 ^inK^* 5 0^0^000 ON w ^ w'S'S isnnp [o tpai aaenbg * ? ?? PJ P) N P) PI JO J33j S-IEnbg ^00 O 10 "l-OO O O 10 O O in O O oo O O O io OVO TJ-VO OvO VC O t^. CvOO - - - M Radiators boxed in Stacks, open below, and with Outlet above for heated Air, the duty of Radiator being determined by the Volume and Tempera- tures of the heated Air. Engineers, Radiators, and Dates. Averages fe ": S^;. 7 4. } Bos " d ~ I - i -S: [^Sl^iMm.indirea ] S; ^Uaia) Compound con } ; ^.S-wtX-h 01 ^^ iSSS: Averages j ; 5fk ^ 11^1 * ^ c' 33 | W. J. Baldwin, j Box coil, nat. draught, water 1886. 1 Compound coil, nat. draught, water J H. Mills, j Albany cast, nat. draught, water 1835. \ Box coil, nat. draught, water W. J. Baldwin, \ Box coil 1886. 1 Compound coil J. H. Mills, j Gold's pin 1885. ) Mills' indirect Staggered Tube Coil Radiator, Shakelton's, water.. J. H. Mills,) Mills' indirect, Shakelton's. water 188^. 1 Gold's pin, Shakelton's, water JO} 'OI M p) r*"> ^- u-jvo tvoO O\ O w fO^-^vo t-00 I! O H N ro * I 9 a It el HEAT GIVEN OFF FROM RADIATING SURFACES. 83 From the general results shown in the table page 80 it is seen that the heat-units given off per square foot per degree difference of temperature equals very nearly the square root of four times the velocity in feet per second. That is, h = V '4^. The tables pages 81 and 82 contain an extensive summary of tests of indirect radiators, abstracted from Mills' work on Heating and Ventilation, and are of especial interest as show- ing the close agreement in results, whether water or steam is used. The higher results in this table agree fairly well with the rule stated ; those for natural draught are much smaller, and approximately equal to the square root of the velocity in feet per second. 53. Conclusions from Radiator Tests. The general re- ;ults of radiator tests can be summed up as follows : First, that ;he values for heat transmission in recent tests of direct radia- tors vary greatly and differ more from an average result than from those given by Peclet, and consequently his results can be used with confidence as applying to modern radiators. Second, the results of the test show greater differences in favor of low radiators as compared with high ones than was shown in the experiments of Peclet. Third, the experiments do not show any sensible difference for different materials used in radiators or for hot water or steam, provided the difference in temperature between the air in the room and that of the fluid in the radiator is the same. Fourth, the internal volume of radiators is of value only in lessening the friction of the fluid. It has no special influence on the results. Fifth, the extended surface radiators, or radiators in which the cast iron projects from the surface into the air, show large results when estimated on the basis of projected or plain surface, but show very small results when estimated on the basis of measured surface. Sixth, thin radiators, or those with one row of tubes, always show higher efficiency than thick ones or those with numerous rows of tubes. Seventh, comparative tests of radiators should only be made between radiators of similar forms, or at least those which have about the same amount of surface. HEATING AND VENTILATING BUILDINGS. 54. Probable Efficiency of Indirect Radiators. The velocity with which the air will move over radiators when heated a given amount can be readily computed as explained in Article 33. With a given velocity we can determine from the experiments cited the probable amount of heat that will be given off per degree difference of temperature per hour for natural and for forced circulation. The results deduced from experiments are given in the following tables : TABLE FOR NATURAL CIRCULATION. Units of Heat per Height in Feet. Temperature of Entering Air above Room. Velocity in Feet per Second. Degree Difference of Temperature, Average per Square Foot per Corresponding Story of Building. Hour. 5 50 2.Q7 1.72 I 10 50 4.17 2. 02 I 17 47 5-3 2.3 2 20 45 5-6 2.36 2 25 45 6.3. 2.52 2 30 42 6.6 2.58 3 35 42 7-2 2.68 3 40 40 7-5 2.72 4 50 40 8.4 2. Si 5 TABLE SHOWING THE HEAT-UNITS PER DEGREE DIFFERENCE OF TEMPERATURE BETWEEN THE ENTERING AIR AND THAT OF THE HEATING SURFACE FOR DIFFERENT VELOCITIES OF AIR APPLICABLE IN FORCED CIRCULATION. .Velocity in Feet per Second. Velocity in Feet per Minute. Gauge-reading. Inches of Water-pressure. Heat-units per Degree Difference of Tem- perature per Square Foot per Hour. I 60 0.002 2 2-5 150 0.014 3.13 5 300 0.064 4-5 7-5 450- 0.124 5-5 10 600 O.22 6-33 12.5 750 - 0.37 7-i 15 QOO 0.50 7-75 17-5 IO5O 0.65 8-35 20 1200 0.82 9 22.5 1350 1. 08 9-5 25 1500 1.28 10 55. Temperature produced in a Room by a given Amount of Surface when Outside Temperature is High. HEAT GIVEN OFF FROM RADIATING SURFACES. 8$ Guarantees are often made respecting heating apparatus that it shall be sufficient to maintain a temperature of 70 degrees when the external air is at some fixed point, as zero, or 10 below. As under the exact conditions of the guarantee the trial can only be made when the external temperature corre- sponds with that specified, it becomes of some importance to establish an equivalent temperature which would indicate the efficiency of the heating apparatus for any specified condition. The following method applicable for suchcomputations and is expressed in the shape of a formula : Let T equal temperature of radiator, /' that of room, and t that of outside air for the conditions corresponding to the guarantee. Let B equal loss from room for i degree differ- ence of temperature ; let c equal the heat-units from I square foot of radiator per I degree difference of temperature for con- ditions corresponding to the guarantee ; let c' denote the same values for other conditions ; let x equal resulting temperature of room, /" outside air for the actual conditions, R equal square feet of radiation. For guaranteed conditions, (/' -;)B = c(T-t')R. ..... (I) For actual conditions, (x-t")B = S(T-x)R. ..... (2) Dividing (i) by (2), When /' 70, T = 220, / = o, and c = 1.8, we have The coefficient of heat transmission c' grows less as the tem- irature in the room becomes higher, as already shown in Art. 46 ; so the equations can only be solved in an approximate manner. The following table gives the temperatures in column \, which a room would have for various tempera- 86 HEATING AND VENTILATING BUILDINGS. tures outside, provided there was sufficient radiating surface to heat the room to 70 degrees in zero weather. The tempera- ture of the radiator in all cases is assumed to be that due to 3 pounds pressure of steam by gauge, or 220 degrees. TABLE.* Temperature Outside Air. Coefficient.t Heat per Square Foot per Hour per Degree Total Heat per Square Foot per Hour. Resulting Temperature of Room. Difference Temperature Radiator and Room. 1O I.S 5 288 64.7 155-3 O .8 270 70 150 10 75 253 75-1 144.9 2O 7 236 81 J 39 30 .65 218 86.5 133-5 40 .6 203 93-i 126.9 50 55 1 88 98.7 129.3 60 5 172 104.7 II5-3 70 45 158 110.5 109.5 80 4 142 117.1 102.9 QO 1-35 130.5 123-5 9 6 -5 IOO i-3 117 130.3 89.7 Example showing Application of Table. To determine by a test of the apparatus, when weather is 60, whether a guarantee to heat to 70 in zero weather is maintained, operate the apparatus as though in regular use and note the average temperature of the room. If the room has a temperature equal to or in excess of 104.7 F., it would have a temperature of 70 in zero weather, all other conditions, such as wind, position of windows, etc., being the same as on the day of the test. * This table, although calculated for steam with radiator at temperature of 220 F., is practically correct for hot- water radiation or for steam at any pressure and temperature. f Value of c' in formulae. \ Vol. i, Transactions American Society Heating and Ventilating En- gineers. CHAPTER V. PIPE AND FITTINGS USED IN STEAM AND HOT-WATER HEATING. 56. General Remarks. In this chapter will be found a concise description of pipe and fittings to be had regularly of most dealers. Such a description is entirely unnecessary to those familiar with current practice in the industry of steam and hot-water heating; but as the writer has found by experi- ence detailed knowledge on this subject is often required, the following descriptions are deemed necessary. It may be remarked in a general way, that for conveying Cheated air, galvanized or tin pipe or brick flues are usually pro- vided, but for the purposes of conveying steam or hot water wrought-iron pipe is used almost exclusively. 57. Cast-iron Pipes and Fittings. Cast-iron pipe was used very largely at one time for both supply-pipe and radiat- ing surface in hot-water heating, but at present it is used only to a limited extent in greenhouse heating. For this purpose one size of pipe only is used, and this is 4%" outside diameter. The pipe weighs about 12 Ibs. to the foot, and has a capacity of gal. per foot. The pipes are usually joined by socket-joints, for which purpose a socket is cast on one end of each pipe. The joints are formed by inserting one end of one pipe into the Fm. 32. CAST-IRON PIPE WITH SOCKET. socket of another and filling the interspace either with melted * lead, iron-filings and sal-ammoniac, sulphur, or cement, and ' calking thoroughly. The lead joint, which is ordinarily used, is formed by making a mould, by wrapping a hemp rope covered with clay around the joint, with a pouring-place on top, into which the melted lead is run. After the joint cools the lead is 87 88 HEATING AND VENTILATING BUILDINGS. driven into place with a calking-iron. The rust-joint is a very excellent joint, and often used. It is made with a cement formed by saturating for ten or twelve hours iron turnings or filings with sal-ammoniac. This cement is pressed into the socket, and then pounded tightly into place with a calking-iron. Joints made with Portland cement are sometimes used, but they are likely to crack from the heat, and cannot be recommended. The regular form of pipe and some of the principal fittings are shown in Figs. 32 to 36. FIG. 33. ELBOW FOR CAST-IRON PIPE. FIG. 34. ROUND TEE FOR CAST- IRON PIPES. FIG. 35. RADIATING SURFACE AND PAN FOR HOLDING WATER TO MOISTEN Ail Two or more lengths of pipe, supported on special brackets are usually run in parallel lines with a slight descent in the direction of the flow, and thus serve both for radiating surfaced and circulating pipes. For green-l house heating, where the air is to be kept moist, a special pan to be filled with water, as shown inl Fig- 35> supported by the pipes,, is used at intervals. For the purpose of checking or stopping the flow a stop conl sisting of a flat plate, which can; be set at any angle with the pipe,: and of a form as in Fig. 36, is used. Each length of cast-, FIG. 36. VALVE OR STOP FOR CAST-IRON PIPE. PIPE AND FITTINGS. 89 iron pipe is sometimes provided with flanges, and joints are made by bolting the pipes together, packing being in- serted to prevent leaks. These are inferior to the calked joints. 58. Wrought-iron and Steel Pipe. Pipe made of wrought iron is now almost exclusively used for the purposes of convey- ing steam or hot water in heating systems. This pipe is made in a number of factories and of standard sizes, so that the pipe obtained from one is reasonably certain to fit that from another. Wrought-iron pipe is manufactured from iron of the proper thickness, which is rolled into pipe shape, and raised to a welding heat, after which the edges are welded by drawing through a die. The smaller sizes, ij inch and under, are butt-welded ; the larger sizes are in all cases lap- welded.* This pipe is put on the market in three different grades of thickness : first the standard grade, which is used principally for heating purposes ; this is tested to a pressure of 250 Ibs. per sq. in. and has the dimensions given in Table XV ; it 'is manufactured in sizes from -J in. to 15 in. in diameter. Thicker pipe, called extra strong, and still heavier pipe-called double-extra strong, is manufactured, and can be obtained if required. The thick piping has the same distinguishing name as pipe of standard weight, having the same external diameter, which is in all cases that of the internal diameter of the stand ard pipe. The extra-strong and double-extra strong have smaller diameters than would be implied by the name ; thus, for instance, inch pipe, standard size, has an inside diameter of * The process of lap-welding is as follows : The sheet of iron is rolled to the desired thickness, width, and length. The edges are then scarfed. It is then drawn while red-hot by means of an endless chain through a bell-shaped die, which rounds it up and laps one edge over the other. The whole length is put into the furnace and heated to a welding heat, and afterward pushed out of the furnace at the opposite end into grooved rolls of a size corresponding to the size of the pipe. The inside lap is supported by a ball attached to a large bar of iron. The ball, the iron, and the groove in the roll all correspond so that the roll shall produce a sufficient pressure upon the iron and the ball to force the laps of the iron firmly together, thus producing the weld. From paper by R. T. Crane, Early History Wrought-iron Pipe, Fifth Annual Convention Master Steam-Fitters' Association. QO HEATING AND VENTILATING BUILDINGS. about one inch, an outside diameter of 1.315 inches, while the extra-strong pipe of the same nominal size has the same out- side diameter and an inside diameter approximately 0.951 inch, while the double-extra strong has the same outside diameter and an inside diameter of 0.587 inch. FIG. 37. SECTION OF STANDARD PIPES \ TO 3 INCHES INTERNAL DIAMETER. The following' table eives the diameters, external and in- o o ternal, and weights per foot, of the various kinds of pipe. In PIPE AND FITTINGS. the table * the normal inside diameter is the actual diameter, or nearly so, for the standard pipe; sizes to ij inch are butt- welded, larger sizes lap-welded : Nom- inal Di- ameter (Name ', Inches, f Actual Out- side Diam- eter, Inches. Actual Inside Diam., In.t Thickness of Iron, Inches. + Weight per Foot, Pounds t Threads per Inch. Extra Strong. Double' Stan- Extra dard Strong. Extra Strong. Double Extra Strong. Stand- ard. Extra Strong. Double Extra Strong M i % % 2 i W ' H 4 i 0.405 0.54 0.675 0.84 0.105 ::li 5 1.9 2-375 2.875 3-5 4 4-5 5-563 6.625 .205 294 .421 542 736 951 .272 -494 933 -315 .892 3-358 3-8i8 0.068 o 088 O.IOO 0.24 0.29 27 18 18 14 M "'i 1114 nJ4 8 8 8 8 8 8 8 0.56 0.84 1.12 1.6 7 2 24 2.68 3-6i 5-74 7-54 9.00 10.66 12 49 o 74 1.09 i-39 2.17 3.00 3-63 5.02 7.67 10.25 '2-47 14.97 1.70 2-44 3-65 5.20 6.40 9.02 13.68 18.56 22.75 27.48 "38-12 53-" 0.244 0.422 0.587 0.885 i. 088 1.491 1-755 2.284 2.716 3-136 o. 109 0.113 0.134 0.140 0.145 0.154 0.204 0.217 0.226 0.237 0.149 0-157 0.182 0.194 0.703 O.22I 0.280 0.304 O.32I 0.341 0.298 0.314 0.364 0.388 0.406 0.442 0.560 0.608 0.642 0.682 4-813 5-75 4.063 4.875 0.259 0.280 0-375 o 437 0-75 0.875 14.50 18 76 20.54 28.58 Steel Pipe. For nearly every purpose of manufacture, soft steel has replaced wrought iron, and this will doubtless be the case some time so far as piping is concerned. Up to the present time, however, the pipe made of steel has not been as soft as that of wrought iron, and is more likely to dull and injure the dies and cutters used by workmen. It is often not so well welded, and is more likely to split.J Solid-drawn pipe has been made to a limited extent, and is very likely at no distant date to supersede welded pipe of all descriptions. Each length of pipe as sold is provided with a collar or coupling screwed on to one end and has a thread cut on the other end. Connections are made by screwing the threaded end of one pipe into the coupling on the other. There is no standard length of pipes, the range usually being from 16 to 24 feet, with occasional short pieces. It can be ordered in lengths, cut as desired for slightly extra prices ; but it can be readily cut any length, and right- or left-handed threads may be cut as desired. It is quite malleable, and when heated may * See more extended table in Appendix. f Approximate, outside diameter only is exact. \ 1898. Steel pipe can be purchased equal in every respect to wrought iron. ^2 HEATING AND VENTILATING BUILDINGS. be bent into almost any shape by a skilful workman without materially changing the form of its cross-section. 59. Pipe Fittings. Fittings for connecting pipes and for giving them any required direction with respect to each other are regularly on the market. These fittings are mostly made of cast and malleable iron, the prominent exception being straight couplings with right-handed threads in both ends, which are usually of wrought iron. Cast-iron fittings are generally preferred to those of malle- able iron in any system of piping for heating, for the reason that, being harder than the pipe and less elastic, they are not likely to stretch and yield sufficiently to permit leakage when the pipes are connected ; if broken, a fracture can readily be detected and a new fitting supplied. Malleable-iron fittings frequently stretch if pipes are screwed somewhat too hard, so that future expansion and contraction is quite certain to cause a leak. If it is necessary to take down a long line of pipe] in which no removable joints occur, a cast-iron fitting can be easily broken, thus often saving more time than the cost of the* fitting, while the malleable fitting cannot be so disposed of. It is quite true that malleable fittings are stronger than cast- iron when of equal weight, but those on the market are much] lighter than the cast-iron ones; and, moreover, the standard] fittings are abundantly strong for any pressures likely to be sustained in ordinary systems of heating. The standard pipes are considerably stronger than the standard fittings, and if extra heavy pressures are required, sayj looto 150 pounds per square inch, it is advisable to use special] fittings, which differ from the ordinary ones principally in weight. The fittings which are on the market can be divided into various classes, depending upon their use. Pipe Connections. For joining pipes in the same line there] is provided, first, the wrought-iron coupling shown in Figs. 38; to 40. The coupling, usually with plain exterior, has right-hand threads cut in both ends, and is used principally in erecting a pipe line where the construction is continuous from one end toj the other. A reducing coupling, Fig. 40, is frequently usedj PIPE AND FITTINGS. 93 for uniting pipes of different sizes. In cases where it is necessary to " make up " or unite lines of piping which come together from different directions, a left-hand thread can be cut on the end of one of the pipes and the junction formed by FIG. 38. FIG. 39. FIG. 40. COUPLING. RIGHT-AND-LEFT COUPLING. REDUCING COUPLING. using a coupling similar to the above, but with a right-hand thread cut in one end and a left-hand thread cut in the other, such a coupling being known as a right-and-left coupling. To use this coupling room is required for end motion of one of the pipes sufficient to insert it. In making up right-and-left couplings care must be taken that both threads on the pipe engage with those in the coup- ling at about the same instant. This can be done by screwing the coupling by hand on the end of each pipe, and counting the number of turns that can be made, noting the number of threads in sight after the joint is made up. This coupling, while sometimes difficult to use, forms the most certain method of uniting two pipe lines so that they will not leak. For join- ing pipes a coupling which separates into three pieces, termed a union, is often employed. The parts of the union are FIG. 41. THE UNION. FIG. 42. SECTION OF UNION. screwed onto the ends of the pipe, and are drawn together by a revolving collar which engages with the thread on one of the pieces. The joint is formed either by drawing flat faces in the union against some elastic and soft material, as packing, or else by producing contact of ground and fitted metallic sur- faces. Pipes are also held together by screwing flanges to the pipes, and drawing these flanges either in contact or against a 94 HEATING AND VENTILATING BUILDINGS. ring of packing by bolts (Fig. 43). Such a joint is called a union FIG. 43. FLANGE UNION. FIG. 44. LONG-THREADED NIPPLE AND LOCK-NUT. Lengths of pipe are frequently made up by a short piece of pipe with a long screw-thread cut on one end, onto which is screwed a very short collar or lock-nut, Fig. 44. The junction^ is made between two ordinary pipe couplings by first screwing' the long thread into one pipe coupling until the piece is short enough to be slipped into position, then it is screwed into the other coupling by unscrewing from the first. When screwed 'home, the collar or lock-nut is turned tightly against the first coupling, forming a steam-tight joint either by metallic contact or by use of packing. Pipe Bends and Elbows. For changing the direction of] pipe lines there can be purchased elbows with bends of 45 or; 90 degrees, also reducing elbows in which one opening is for smaller size of pipe than that of the other. The QO-degree elbow can be had either with right threads in both ends or with right and left threads, as required. The right-and-left threaded elbow can be used for making up two pipe lines in a manner similar to that described for a right-and-left coupling. FIG. 45 '90 CAST-IRON ELBOW. FIG. 46. 45 CAST-IRON ELBOW. FIG. 47. 90 REDUCING ELBOW. The internal diameter of elbows is somewhat in excess oi that of the external diameter of the pipe, and the radius of the .bend is, according to Briggs' table (Van Nostrand Science PIPE AND FITTINGS. 95 Series, No. 68), equal in nearly every case to the diameter of the pipe plus a constant which varies from f inch for the smallest size of pipes to \ inch for the largest size. For the sizes of pipes used in heating the radius of curvature is practically equal to that of the diameter of the pipe plus inch. Where the friction caused by a standard elbow is detri- mental, special fittings (Figs. 48 and 49) can be obtained FIG. 48. LONG-RADIUS ELBOW. FIG. JQ. QUARTER BEND OF PIPE. in which the radius of curvature is from two to three times that given. Such fittings are especially desirable in heating by hot-water circulation, and often permit the use of smaller pipes than would be possible with standard fittings. Pipe Junctions, Tees, Y's, etc. For the purpose of taking off one pipe line from another special fittings can be had, FIG. 50. PLAIN TEE OPENINGS ALL SAME SIZE, THREADS RIGHT-HANDED. FIG. 51. REDUCING TEE OPENINGS VARIOUS SIZES. (In describing state diam- eter of branch last.) FIG. 52. LONG-RADIUS TEE. FIG. 53. Y FITTING. FIG. 54. LONG-RADIUS Y. 90 HEATING AND VENTILATING BUILDINGS. which are designated, according to their shape, as tee, cross, side-outlet elbow, and Y-branch, all of which can be bought with the openings for the same or different sized pipes in any combination required. These various fittings are shown in the annexed engrav- ings. FIG. 55. ' SIDE-OPENING ELBOW. FIG. 56. CROSS. FIG. 57. REDUCING CROSS Miscellaneous Fittings. For reducing the size of opening in a fitting, bushings of cast (Fig. 58) or malleable iron can be| used; for closing up the end of fittings a screwed plug (Fig. 59) can be employed ; and for closing the end of a pipe a screwed cap (Fig. 60) can be used. Where a coil of pipe is desirable, it can be formed by screwing pipes into U-shaped fittings, called return bends. These can be had with either right threads or right-and-left threads, and inclose (Fig. 61) or open pattern (Fig. 62), and with the threads tapped so as to give nearly any pitch or rake of the pipe. For slightly changing the position of a pipe an offset (Fig. 63) can be used. To prevent leaking where a long-threaded nipple has been used, a lock-nut can be screwed on against a grummet, or ring of packing. FIG. 58. BUSHING. FIG. 59. PLUG. FIG. 60. CAP. FIG. 6r. FIG. 62. RETURN BENDS. FIG. 63. OFFSET. FIG. 64. LOCK-NUT PIPE AND FITTINGS. 97 Fittings can also be had for erecting parallel lines of pipe, as shown in Figs. 65 and 66; they are termed branch tees, and FIG. 65. BRANCH TEE, PLAIN. FIG. 66. BRANCH TEE, WITH BACK OUTLET. can be had for almost any number of pipes, and for sizes varying from three-quarter to three inches. The distance be- tween centres cf branches is varied somewhat, but is usually 2 inches for three-quarter-inch pipe, 2^ inches for one-inch pipe, 3 inches for one-and-a-quarter-inch pipe, and 3^ inches for one- and-a-half-inch pipe. The branch tees are fitted with opening for supply-pipe and discharge-pipe either in end or side as specified. In those made for circulation the holes are tapped with right-hand threads ; those made for box-coils are tapped for left-hand thread on branches. Short pieces of pipe called nipples can be had of any length required, provided with right-hand threads cut on both ends, or with right thread on one end and left thread on the other. ' Short pieces of pipe called quarter or eight- ) bends (Fig. 49) may be used in place of SHOULDER * elbows when a long-radius turn is required. NIPPLE. In addition to the fittings mentioned there can be had, for supporting the pipes to side walls, hooks and hook-plates with ( curved or straight arms, ringed plate, and coil-stand, as desired. FIG. 67. FIG. 68. CLOSE NIPPLE. FIG. 69. HOOK-PLATE. 9 8 HEATING AND VENTILATING BUILDINGS. There can also be had hangers of various patterns for sup- porting and holding pipes from ceilings. These are of great variety of pattern, and are made so that, if desired, they can b put on after the piping is in place. The principal standard fittings as above described are als made of brass. FIG. 70. EXPANSION-PLATE. FIG. 71. RING-PLATE. FIG. 72. COIL-STANDS. Ceiling and Floor Plates are collars used to hold the pipe in place, and to prevent overheating of woodwork by the stearr or hot water. These are often made in halves, which may b slipped on over the pipes, and are fastened to the woodwor by screws, thus holding the pipe in position and keeping it frorr contact with wood. 60. Valves and Cocks. The fittings used for the purpos of stopping the passages in pipes are operated by movin, a disk across the pipe with or without rotation, or by simpb turning through an angle. The first class have been general^ called valves, the second cocks. Valves are of two classes: the globe valve (Fig. 73), whic closes an opening in a diaphragm parallel to the direction o flow, and the gate valve (Fig. 74), which closes an opening a right angles to the pipe. The globe valve forms a serious obstruction, since any flui< in passing through it must make two turns, each nearly PIPE AND FITTINGS. 99 right angle; while the gate valve when open presents little or no resistance. FIG. 73. GLOBE VALVE. FIG. 74. GATE VALVE. The globe valve is much more simple in construction than the gate valve, is cheaper, and often will answer all require- ments for steam-heating, but will seldom do for hot-water heat- ing. It should be set so that the valve closes against the flow ; when set in the opposite way accidents might happen for in- stance, if the valve should be detached from the stem it could not be opened, although the stem would move apparently all right. It will be noted that the diaphragm of the globe valve forms an obstruction in the pipe, which extends to the centre, and if the stem of this valve be set vertical when used for a horizontal pipe it is likely to cause the pipe to stand half full of water. Whenever used in steam-heating, on a horizontal pipe, the stem should be placed in a horizontal position, so that it will not interfere with the drainage of water of condensation from the pipe. The construction of the gate valve varies in detail as made by different manufacturers, but it in general consists of a gate which is moved across the opening in the pipe by turning the stem. When the gate reaches the bottom of the pipe it moves laterally sufficient to bring a strong pressure on the seat. 100 HEATING AND VENTILATING BUILDINGS. These valves are made with a stem which rises with the gate as shown in Fig. '74, or with one which remains in one position, the gate travelling up the stem. This latter form is objection- able, as one cannot tell by looking, whether the valve is open or closed. Globe valves are made with a solid metallic seat, as in Fig. 73 ; or with a seat made of soft metal or packing, as in Fig. 75, of such a form that it can be replaced whenever the valve begins to leak. FIG. 75. GLOBE VALVE WITH DISK SEAT. FIG. 76. ANGLE VALVE. Angle Valves (Fig. 76) are made in the same general way as globe valves, except that the openings are at right angli s to each other. They cause a slightly greater resistance to mc-tion than the ordinary elbow, but not sufficient to prevent their use for any system of heating. The seats are either metallic or of soft material, which can be removed. Stuffing-boxes. In all classes of valves a cavity is left around the stem, which must be filled with some packing material by turning back a cap-screw. Hemp, lamp-wicking, asbestos fibre, well oiled and, if possible, covered with plumbago, will make satisfactory packing for this purpose. Patent ring packing can be purchased, usually made of asbestos fibre soaked in oil, and serves an excellent purpose. PIPE AND FITTINGS. IOI Radiator Valves. These are forms of angle valves with fittings making them especially convenient for radiator connec- tions, being plain as shown in Fig. 77 or with an attached union as in Fig. 78. These are often nickel-plated. Radiator valves can be had with pedal attachment, so that they can be opened or closed with the foot. The various kinds of valves which have been described are made with sockets for screwed connections to the pipes, or with flanges which are to be bolted to similar flanges screwed on the pipes as desired. They can also be had, especially for the larger sizes, with either brass or iron bodies. FIG. 77. RADIATOR VALVE. FIG. 78. HOT-WATER VALVE. Cross Valves. A form of angle valve with one supply and ind two opposite discharge openings is sometimes convenient, md is termed a cross valve. (See Fig. 83.) Corner Valves, in which the openings are at the same >vel but at right angles, can be purchased if desired. Cocks. A plug, slightly conical, provided with one or more >rts or holes through it, and arranged so that it can be turned any direction, is termed a cock. When there is but a single role it is called a plain cock. When two or more holes at ingles to each other, it is called a two-way or three-way cock, dnce water can be directed in two or more directions by vary- ing the angle through which the plug is turned. Cocks are rery little used in steam-heating ; as ordinarily made they are )t to leak, and, besides, do not provide a full opening for the luid. IO2 HEATING AND VENTILATING BUILDINGS. Improved cocks with larger openings and with packed ends are now much used on the blow-off pipes from boilers, and are for this purpose su- perior to valves. Quick-opening valves (Fig. 79) for use on hot-water pipes are often made on the same plan as cocks, and do excellent ser- vice in these places. Check Valves. Where it is necessary that the flow should always take place in the same direction and there is danger of a reverse flow, check valves are employed. These are usually of a similar pattern to the globe valve, the seat being at right angles to the direction of flow, with either a flat or ball valve (Figs. 80, 81). FIG. 79. QUICK-OPENING In t hi s class the valve is held in place RADIATOR VALVE FOR HOT-WATER. by its own weight or by the weight of the fluid in case of reverse flow. They are made for hori- zontal pipes, vertical pipes, or angles. One known as the swinging-check valve, in which the seat is at an angle of about 45 degrees to the direction of flow (Fig. 82), offers less resist- ance to the fluid, and is generally to be preferred. 6l. Air- valves. It is necessary to provide means for allow- ing the air to escape in systems of steam and hot-water heating. Air is heavier than steam, and although it will mix with it to a great extent, it will finally settle at or near the bottom of a radiator or pipe filled with steam. Air is, however, much lighter than water, and it will gather in any bends that are convex upward and in the upper part of radiators filled with water, and unless removed it will prevent the circu- lation. For removal of the air several forms of valves and cocks have been especially manufactured. These are usually made of J- or ^-inch pipe size, and vary in quality and design from the simplest valve to be opened by hand to a complicated auto- matic pattern, which permits the escape of air, but not of water or steam. One of the simplest patterns of air-valves is shown in Fig. PIPE AND FITTINGS. 103 FIG. So. HORIZONTAL FIG. ST. HORIZONTAL CHECK WITH BALL CHECK VALVE. CLACK. FIG. 82. SWINGING CHECK. Globe Valve. Angle Valve. Cross Valve. Horizontal Check Valve. Angle Check Valve. Vertical Check. Steam Cock, Flanged Ends. Expansion or Slip Joint. Steam Cock, Screwed Ends. FIG. 83. PRINCIPAL VALVES AND STOPS USED IN HEATING. 104 HEATING AND VENTILATING BUILDINGS. 84. This can be had with a bibb if desired, also with various forms of handles or keys, and with nickel or brass finish. Automatic air-valves are made of a great variety of pat- terns. Those for steam-radiators are all closed by the expan- sion of some material Fig. 85 shows an expansion air-valve, in which the valve is closed by the expansion of a curved metallic strip. The valve will remain open until this curved FIG. 84. SIMPLEST PATTERN AIR-VALVE. FIG. 86. AUTOMATIC AIR- VALVE. FIG. 87. COMPOSITION AUTO- MATIC VALVE. FIG. 85. BRECKEN- RIDGE AUTOMATIC AIR-VALVE. strip becomes nearly equal in its temperature to that of the steam ; the heat then increases its length and it bends out sufficiently to close the valve. A drip-pipe is provided for re- moving any water of condensation escaping from the air-valve. Another form, which has in the past .been extensively used, is shown in Fig. 86. In this case the interior tube A is heated more than the frame bb ; this serves to press the valve c against the end of the tube when it is heated, thus closing the orifice. This is best adapted for use in a vertical position. PIPE AND FITTINGC. 105 A form of air-valve now in extensive use is shown in Fig. 87. In this a composite material which expands rapidly when heated is used instead of metal. It is claimed for some of these valves that with suitable adjustment of the top screw the temperature of the radiator will be automatically maintained at any desired point a mixture in any required proportion of air and steam being maintained in the radiator by this action. To prevent escape of water and injury to furniture a radia- tor-valve with a float attachment is often used, as shown in iFig. 88. The valve is closed when heated, as in Fig. 87, by the expansion of a composite substance ; it is connected to a ifloat, so that if water passes into the air-valve the float will rise and close the orifice regardless of the temperature. FIG. 88. RADIATOR AIR-VALVE WITH FLOAT. FIG. 89. HOT-WATER AIR- VALVE. An automatic air-valve for hot-water radiators is shown in the sketch, Fig. 89. The air escapes at A, the orifice being closed by the float /'"acting on the lever L. So long as only air surrounds the float it sinks and keeps the orifice open, but FIG. 90. FLANGED EXPANSION-JOINT. as soon as water surrounds it it rises and closes the orifice. 62. Expansion-joints. In the erection of any system of piping means must be provided so that the elongation of the 106 HEATING AND VENTILATING BUILDINGS. pipe due to expansion will not cause a leak.* For all ordinary purposes of heating the expansion can be provided for by trn use of elbows and right-angled offsets, of such length that th< expansion will simply cause one pipe to slightly unscrew in on or more joints. This requires the use of two or three elbows and so causes a slight increase of resistance to flow due to fric tion ; but it. is a very satisfactory arrangement, and will stan< for years without developing leaks, even with high-pressur steam, if properly erected. It is sometimes necessary to provide for expansion in long line of straight pipe, in which case expansion-joints o some kind must be used. The ordinary expansion-joint, Fig 90, consists of a sleeve sliding into an exterior pipe, providec with a stuffing-box. This joint, when heavy and providec with a catch to prevent it pulling apart, is a very durable anc satisfactory construction. The packing will have to be renevvec occasionally, and one part needs to be solidly anchored t< prevent motion. Expansion-joints are often used constructed of copper pip in form of a U-shaped bend ; also of one or more diaphragms connected to each othe at the edges and to the pipes near the centre (Fig. 91). The copper bend is always satis factory. The last-named device works very well if means can be adopted to thoroughly drain ofif any water lodging against the dia FIG. 91. BUNDY phragm. If used in a horizontal position ELASTIC COUPLING. and Qn large pipes it is likdy to gathe sufficient moisture to form a water-hammer that may product rupture when steam is turned on. * The expansion of iron is one part in 148,000 of length per degree. This equivalent to about 1.45 inches per 100 feet in changing from temperature o freezing to boiling. CHAPTER VI. RADIATORS AND HEATING SURFACES. 63. Introduction. The amount of heat which will pass I through various kinds of radiating surface is determined I largely by experiment, and has been fully discussed in Chapter IV. In this chapter we will consider briefly the methods of Iconstruction. When steam and hot water-heating were first employed the t radiating surface consisted almost entirely of cast-iron pipe ar- | ranged in horizontal lines, as shown in Fig. 35, page 88. I With the invention and use of wrought-iron pipe, cast-iron pipe I was superseded by coils of this pipe, and at a somewhat later I day largely by the radiator with vertical surfaces made either of least or wrought iron. The change from pipe surfaces to radi- ators was, no doubt, largely due to the attempt to economize 1 space in the room, as well as to improve the appearance. 64. Radiating Surface of Pipe. Very efficient radiating faces can be made of coils of piping arranged as shown in j Figs. 92 and 93. The return-bend coil shown in Fig. 92 is made by connecting return-bends, Fig. 61, page 96, with lines of [Straight pipe. The pipe mostly used is one inch in diameter, although, when the bends are numerous, i^- or 2-inch pipe should be used to reduce the friction. In use the flow is con- tinuous, the fluid entering at the top and thence with a gradual descent flowing to the right and left alternately, finally dis- charging at the bottom. There is a great deal of friction in coils of this class, and air is likely to gather in the bends and stop circulation. The writer would, therefore, recommend that they be employed only when other forms will not answer. The branch-tee or manifold coil is constructed by connect- ing branch-tees with parallel lines of pipe. In each pipe-line one or more elbows must be placed to counteract the effect of unequal expansion. 107 io8 HEATING AND VENTILATING BUILDINGS. The coil may be arranged on a flat wall-surface so as to form a mitre branch-tee coil as in Fig. 93, lower part, or with both branch-tees at one end and elbows and nipples at the opposite end ; the fittings at ends being connected by pipes hav- ing the proper pitch. Such a construction is called a return branch-tee coil, see upper part Fig. 93. The coil may be ar- ranged on two sides of a room with the elbows placed in the intervening corner, in which case it is called a corner coil. The various types of branch-tee or manifold coils as de- scribed present small frictional resistance to the flow of steam or water and give satisfactory service for either steam or hot- water heating. FIG. 92. RETURN-BEND COIL. FIG. 93. BRANCH-TEE MITRE COIL AND RETURN-COIL. If two connections are used the steam should be supplied at the highest point of the coil, and the return taken off at the lowest; if one connection, steam is to be supplied at the lowest point. The horizontal portion should be given a RADIATORS AND HEATING SURFACES. 1 09 pitch of one inch in ten or twelve feet, and an air valve or cock should be connected to each coil. When several return-bend coils are grouped together, as in Fig. 94, the construction is termed a box coil. This has all the faults in an aggravated manner that were ascribed to the return-bend coil, and in addi- tion causes a loss of efficiency due to close grouping of surface. FIG. 94. THE Box COIL. The pipe coils, Figs. 92 to 94, will do equally well for steam j or hot-water circulation. 65. Vertical Pipe Steam-radiators. These were at one j time used extensively, and were made by screwing short pieces j of vertical pipe into a cast-iron base and connecting.the pipes in pairs at the top with return-bends, which were usually ! screwed but sometimes pressed on. One form still in extensive j use was made by screwing pipes, having the upper end closed land provided with an internal diaphragm, into a cast-iron base. JThe diaphragm being so placed as to produce the same circula- ition in one pipe that was obtained in two pipes with the other 'form. The pipes are arranged in two or more rows as necessary jto secure the desired radiating surface. In early radiators of 'this class the base was provided with a diaphragm, and each i return-pipe was trapped by a cavity filled with water so as to insure a continuous circulation of the steam through each pipe. In some of the recent radiators the return-pipes are trapped 1 no HE A TING AND VENT7LA TING B UILDINGS. as explained above ; but in nearly every case the base is entirely open and arranged so that it will drain freely, no attempt beins made to force circulation in any direction. In some of tin recent radiators of this type the base, instead of being in on< piece, is made up of sections connected by nipples, so that it can be lengthene< or shortened at pleas ure. An air-valve must always be provide< with these radiatorsj the best location foi which is at about on< third the height of tin radiator, and on tl end opposite the a< mission. The wrought - iroi radiator is construct* in nearly every case one-inch pipe, take of such length th: there is one squai foot of exposed radiat FIG. 95. PIPE RADIATOR. ing surface for pipe in the radiator. The form being quite regular its surfa( can be accurately measured. 66. Cast-iron Steam-radiators. Cast-iron radiators ai now mostly used in direct heating. Those principally used have vertical radiating surfaces, ai are made either by screwing loops or sections into a holl< base provided with the requisite openings, or by connectii at the bottom a series of parallel vertical sections by nippli screwed from the outside or inside of the base. The first foi of radiators, having a base of fixed dimensions, is often call< the standard form ; the latter, which can be increased diminished in length by adding or taking off sections, is callej a sectional radiator. The radiator is in some instances provided with a flat top which is held in place by screws, but the greater portion of RADIATORS AND HEATING SURFACES. Ill ] those of recent design have a highly ornamented surface and r are used without top or screen of I any description. The illustra- | tions, Figs. 93 to 106, give a very I. fair idea of the appearance of those in use. They are painted in various colors, enamelled or bronzed, as may be required by the house owners or architects. The efficiency of direct radia- tion is somewhat increased by painting or bronzing, but is les- Isened by varnishing or enam- lelling: but that of indirect is not |:so affected. These radiators are made in Igreat variety of forms, and can I be had of such shape as to sur- 1 round columns, or fit in corners; land of almost any height de- ll sired. Some of the radiators are fitted with warming closets. FIG. 96. STANDARD CORNER RADIATOR. i(See Fig. 98,* frontispiece, for illustration of styles in use.) FIG. 97. SECTIONAL RADIATOR. FIG. 99. CRESCENT FI,UE RADIATOR. With permission from Heating and Ventilation. 112 HEATING AND VENTILATING BUILDINGS, The sectional radiators are in many cases built in such a manner as to form flues for the passage of air from the bottom \ to the top of the radiator for the purpose of increasing the air- heating capacity. Such radiators are termed flue radiators (Fig- 99)- FIG. 100. WHITTIER EXTENDED SURFACE RADIATOR. Radiators are sometimes built with projecting fins or orna- ments of cast iron for the purpose of greatly extending thet surface in contact with the air. Such a radiator is termed am extended surface radiator, and is now little used for direct heat-! ing (Fig. i oo). The radiators in principal use are constructed as described, but radiators have been built by many other methods and ini* many other shapes. They have been constructed of one soliql casting, and by uniting sections of various forms by bolts andj packed joints. 67. Hot-water Radiators. Hot-water radiators differ j essentially from the steam-radiators in having a horizontal passage at the top as well as at the bottom. This construction ! is necessary in order to draw off the air which gathers at the top of each loop or section. Aside from this the construction may be the same in every particular as that for steam-radiators ; in RADIATORS AND HEATING SURFACES. 113 genera, the hot-water radiator will be found well adapted for FIG. 101. SECTION OF HOT-WATER RADIATOR. , FIG. 102. SECTIONAL HOT-WATER RADIATOR. team circulation, being in some respects superior to trie rdinary form. 114 HEATING AND VENTILATING BUILDINGS, Many of the hot-water radiators, as shown in Fig. 101, are made with an opening at the top for the entrance of water and at the bottom for its discharge, thus insuring a supply of hot water at the top and of colder water at the bottom. Some of the hot-water radiators are constructed with a cross-partition so that all water entering passes at once to the top, from which it may take any passage toward the outlet. The hot-water radiator, is however, usually made with continuous passages at top and bottom, and the warm water is supplied at one side and drawn off on the other, as shown in Figs. 102 and 105 (right hand). The action of gravity is depended on for making the hot and lighter water pass to the top and the cold water to sink to the bottom and flow off in the return. FIG. 103.* RADIATORS WITH TOP AND BOT- TOM CONNECTIONS. FIG. 104. SECTIONAL HOT-WATER RADIATOR. Hot-water radiators are also made by joining vertical pipe sections with nipples at top and bottom, as shown in Fig. 1 06. * Heating and Ventilating of Residences, by Willet. RADIATORS ANL HEATING SURF A ES. 11$ (STEAM.) (HOT-WATER.) FIG. 105. SECTION OF CAST-IRON RADIATOR. FIG. 1 06. SECTIONAL-PIPE HOT-WATER RADIATOR. HEATING AND VENTILATING BUILDINGS. 68. Direct-indirect Radiators. Radiators arranged with a damper under the base and located so that air from the out- Fio. 107. DIRECT-INDIRECT RADIATQR IN POSITION. FIG. loS. DIRECT-INDIRECT RADIATOR. side will pass over the heating surface before entering the room are often used to improve the ventilation. The surface of these radiators should be about 25 per cent greater than that of a direct radiator for heating the same space. The styles and kinds either for steam or hot water are the same as the direct. 69. Indirect Heaters. Radiators which are employed to heat the air of a room in a passage or flue which supplies air are termed indirect. These heaters are made in various forms, either of pipe arranged in return bend or in manifold coils, as in Fig. 93, or of cast-iron sections of various forms united in different ways. When cast-iron surfaces are used, they are generally covered with projections like the extended surface radiator. The sections, or, as they are sometimes called, the stacks for indirect heating, are usually held together by bolts. The joints being formed by inserting packing between faced surfaces. The sections are sometimes united by nipples screwed into branch-tees above and below, as shown in Fig. 109, which is an excellent form for hot-water circulation. RADIATORS AND HEATING SURFACES. Indirect radiators should be placed in a chamber or box as FIG. 109. INDIRECT HEATING SURFACE. vent FIG. no INDIRECT PIPE COIL. nearly as possible at the foot of a vertical flue leading to the room to be heated. Air is admitted through a passage from the out- side provided with suit- able dampers to a point beneath the indirect stacks. It is taken off generally on the opposite side, and directly into the flue leading into the room to be heated. The chamber surround- ing the indirect radi- FIG. III.-ARRANGEMENT OF INDIRECT ator is usually built of HEATER. a casing of matched wood, as in Fig. ill and Fig. 112, sus- nS HEATING AND VENTILATING BUILDINGS. pended from the ceiling of the basement, and lined inside with bright tin ; but a small chamber of masonry at the bottom of a flue is a better and more durable construction. The flue leading from the chamber is of masonry or galvanized iron ; that supply- ing the cold air, of matched wood and sheet iron. There should be a door in the chamber so that the in- direct heater can be examined and cleaned when required. It is often of advantage to have a passage and deflecting damper so arranged that air can be drawn into the FIG. 112. ARRANGEMENT OF INDI- RECT HEATING SURFACE. room for ventilation without passing over the heater. The registers for admitting the heated air into the rooms can be located as desired, either in the walls or the floor ; for ventilation purposes it is prefer- able to admit the air near the ceiling, and as shown in Fig. 113. The size of registers and air- flue will be given in Chapter XIII. Setting of Indirect Heaters. The indirect heating-surface is supported usually by bars of iron or pieces of pipe held in place by hangers fastened at the ceiling (Fig. 1 1 1). This heater should be set so as to give room for the freest possible circulation of air, and so that all parts will be at least ten inches from top or bottom of casing, and arranged so FIG. 113. INDIRECT HEATER ARRANGED FOR VENTILATION. RADIATORS AND HEATING' SURFACES. that no air can pass into rooms without being warmed. An automatic air-valve should be used to remove the air from the sections of the heater. If the sections are of proper form, one connection will be sufficient for steam ; but in nearly every case two connections, one for the supply and one for the discharge, will be re- quired for water circulation. 70. Proportions of Parts of Radiators. There is great difference regarding the relative volume of radiators of differ- ent make as compared with the surface ; but the practice is quite uniform as regards the sizes of supply-pipes for either steam or hot water. Because of the high efficiency of a radiat- ing surface formed of one-inch horizontal pipe, it has been argued that this should form a standard for relation of contents to surface. It is seen, however, by consulting the tests given in Chapter IV, that inch-pipe vertical radiators are not more efficient than cast-iron radiators with larger volume ; so that it is doubtful if the relative ratio of volume to surface is of importance. It is of importance that the steam or water should circulate through the radiators with the least possible friction, and that in the case of steam-radiators the base should be of such a form as to perfectly drain ; otherwise the water which remains in will be certain to cause the disagreeable noise and pounding known as water-hammer. The following table gives the standards which are almost uni- versally adopted by the different makers for the size of inlet and outlet to the direct radiators ; those for indirects are to be taken one size larger : Size of Radiator, Sq. Ft. Diameter of Openings. Two Openings. One Opening. o to 50 50 to 125 125 to 2OO 200 tO 300 i inch. i inches, i* " 2 i inches, i* " 2 2k CHAPTER VII. STEAM-HEATING BOILERS AND HOT-WATER HEATERS. 71. General Properties of Steam Explanation of Steam- tables. Steam has certain definite properties which always pertain to it and distinguish it from the vapor of other liquids than water. Steam, at any given pressure above a vacuum, possesses a definite temperature. The atmospheric pressure is different at different localities and for different conditions of the weather, thus causing slight changes in temperature of the boiling-point. The pressure which is read by any steam-gauge is that in excess of the atmosphere ; the pressure which is given in the steam-tables is that which is reckoned from a perfect vacuum, \ and is usually called absolute ; hence, in order to use the steam- \ table which is given in the back of the book, the pressure as determined by a steam-gauge reading must be increased by the atmospheric pressure. The atmospheric pressure is given! accurately by a barometer, but it will be sufficiently accurate, I for most cases, to consider it as 14.7 pounds. To use the table add this quantity to the gauge-reading and the result j will be the absolute pressure. For approximate purposes the] atmospheric pressure maybe considered as 15 pounds. The j steam-tables referred to give, in the first column, the pressure! above a vacuum ; in the second column, the temperature Fahr-| enheit ; in the third, the heat, expressed in heat-units, required to raise one pound of water from zero Fahrenheit to the re-j quired temperature. If the; specific heat of water were unity at all temperatures, the heat contained in one pound of water' would be numerically the same as the temperature. The difference is not great in any case. The fourth column gives the value in heat-units of the la- tent heat of evaporation for each pound of steam. This quan J S TEAM-HE A TING BOILERS. HO T- WA TER HE A TERS. 1 2 1 tity expresses the amount of heat which is stored, without change of temperature or pressure, during the physical change of condition from water to steam ; and it has been termed latent because it cannot be measured by a thermometer (see Art. 13, page 15). It will be noted that this quantity is rela- tively large as compared with the sensible heat. It is of im- portance, since it expresses the amount of heat which is con- tained in one pound of steam in excess of that in one pound of water at the same temperature. The fifth column gives the total heat contained in one pound of steam ; this is the sum of the sensible and latent heat. The sixth column gives the weight in pounds of one cubic foot of steam for various pressures. In many instances steam- tables are arranged so as to give the heat in one pound of steam above 32 Fahr., the freezing-point of water, instead of above zero. It should be noted that the temperature of steam corre- sponding to different pressures, as given in column (2), is also the boiling-point of water corresponding to the same pressure. As the temperature and absolute pressure of steam al- ways bear definite relation to each other, it is quite evident that a steam-table could be arranged giving the properties of steam from measurements of .temperature. This is generally not so convenient as the present arrangement. If tempera- tures are known, the corresponding pressure can be determined by inspection and interpolation in the present table. 72. General Requisites of Steam-boilers. The steam- boiler is a closed vessel, which must possess sufficient strength to withstand the pressure to which it may be subjected in use ; j but it may have almost any form, and may be constructed of j various materials. It is used in connection with a furnace, from which the heat required for evaporation is obtained by combustion .of fuel. The heat is received on the surface of the boiler, and passes by conduction through the metallic walls to the water or steam. The surface which receives this heat is called heating surface, and is partly situated so as to receive the direct or radiant heat, and partly located so as to receive the convected or indirect heat from the gases only. The heating surface in UNIVERSITY 122 HEATING AND VENTILATING BUILDINGS. most modern boilers is made relatively great, as compared with the cubic contents, by the use of tubes containing water or heated gases, or by subdividing the boiler so as to make the surface large with respect to the cubic contents and weight. The steam generated rises in the shape of bubbles through the water in the lower part of the boiler, and is liberated from the surface of the water at the water-line. The power of the boiler depends upon the amount and form of heating surface, upon its capacity for holding water and steam, and upon the extent of fire-grate surface. Its economy depends upon the relative proportions of these, and the character and amount of fuel burned. Its ability to pro- duce dry steam depends upon the circulation of its liquid contents, and also upon the extent of surface at the water-line. For safety, the boiler must be provided with safety-valve, pressure and water gauges. For convenience automatic damper-regulators, water-feeding apparatus, etc., are desirable. 73. Boiler Horse-power. As a boiler performs no actual work, but simply provides steam for such purposes, a boiler horse-power is entirely an arbitrary quantity, and may be transformed into a lesser or greater amount of work, as the character of the engine which uses the steam varies. The standard established by the Committee of Judges at the Centennial Exhibition in 1876 as a boiler horse-power has been universally adopted, and would, no doubt, in absence of other stipulations, constitute a legal standard of capacity. This committee defined a boiler horse-power as the evapora- tion of 30 pounds of water from feed-water at 100 Fahr. into steam at 70 pounds pressure ; this is equivalent to the evapo- ration of 34.5 pounds of water from a temperature of 2I2 C Fahr. into steam at atmospheric pressure.* Engines require from 12 to 40 pounds of steam per horse-power per hour, depending upon the grade or class to which they belong ; hence the steam required to perform one horse-power of work in an engine bears no definite relation to a boiler horse- power. ''The condition of evaporating from water at 212 into steam at the same temperature will be referred to hereafter as evaporation, without other qualification. S TEA M-HEA TING BOILERS. HO T- IV A TER HE A TERS. 1 2 3 Since the evaporation of one pound of water from and at 212 Fahr. requires 966 heat-units, one boiler horse-power is | equivalent to 33,327 heat units. For heating purposes a more convenient standard of power j is the square foot of radiating surface. Each square foot \ of direct steam-radiating surface gives off 270 to 330 heat-units j per hour when the difference of temperature is 150 degrees (see Art. 51), which is that usually existing in low-pressure steam- heating. About two thirds as much is given off by one square j foot of hot-water radiating surface. As the evaporation of one I pound of water requires 966 heat-units, there is needed about tone third of a pound of steam for each square foot of steam- Lradiating surface per hour, hence one boiler horse-power will be 1 sufficient to supply somewhat more than 100 square feet of j direct radiating surface; that is, we can consider the boiler j horse-power as equivalent to 100 square feet of direct steam "\ radiation, with sufficient allowance to meet ordinary losses. 74. Relative Proportions of Heating to Grate Surface. I The relative amount of grate surface and heating surface re- \ quired in a steam-boiler depends, to a large extent, upon the I nature and amount of coal burned per unit of time. That part of the heating surface which is close to the fire and receives directly the radiant heat is much more effective than that which is heated by contact with hot gases only ; but it will be found \ that considerable indirect heating surface will in every case be required, in order to prevent excessive waste of heat in the chimney. Power-boilers have been rated for a long time not I on their actual capacity, but on the amount of heating surface ; j and this would seem to be a fair standard of rating for heating- boilers. It is the general practice to consider 11.5 square feet j of heating surface in water-tube boilers or 15 square feet in plain tubular boilers as equivalent to one horse-power. The actual power of the boiler depends more upon the method and management of the fires than upon the size ; and | either of the above classes of boilers can be made to develop \ under favorable circumstances from two to three times the capacity for which they are rated. A rating of 15 sq. ft. of heating surface to one horse-power requires an evaporation of 2.3 Ibs. of water per square foot of 124 HEATING AND VENTILATING BUILDINGS. heating surface per hour, and a rating of 11.5 sq. ft. per hors power requires an evaporation of 3 Ibs. Experience for number of years with power-boilers 20 horse-power and largei indicates these proportions to be safe ones and to result durable construction. With the small boilers often used in house-1 heating the waste due to loss of heat from the heating surfaces, imperfect combustion, and bad management generally are much greater, so that it is necessary to use boilers somewhat larger than would be required by the data given. Knowing the; amount of coal per hour and the evaporation per pound of coal, we could readily calculate the steam produced in pounds.) This result multiplied by three would give very closely the extent of direct radiating surface which could be supplied. With perfect combustion and no waste, one pound of pure! carbon would evaporate about 15 Ibs. of water; all coal con- tains considerable ash and refuse, on account of which the best! results are lower, so that one pound of- best anthracite coal; might evaporate 13 Ibs. of water, and of bituminous from 10 toj 14 Ibs. Our average evaporation in power-boilers is probably! about 9 Ibs. when served by good firemen, and in heating- boilers it is usually much less, not because of faulty construc-1 tion of the boiler, but for lack of proper and careful manage-; ment. The amount of coal burned per square foot of grate; per hour is rarely less than 15 Ibs. with power-boilers, and in some cases is very much greater, but is usually less than 10 IbsJ and is sometimes as small as 3 or 4 with heating-boilers. For these reasons no hard and fast rule can be given for thej proportions of different boilers and heaters, and a considerable- variation may be expected in the relative proportions of heat-: ing, grate, and radiating surface existing in successful plants. By making allowance for the probable loss of efficiency in small heaters, we can, by starting with the proportions which have! been found to be satisfactory in large plants where power-! boilers are used, compute a table which will be based on thej results of actual trial and experiment. This table will give di- mensions which are well within the limits of those in actual usej but it should not be inferred that satisfactory plants cannot bJ constructed with proportions varying ten or twenty per cent- from those given. The table is computed from the follow i S TEA M-HEA TING BOILERS. HO T- WA TER HE A TERS. 1 2 5 data, which were assumed for reasons already stated : ist, one pound of steam will supply 3 sq. ft. of direct steam-radiating surface; 2d, 15 sq. ft. of heating surface (one horse-power) in the boiler will supply 100 sq. ft. of steam or 150 sq. ft. of hot-water direct radiating surface, when the boilers con- tain 450 sq. ft. and above of heating surface ; $d, loss in ef- ficiency assumed to be 10 per cent for reduction in capacity of 50 per cent ; 4th, rate of evaporation for steam-boilers is taken so as to agree with the experience of the writer. Two cases are considered in the table : (A) when the rate of coal consump- tion is 10 Ibs. and (B) when the rate of coal consumption is 8 Ibs. per sq. ft. of grate per hour. The latter in every case gives a somewhat larger grate, and for hot-water heating is no doubt to be preferred. PROPORTION OF PARTS OF STEAM-HEATING BOILERS. Radiating Surface, Square Feet. 250 500 750 1000 1500 2OOO 3000 4000 5000 ; 7500 10000 Nominal horse-power 2 5 5 7.5 10 15 20 30 40 5 75 IOO Ratio radiating to heating surface. . . 4-5 5-4 5-6 6 6.2 6.7 6.9 f j. h. J. Probable evaporation per Ib. coal.. . Pounds of steam per sq. ft. grate (A) " " (B, 5-5 55 44 5-7 6 60 48 6-5 65 S2 *7 5 7-5 8 80 64 ti 68 9 ! 9-5 9o | 95 72 1 76 10 IOO 80 Ratio radiating to grate surface (A) 165 171 1 80 195 2IO 225 240 255 270 [285 300 (B) 132 138 1144 JI5& 1 08 1 80 192 204 216 228 240 heating to grate surface (A).. 36.5 33-2 33-2 34-8 35 36.2 36-5 37 38.5] ! ;|* 33-3* ' (B).. 28.5 27 26.7 27.7 28 29 28.5 29.6 30. s -j i l 2 /^ 26.'?* Heating surface, sq. ft 55 98 138 178 250 322 447 580 710 j j I0 7^ 1430 1111* Grate surface sq ft (A) r 68 8 o 41 (B) 1.88 3.88 5-4 i 6.77 8.92 II .2 T 5-5 iQ-S 23.2 i 32.5 4 1 -5 Diameter safety-valve, inchest .... 7 2.25 10 2.502.75 II 12 3 15 3-25 17 3-5 9 4 2 3 4 2 of 3 25 , 28 2 of 4 34 " smoke-flue, inches HOT-WATER HEATERS. itio radiating to heating surface. " grate(A) (B) ' heating to grate (A) ' (B) Heating surface, sq. ft Grate surface, sq. ft. (A) " (B) Diameter smoke-flue, inches 6.8 7.6 8.1 8-4 9 9-3 10 10.4 10.5 247 256 207 270 216 292 232 315 252 337 270 360 288 382 306 405 324 360 33-2 33-2 34-8 35 36-2 36.5 37 38.5 28.5 27 26.7 27.7 28 29 28.5 29.6 30.8 36.5 1% 9i-5 2 .7 c 118 3<7C 166 215 5.O 296! 385 8. 2 T<->., 470 1.25 2*58 3-6 /D 4.25 4* 75 5-9 y 7- 1 10.3 13 15-3 7 10 11 12 15 17 19 23 25 10.5 13-5* 427 342 40-5 31-5 s* a- 5 10.5 13 5* 450 360 42.5 33-3 34-5 26.5* 905 22.2 27-5 34 * Water-tube boiler. f Safety-valves by Board of Trade rule. 5 and 10 Ibs. Smaller boilers figured to blow at 126 HEATING AND VENTILATING BUILDINGS. A very interesting comparison of relative proportions of various boilers used for steam-heating was made by S. Q. Hayes from published statements of manufacturers in Heating and Ventilation, April 15, 1895, and from which the following table is abstracted. It will be seen that the proportions of radiating surface to grate surface agree well, when the fact is considered that many published statements are far from accurate, with the values recommended for a coal consumption of 8 Ibs. of coal per hour, per square foot of grate. TABLE SHOWING PROPORTIONS CLAIMED BY MAKERS FOR STEAM-HEATING BOILERS. Steam-heating Boilers. Ratio Radiating to Grate Surface. Ratio Heating to Grate Surface. Ratio Radiating to Heating Surface. Square Foot of Radiation. 250 500 750 1500 2000 250 500 '5 1500 2000 250 5 oo 750 1500 2OOO KIND OF BOILER. Tubular, vertical, magazine.... " surface " " steel Vertical shell, drop- and fire- tubes. Pipe boiler Pipe-coil boiler Drop-tube, wrought iron 4 ' cast-iron magazine. " surface. . ' ' magazine. 4 ' wrought iron Coil and drop-tube .. Horizontal sectional. Vertical sectional 134 i So 170 140 i So 75 185 198 240 rts i 5 o 1 60 i 7 o 130 130 ,6 7 1 90 '47 170 1 80 75 *9S 172 186 rSo 6j 150 240 ',>( JO i So H7 II 2 '35 US 192 167 200 138 170 i So 75 205 204 224 170 200 216 200 I 3 8 I 3 150 IS'? 200 1 80 I 9 180 180 75 228 22O '180 75 23 30 30 26 20 25 42 3 6 43 35 22 32 3 3 2 24 32 23 I 3 2 36 37 25 44 35 -36 24 24 3 23 32 23 33 25 30 25 25 33 35-7 40 27 24 34 P I- 8 56 i- 3 7-4 6 7-7 6 6 ' 7 '*-3 '&" 6-3 6 3 27 3 I., 3 4-4 5-5 5-4 4 4 5 5-7 e" 5-3 6-5 3 ^ 5-8 5 ^ 5 5 5-7 5 5 5 5-3 f;- 5 5-5 1 5-7 5-7 5 6.2 6 6 4.7 5-7 6 7 6 i' 7 '5 6 I' 3 6-5 6 5-7 5-7 6 32-7 23 22 170 210 216 300 130 155 163 230 '180 230 1 26 25 24 25 20 33 1 36 27 '55 167 250 3 1 6 28 24 25 25 37 24 30 40 41 sectional, tubular 75. Water Surface Steam and Water Space. The surface on the water-line from which ebullition takes place should be so large that the velocity of steam will not be great enough to project particles of water into the main steam-pipes. Practice is variable in this respect ; in successful plants it will be found that from one third to one square foot of surface is provided per horse-power or per 100 square feet of radiating surface. The greater this surface the less water will be carried out of the boiler with the steam, other things being equal. There is much variation in the amount of water and steam space provided in various kinds of boilers : in the fire-tube and STEAM-HE A TING BOILERS. HO T- WA TER HE A TERS. 1 2/ shell boilers there is much more space than in water-tube and sectional boilers. A large amount of water and steam absorb the heat slowly, but on the other hand they require less fre- quent attention and are more regular in operation. The fol- lowing rules have been given : Tredgold* states that the volume of steam space should be sufficient to prevent variations in pressure exceeding I in 30, by irregular use. The Artisan Club allowed 5 cubic feet of water space and 3.2 cubic feet of steam space per horse-power for Cornish boilers. In the ordinary tubular boilers to-day there will be -found about 2.0 cubic feet of water and i.o cubic foot of steam per horse-power, and about one third the above amounts for the water-tube boilers. 76. Requisites of a Perfect Steam-boiler. The late Mr. George H. Babcock of Plainfield, N. J., gives as the results of his experience the following requisites for a perfect steam- boiler for power purposes : ist. The best materials sanctioned by use, simple in con- struction, perfect in workmanship, durable in use, and not liable to require early repairs. 2d. A mud-drum to receive all impurities deposited from the water in a place removed from the action of the fire. 3d. A steam and water capacity sufficient to prevent any fluctuation in pressure or water-level. 4th. A large water surface for the disengagement of the steam from the water in order to prevent foaming. 5th. A constant and thorough circulation of water through- out the boiler, so as to maintain all parts at one temperature. 6th. The water space divided into sections, so arranged that should any section give out, no general explosion can occur, and the destructive effects will be confined to the simple escape of the contents ; with large and free passages between the different sections to equalize the water line and pressure in all. /th. A great excess of strength over any legitimate strain ; so constfucted as not to be liable to be strained by unequal * Thurston's Steam-boilers. 128 HEATING AND VENTILATING BUILDINGS. expansion, and, if possible, no joints exposed to the direct action of the fire. 8th. A combustion-chamber, so arranged that the combus- tion of gases commenced in the furnace may be completed be- fore they escape to the chimney. 9th. The heating surface as nearly as possible at right angles to the currents of heated gases, and so as to break up the currents and extract the entire available heat therefrom. 10th. All parts readily accessible for cleaning and repairs.' This is a point of the greatest importance as regards safety and economy. nth. Proportioned for the work to be done, and capable of working to its full rated capacity with the highest economy. 1 2th. The very best gauges, safety-valves, and other fix- tures. The same requirements apply equally well to a boiler for heating, but the relative importance of the various require- \ ments might be different, and some might be omitted as un- important ; thus, for instance, the mud-drum, which is of im-J portance in a boiler for power, because it is receiving constant accessions of water with more or less impurities, is seldom on heating boilers when they are supplied with water of condensation. The importance of provisions for cleaning is; less in heating than in power boilers, but should not bJ neglected. 77. General Types of Boilers. Power-boilers. It seems necessary to consider boilers built for high-pressure steam andj of large sizes as a separate class from those used principally ini heating small buildings, although boilers of similar structure^ may be constructed for heating. These boilers will be spoken of as power-boilers, and are required t^ fulfil conditions as tol strength and capacity not needed in heating-boilers. The principal boilers of this type now in use can be grouped into two classes, viz., fire>tube and water-tube boilers, and onej or the other of this type must be used for heating purposes, with the present condition of the market, whenever high- pressure steam is required. The fire-tube or common tubular boiler consists of a cylin- drical boiler with plain heads, connected by a large number of S TEA M-HEA TING B OILERS. HO T- &A TER HE A TERS. 1 29 tubes which serve as passages for the smoke or heated gases. The fire is built underneath, and the smoke passes horizontally either twice or thrice the length of the boiler. The general form of this boiler is shown in Fig. 1 14. This boiler is also FIG. 114. HORIZONTAL TUBULAR BOILER. used sometimes in a vertical position with the fire beneath one head, in which case it is called a vertical tubular. The water- tube boilers have the water in small tubes, and the heated gases pass out between the tubes. In this class of boilers the steam is contained in drums or horizontal cylinders, which are located above the heating surface. The tubular boilers are made in small sizes, 10 horse-power and larger, while the water-tube boiler for power is seldom less than 60 horse- ' power capacity. Heating-boilers. The boilers which are used for steam-heat- ing are designed in a multiplicity of forms, and present examples of nearly every possible method of producing extejid^d-aujiaces, both of the water-tube and fire-tube types. They are generally built for low-pressure steam, and are expected to be used ,'mainly in buildings where the condensed water is returned by gravity to the boiler without pumps or traps. They are usu- ally built in small sizes having a capacity of 250 to 2000 ft. of radiating surface (2^ to 20 H.P.), and are fitted with safety- valves, water and steam gauges and damper regulators. The limits of this book prevent a detailed description of any make of heating-boiler, but, the leading general types are described. Several types of the power-boiler are described quite in detail, and much that is said with respect to them will ipply in a general way to heating-boilers. 130 HEATING AND VENTILATING BUILDINGS. The following classification of steam-heating boilers was suggested by one presented by Mr. A. C. Walworth in a paper before the New York Convention of Master Steam and Hot* water Fitters, June, 1894: CLASSIFICATION OF HEATING-BOILERS. Plain ( S P herical , Ver , Surface j Cylindrical \ 3# . ( Wrought Iron, Projecting Tubes Boiler Surface j rregu i ar sur face Divided Surface r Fire-tube Vertical Horizontal Locomotive Tubular f Straight tubes | Curved " Water-tube -{ Spiral ' | Coil of " LDrop Sectional < Horizontal Packed joints Screwed " Faced Packed joints Screwed " Faced 78. The Horizontal Tubular Boiler. This boiler manufactured in many places, so that in many respects it is standard article of commerce, and it can be purchased in neai every market for a slight advance over the cost of materials ai labor used in its construction. In the construction of this boil< the shell is now almost invariably made of soft steel of a thi< ness depending upon the pressure which the boiler is expect( to sustain. The heads of the boiler are made of flange st( and are generally -fa inch thicker than the material in the sh< Lap-welded iron tubes are almost invariably used, the stand; sizes being as given in Table XVII. The tubes are expandi into the heads of the boiler and may or may not be beaded, ai are generally arranged in parallel vertical rows in the lower thirds part of the boiler. In some instances the middle row tubes is omitted with good results. It is not a good plan stagger the tubes, since in that case they are difficult to cl( S TEA M-HEA TING B OILERS. HO T- WA TER HE A TERS. \ 3 1 and also act to impede the circulation of the water. The boiler should be provided with manholes, with strongly reinforced edges, so that a person can enter for cleaning. The heads of the boiler above the tubes should be thoroughly braced in order to sustain safely any pressure from the inside of the boiler. Domes are often placed above the horizontal part of the boiler, and serve to increase the capacity for the storage of steam and also provide ready means of drawing off dry steam. The dome is always an element of weakness, and if used it should be staved and reinforced in the strongest possible man- ner. The dome is frequently omitted, and steam taken directly from the top of the shell or djrawn through a long pipe with numerous perforations, termed a petticoat pipe. In construction this boiler must be strongly braced wher- ever any flat surfaces are exposed to pressure, and the girth and longitudinal seams must be riveted in such a manner as to secure the maximum strength. The following table gives principal dimensions for a series of horizontal tubular boilers designed for a working pressure of So to 100 pounds per square inch : 8000 i 16 60 80 Diameter of boiler inches 36 3 fi 48 60 66 Length of boiler, feet 1/4 J! 8 10 10 12 9/32 12 9/32 12 sA6 14 s/ifi 16 16 3/8 Thickness of shell, inches Thickness of heads, inches 5/16 S/i6 5/16 V8 3/8 3/8 3/8 V8 "1/8 1/2 1/2 Length of flues, feet 6 8 10 10 12 12 16 16 Number of flues S2 32 3 32 40 40 52 70 70 83 104 Diameter oi flues, inches 2* fk 3 3 3 3 3 3 Square feet of heating: surface. Proper diam. of smoke-pipe (20' 155 192 239 310 385 462 60^ 765 901 1206 1504 chimney), inches M 14 15 17 18 2O 24 26 7l8 3 2 37 Approximate weight, Ibs V* t. of grate and fixtures, Ibs 1800 1200 2000 I4OO 2700 3100 1600 1800 4000 2100 4600 2200 5600 2800 7000 5200 8000 54oo 10500 7200 12500 7500 Fifteen square feet of surface to each horse-power. 79. Locomotive and Marine Boilers. Boilers of the horizontal tubular type with a fire-box entirely enclosed and surrounded by heating surface are usually termed locomotive .boilers from the fact that such construction is common on locomotives. Boilers of this style are sometimes used for sta- 132 HE 'A 7 'ING AND VENTILATING BUILDINGS. tionary power purposes, and possess the advantage over the plain tubular boiler of requiring no brick setting. They are not, however, as strong in form as the plain tubular, since large flat surfaces have to be used over the fire-box. Marine Boilers. A cylindrical boiler with an internal cylin- drical fire-box is principally used on large boats. The fire-box FIG. 115. LOCOMOTIVE BOILER. is often corrugated. This form of boiler is very strong and efficient, but because of cost of con- struction has been little used for station- ary purposes. 79. Vertical Boilers. Vertical boil- ers of large size are made in every respect like the horizontal tubular boiler, but are set so that the flame plays di- rectly on one head and the heated gases pass up through tubes. These boilers are generally provided with a water-kg which extends below the lower crown sheet and is intended to receive deposits of mud, etc., from the boiler. They are usually made so that the heat passes directly out of the top of the flue, but in some cases the heat is made to pass down a portion of the length of the ex- FIG. 116. UPRIGHT TUBU- . i i n i_ r i. j- i LAR BOILER. ternal shell before being discharged. They are economical in the use of fuel and occupy very small amount of floor-space ; they require, S TEA M-hEA TING ROILERS. HO T- WA TER HE A TERS. 133 however, a great deal of head-room, are very easily choked up with deposits and sediment, very difficult to clean, and very likely to leak around the tubes in the lower crown-sheet, and consequently have a short life. Vertical boilers with horizontal radial tubes projecting outward with ends closed, known as porcupine boilers, are also on the market, and quite recently a vertical boiler of the water-tube type has been constructed. 80. Water-tube Boilers. The water-tube boilers, which are used for power purposes, are designed to withstand great pressures, and can be purchased in sizes ranging from 60 to 500 horse-power per boiler. The general construction of these boilers is such as to have the water on the inside of the tubes and the fire with- out. There are two gen- eral forms : first, those with straight tubes, and second, those with curved tubes. In all cases they have large steam-drums at the 1-1 , . FIG. 117. BABCOCK & WILCOX BOILER. top, which are connected to the heating-surface by headers filled with water. In the Bab- cock & Wilcox, Heine, and Root the tubes are inclined and parallel, and are connected at the end with headers, the fire being applied in each case under the elevated portion of the inclined tube, so as to insure circulation uniformly in one direction. In the Babcock & Wilcox boiler, cast-iron zigzag headers are used ; in the Root boiler, the tubes are connected together by external U-shaped bends; in the Heine boiler (Fig. 120), the tubes are connected to large, flat-stayed surfaces. In the Babcock & Wilcox and Heine boilers, feed-water is supplied at the lower part of the top drums ; while, in the Root boiler, it is supplied to a special drum in the down-circulation tubes at the back end of the boiler. The Stirling boiler has three hori- zontal drums at the top connected by curved tubes to a single lower drum at the back end of the boiler ; the Hogan has one drum at top and two at bottom, which are parallel and 134 HEATING AND VENTILATING BUILDINGS. connected by curved tubes, and also a series of down-circu- lating tubes connecting the same drums, but not exposed to the heat of the fire. In the Stirling boiler, the feed-water is intro- FIG. 118. ROOT BOILER. duced in the top drums ; in the Hogan boiler, into a special heater and purifier arranged as a part of the downward circu- lation. FIG. 119. STIRLING BOILER. The Harrison boiler consists of an aggregation of spheres of cast iron or steel connected by necks, forming what is to be considered rather as a sectional, than a water-tube boiler. These S TEA M-HEA TING BOILERS. HO T- WA TER HE A TERS. 1 3 5 spheres are held in place by bolts, which will stretch and act as safety-valves in case of excessive pressure. In addition to the water-tube boilers for power purposes which have been mentioned here, there are many others which cannot be described in the space at our command, but of which we may name the National, Campbell & Zell, and the Caldwell as worthy of notice. All the water-tube boilers are provided with mud-drums, which are usually cast-iron cylinders removed from the circu- FIG. 120. HEINE BOILER. lation and intended to receive any deposits of scale or material which is loosened in the process of circulation. 8l. Hot-water Heaters. Hot-water heaters differ essen- tially from steam-boilers, principally in the omission of a reservoir or space for steam above the heating surface. The steam-boiler might an- swer as a heater for hot water, but the large capacity left for the steam would tend to make its operation slow and quite unsatisfactory. The passages in a hot-water heater need not extend so directly from bottom to top as in a steam-heater, since the problem of providing for the early liberation of the steam- bubbles does not have to be con- sidered. In general, the heat from the furnace should strike the surfaces FIG. 121. VERTICAL MAGAZINE in such a manner as to increase the HOT-WATER HEATER. natural circulation, and not act to produce a backward circula- tion. This may be accomplished in a certain measure 'by ar- 136 HEATING AND VENTILATING BUILDINGS. ranging the heating-surface so that a large proportion of the direct heat will be absorbed near the top of the heater. There is a great difference of opinion as to the relative merits of horizontal and vertical heating-surfaces for this pur- pose, but the writer cannot find that any experiments have been made which satisfactorily decide this question. Where the sur- face is very much divided, and the fire is maintained at a high temperature, considerable steam is likely to be formed, and this always acts in a certain measure to increase circulation in the heating-pipes and diminish it in the heater ; it is likely also to produce a disagreeable crackling noise. Practically, the boilers for low-pressure steam and for hot water differ from each other very little as to the character of the heating-surface, and in describing the general classes which are in use no attempt will be made to make any distinction as to whether the apparatus will be used for hot-water or steam heating. If designed for steam-heating, a reservoir or chamber connected with the circulating system is in every case pro- vided, containing water in its lower part and considerable steam capacity above the water-line, also sufficient area of water-surface to permit the separation of the steam from the water without noise and violent ebullition. 82. Classes of Heating-boilers and Hot-water Heaters Plain-surface Boilers. There are probably no boilers or heaters built at the present time with a plain surface, either spherical or cylindrical, since the expense of a given amount of surface in that form would practically preclude its use. Extended-surface Heaters (Figs. 122 and 123). Heaters of class with extended and irregular surface, are used quite extensively in hot-water heating, and with the addition of domes are used to some extent in steam-heating. In these heaters the water is received at the lowest point, as at A, and is heated as it gradually rises, receiving the effect of the fire at various projections, and is finally discharged at B. The grate is at G, the smoke being discharged at 5. The smoke and heated gases move in nearly a direct line in Fig. 122, and in a sinuous course in Fig. 123. A form which is in extensive use, and in which water and smoke are each grouped in one body, is shown in STEAM-HE A TING BOILERS. HO T- WA TER HE A TERS. I 37 Fig. 124. In this case the extended surface is produced by the wedge-shaped hollow prisms extending over the fire-space. The heated gases have a return circulation around the lower portion of the heater, and also come in contact with a top dome from which the heated water is drawn off. FIG. 122. EXTENDED-SURFACE FIG. 123. EXTENDED-SURFACE HEATER. HEATER. FTG. 124. EXTENDED SURFACE, VERTICAL PRISMS. FIG. 125. RADIAL AND CURVED WITH EXTENDED SURFACE. Heaters belonging to the extended-surface class made with vertical cylinders, into which are connected either straight hori- zontal tubes with closed end, as shown on the right-hand side of Fig. 125, or U-sHaped projections of pipe either horizontal or slightly inclined, are in use for both water- and steam-heat- 138 HEATING AND VENTILATING BUILDINGS. ing. In case they are used for steam-heating the water-line is carried at sufficient distance from the top of the cylinder to give the required steam-space, and the heater is supplied with both pressure- and water-gauges. The heated gases pass around the cylindrical part of the boiler and may be made to circulate among the projections by means of baffle-plates. Tubular Boilers. Heating-boilers with fire-tubes and with a steel shell similar in construction to the horizontal and vertical tubular boiler described in Articles 76 and 78, are in use for heating to considerable extent in the forms already de- scribed. Modifications of these, with return flues arranged so that the heat passes both upward and downward, and also with two or more short cylindrical shells connected together by tubes filled with water, are in extensive use. Very few hori- zontal tubular boilers, or boilers of the locomotive type, are used for the heating of small buildings. Water-tube Boilers. Water-tube boilers of all classes and various modifications are in extensive use for heating. The tubes are made of either cast-iron or wrought-iron pipe. The pipe-boilers which are in the market are arranged with nearly FIG. 126. FIELD TUBE. every form of heating-surface; some are built with heating- surface in the form of the pipe-coil, as shown in Fig. 92, page 108, and others in the form of a manifold coil, as shown in Fig. 93, page 108. Still other boilers have the pipe arranged in the form of a spiral connecting with a receiving-drum below and a steam-drum above. The heated gases are arranged to move S TEA M-HEA TING BOILERS. HO T- WA TER HE A TERS. 1 39 in some cases parallel with the surfaces, and in other cases at right angles. The Field tube is used extensively for the purpose of in- creasing the heating-surface; in its original form it consisted of a tube with a closed end projecting downward and expanded into the boiler-shell ; into this extended another tube which did not reach quite to the bottom, and was held in position by an internal perforated support, as shown in Fig. 126. This is used in heating-boilers with various modifications both pro- jecting downward and horizontally. When used projecting downward, it is termed a drop-tube, and is supplied either with an internal tube, as shown, or a partition ; when used hori- zontally the internal tube is frequently supplied from a com- partment separated from that to which the external tube is attached. Fig. 127 illustrates a type of heating-boiler which is quite extensively used for both hot water and steam, and is built by different manufacturers, either of steel or cast iron. The heater consists of a cylindrical drum, the lower surface of A& B B IHkH I | . . . i"i i" r^ L fdi 4 fei fei J=S P - F= f= F DROfJTUBE FIG. 127. DROP-TUBE SURFACE. FIG. 128. DROP-TUBE AND COIL-HEATER. which is covered with tubes of the type described which pro- ject downward. The tubes directly over the fire and over the fire door are short, while those around the fire are sufficiently long to form the external walls of the heater. The return water is received in one of the long pipes near the bottom of the heater, and the steam or heated water is taken off at the top. The drum in one of these heaters is provided with a baffle-plate connected to the diaphragm in the drop-tube, so 140 HEATING AND VENTILATING BUILDINGS. that the circulation must take place in a vertical direction in the tube. Fig. 128 shows a heater in which the surface is made up partly of pipe-coils and partly of drop-tubes. The return water is received in the lower concentric drum, and as it is warmed passes to the top drum of the heater, from which it flows to the building; a type of heater in many respects similar is made without drop-tubes, the whole surface being obtained by use of pipe-coils, made either with return bends or with branch tees. Sectional Boilers. The greater number of cast-iron boilers are made by joining either horizontal or vertical sections. These sections are joined in some instances by a screwed nipple, in other cases by a packed or faced joint, and are held in place with bolts. The sections generally contain water and O* O O Oo 1 Oo Co FIG. 130. BOILER WITH HORIZONTAL SECTIONS. PLAN OF SECTION FIG. 129. BOILER WITH HORIZONTAL SECTIONS. steam, and the heated gases circulate around the sections in flues provided for that purpose. The joints in the flues are usually made tight enough to prevent the escape of smoke by the use of an asbestos or similar cement. STEAM-HEATING BOILERS. HOT-WATER HEATERS. 14* Horizontal Sections. Fig. 129 represents a type of heater in which the various sections are horizontal, the surface being in- creased to any amount by adding sections. This form is used extensively in a number of hot-water heaters. Fig. 130 shows another form of boiler made in a similar manner, but with the sections of such form as to produce both an up and down circulation within the heater. The up circulation takes place over the hottest portion of the fire, the down circulation in special external passages which are not heated. Vertical Sections. Boilers with vertical sections are made in the same manner in many respects, the sections being united by internal or ex- ternal connections. When united by ex- ternal connections, screwed nipples con- necting the sections to outside drums, of the general form as shown in Fig. 131, are usually employed. In this case the return-water is received into horizon- tal drums AA, which extend the full length of the heater, and flows into the lower part of each section. The steam or hot water is drawn off from a similar drum, B, which extends over the top of the heater and is connected with each section by a screwed nipple. Fig. 130 shows methods of attaching steam- and water gauges. This form is used quite extensively in steam- heating and to some extent for hot-water heating. 83. Heating-boilers with Magazines. Nearly all of the heating-boilers are manufactured as required with or without a magazine to hold a supply of coal. The magazine in most cases consists of a cylindrical tube opening at or near the top of the heater and ending eight to twelve inches above the grate. The magazine is filled with coal, which descends as com- bustion takes place at the lower end, and provides fuel for further combustion (see Fig. 121). The magazine works suc- cessfully with anthracite coal, which is that ordinarily employed in domestic heating, but it takes up useful space in the heater, decreases the effective heating surface for a given size, and in 142 HEATING AND VENTILATING BUILDINGS. that respect is objectionable. The writer's own experience would lead him to believe that the magazine heater, except in very small sizes, requires as much attention as the surface burner, and consequently has no special advantage.* 84. Heating-boilers for Soft Coal. It is quite probable that no furnace, either for power or heating boilers, has yet been produced which will consume soft coal without more or less black smoke. This smoke is due principally to the imper- fect combustion of the hydrocarbons contained in the coal. The! hydrogen burning out after the gases have left the fire leaves solid carbon in the form of small particles, which float with and discolor the products of combustion. The amount of loss as found by experiment in Sibley College,f even when dense black smoke is produced, seldom reaches one per cent, and is of noi economical importance. The sooty matter produced in the| combustion of this coal is likely to adhere to the water-heatingl surfaces, and if these are minutely divided it will be certain to3 choke the passages for the gases of combustion. For the = combustion of soft coal those heaters have been the most successful which have a grate with small openings, and with an = area 50 to 70 per cent as large as that needed for anthracite coal, also with the heating-surface of comparatively simple form! and arranged so as to be easily cleaned. It is considered im- portant that the air-flues be so arranged as to keep the products of combustion as hot as possible. This coal is likely to swell when first heated, and cannot be fed successfully by a maga- zine. * Magazine heaters have been constructed with a magazine set obliquely above and to the side of the grate, and in that position are not open to all the objections stated. f See Table XII, page 390. CHAPTER VIII. SETTINGS AND APPLIANCES -METHODS OF OPERATING BOILERS AND HEATERS. 85. Brick Settings for Boilers. Horizontal tubular boilers and a few heating-boilers require to be set in brickwork, of which the general arrangement is shown in Fig. 132. The horizontal tubular boiler is usually supported from cast-iron flanges which are riveted to the sides of the shell, and which rest ,.., FIG. 132. PERSPECTIVE VIEW OF TUBULAR BOILER st/i IN BRICKWORK. directly on the walls of brickwork, or are supported b)- sus- >pension-rods from above. In some instances the boiler-lugs 'rest on cast-iron columns embedded within the brickwork, and of such a length that all the brickwork above the grates can be removed without affecting the setting. In setting the boiler 143 144 HEATING AND VENTILATING BUILDINGS. the back end should be slightly lower than the front, in ord< that the entire bottom of the boiler may be drained at the blow- off pipe. One of the lugs of the boiler on each side should anchored in the brickwork ; the others should rest on rollei which in turn rest on an iron plate embedded in the bricl *TS^w k walls. This permits expansion due to heating and cooling take place without straining the boiler. If the boiler is 'n< over 14 feet in length, two lugs on a side will be sufficient sustain it, but if it is of greater length, more lugs will need SETTINGS AND APPLIANCES. 145 be supplied. The brickwork surrounding the boiler is more durable if built with an air-space, as shown in Fig. 134. It must be thoroughly stayed, by means of cast-iron braces, con- nected with tie-rods at top and bottom of wrought iron to FIG. 134. SECTIONAL VIEW OF BOILER- SETTING. prevent transverse or longitudinal motion. The top may be I arched over so as to leave a passage for the hot gases directly ver the shell, as in Fig. 132, or made to rest directly on the . boiler, and the hot gases taken away at the front end by j! means of a flue, usually termed a breeching, which extends to the chimney. The practice of taking the heated gases from Hhe front end of the boiler is rather more common than that of Returning them to the back end over the top, and there are I many engineers who believe that the hot gases injure the boiler ||when coming in contact with the shell above the water-line. I Fig 5 - 133, 134, and 135 show longitudinal and transverse sections p)f a boiler-setting, with smoke-pipe or breeching in front, which lean be highly commended as representing the best practice. The depth of foundation to be used in boiler-setting will depend upon the character of the soil and the weight of the pboiler. For large tubular and water-tube boilers it should gen- erally be not less than 3 feet. Fire-brick of the best quality 146 HEATING AND VENTILATING BUILDINGS. should be used to line the brick walls for a height equal to that from the grate to the water-line of the boiler, and these should be arranged so that if necessary they can be relaid without disturbing the outer brickwork. In the setting shown in Figs. 133-134 the top of the boiler is covered with a coating of some good, non-conducting material, for which magnesia, asbestos or mineral wool may be recommended, put on while in a plastic condition to the depth of 2 inches with a mason' SETTINGS AND APPLIANCES. FIG. 136. BRICK-SET MAGAZINE BOILER. trowel. Brickwork is often used ; but it is heavier, and quite liable to crack from the effects of heat. 86. Setting of Heating-boilers. If heating-boilers are to be set in brickwork, the special directions which have already been given can be applied, with such modifications as may be needed for the boiler in ques- tion. Nearly all heating-boilers are now set in what is called a portable setting, in which no brick whatever is used. Some of the heaters are made by the system of manufacture adopted so that no outside casing is re- quired, as in Fig. 138; others require a thin casing of galvan- ized or black iron which is lined with some non-conducting ma- terial, as magnesia, asbestos fibre, or rock wool, which is placed outside the heater and arranged so as to enclose a dead-air space, as in Fig. 137. These coverings are nearly as efficient |jn preventing the loss of heat as brickwork, and they form a more cleanly and neater appearing job. The slight amount of heat which escapes from such a setting is seldom more than that required to warm up the jlbasement or room in which the heater is located. The boiler must in all cases be provided with a steam- i;gauge, safety-gauge, and damper regulator, all of which are \ specially described later. The steam-gauge should be either Connected below the water-level or else provided with a siphon jlto prevent dry steam entering the interior tube. A safety- -valve of the single-weighted type is preferable and should be connected at the top of the heater. The damper regu- i lator usually consists of a rubber diaphragm which is acted pon by pressure so as to open and close the dampers as required. |: It will prove more durable, generally, if connected below the |%ater-line and located about on a level with the top of the I heater, as this will insure the contact of water against the rubber diaphragm. Fig. 137 represents a boiler with portable setting 148 HEATING AND VENTILATING BUILDINGS. with external iron casing and equipped with all appliances, and Fig. 138 represents a portable setting without enclosing case. Hot-water heaters are set in the same general manner as steam-boilers. Each should be provided with thermometers showing both the temperature of the flow and the return water, FIG. 137. HEATING-BOILER WITH PORTABLE SETTING. FIG. 138. HEATING-BOILER WITH; PORTABLE SETTING. and with a pressure-gauge graduated to show pressure of water in feet and sufficiently large to show any variation in height in the open expansion tank. The dampers to a hot-water heater FIG. 139. SECTION OF LEVER VALVE, OLD FORM. cannot be opened and closed by variation in pressure, but reliable thermostats are now on the market which will operate the dampers by change of temperature in the various rooms of the building. SETTINGS AND APPLIANCES. 149 87. The Safety-valve. The safety-valve has been used since the earliest days of boiler construction for reducing the pressure when it reached or exceeded a certain limit. It has been built in various forms, but in every case has con- sisted essentially of a valve opening outward and held in place by a weight or a spring. One form in common use con- sists of a valve held in place by a weight on the end of a lever, shown in Fig. 139 in section and in Fig. 140 in elevation. In this form of safety-valve the force required to lift the valve FIG. 140. LEVER SAFETY- VALVE, MODERN FORM. can be regulated by sliding the weight to different positions on the lever. The form shown in Fig. 141 consists of a single weight suspended from the valve and hanging in the upper FIG. 141. DEAD-WEIGHT SAFETY-VALVE WEIGHT INSIDE OF BOILER. part of the boiler. This form is to be commended, since it cannot be adjusted without opening the boiler. A form used very extensively for low-pressure heating- boilers consists of a single weight resting on a valve, as shown in Fig. 142 ; its principle of operation is the same as that of the ISO HEATING AND VENTILATING BUILDINGS. other valves. A form much used on power-boilers, and frequently called, from the suddenness with which it opens, a pop-valve consists of a very quick-opening valve held in place with a spring, one form of which is shown in Fig. 143. FIG. 142. EXTERNALLY WEIGHTED SAFETY-VALVE. FIG. 143. SECTION OF SPRING OR POP SAFETY-VALVE. It is desirable that the safety-valve be made in such a manner that the engineer or attendant to the boiler cannot manipulate it at pleasure so as to maintain a higher pressure on the boiler than prescribed. Serious accidents have been caused by excessive weighting of the safety-valve through ignorance or carelessness on the part of the attendants, and for this reason a class of valves should be selected which cannot be tampered with. Some of ; the safety-valves are provided with an external case which can be locked, and others are provided with internal weights, as already described. The lever safety-valve offers the most temptation for extra weighting and should rarely be used. The area of a safety-valve must be sufficiently large to effectually reduce the boiler pressure when the valve is open and when a brisk fire is burning on the grate. It may be computed from the following considerations : The steam which will flow through one square inch of open- ] ing in one hour of time was found by Napier* to equal in \ *Rankine's "Steam Engine." SETTINGS AND APPLIANCES, pounds nearly 50 times the absolute pressure of the steam; further, it has been found by experiment that the safety- valves in ordinary use open only to such an extent as to make \ of the total area of the valve effective in reducing the press- ure. From these considerations it will be seen that the area of the safety-valve in inches should be -fa the weight of steam generated per hour, divided by the absolute pressure. Considering that 100 Ibs. of steam can be generated from each square foot of grate per hour, this would be equivalent to the following rule: The area in square inches is equal to 18 times the grate surface in square feet, divided by the absolute pressure. The following table gives the area of safety-valve in square inches per square foot of grate required on marine boilers by the English Board of Trade : Boiler Pressure. Boiler Pressure. Absolute, Pounds per Above atmos- Area in square inches for each sq. ft. grate. Absolute. Above atmos- Area in square inches for each sq. ft. grate. sq. inch. phere. phere. 15 O 1.25 60 45 0.50 20 5 1.07 70 55 0.44 25 10 0.94 80 65 0.40 30 15 0.83 QO 75 0.36 35 20 0-75 100 85 0-33 40 25 0.68 no 95 0.30 45 30 0.625 120 105 0.277 50 35 0.576 130 H5 0.258 The following formula gives results very closely in accord with the English Board of Trade table. Let A = area of safety-valve in square inches, P = absolute pressure = gauge pressure plus 15, G = number of square feet of grate surface. Various rules quite different from the above are given in treatises on boiler construction, but it is believed that the above table represents the best practice of to-day and forms a safe guide for estimating the size of safety-valves. Safety-valves are liable to stick fast to the seat, through corrosion, in which case they fail to raise with excess of press- 152 HEATING AND VENTILATING BUILDINGS. ure ; for that reason tliey should be periodically lifted from their seats and otherwise inspected. In case the area of the valve required is greater than 4 inches in diameter, two safety-valves should be provided for each boiler. 88. Appliances for showing Level of Water in the Boiler. In the first boilers constructed floats were used, and such appliances are still common on European boil- ers. In this country water-gauge glasses and try-cocks are now used, to the exclusion of all other devices. The water-gauge (see Fig. 144), consists of two angle-valves, one of which is screwed into the boiler above the water line ; the other is screwed about an equal distance below, and these are connected by means of a glass tube usually! to f inch external diameter and strong enough to withstand the steam-press- ure. When both angle- valves are open the water will stand in the gauge-glass the same height as in the boiler, but if either valve is closed the water-level shown in the glass will not accord with that in the boiler. Three try-cocks are usually put on a boiler in addition to the water-; gauge. The try-cocks are made in various forms, one kind being shown in Fig. 145, these are located so that one is above, the other FIG. 144. GLASS . WATER-GAUGE, below, and the third at about the mean posi- tion of the water-line. When the top one is opened, it should show steam ; when the bottom one is opened it, should FIG. 145. REGISTER GAUGE-COCK. show water. Both try-cocks and gauge-glasses should usually be put on boilers, so that the reading as shown in the water- gauge glass can be checked from time to time. This is neces- sary, because if dirt should get in the angle-valves or passages SETTINGS AND APPLIANCES. '53 leading to the gauge-glass the determination would be inac- curate. Water-columns attached to the boiler by large pipes, both above and below the water-line, and fitted with try-cocks and water-gauge as shown in Fig. 146, are often provided. These columns frequently contain floats (Fig. 147), so arranged that steam is admitted into a small whistle if the water falls below or rises above the required limits, and thus gives an alarm. FIG. 146. WATER-COLUMN rics. 147. RELIANCE ALARM WATER-COLUMN. 89. Methods of Measuring Pressure. The excess of pressure above that of the atmosphere is measured by some form of manometer or pressure-gauge. Where the pressure is small in amount, a siphon, or U-shaped tube rilled with some liquid is a very convenient means of measur- ing pressure. The method of using a simple manometer of this character is shown in Fig. 148, in which a U-shaped tube, G F E D, has one branch attached to the vessel containing the fluid whose pressure is to be measured ; the other, as at D, is open to the air. If water, mercury, or other liquid be placed in the U-shaped E FIG. 148. U-SHAPED MA- NOMETER. 154 HEATING AND VENTILATING BUILDINGS. tube it will be forced down on the side of the greater pressure and upward on the side of the less, a distance proportional to the pressure. The height of the fluid in one side in excess of that on the other will be a measure of the difference of pressure be- tween that of the atmosphere and that in the vessel. Various forms of manometers are used, of which several are shown in Fig. 149. For very low pressures water is the liquid generally employed; for mod- erate pressures up to 15 or 25 pounds mercury is very convenient, and often used ; while for high pressures a pressure- gauge (Fig. 150), as described later, is commonly employed. The Bourdon pressure-gauge is or- dinarily used. This consists of a tube of elli P tical cross-section bent into a circular form. The free end of the tube is attached by gearing to a hand which moves over a dial. Pressure on the interior of the tube tends to straighten it, and FIG. 150. BOURDON GAUGE moves the hand an amount proportional to the pressure. Fig. 150 shows the interior of a pressure-gauge of this char- SETTINGS AND APPLIANCES. 1 55 .acter with the dial removed. In place of the tube a corrugated diaphragm is sometimes employed. A section of such a gauge is shown in Fig. 151. In the use of gauges of the character just described it is necessary to protect them from extreme heat, this purpose when they are connected to a steam-boiler a FIG. 151. DIAPHRAGM GAUGE. siphon or U-shaped form of pipe is to be used in the connec- tion, so that water and not steam will be forced into the inte- rior of the gauge. The manometers and gauges described in every case measure the pressure above or below that of the atmosphere. If they [measure a pressure lower than that of the atmosphere they are commonly called vacuum-gauges, but the principle of construc- tion is the same as described. The relations of various units used in measuring pressure can be readily determined from the following table of equiva- lents : i inch of mercury 13.619 inches of water = 1.134 feet [of water = 0.49101 pound = 399.51 feet of air at 60 degrees Fahrenheit and barometer pressure 30 inches. The pressures are usually taken as acting on one square inch of a body. 156 HEATING AND VENTILATING BUILDINGS. 90. Thermometers. The methods of constructing various kinds of thermometers have been described in Articles 8 to 12. In any hot-water heating system it is quite important to know the temperature of the water leaving the heater, and in many cases also that of the return. This information, while not so vital to the safety of the heater as that given by a pressure-gauge on a steam-heat- ing system, is of the same character, and will prove to be equally valuable in indicating the work done by the heater, and the heat absorbed by the system. Any of the suitable forms described in Chap- ter I can be used, but special forms in which the thermometer-bulb sets in a cup of mercury (Fig. 152) are often used, the cup being screwed into the pipe whose temperature is required. These thermometers should be set so as to ex- tend deep into the current. of flowing water, and there should be no opportunity for air to gather around the bulb ; otherwise the readings will not be the true temperature. 91. Damper-regulators. Nearly all steam- boilers are provided with an apparatus for open- ing or closing the dampers and draft-doors to the boiler as may be required to maintain a constant steam-pressure. For low-pressure FOR steam-heating plants the regulator consists in FIG. 152. THER- MOMETER FOR HOT -WATER HEATING. nearly every case of a rubber diaphragm (tig. 153), which receives the steam-pressure on one side, and acts against a counter-weight resting on a plate on the opposite side. The plate is connected by a rod to a lever pivoted to the external case, which in turn is connected to the various drafts by means of chains, and so arranged that if the pressure rises the lever is lifted and the drafts closed, while if the press- ure falls the lever also falls, and the drafts are opened. By means of weights on the lever the regulator can be set to operate at any pressure. The regulator should be connected to the boiler below the water-line, or by means of an U-shaped pipe, arranged so that the part of the vessel below the dia- SETTINGS AND APPLIANCES. 1 57 phragm will remain full of water ; otherwise the heat in the steam will cause the rubber to deteriorate rapidly. The form shown in Fig. 153 is so arranged that the diaphragm must in every case be in contact with water. While rubber diaphragms are usually durable for low-pres- sure steam-regulators, still they occasionally are ruptured. In order to prevent accident from such a cause, the Nason Manu- facturing Co. have devised a form of such a character that the draft-doors will close, instead of open, in case of rupture. This is done by using a link in the connecting-chain to the draft- doors of some metal that will be fused at a temperature below that of boiling water, and arranged so that in case of rupture the escaping steam and hot water will impinge upon and melt it ; the damper will be closed by its own weight when the link breaks. Damper-regulators for high-pressure steam are constructed so as to operate on the same principle as those described, but instead of a rubber diaphragm either a metallic diaphragm or a piston working in a cylinder, and operated by water-pressure, is employed. The following cut shows the external appearance of one of the many forms in use. FIG. 153. DIAPHRAGM FIG. 154. PISTON DAMPER-REGULATOR. DAMPER-REGULATOR. 92. Blow-off Cocks or Valves. Every steam-boiler should be provided with an appliance for emptying all of the water at any time. This may be done by leading a pipe from the lowest part of the boiler and providing a cock or valve so that it can be discharged at pleasure. The pipe leading from the boiler should have a visible outlet, so in case there is any leak it can HEATING AND VENTILATING BUILDINGS. be seen and stopped. The writer prefers a cock (Fig. 155) toj a valve for use on the blow-off pipe, since it is less likely to be stopped by scale or sediment from the boiler. In case the water of condensation from the heating coils is not returned to the boiler it is necessary to blow off some of the water very frequently in order to lessen the deposition of scale or dirt on the bottom of the boiler. 93. Expansion-Tank. An expansion- tank will be needed in hot-water heating of FIG. 155. PACKED PLUG COCK. systems. With increase of temperature from 40 F. to the boiling-point, water expands 4.66 parts in 100, or nearly 5 per cent. The force of expansion is nearly irresistible, and the increase in volume due to it must be provided for, so as not to produce a dangerous press- ure. The method ordinarily adopted con- sists in the use of a vessel called an expansion-tank, whose cubical contents must be somewhat greater than one twentieth of the total cubical contents of heater, pipes, and radiators. It must be connected to the heating sys- tem in such a way as to receive the in- crease in volume, and should be placed on a level somewhat above that of the highest radiating surface. If there is to be no sensible increase in pressure due to expansion the tank is connected with the outside air by a vent-pipe, and in this case the pressure inside will be atmospheric ; the pressure on the heating system will depend on the distance from the water-level in the tank, each foot corresponding to 0,435 pounds per square inch (2.4 feet being equivalent to one pound oi pressure at 212 F.). FIG. 156. EXPAN- SION-TANK. SETTINGS AND APPLIANCES '59 In case a pressure in excess of the atmosphere is required, the vent pipe is closed and a safety-valve attached which will open when the pressure reaches the desired point. By increas- ing the pressure on the system the boiling temperature of the water will be much increased, and hence it will be possible to ^maintain a higher temperature throughout the system. As showing the increase in temperature of the boiling point with excess of pressure, the following table is inserted : Pressure. Pounds per sq. in. above Equivalent Head, in Feet. Temperature of Boiling Point (degrees F.). Atmosphere. O O 212 5 12 228 . . . 10 24 240 15 3^ 250 20 43 259 25 60 26 7 30 72 274 35 84 280 40 96 287 45 1 08 292 50 1 20 297 55 132 302 60 M4 307 70 168 36 - 80 192 324 90 216 332 IOO 240 33 8 125 300 352 150 360 365 175 420 378 200 480 388 Pressure systems of hot-water heating were used at one time to a considerable extent in England, under what was known as the Perkins* system, in which small pipes and exceedingly high pressures and temperatures were used. It has also been used to some extent in this country in the Baker system of car-heating. The advantages of the pressure system are those which are due simply to the use of higher temperatures and smaller radi- cating surfaces ; the disadvantages are the danger of an explosion * Hood's " Heating and Ventilating of Buildings." 160 HEATING AND VENTILATING BUILDINGS. which would be likely to happen were the safety-valve inoper! ative, or did any part of the apparatus give way. The sudden liberation of a considerable body of water having a temperatun above the boiling point would result in the instantaneous prof duction of a large amount of steam, which might produce disl astrous results. With the open expansion-tank it seems hardly possible thaw any serious accidents could result even from the most carelesil management, since the escape of steam from the top of thet expansion-tank would prevent the accumulation of pressure,! To prevent accident the expansion-tank should be connected to the heater by a pipe protected from frost and without! stop or valve, so as to render it impossible to increase the] pressure on the system by stoppage of the connection. It is desirable to provide the expansion-tank with a glass water-gauge showing the depth of water, and a connection tc the supply-pipe for adding water to the system. In case the expansion-tank occupies a cold location where it might freeze in extreme weather, a small pipe connected with thei circulating system, in addition to those described, should be run to the tank and connected at a higher level than the ex- pansion-pipe, so as to insure circulation of warm water. 94. Form of Chimneys. The form and size of the chim* ney is of great importance in connection with the satisfactory! operation of a heating plant, and it should in every case receive the closest inspection before guarantees of capacity arm made. It will be found that for a specified area a round chimney will have the most capacity, but in ordinary building construe! tion such a chimney is difficult to construct and is not ordi^ narily built. A square chimney of the same area has some* what more friction, and one with a rectangular narrow fluJ very much more, so that an increase in area proportional to ex| cess of perimeter should be made for such cases. The chimneyf should be as smooth as possible on the inside in order to prej vent loss of velocity by friction, and, if of brick, the flue should in every case be plastered. In the construction of chimneys it is better that the inside be made with a thin wall not con- nected in any way with the outside, both in order to permit SETTINGS AND APPLIANCES. l6l free expansion of the inner layer of the chimney with the heat and also to secure the advantage of the non-conducting power [of an air space between the inside and outside walls. Such a construction is common for chimneys for power purposes, but is not ordinarily applied to those used in buildings. 95. Sizes of Chimneys. The area of cross-section required for a given chimney will depend upon its height and also upon [the amount of coal to be burned. The conditions which affect chimney draft are so numerous, and so difficult to consider in [any theoretical discussion, that empirical or practical formulae [derived from the study of actually existing plants are prob- ably more satisfactory than those obtained from purely theo- Iretical computations. Of the various formulae which have peen given for the capacity of chimneys the writer prefers that of William Kent, from which the accompanying table is computed. Kent's formula is computed on the assumption that the chimney shall have a diameter two inches greater than that required for passage of the air, in order to compensate for friction. The following is his formula : S= 12 tf h = ; in which A actual area in square feet of the chimney, = effective area, h = height in feet, S side of the square in inches, H = horse-power of plant. If we let fi = number of square feet of radiating surface to be supplied, then, Article 73, page 173, .003!? from which E = - The table gives the diameter of round or side of square chimneys in inches for various heights computed from the above formulae, with the diameter in- creased by 2, to allow for friction. A square chimney is considered the equivalent of the inscribed round one. 162 HEATING AND VENTILATING BUILDINGS. DIAMETER OR SIDE OF CHIMNEY IN INCHES REQUIRED FOR VARYING AMOUNTS OF DIRECT STEAM-RADIATING SURFACE. Height of Chimney in Feet 20 30 40 50 60 80 100 120 Square Feet of Steam Ra- Horse- diation. power. 250 2.5 7-4 7.0 6.7 6. 4 6.2 6.0 6.0 6.0 500 5.0 9.6 9 .2 8.8 8.2 8.0 6.6 7-3 7.0 750 7.5 ii. 3 10.8 10.2 9.6 9-3. 8.8 8.5 8.2 I,OOO 10.0 12.8 12. ii. 4 10.8 10.5 10. 9-5 9-2 1,500 15.0 15-2 14.4 13-4 12.8 12.4 ii 5 II .2 10.8 2,000 20.0 17.2 I6. 3 15-2 14.5 14.0 13-2 12.6 12.1 3,000 30.0 20. 6 I8. 5 IS.2 17.2 16.6 15-8 15.0 14.4 4,000 4O.O 23.6 22.2 20.8 19.6 19.0 17.8 17.0 16.3 5,000 5O.O 26.0 24.6 23.0 21.6 21 .0 19.4 18.6 18.0 6,000 60.0 28.4 26.8 25.0 23.4 22.8 21.2 2O. 2 19-5 7,000 7O.O 30-4 28.8 27.0 2^.5 24.4 23.0 21 .6 20.8 8,000 So.o 32-4 30.6 28.6 26.8 26.O 24.2 23-4 22.2 9.000 90.0 34-0 32-4 30.4 28.4 27.4 2 5 .6 24.4 23-4 10,000 IOO.O 37-0 34-0 32.0 30.0 28.6 27.O 25-4 24.6 I ^ OOO I^O O 18 4 -16.2 2C .0 2-2 O 21 O 2Q 2 1 D> < ~' v -' v -' 20,000 fc y* . ^ 2OO.O O^ *T 4-T.O o 42.0 j j w 41 .0 JO ' ^ 1.-] .0 j i . v/ ic O **f * 34 O 30,000 3OO.O *T J W 50.0 48.0 J 1 ' w 46.0 3D ' w 43-o }*T * v ^ 41.0 For other kinds of heating multiply the radiating surface by the following factors : Hot- water heating 1.5, indirect steam 0.7, hot-blast heating 0.2. 96. Chimney-tops. The draft of a chimney is influenced! to a great extent by the conditions of the surrounding space. If other buildings exist in the vicinity of such a form as to de- flect the currents of air down the chimney, the draft will bej impaired and may be entirely destroyed. The objects which] tend to produce downward air-currents may sometimes be situated a considerable distance from the chimney and thus ren- der the specific cause of poor draft very difficult to determine.! The remedy for a smoky chimney is sometimes difficult to ap-1 ply, but usually the draft will be improved, first, by increasing; the height of the chimney ; second, by adopting some form of, chimney-top which utilizes the force of horizontal currents to aid by induction in increasing the draft. The writer found that curved trumpet-shaped tubes located! with the small ends projecting into the chimney in an upwarJ direction increased the draft materially when the wind was blowing into the openings, and there is little reason to doubt; but that a chimney-top may be constructed in such a manner as to materially increase the draft. SETTINGS AND APPLIANCES. 163 97. Grates. For supporting the fuel during its combus- tion in such a manner as to allow a free passage of air, a per- forated metallic construction of some sort is required. For burning very fine coal the perforation must be small and close together ; for burning larger sized coal the perforations may be larger and further apart. The area of the air-spaces compared with the total area of the grate should be about 50 per cent in order to secure best results, but they will more generally be found to be 30 to 40 per cent. The grates are usually con- structed of cast iron and in a very great variety of forms, jas shown in Figs. 157 and 158. In some instances a series of parallel bars is used ; in others the grates are made in one solid FIG. 157. DIFFERENT FORMS OF GRATES. casting. This latter practice is never one to be recommended. The solid grate is likely to break from expansion strains due to heating unless made in such form that the various parts are free to expand independently. Nearly all heating-boilers, hot-water heaters, and furnaces are supplied with some form of shaking- and dumping-grate. Many of these grates are known from experience of the writer to give most excellent satisfaction, and doubtless all present points of merit. The various shaking-grates operate in nearly every way, and it is hard to conceive either a form of grate-bar or a method of shaking which is not exemplified in some of these grates. Some of the bars are flat or rectangular in shape, and are operated by shaking backward and forward ; others are triangular and are continually rotated so as to pre- sent successively new surfaces to the fire each time they are shaken. The shaking-grate will, in general, be found much superior to the fixed one, and a furnace fitted with such grates 164 HEATING AN> VENTILATING BUILDINGS. is more easily managed and more cleanly than one with a fixed grate of any description. 98. Traps. In all systems of gravity steam-heating, the water of condensation returns directly to the boiler, and no appliance either for maintaining a water-line in the building or returning the condensed steam to the boiler is required. But there are cases in which it is necessary to maintain the water- line at a certain definite height, and also to prevent the escape of steam without interfering with the discharge of condensing water. For this purpose a steam-trap is re- quired. One form of a steam-trap which has always been used to a greater or less extent for this purpose is a siphon made in the shape of '0 a U bend, or its equivalent of pipe and fit- tings, as shown in Fig. 159. It consists of two legs, AB and BC, which may be close to- gether or any distance apart, but the length of which must be sufficiently great to prevent pressure acting through the pipe FA forcing the water out of BC. CE is a vent-pipe ex- tending to the air ; D is the discharge for the condensed water. In ordinary operation the leg CB is filled with water which is constantly overflowing, and AB with steam and water; the total pressure in both legs being in each case equal. The siphon-trap may be open to the objection that it will require a great deal of vertical room if the pressure is great ; FIG. 159. SIPHON-TRAP. FIG. 1 60. FLOAT-TRAP. for this reason traps with mechanical movements of some kin< are usually preferred. The simplest of these traps contains float (Fig. 160) which rises and falls with change of level of th< SETTINGS AND APPLIANCES. i6 5 water in the vessel. Rising above a certain point, it opens a discharge-valve ; falling below, it closes it. Traps of this class are made of a great many designs. In some instances traps are made as in Fig. 161, in which a weight W \s used instead of FIG. 161. COUNTER-WEIGHTED TRAP. a float and is nearly counter-balanced by the weight D. As the water rises in the trap it tends to lift the weight PFan amount proportional to its volume, thus opening a discharge-valve at^. When the water falls, the valve is closed. It is noted that the counter-weight D is always above the water-line P. A large number of traps are made with a hollow metallic float or bucket, so arranged as to open a valve when the bucket is full of water. One form is shown in Fig. 162, in which the water enters the trap at A, filling the FIG. 162. BUCKET TRAP. space 5 between the bucket and the walls of the trap. This causes the bucket to float, and thus to close an orifice in the discharge-pipe V. When the water rises above the edges of the bucket it flows into it and causes it to sink, which opens the discharge-valve at V. The water is forced out through the pipe B by the steam pressure acting on the surface 55. The bucket traps are made in great variety, both as to form of valve, guides for bucket, etc. Fig. 163 shows one of the traps which is in common use, with all details of con- struction. Another extensive class of traps are made so as to be closed by the expansion due to increase in temperature. These traps differ from each other very much in form ; the principle, how- i66 HEATING AND VENTILATING BUILDINGS. ever, is in all cases the same. Thus in the diagram, Fig. 164, steam is supplied at A and discharged at B. The bent springs 5 are prevented by'guides from moving laterally, so that the expansion due to heat causes a motion which closes the orifice in the discharge-pipe B. When the water in the traps cools FIG. 163. BUCKET TRAP. the valve opens. The materials used for traps of this clase can be metallic or some composition of material like that em- ployed for air-valves. The discharge can be arranged to tak< place from the bottom or, as sho\vn in the diagram, from tin side. FIG. 164. EXPANSION-TRAP. Traps which combine one or more of the principles oi operation as described are on the market. Thus Fig. 165 re] resents a trap with two valves in which one valve is opened b; expansion, the other by a float. The bucket traps have generally proved the most reliabl< and less likely to be injured by use. The float-traps have beei liable to failure because of leakage of the float, but receni improvements in manufacture render this accident quite im SETTIA-GS AND APPLIANCES. I6 7 probable. All traps need periodical inspection, as the valves are likely to become more or less choked up, in which case the trap may fail to operate. All of the traps described FIG 165. COMBINED FLOAT- AND EXPANSION-TRAP. will discharge the water to a height which corresponds to the steam-pressure in use, and hence when used with high-pressure steam will lift water to a considerable distance; but in no case will they return the water into the boiler from which the steam was received. For this purpose a trap of considerable more complexity, known as a return-steam trap, must be used. 99. Return-traps. Traps which receive the water of con- densation and return it to a boiler having considerably higher- *pressure steam than that acting on the returns, are known as c' FIG. 1 66. DIAGRAM SHOWING ACTION OF RETURN-TRAP. return-traps. They are made in quite a variety of forms, but the general principle of operation is shown by the diagram Fig. 1 66. In this figure D represents the boiler and AB the trap, i68 HEATING AND VENTILATING BUILDINGS. which is located above the boiler and is supplied with steam from the boiler at A. It is connected with the return system by a pipe leading from the tank or drum P, and pipe dis- charging into the trap at E. A pipe leads from the bottom of the trap B and connects below the water-line with the boiler. Check-valves are located at C and C, which permit the flow to take place toward the boiler only. The essential method of operation of the trap is as follows : First, water flows into the trap from the return P, until it reaches a certain level, when it acts on the float B so as to open a balanced steam-valve, FIG. 167, BUCKET RETURN-TRAP. called an equalizing-vavle, connected, to the main pipe A. This permits steam from the boiler to enter the trap, which equal izes the pressure of steam in the trap and boiler. The watei in the trap, because of its greater density, then commences to flow out through the pipe B, and need only cease when the level becomes nearly the same as in the boiler. The dis charge of the wafer causes the float B to fall, which closes the equalizing valve, and the operation as described is again re- -peated. Instead of a float a bucket may be used to operate the SETTINGS AND APPLIANCES. 169 equalizing-valve, acting in a manner similar to that described for the ordinary bucket trap. A section of such a trap is shown in Fig. 167. The bucket is probably superior to the float for this pur- pose, since it is less likely to be affected in its operation by change in density or pressure of the steam. Various other systems, for opening and closing the equaliz- ing-valve have been adopted, of which one, shown in Fig. 168, FIG. 168. GRAVITATING RETURN-TRAP. ^consists in mounting the trap so that it will move into one position when empty and into another when full, the motion 350 obtained being used to open and close the equalizing-valve. A different construction for accomplishing the same pur- pose is shown in Fig. 169. FIG. [69 RETURN-TRAP. ioo. General Directions for the Care of Steam-heating Boilers. Special directions will be no doubt supplied by the HEATING AND VENTILATING BUILDINGS. maker for each kind of boiler, or for those which are to be managed in a peculiar way. The following directions are gen- eral and should always be observed, regardless of the kind of boiler employed : 1. Before starting the fire see that the boiler contains water. Its surface should stand a distance of from one third to one half the height of the gauge-glass. 2. See that the smoke-pipe and chimney-flue are clean and that the draft is good. 3. Build the fire in the usual way, using a quality of coal which is adapted to the heater. 4. In operating the fire keep the fire-pot full of coal and shake down and remove all ashes and cinders as often as the state of the fire requires it. If a magazine heater is used it must be kept full of coal. 5. Hot ashes or cinders must not be allowed to remain in the ash-pit under the grate-bars, but must be removed at stated; intervals to prevent burning out of the grate. 6. To control the fire, see that the damper regulator is properly attached to draft-doors and damper; then regulate the draft by weighting automatic draft-lever as required, lightly or not at all in mild weather, but increasing as the weather be- coming colder. 7. Should the water in the boiler escape, by means of a broken gauge-glass or other mishap, it will be safer to dump the fire and let the boiler cool before letting in cold water. In no case should an empty boiler be filled wlien hot. If the water gets low, but not out of sight, in the gauge-glass, extra water may be added at any time by the means provided for this purpose. 8. Occasionally lift the safety-valve from its seat to see that it is in good condition. 9. Clean the boiler, if used in a gravity system of circulation, once each year by filling with pure water and emptying througl the blow-off pipe. If the steam is used largely for power, the boiler must be cleaned at frequent intervals. In case the; boiler should become foul or dirty it can be thoroughly cleaned by adding a few pounds of caustic soda and allowing it to stand one day, then emptying and thoroughly rinsing. Kero- sene oil will loosen boiler scale and not injure the boiler, but] SETTINGS AND APPLIANCES. I /I its odor will be quite likely to penetrate the whole building in which the heating system is located. 10. During the summer months the writer would recom- mend that all the water be drawn off from the system and that air-valves and safety-valves be opened, to permit the heater to dry out and remain so. Good results are, however, obtained by filling the heater full of water, driving off the air by boil- ing slowly, and allowing it to remain in this condition until needed in the fall. The water should then all be drawn off and fresh water added. 11. Keep the fire surfaces of the boiler clean and free from soot. For this purpose a brush is provided with most heaters. 12. In case any of the rooms are not heated, look out for the steam-valves at the radiators. If a two-pipe system, both valves at each radiator must be opened or closed at the same time, as required. See that the air-valves are in proper condi- tion. If a one-pipe system, one valve only has to be opened or closed. 13. If the building is left unoccupied in cold weather, draw all the water out of the system, which can only be done by opening blow-off pipe, all radiators, and air-valves. 101. Care of Hot-water Heaters. The general direc- tions for the care of steam-heating boilers, Article 100, apply in a general way to hot-water heaters as to the methods of caring for the fires and for cleaning and filling the heater. The special points of difference only need to be considered. All the pipes and radiators must be full of water and the expansion-tank should contain some water, as shown by the gauge-glass or by the pressure-gauge; and this condition should be determined before building a fire and whenever visiting the heater for the pur- pose of replenishing the fuel. Should any of the radiators not circulate, see that the radiator valve is open then open air- valve until the water runs out, after which it must be closed tight. Water must always be added at the expansion-tank when for any reason it is drawn from the system. 102. Boiler Explosions. Boiler explosions sometimes occur with disastrous results. They are not limited to boilers in which high-pressure steam is employed, but also occur in some instances with low-pressure boilers employed in heating. 172 HEATING AND VENTILATING BUILDINGS. The cause of a steam-boiler explosion is in every ease an excess of pressure above that of the strength of the boiler. The effect of this is primarily to rupture a part or portion of the boiler, relieving the pressure on the side of the rupture. This leaves unbalanced all the pressure acting on the opposite side of the boiler, which usually is sufficient to project the boiler into the air with considerable velocity. As showing the amount of force which exists even with small pressures we would have for each square foot of the boiler with 10 pounds pressure above the atmosphere a force of 1440 pounds per square foot of surface, applied to move it as a projectile. If the pressure were ten times as great the force would be ten times greater, and the effect many times worse. The disaster caused by the explosion would depend largely upon the sud- denness with which this force was applied ; if it were applied gradually no bad results might follow; if applied instantly the results might equal the explosion of a large amount of dyna- mite. Boilers sometimes explode because of defective mate- rial, poor construction, or overheating of parts ; they also some- times explode because of defects in the safety-valve or in the appliances for showing the true level of the water; but in all cases the immediate cause of the explosion is over-pressure. The causes which lead to the formation of steam with a pres- sure in excess of that of the strength of the boiler are vari- ous ; one of them is the practice of permitting the water in the boiler to get low and then supplying feed-water, which because of the highly heated condition of the surfaces is rapidly converted into steam, causing the pressure to become exces- sively high. It is not necessary to suppose that boiler explosions are caused by any mysterious force which is suddenly developed in the boiler. On the other hand, the amount of force which is stored in the hot water and steam is sufficient to produce at any- time a terrific explosion, provided the necessary opportunity is presented. Dr. R. H. Thurston has computed the energy stored in varius classes of boilers under the ordinary conditions of working, and the following table shows some of the principal results of that calculation and will give some idea of the enor- mous force stored in heated water and steam : SETTINGS AND APPLIANCES. 173 STORED ENERGY OF STEAM-BOILERS.* Type. Pressure, Ibs. per sq. in. \ . < 033 i Total Stored Energy Available. Energy per Ib. of Boiler. Foot-lbs. Maximum Ht.of Proj't'n of Boiler. Feet Initial Velocity. Total i. Plain cylinder. . . 2. Cornish cylinder. 3. Two-flue cylind'r 4. Plain tubular. . . . 5 Locomotive IOO 30 150 75 joe 10 60 35 60 C2C 47,281,898 58,260,060 82,949,407 51,031,521 54 O44.Q7I 18,913 3,43' 12,243 5,3/2 2,786 18,913 3,431 12,243 5,372 2 786 606 290 625 430 275 9. Scorch marine. . 10. . . ii. Flue and return . 13. Water tube ... . 14 " " 125 125 125 75 75 30 30 IOO IOO 650 6OO 425 300 350 2OO 1 80 250 2CQ 71,284,592 66,213,717 65,555,591 72,734,800 109,724,732 92,101,987 104,272,264 174,56^,380 2^0,870,830 2,851 3,219 4,077 2,687 2,889 1,644 1,862 5,067 5,130 2,851 3,219 4,677 2,687 2,889 1,644 1,862 5,067 CT-JQ 379 397 455 348 356 245 253 445 4.50 15. " " IOO 250 109,624,283 2,030 2,030 323 "Steam-boiler Explosions, in Theory and Practice," by R. H. Thurston. Considering the total number of heating-boilers in use in the United States the number of explosions is very small, so that if we suppose no improvement in construction over the ordi- nary methods, the risk which any person would run is very slight ; and it seems quite probable that if one were to use a heating-boiler as safe as the average boiler, the chances would be [that if he did not die until killed from this cause he would live to- be 10,000 years old. That is, estimating from the total number ; of boilers in use for heating, as compared with the number of explosions of such boilers, the chances are that one per year tin ten thousand would explode. Some disastrous explosions of heating-boilers have, how- ever, occurred in the United States, of which may be mentioned that at the Central Park Hotel, Hartford, Feb. 17, 1889, m which fifteen people were killed and the hotel entirely de- [stroyed ; also the boiler explosion at St. Mary's Church, Fort Wayne, Ind., in which the church and priest's house were nearly torn down, which occurred Jan. 13, 1886; another at Dell [Brown's Hotel, Eagle Bridge, N. Y., Dec. 20, 1888, in which [several people were injured and the building badly wrecked. Also various other explosions doing less damage. It would seem, from a study of the boilers which are in- [ jured by explosions, that no boiler is entirely free from the dis- 174 HEATING AND VENTILATING BUILDINGS. astrous effects of an explosion when it is badly managed; but on the other hand it also appears that the sectional boilers, or boilers in which the water occurs in small quantities, are subject to injuries which are comparatively slight and generally easily repaired. So far as the writer can find from a study of all the explosions recorded in the United States, the water- tube boilers, or those with small masses of water, are singu- larly exempt from disastrous explosion. They are, however, quite likely to have some part broken away, in which case the pressure on the boiler is relieved quickly enough to avert a serious explosion. The worst accidents which usually happen to the sectional boilers are those due to the burning out of a tube or some easily replaceable part. This results ordinarily in a very severe leak, which can, however, be repaired. The total number of boiler explosions for the United States for all classes of boilers average about 255 per year, and, as re- ported by the Locomotive, they have been as follows for the last ten years : BOILER EXPLOSIONS IN THE UNITED STATES. Year. Total No. Explo- sions. Station- ary, etc. Portable. Saw- mills. Railway Locomo- tives. Steam- boats. Total Killed. Total Injured. < 1884 152 48 18 56 15 15 254 26l 1885 155 80 16 33 10 16 220 288 1886 185 88 16 45 22 14 254 3 f 4 1887 198 67 2O 73 14 14 26 4 388 1888 246 104 30 69 23 20 331 505 1889 1 80 85 21 56 15 13 304 433 1890 226 94 16 75 25 16 244 35i 1891 257 "5 35 68 22 17 263 371 1892 269 122 24 79 33 II 298 442 1893 245 22O 151 1894 The following table gives the total number in Great Britaii for the same time : BOILER EXPLOSIONS IN GREAT BRITAIN. Years. 1882-83 1883-84 1884-85 1885-86 1886-87 1887-88 1888-80 Explosions. 45 41 43 57 37 61 67 Killed. 35 18 40 33 24 31 33 Years. 1889-90 1 890-9 1 1891-92 1892-93 Total... Ratio. . Explosions. 77 72 88 72 .. 660.... Killed. 21 32 23 20 313 ,d82 SETTINGS AND APPLIANCES. 175 This table would seem to indicate that the explosions in this country were more disastrous, so far as taking life is concerned, as in this country two people were killed for about every three ex- .plosions, whereas in Germany and Great Britain we have about twice as many explosions as deaths. This is probably due to the fact that the statistics in this country classify as boiler explosions only those which ?are markedly disastrous, whereas in France and Germany every leak or break which appears from this cause is recorded as an explosion. As showing the disastrous effects often produced by a boiler explo- sion, the following is abstracted from Thurston's Manual of Steam- boilers. room before the explosion. The boiler was made of T 5 ^ iron, was 3 feet in diameter, and was 7 feet high ; the upper tube-head was flush with the Fig. 170 shows the boiler- THE BoI1ER F F ^ R E ExPLOSION . FIG. 171. PATH TAKEN BY THE BOILER. top of the shell, the lower forming the crown of the fur- nace, which was about 2 feet above the grates and the base 17^ HEATING AND VENTILATING BUILDINGS. of the shell, and was flanged upon the inner surface of the furnace. There was a safety-plug in the lower tube- head which was not melted out. The working pressure was 60 pounds per square inch, and the explosion probably took place at or a little below this pressure,, throwing the boiler through the roof and high over a group of buildings and a tall; tree close by, finally burying itself half its diameter in the frozen ground. There had been a leak in the lower head which had reduced by erosion the thickness of the tubes and the lower head, so that the pressure was sufficient to force the lower head down away from the tubes, opening fifty or more holes 2 inches in diameter from which the fluid contents of the,' boiler issued at a high velocity, relieving the pressure belowj and converting the whole boiler into a great rocket weighing'; about 2000 pounds. 103. Explosions of Hot-water Heaters. While hot-; water heaters provided with an open expansion-tank are to a; great extent free from the dangers of explosions, still it is quite possible that extreme carelessness in erection, the freez-| ing up of connections to expansion-tank, or other mishaps, might render the apparatus fully as dangerous as the steam- boiler under its most unfavorable conditions. Some very disi astrous explosions have occurred of hot-water heating plants.- when operated under the Perkins or high-pressure system, and.: it seems quite probable that such a system, even under the^ most favorable conditions, is more dangerous than the steam* heating system. The hot-water heating system should be* constructed so that the connection between the expansion* tank and heater cannot by any possible means be closed! The placing of a valve in this connection was the cause of I very disastrous explosion in a residence in New York CitJJ quite recently, and emphasizes the necessity for caution in this respect. 104. Prevention of Boiler Explosions. Boiler explo-j sions are probably preventable in every single case by using, first, boilers properly designed, and constructed of excellent! SETTINGS AND APPLIANCES. 177 material and with good workmanship ; and second, by seeing that all appliances, as safety-valves, blow-off cocks, feeding apparatus, etc., are in excellent order ; and third, by providing skilled and intelligent attendance. Disastrous results are usually almost entirely prevented by the use of sectional boilers, and for heating purposes there !are at the present time comparatively few of any other kind in use. As a rule heating-boilers, especially those of small sizes, are not under close supervision, but are attended to and visited only at comparatively long intervals. For this reason automatic appliances for feeding the boiler and for regulating the pressure, opening and closing the dampers, are usually supplied ; hence the person erecting the plant should exercise ;the utmost care to see that such appliances are in excellent order and of such character as are likely to prove durable and reliable. While it is quite certain from our statistics that not one boiler out of ten thousand is likely to explode per year, yet nevertheless the contractor should always bear in mind that a steam-boiler is in every case a magazine of stored energy, and if badly constructed, poorly erected, or carelessly managed may do an immense amount of damage. CHAPTER IX. VARIOUS SYSTEMS OF PIPING. 105. Systems employed in Steam-heating. There are two systems of heating, in the first of which, known as the Gravity Circulating System, the water of condensation from the various radiators flows by its own weight into the boiler at a point below the water line ; in the second the water of con- densation does not flow directly into the boiler, but is returned by some special machinery or, in some cases, wasted. The second system is often called the High-pressure System, be- cause steam of any pressure can be produced in the boiler, a por- tion of which may be employed in operating engines, elevators, etc. It is very seldom, however, that this high-pressure steam is used in radiators, low-pressure steam being obtained directly from the boiler by throttling or passing through a reducing- valve, or, in some instances, indirectly by using the exhaust- steam from engines or pumps. In this chapter we shall discuss only the systems of piping used with gravity circulating systems of heating, reserving for a later chapter a description of the methods employed in the other system of heating, although there is in the arrange- ment of pipe lines very little which pertains to either system exclusively. 106. Definitions of Terms used. Certain terms have been adopted which are always used to describe definite parts in a system of piping, as follows : The main or distributing pipe is the pipe leaving the boiler or heater and conveying the heated products to the radiating surfaces. In steam-heating this is termed the main steam-pipe, and in hot-water heating the totain flow-pipe. It maybe car- ried from the boiler without branches to the top of the build- 178 VARIOUS SYSTEMS OF PIPING. 1/9 ing (Fig. 173), where the distributing-pipes are taken off, or it may run in a horizontal or vertical direction from the heater, and branch pipes taken off as required. The pipes in which i the flow takes place from the radiating surface toward the boiler are called return-pipes. The pipes which extend in a ; vertical direction are termed risers; when the flow in these pipes is downward they are called return-risers. A relief or drip is a small pipe run from a steam-main, so as to convey any water of condensation to the return ; it must be employed at all points where water is likely to gather. For illustration of use see Fig. 176. Pitch is the inclination given to any pipe when running in ; nearly a horizontal direction. In general the inclination or pitch of a supply-pipe should, in steam-heating, be downward from the boiler, and arranged so that the water of condensa- tion will move in the same direction as the current of steam. In hot-water heating the pitch should be upward from the boiler. In all return-pipes the inclination should be down- rward, toward the heater or boiler. A relay is a term sometimes used to describe a sudden change of alignment, or " jumping up," of a horizontal pipe. This is often necessary in a long line of piping to keep the pipe near the ceiling and preserve the necessary pitch. At such points a drip or relief must permit water of condensation to flow into the return. Water-line is a term used to denote the height at which the : water will stand in the return-pipes. It is usually very nearly the same as the level of the water in the boiler, being higher only in case there is considerable reduction in pressure due to friction. In heating with high-pressure steam it is desirable to have all the relief-pipes discharge into a return filled with water, so that circulation of steam shall be continuously in one direction ; this is of less importance with low-pressure steam, provided the water which gathers in returns can move freely and quickly to. the boiler. The term siphon is applied to a bend below the horizontal ; it is sometimes used in the main return to hold water at a dif- ferent level from that in the boiler. This is done by admitting steam to the top part of the bend on the boiler side by a relief ISO HEATING AND VENTILATING BUILDINGS, from the main steam-pipe. It is similar to the siphon-trap, Fig. 159, Article 98. If the relief were not connected to the top of the bend the water would pass over by suction into the boiler. Steam-traps are vessels designed with valves which open automatically so as to preserve the water-level in the re- turns at any desired point. Various kinds are described in Chap. VIII, Article 98. Water-hammer is a term applied to a very severe concus- sion which often occurs in steam-heating pipes. It is caused by water accumulating to such an extent as to condense some of the steam in the pipe, thus forming a vacuum which is filled by a very violent rush of steam and water. The water strikes the side of the radiators or pipes with great force, and often so as to produce considerable damage. In general a water-hammer may be prevented by arranging the piping in such a manner that the water of condensation will immediately drain out of the radiator or pipes. A bend in the return of a steam- or water-heating system, when convex upward, will frequently accumulate air to such an extent as to prevent circulation in the system. This is designated as an air-trap. When bends of this character must be used a small pipe for the escape of the air should be con- nected with the highest portion of the bend and led to some pipe which will freely discharge the entrapped air. An air-valve is not ordinarily to be recommended for such situations. 107. Systems of Piping. The systems of piping ordinar- ily employed provide for either a complete or a partial circulat- ing system, each consisting of main and distributing pipes and returns. Several systems of piping are in common use, of which we may mention : First, the complete-circuit system, often called the ojie-pipe system, in which the main pipe is led directly to the highest part of the building ; from thence distributing-pipes are run to the various return-risers, which in turn connect with the radiat- ing surface and discharge in the main return. The supply for the radiating surface is all taken from the return-risers, and in I' A RIO US SYSTEMS OF PIPING. 181 some cases the entire downward circulation passes through the radiating system. This system was employed by Perkins in his method of high- pressure hot-water heating, and is mentioned by Peclet as in use in France in 1830. In this country it seems to have been introduced into use by J. H. Mills, and is often spoken of as the Mills system of piping. The system is equally well adapted for either steam or hot-water heating, and on the score of posi- tiveness of circulation and ease of construction is no doubt to 182 HEATING AND VENTILATING BUILDINGS. be commended as superior to all others. It is principally ob- jectionable because the horizontal distribution-pipes have to be run in the top story of the building instead of the basement, which may or may not be of serious importance. Second, a partial-circuit system, in which the main flow-pipe rises to the highest part of the basement by one or more branches, from whence the distributing-pipes run at a slight incline, often nearly around the basement, and finally connect with the boiler below the water-line. The radiators are con- VARIOUS SYSTEMS OF PIPING. 185 nected by risers which carry both flow and return from and to the distributing pipes, as shown in elevation in Fig. 174 and in plan in Fig. 175. This method of piping is employed exten- sively for steam-heating, and is perhaps less open to objection than any other. Third, a system of circulation in which each radiator is pro- vided with separate flow- and return-pipes (Fig. 176). In this case the riser and distributing pipes are run as before, but are connected to the return by a drip-pipe ; the return is located 1 84 HEATING AND VENTILAJ^ING BUILDINGS. below the water-line of the boiler. The supply-riser from each radiator is taken from the main flow-pipe, and the return-riser is connected to the main return below the water-level. In case two connections are made to a radiator, one for supply and the other for the return, it is quite important that the connection of the return-riser to the main return be made below the water level of the boiler, in order to prevent steam flowing from two directions to the radiator. Such a condition is certain to cause VARIOUS SYSTEMS OF PIPING. 1 85 fater-hammer, as the radiator will retain water of condensa- ion. Various modifications of this third system have been used from time to time with greater or less success. For instance, ;ach radiator has in some cases been connected to a separate >w and return riser, and in other cases simply to a separate 'turn riser. These modifications are unimportant and hardly 'orthy of notice. 108. Methods of Piping Used in Hot-water Heating. A system of hot-water heating should present a perfect system of circulation from the heater to the radiating surface and thence back to the heater through the returns; an expansion-tank being provided, as explained, to prevent excessive pressure due to the heating and the consequent expansion of the water. The direct-circuit system, as described for steam-heating, Fig. 173, is well adapted for hot-water heating, and has been used to a limited extent. When this system is employed for hot-water heating two connections are usually taken off from the return riser at different levels for each radiator, as shown in Fig. 103, page 114; although in some cases a single connection is made and a radiator of ordinary form employed, otherwise the method of piping is exactly similar to that described for steam- heating. The system of piping ordinarily employed for hot-water heating is illustrated in Fig. 177. In this system the mains and distributing pipe have an inclination upward from the heater; the returns are parallel to the main and have an inclina- tion downward toward the heater, connecting at its lowest part. The flow-pipes are taken from the top of the main and supply one or more radiators. The return-risers are connected with the return-pipe in a similar manner. In this system great care must be taken to produce nearly equal resistance to flow in all the branches leading to the different radiators. It will be found that invariably the principal current of heated water will take the path of least resistance, and that a small obstruction, any irregularity in piping, etc., is sufficient to make very great dif- ferences in the amount of heat received in different parts of the same system. For instance, two branch pipes connected at opposite ends of a tee, which itself is connected by a centre 1 86 HEATING AND VENTILATING BUILDINGS. opening to a riser, are almost certain to have an irregular and uncertain circulation. The method of piping generally adopted for the closed or high-pressure system is that of the complete-circuit or one-pipe system, as illustrated in Fig. 173. .This system when now employed is used only for moderately low pressures, and a safety-valve is provided on the expansion-tank to prevent excessive pressure. In this system, or, in fact, in any of the systems for hot-water heating, the level of the return-pipe can VARIOUS SYSTEMS OF PIPING. I8 7 be carried below that of the heater without bad results. The lethod of applying this system is shown in Fig. 178, which is > n *i ^ w _ - ^r w o * 5 H ^ > G g." 2 > PJ -: B 5 similar in many respects to that used in the Baker system of ir-heating. The expansion-tank must in every case be connected to a ine of piping which cannot by any possible means be shut off from the boiler. It does not seem to be a matter of im- portance whether it is connected with the main flow or with 1 88 HEATING AND VENTILATING BUILDINGS. the return. The form of expansion-tank and the different kinds of fittings have been described in Art. 93, page 158. '"'""Single-pipe systems for hot-water heating have been used to some extent. In this case there is a gradual flow of the heated water to the top, and the consequent settlement of the colder water to the bottom. The form of piping would be essen- tially the same as that shown in Fig. 173 or 174. The writer erected such a system at one time as an experiment, and found that it worked well after the water had once become heated. Where, there is no objection to a system which heats slowly, this would probably do well on a small scale, but could not be recommended for an extensive job. 109. Combination Systems of Heating. Several methods have been devised for using the same system of piping alter- nately for steam or hot water as the demand for higher or lower temperature might change. The object of this is to secure the advantages which pertain to the hot-water system of heating for moderate temperature and to steam-heating for extremely cold weather. As less radiating surface is re- quired for steam-heating, there is the advantage due to reduc- tion in first cost. This may be of considerable moment, since \ a heating system must be designed of such dimensions as to be ; satisfactory in the coldest weather, and this involves the ex- penditure of a considerable amount for surfaces which are needed only at rare intervals. The combination system of hot-water and steam heating must require, first, a heater or boiler which will answer for either purpose ; second, the construction of a system of piping which will permit the circulation of either steam or hot water ; third, the use of radiators which are adapted to both kinds of ) heating. These requirements will be met in the best manner by using a steam-boiler provided with all the fittings required for steam- heating, but so arranged that the damper regulator may be closed off from the heater by means of valves when the system is needed for use in hot-water heating. The addition of an j expansion-tank is required, which must be arranged so that j it can be closed off when the system is required for steam- heating. VARIOUS SYSTEMS OF PIPING. 189 Of the different systems of piping, that designated as the complete-circuit or one-pipe system (Fig. 173) is the only one which is equally well adapted for both hot water and steam. In case that system cannot be conveniently installed, the one shown in Fig. 177 for hot water will be found to give fairly good results, it being objectionable in steam-heating only because of the fact that the condensation jn the main pipe flows against the current. The radiators and connecting pipes should be of the form required for hot-water heating, but the proportions and dimensions the same as for steam-heating. While this system has many advantages in the way of cost over the complete hot-water system, yet the labor of changing from steam to hot water will in some cases be troublesome, and should the connections to the expansion-tank not be opened, serious results would certainly follow. A combination hot-air furnace and hot-water system has been employed to considerable extent. In such a case the water-heating surface is obtained by inserting a coil of pipe or suitable vessel into the hot-air furnace, and certain rooms and portions of the house are warmed by the heated air directly from the furnace, while other parts are heated by the circula- tion of hot water. This system is an admirable one from every point of con- sideration, theoretically ; but practically it is a very difficult one to design and construct in such a manner that the supply of heat to the different rooms shall be positive and well dis- tributed. Fig. 179 shows the arrangement of such a system.* In this case the hot-air furnace supplies heat to the lower floors and the hot-water circulating system to the upper floors. Any system of piping suitable for hot-water heating can be employed for this purpose : the one shown is that of the com- plete-circuit or one-pipe system, the heated water being taken directly to the top of the building and all radiating surface supplied by the descending current. As the writer knows from experience, it is very difficult indeed to proportion the heating surface in the furnace and the radiating surface in the room so as to give in all cases satisfactory results without an * An admirable series of articles were written on this subject by J. W. Hughes, and appeared in Metal Worker, February' 1895. HEATING AND VENTILATING BUILDINGS. irregular and uncertain distribution of heat. It will generally be found that the fire maintained in a hot-air furnace is much more intense than that in a steam or hot-water heater ; and further, the heating surface which is usually employed is sub- jected to the full heat of the fire, consequently a smaller amount of heating in proportion to radiating surface must be FIG. 179. COMBINATION SYSTEM. HOT-AIR FURNACE AND HOT WATER. -employed. Whereas in the ordinary hot-water heater one foot of heating surface supplies from 8 to 10 of radiating surface, in this system I foot of heating surface will supply 25 to 35 feet qf radiating surface in coal-burning furnaces and 50 to 75 in wood-burning furnaces. Similar combination systems of hot air and steam are also used, but in such cases the heater must be very much like a steam-boiler, and possess all its appliances and also storage capacity for steam. In the case of the hot-water and hot-air system the heater is substantially a hot-air furnace, to which is added a coil of pipe or vessel of suitable form, which serves as the heating surface for the hot water, so that the change in construction is very slight ; but for steam-heating the change of construction must be more marked, and is likely to be more expensive and complicated. VARIOUS SYSTEMS OF PIPING. no. Pipe Connections, Steam-heating Systems. The manner in which branches are taken off may have great effect on the results obtained in any heating system, since any in- crease in friction in any part of the system will cause the flow to be sluggish in that portion, and require more press- ure to induce circulation. The size of pipes required in order that resistances may not exceed a certain amount are given in the next chapter; but it should be noted that bad workman- ship may defeat the operation of a steam-heating plant having the best proportions possible, and that great care is needed, (i) to secure the alignment of every part, (2) the absence of air- traps or any obstructions whatever which would reduce the circulation or make it irregular or uncertain. Some details which are to be considered rather as suggestions than as formal directions are given. In general, pipe connections should be made so as to afford 'as little resistance as possible to the flow of steam, and in such a manner as not to interfere with the expansion of $he main pipes. The line of piping should present the freest ^possible channels of circulation for the steam as it leaves the boiler and for the water of condensation as it returns. JTne expansion, which is not ^essentially different from if inches for each 100 feet in length, can usually be well provided for by the use of two or more right-angled el- bows substantially as shown tin Fig. 1 80. No general rule can be laid down for all cir- cumstances and conditions. The following examples and illustrations from Heating and Ventilation show the methods of piping commonly employed in setting steam-radiators with FIG. 180. CONNECTION TO RADIATOR one-pipe connections. Fig. 180 FROM STEAM MAIN - illustrates the method where the radiator is set close to the main and no special drip is required. IQ2 HEATING AND VENTILATING BUILDINGS. The method often employed in connecting a riser to a horizontal steam main and running a special drip-pipe for con- densed water to the return main is shown in Fig. 181. RETURN MAIN FIG. 181. CONNECTION TO RISER FROM MAIN AND RETURN. The method often employed in connecting radiators to risers is shown in the upper portion of Fig. 182. The lower portion illustrates an essentially different method from that! shown in Fig. 181 of connecting the riser to the main, and the drip-pipe to the return. This method, however, does not allow for expansion of the steam main ; hence this must be provided for in some other portion of its length. The area of the main pipe must in every case be equivalent in carrying capacity to that of all the branches taken off ; it consequently may be reduced as the distance from the heater becomes greater and as more branches are supplied. Table XVI., Appendix, gives the equivalent capacity of pipes of different diameters, and can be used in determining the rela- tive number of branches of a given size, and also the reduction;! in pipe area which may be made after a certain number of 1 branches have been connected. It will, however, in general^ be found, except when large pipes are used, less expensive to^ run the main full size than to use reducing fittings. VARIOUS SYSTEMS OF PIPING. I 9 3 in. Pipe Connections, Hot-water Heating Systems. If the system of circulation adopted is the complete-circuit system, as in Fig. 173, in which the heating main is first taken directly to the top of the building and thence run horizontally FIG. 182. CONNECTION OF RADIATOR TO RISER. to the various lines of return risers, the system of construction would be essentially the same as that described for a steam- heating plant. The main riser should connect into a drum, from the top of which the distributing-pipes leading to the return risers are taken. The size of the distributing-pipes should be proportional to the amount of radiating surface, and the various distributing-pipes should be arranged so that the resistance in each will be substantially equal. The flow connection for each radiator should be taken off at a point coout level with the top of the radiator, as in Fig. 103, IQ4 HEATING AND VENTILATING BUILDINGS. page 1 14, and the return should enter the same pipe at a point below the radiator. A valve affording as little resistance as^ possible is to be put in each connection. Hot-water heating systems have been erected in which the radiators are joined to the riser by one connection only ; and while this system seems to be somewhat slower in heating than that with two connec- tions, it is otherwise quite satisfactory. In the system commonly employed the main and distribut-1 ing pipes are erected in the basement, as shown in Fig. 177. An offset from the main to the foot of the riser has usually to| be made, which should be done as from the steam main in Fig. 1 80, and in such a manner as to take the flow from the upper part of the pipe ; such a connection is also shown in No. 3!] Fig. 183. The connection to the main return may be made on . j i h i FIG. 183. CONNECTIONS TO MAINS, HOT-WATER HEATING. the side or at the top, as convenient. In some instances a tee j turned at an angle and a 45-degree elbow can be used with good results, as shown at No. 2, Fig. 183. The method offj connecting shown at No. I should only be employed in case f the room is not sufficiently high for connections, as shown at No. 3, as its use is attended with doubtful success in many cases. In taking off branches from the top of a riser a tee should | seldom or never be employed, since it will be found that ifiii for any reason the current becomes established in one directioiil it will be very difficult to induce it to flow in the other|| When branches running in opposite directions have to be takefl|| from the main riser, long-radius tees, as shown in Fig. 5211 page 95, should be employed; but unless the riser is long it wiUpjj in general be better to erect a separate line for each branch|| Precautions should be taken in every case that the junction ofjili two currents shall not exert an opposing force which will imll pede the circulation. VARIOUS SYSTEMS OF PIPING. 195 The connections to radiators^ for this system need to be made in such a way that the horizontal branches which are taken off from the risers will receive a strong current of water. There is a tendency for water to flow directly in the line of motion, and to the highest radiators in the system. ^This renders it necessary to increase the resistance in the riser beyond the branch a greater or less amount in order to induce circulation into the side connections. This may be jdone in several ways, as shown in Fig. 184: (i) by connecting FIG. 184. CONNECTION TO RADIATORS, HOT-WATER HEATING. the radiator to an elbow placed on the main pipe and con- Etinuing the main pipe from the side opening of a tee or Y, las shown at A and B ; or (2) by using a reducing fitting, as [shown at C, and continuing the riser with a reduced diameter. The return connections can be made in a similar manner, but tthey will in every case work well if the return riser be run in a direct line and the connection be made into the side opening of a Y. 112. Position of Valves in Pipes. If a valve has to be used on a horizontal pipe it should be located so as to afford the least possible obstruction to the flow of water in the required direction. If a globe valve be used with the stem set vertically, Fig. 185, it will form an obstruction sufficient to fill the pipe very nearly full of water ; if the stem be placed in a horizontal direction the flow of water will be less impeded. Globe valves form a great obstruction to the flow in water-heating pipes, and under no circumstances should they be used for that work. In the case of steam-heating they are less objectionable, provided they are located in such a manner as to permit free drainage 196 HEATING AND VENTILATING BUILDINGS. of the pipes. In general, angle or gate valves can be used, however, in every place with better satisfaction. For hot-water heating special valves have been designed, FIG. 185. ILLUSTRATION OF WATER HELD BY GLOBE VALVE. which when open offer no special impediment to the flow, and which close sufficiently tight to prevent circulation, although not sufficient to prevent leaks. See page 88. 113. Piping for Indirect Heaters. Indirect radiators have been described and methods of setting them illustrated in Article 69, page 116. These radiators are gen- erally set in a case or box which is suspended from the basement ceiling and made of matched boards lined with tin, Fig. 186. The sides of the casing should be removable for repair of the radiator. The system of pipes which supply the indirect radiators are generally most conveniently erect- ed, like those shown in Fig. 175 or 177 for steam-heating, and like that shown in Fig. 179 for hot-water heating. The heater should be located above the water-line of the boiler a sufficient distance to afford ready means of draining off the water of con- densation. In case this is impossible, a style of radiator should FIG. 1 86. INDIRECT SURFACE. VARIOUS SYSTEMS OF PIPING. 197 be adopted which can be heated by water circulation. An automatic air-valve should be connected to the heater, and every means should be taken to obtain perfect circulation to and from the boiler. The chamber which surrounds the indirect surface is to be supplied with air from the outside by a properly constructed flue. The air passes up through or over the heater and into the rooms by means of special flues, the sizes of which are given in Chapter X. 114. Comparisons of Pipe Systems. As to the best sys- tem of piping to be adopted little can be said in a general way- The circuit-system, Fig. 173, no doubt gives the freest circula- tion and is applicable to either hot-water or steam heating. In some respects it is simpler to construct, and it seems quite probable that small errors of alignment, minute obstructions, and error in proportioning the pipes would not be so fatal to the perfect operation of this system as of the others. It requires, however, that distributing pipes be placed in the top story of a building, and this in many cases will be so objection- able that it cannot be used. Regarding other systems there is little to be said. For steam-heating there seems to be little or no use in making more than one connection to any radiator I and this practice, which is now common, will I think become universal. 115. Systems of Piping where Steam does not Return to the Boiler. For such systems the method of piping and of making connections would be in every case essentially as described ; and usually this can be done with less care because of the fact of greater difference of pressure between the supply and the return. Such systems are not often employed except in connection with use of exhaust steam, which is considered in Chapter XL 116. Protection of Main Pipe from Loss of Heat. The loss of heat which takes place from an uncovered main steam or hot-water pipe is, because of its isolated position, considerably greater than that which takes place from an equal amount of radiating surface. Unless this heat is actually required it will cause an expenditure of fuel the cost of which is likely to be in a few seasons many times that of a good cover- ing. 198 HEATING AND VENTILATING BUILDINGS. The heat lost per square foot of surface from a small un- covered pipe is from 375 to 400 heat-units per square foot per hour in steam-heating, or an amount equal to that required for the evaporation of 0.4 pound of steam. Computing this loss for 100 square feet for a day of 20 hours and for a season of 150 days, it will be found equivalent to the coal required to evaporate 120,000 pounds of steam; this would not be less than 12,000 pounds of coal, which at $5.00 per ton would cost" 30.00. The cost per square foot per annum will be found on the above basis to be 30 cents, of which 75 to 80 per cent* would have been saved by using the best covering. The loss from hot-water pipes would be about two thirds of the above. The best insulating substance known is air confined in minute j particles or cells, so that heat cannot be removed by convec- tion. No covering can equal or surpass that of perfectly still and stagnant air ; and the value of most insulating substances depends upon the power of holding minute quantities in suchl a manner that circulation cannot take place. The best known insulating substance is a covering of hair felt, wool, or eider- 1 down, each of which, however, is open to the objection that, if kept a long time in a confined atmosphere and at a temperature of 150 degrees or above, it becomes brittle and partly loses 1 its insulating power. A covering made by wrapping three or more layers of asbestos paper, each about -^ inch thick, on the pipe, cover- ing with a layer of hair felt f inch in thickness, and wrap- ping the whole with canvas or paper, is much used. This covering has an effective life of about 5 years on' high-pressure steam-pipes and 10 to 15 years on low-temperature pipes. There are a large number of coverings regularly manufactured for use, in such a form that they can be easily applied or removed if desired. There is a very great difference in the value of these coverings ; some of them are very heavy and j contain a large amount of mineral matter with little confined air, and are very poor insulators. Some are composed entirely of incombustible matter and are nearly as good insulators as hair felt. In general the value of a covering is inversely pro- portional to its weight the lighter the covering the better its VARIOUS SYSTEMS OF PIPING. 1 99 insulating properties ; other things being equal, the incombus- tible mineral substances are to be preferred to combustible material. The following table gives 'the results of some actual tests of different coverings, which were conducted with great care and on a sufficiently large scale to eliminate slight errors of observation. In general the thickness of the coverings tested was i J^i. Some tests were made with coverings of different [thicknesses, from which it would appear that the gain in in sulating power obtained by increasing the thickness is very slight compared with the increase in cost. If the material is a igood conductor its heat-insulating power is lessened rather [than diminished by increasing the thickness beyond a certain point. ^PERCENTAGE OF HEAT TRANSMITTED BY VARIOUS PIPE- COVERINGS, FROM TESTS MADE AT SIBLEY COLLEGE, CORNELL UNIVERSITY, AND AT MICHIGAN UNIVERSITY.* Relative Amount Kind of Covering. of Heat Transmitted. Naked pipe 100. [Two layers asbestos paper, I in. hair felt, and canvas cover 15.2 [Two layers asbestos paper, i in. hair felt, canvas cover, wrapped with manilla paper 15 . Two layers asbestos paper, i in. hair felt 17. Hair felt sectional covering, asbestos lined 18.6 One thickness asbestos board 59-4 Four thicknesses asbestos paper 50 . 3 ; Two layers asbestos paper , 77 . 7 Wool felt, asbestos lined 23.1 ; Wool felt with air spaces, asbestos lined 19.7 Wool felt, plaster paris lined 25.9 Asbestos molded, mixed with plaster paris 31.8 Asbestos felted, pure long fibre 20. i Asbestos and sponge , 18 . 8 Asbestos and wool felt 20.8 Magnesia, molded, applied in plastic condition 22.4 Magnesia, sectional iS.8 Mineral wool, sectional " . ICj . 3 Rock wool, fibrous \ 20 . 3 Rock wool, felted 20! 9 Fossil meal, molded, inch thick 29 . 7 Pipe painted with black asphaltum 105 . 5 Pipe painted with light drab lead paint 108 . 7 Glossy white paint 95. o * These tests agree remarkably well with a series made by Prof M. E. Cooley of Michigan University, and also with some made by G. M. Brill, Syracuse, N. Y., and reported in Transactions of the American Society of Mechanical Engineers, vol. xvi. 200 HEATING AND VENTILATING BUILDINGS. The following table translated from Peclet's Traite de la Chaleur gives in a general way the amount of heat transmitted through coverings of various kinds and of different thicknesses ; the loss from a naked pipe is taken as 100. LOSS OF HEAT THROUGH VARIOUS PIPE-COVERINGS. ti, | Thickness, in inches. "3 TJ C O u 0.4 0.8 I.O 1.6 2.0 4.0 6.0 Kind of Covering. 01 1 Relative Loss of Heat. 0.04 29 20 1 8 13 II 7 6 Eider down, loose wool, hair felt, etc. 0.08 43 3 2 29 23 20 13 ii Powdered charcoal. 0.16 56 48 45 38 35 25 22 Wood across fibres. 0.32 66 63 62 58 55 44 41 Sand. 0.64 73 73 73 72 70 68 Clayey earth. 1.28 77 83 85 92 96 102 109 Stone, rock. 2.56 78 87 103 no 130 150 White marble. 5.12 79 90 95 109 118 149 1 80 Solid gas carbon. 10.00 IOO IOO IOO IOO IOO IOO IOO Naked, or unprotected surface, iron* CHAPTER X. DESIGN OF STEAM AND HOT-WATER SYSTEMS. A 117. General Principles. The general problem of design includes the proportioning of, first, the amount of radiating surface which will be located directly in the rooms to be heated in all systems of direct heating, and in the air-passages or flues leading to the rooms in all cases of indirect heating ; second, the size of the pipes which are to convey the heated [fluids to the radiating surfaces ; and third, the proper size of boiler or heater. The question of the system or method of heating which is ;to be adopted will usually depend upon considerations of cost or of personal preference on the part of the proprietor. The various systems of heating, whether by steam, hot water, or hot air, as commonly practised in this country, do not often come in direct competition. Hot-air heating, where the air is moved by natural draft, is adapted only to the smaller sizes of dwelling-houses, and where heat does not need to be carried fkny considerable distance horizontally. It is generally found that if the horizontal distance exceeds 15 or 20 feet the supply of heat becomes uncertain in amount. With steam and hot- water heating there is no such limitation as to distance ; the first cost is, however, considerably greater than that of hot air, |t>ut heat can be supplied with certainty to all parts of the sys- tem under all atmospheric conditions. Regarding the relative merits of systems of steam and hot-water heating, little can be said. It will generally be found that the first expense of steam-heating is considerably less, and that there is considerable difference of opinion regarding the relative economy of oper- ation of steam and hot-water heating plants. The tests which have been made have generally shown somewhat in favor of 201 2O2 HEATING AND VENTILATING BUILDINGS. water.* The difference, however, is not great, and may due to local conditions, but is probably due to the fact that the temperature of the discharged gases may be somewhat lower for the hot-water heater than for the steam-boiler, and also to the fact that in comparatively mild weather the fire in the hot-water heater may be regulated somewhat closer, to meet the demand for heat. The hot-water system in general requires rather better workmanship in the erection of pipe' lines than steam-heating, and more care must be taken in pro-| portioning the various pipes and fittings. The heat from hot-| water radiators is somewhat less in intensity and more pleasant than that from steam-radiators, and the temperature can be regulated by simply throttling the supply-pipe of the radiators,i which is not the case with steam. Whether direct or indirect heating shall be used will de- pend also on circumstances. It will be found that in general the surface required for indirect heating is one third to one] half greater than that for direct, and it will give off 50 per cent; more heat per square foot, so that the operating expense isJ practically twice that of direct heating. Indirect heating asJ sures excellent ventilation, and it is advisable to use it for certain rooms of residences because of that fact. 118. Amount of Heat and Radiating Surface required for Warming. The amount of heat required for buildings cf various constructions has been considered quite fully in Chapter III. From which it may be seen (page 59) that in; ordinary building construction the amount required in heatl units, for each degree difference between inside and outside temperature, is approximately equal to the area of the glass surface plus one fourth the area of the exposed wall surfacel plus one fifty-fifth of the number of cubic feet of air required! for ventilation. The air required for ventilation will vary with the con- ditions ; but in direct heating it seems necessary to allow foil three changes per hour in halls, two in rooms on first floor, and one in rooms on upper floors. (See page 59.) * See Transactions American Society Mechanical Engineers, vol. x, paper by *he author. See also Report Massachusetts Experimental Station No. 8,4 1 870. DESIG'N OF STEAM AND HOT-WATER SYSTEMS. 2O3 The amount of heat given off ^by one square foot of radiat- ing surface, as determined by a great number of experiments, is given in Chapter IV, from which it is seen (pages 66 and 80) that for the ordinary radiating surface, with a temperature of 150 degrees above the surrounding air, 1.8 heat-units will be ;given off per square foot of surface per degree difference of temperature per hour, and when the temperature is no above the surrounding air about 1.7 heat-units are emitted. The total heat emitted from radiating surfaces of different characters, corresponding to the average results of experiments lis shown on the diagram, Fig. 187, in which the horizontal distances correspond to the mean difference of temperature between the air in the room and the radiator, while vertical distances, the value of which is read on the scale at the left, correspond to the total heat-units transmitted per square foot per hour. To use the diagram assume the difference of temperature between the air of the room and the radiator, then look on vertical line until intersection with the line representing the desired condition is found, thence read results on the left. Thus, for instance, if the difference of temperature is 150 de- grees the intersection of the line from this point with that representing direct ordinary radiation corresponds to 275 heat- units, and with that representing i-inch horizontal pipe, 375 heat-units, as read on the scale at the left. The dotted lines in the diagram give the heat transmitted from various indirect surfaces for different velocities of the moving air. The results are to be found as for direct radiation, but the difference of temperature is that estimated from the mean of the surround- ing air and the radiator. Having the total heat required for warming and that which is given off from one square foot of radiating surface, it is quite evident that the surface required may be computed by the process of dividing the former by the latter. Expressing results algebraically we can produce a formula from which the radiating surface may be calculated quickly and easily as follows : Let R equal the total radiating surface required, / the required tem- perature of the room, t' the temperature of the outside air, T the tern 204 HEATING AND VENTILATING BUILDINGS. units par square foot per hour 1 1 1 S 1 1 s 1 1 Diagram show n,T ital h aattr ansmitted per squar e foot per hour 71 1 \ rect Iheati direo't hea I? \ . ;ing yariou 5 velocities X In it fron idirec i mea t hea n ten ting, tpera diffe ;ure 'ence )f air ofte surrc mper undii ature to b g heater. i rect oned / / / / / 2 / / , "V' / / / 'V / 7 x / ^ // / / / X 1 . -j g 7 ,' / / Xj^' * / y / , x ' x x s / / AC, y % x' . x ^ ^ &; V< ;/ / / / x * j X^ ' / y >y / , / ^ x! x ' v x / x'' i y *\ / % / . 'V ' / / x ; y / $/ * y .- '' ! Second, the radiating surface is H multiplied by difference of temperature between room and outside air divided by that given off from one square Jt. Hence we have A> * ~ ^ u t t ( r , " T-T" 7T" * == T'r 7T L. -\- Lr {.* *)& (.* v)^\55 The heat required per degree difference of temperature between jrTuom and outside air, as expressed in equation (i), must be computed for |every given case. The other quantities which constitute a factor to be multiplied in the above are readily computed and expressed in the table on p. 206, which is calculated for a great variety of conditions. From this table it is seen that we need to multiply the area of the glass, plus \ the ^vall surface, plus of the cubic feet of mair supplied per hour, by factors which are approximately as follows: If we arc to heat to 70 degrees in zero weather with fsteam of 10 pounds pressure, multiply by ^ ; if we are to heat to 60 degrees, multiply by -J- ; if we are to heat to 50 degrees, multiply by |. As the steam pressures increase, these factors are reduced. As a method of applying the rule consider a ? room 20 feet by 12 feet floor surface, and 10 feet high, contain- ing 2400 cubic feet, in which the air is to be changed twice per hour. Suppose that it has 320 square feet of exposed wall I surface and 48 square feet of glass. The heating surface re- Equired will be found by taking the area of the glass, 48, J the exposed wall, 80, and -^ the cubic contents, which is equal to 87 ; the total heating surface required would be (48 + 80 -f- 187) 215, multiplied by the factor given in the table, which is about J, so that the radiating surface required equals 54 square feet. In this case there is about one square foot of heating surface to 44 cubic feet of space. OF THE UNIVERSITY Of 206 HEATING AND VENTILATING BUILDINGS. FACTORS FOR PROPORTIONING DIRECT RADIATORS FOR DIP FERENT TEMPERATURES ROOM AND OUTSIDE AIR. Number of Column. 1 2 3 4 5 Coefficients for Steam 1.6 x -7 1.8 i. 9 2.4 Temperature Temperature Air. Room. IO I OO .61 54 43 .31 .19 O 100 .55 49 .40 .28 17 + 10 100 50 .44 .36 25 .16 IO 80 .42 38 31 .23 .145 O 80 .38 33 .275 .20 13 + 10 80 33 30 .24 .18 .11 IO 70 35 32 .262 .19 .122 O 70 32 .28 -23 17 .109 + 10 70 .26 .24 .20 .14 .092 IO 60 .29 .26 .22 .16 .104 60 .25 .22 .19 .14 .089 * + 10 60 .21 .18 15 .12 075 IO 50 23 23 .18 15 .03 7 50 .20 .19 15 .12 .072 ^ + 10 50 .16 .14 .12 .10 .058 ' Usual conditions of steam-heating correspond to a mean of columns twof and three. HOT WATER. (.Coefficient 1.6.) Temperatures water 140 1 60 1 80 200 212 - 10 80 93 .70 56 47 42 80 .83 .62 50 .42 .38 + !0 - 80 73 54 435 36 33 IO 70 71 55 45 38 35 O 70 .62 47 .40 333 32 + 10 70 53 .41 34 .28 .26 IO 60 54 44 .41 3i .28 60 47 37 36 27 23 + 10 60 39 31 3i 27 .21 10 50 .41 33 .25 25 255 O 50 38 .28 30 .20 .196 -f 10 50 275 .225 .20 175 .156 1 The radiating surface is in each case found by multiplying heat as require to supply loss from building per degree difference of temperature inside am outside by factor as given in the table. This factor is in formula (2). DESIGN OF STEAM AND HOT-WATER SYSTEMS. For a room with the same dimensions but on the second floor the quantities will be computed in the same way, except that we will take -^ of the cubic contents to supply that re- 'quired by ventilation, so that the total heat required for one Kegree difference of temperature would be 48 -f- 80 + 44 = 172. One fourth of this quantity gives the radiating surface for low- Spressure steam-heating, which in this case would be 43, or one bquare foot of heating-surface to 55 cubic feet in the room. |For hot-water heating the method of computation would be exactly the same, but the factor would be 0.4 instead of J. the radiating surface would then be, for the case considered, |>.4 of 216, which is 86, or one to 28 cubic feet for a room on ihe first floor, and 0.4 of 172 or 69 square feet, which is in ratio of I to 35 cubic feet for -the second floor. Many designers of heating apparatus compute the amount of radiating surface required by approximate " rules-of-thumb " which are in current use in their localities. These rules differ In many cases very greatly from each other, and often have to pe modified materially in order to give satisfactory results. In {the application of the more scientific rules which have been given there will still always be an opportunity for applying Kudgment and the results of experience and practice, since it is Iquite impossible that any table of coefficients, no matter how extensive, could be given which would apply to all cases of (building construction and to all exposures. Allowance for un- lusual conditions are given by Mr. Wolff as follows (see page IS7)' The amount of radiating surface as given should be in- Icreased respectively as follows : 1 Ten per cent where the exposure is a northerly one and winds are to foe counted on as important factors. Ten per cent when the building is heated during the daytime only jand the location of the building is not an exposed one. Thirty per cent when the building is heated during the daytime only, land the location of the building is exposed. Fifty per cent when the building is heated during the winter months [intermittently, with long intervals (say days or weeks) of non-heating. Certain allowances, in addition to the above, the amount of iAvhich must be determined by the judgment or experience of 208 HEATING AND VENTILATING BUILDINGS. CRUDE ESTIMATE OF SPACE HEATED BY i SQ. FT. OF DIREC STXAM-HEATING SURFACE. A B c D E DWELLINGS. First floor a c to 60 }; to 50 Second floor 50 to 80 50 to 75 Average ...... . 60 to So CQ Living rooms eo CQ 2 sides ' ' 45 " " 40 Halls and bath-rooms. 40 to 5 65 to 90 j- 65 to 90 i 130 to 180 5- 130 to 180 Factories Stores, wholesale . . . " retail " dry-goods... " drugs Assembly halls 75 to 1 30 75 to 130 80 to zoo 80 to loo ation, but both of these quantities must be considered in order to give results which are even approximately correct. In any locality it would seem that the rules which are in common use when modified as to the condition of buildings n which they have been successfully applied would be of con- siderable value ; for that reason the preceding tables are given showing the relation of radiating surface to cubic feet of space to be heated as stated by various authorities ; it will be noticed, lowever, that there is such extreme variation in the amount of heating surface required for the same conditions that the results are almost valueless, and indicate that wide variation is common in the practice of different designers. 119. The Amount of Surface Required for Indirect Heating. For this case the heat received by the rooms is all supplied by air which passes over the radiating surfaces and is heated by convection. A large number of tests have been quoted of these heaters, both with natural and mechanical draft 210 HEATING AND VENTILATING BUILDINGS. (see Article 52, page 79). From these experiments it is seen that the amount of heat given off by one square foot of surface varies with the velocity of the air, as shown by the table on page 84 and also in the diagram Fig. 187, the use of which has been explained. From the table on page 84 it will be noticed that with natural circulation the velocity in feet per second will vary from 2.97 for a height of 5 feet to 8.4 for a height of 50 feet, and the corresponding convection expressed in- heat-units per degree difference of temperature per -square foot per hour, which in the preceding table is termed the coefficient^ varies from 3 to 6. The entering air is brought into the room usually at a temperature 20 to 40 degrees above that in the room. If this entering air is about IOO degrees, I heat-unit will warm 58 cubic feet I degree, an amount about 5 per cent greater than when the entering air was 70 (see Table VIII). From these data we can readily compute the number of cubic feet of air which must be supplied to bring in the neces- sary heat, and the size of heating-surface required. The amount of heat to be supplied must be sufficient to compen- sate for loss from the room, which is approximately equal to] the glass surface +^ the exposed walled surface multiplied byj the difference between the temperature of the room and the outside air, or it may be obtained more exactly from Wolff's' data, page 57. The number of cubic feet of air required will be found by dividing this quantity by the excess of temperature of the heated air over that of the air in the room and multiply- ing this result by 58. The extent of heating surface in square feet will be obtained by dividing the number of cubic feet of air as obtained by the previous calculation by the number of cubic feet heated by one square foot of surface. If air is heated to 100 F. each heat-unit will warm 58 cubic feet one degree. These results are better expressed in shape of formulae from which tables suited for practical application may be computed. Let / equal the temperature of the room, t' that of the outside air, t" that of the mean temperature of the air surrounding the heating surface, 7" that of the heated air, T'that of the radiating surface, //the heat required per houri per degree difference of temperature to supply loss from the room, a the DESIGN OF STEAM AND HOT-WATER SYSTEMS. 211 beat given off from i sq. ft. radiating surface per degree difference of temperature. We have the following formula : , Loss from the room per hour (/ t')H =(/ /') (G + W) nearly; (i)* ' Heat brought in by i cu. ft. of air 1/58(7^' /) ; ...... (2) Heat given off from i sq. ft. of radiating surface per hour = a(T-n\ (3) '. Cubic feet of air required per hour = - ; ..... (4) Cubic feet of air heated by i sq. ft. of radiating surface per hour = 1*58(7""?) (see Artide 3'. page 39); . (5) if _ t'}(T' _ Radiating surface = , _ t . (T _ ',, = (Factor as in table) H; . (6) The table,* page 212, computed from the above formulae for [various conditions gives a series of factors which, multiplied pnto the building loss H per degree difference of temperature, prill give the radiating surface required ; it also gives the num- fcer of cubic feet of air heated the required amount per square foot of radiating surface per hour. To use the table, we need simply to know, in addition to ^temperatures, the probable coefficient of heat transmission, "all other conditions being given. For ordinary indirect heat- Ing, first floor, the velocity of air can be considered as 2 to 4 -feet per second, and the corresponding value of this co- 'efficient as 2. For higher floors the velocity is higher, and co- efficients may be taken as 3. (See page 84.) As an example, ^assume outside temperature zero, inside temperature 70, and the air leaving the indirect at IOO, the factor with which to multiply the building loss to obtain radiating surface is 0.69. : This is practically 3.00 times that for direct heating. Com- puting the radiating surface required for the same room as that considered in the case of direct heating (page 206), in which there was 48 square feet of glass and 320 square feet of exposed wall surface, and in which the total loss of heat per degree difference of temperature was 128 heat-units, the indi- rect surface required would be this quantity multiplied by the factor 0.69, which is 88 square feet, or about one half more than required in the calculation for direct heating. For the * In the table the term coefficient is used for the heat transmitted per degree 212 HEATING AND VENTILATING BUILDINGS. TABLE OF FACTORS TO OBTAIN INDIRECT HEATING SURFACE AND OF CUBIC FEET OF AIR HEATED PER SQUARE FOOT * OF SURFACE PER HOUR. Temperatures. B. T. U. Total Heat per Sq. Ft. Heater. Factors for Heater Surface.* Cu. Ft. Air per Sq. Ft. Heat. Surf, per Hour. be c 4f fc.l C m 4- vd M w n 4 vd M oi A *- 8 "o 3 U <"S Q g c i .1 c c c c c | c u c 1 C V c u c TJ u 1 S JE 1 S JE i i !fi u < *** | S - a i u U d a 5 a $ U i u 8 u i u 8 u 3 G O U T' t" 7-' - t" (i) (2) (3) (4) (6) (5) (6) (7) (8) (9) (10) (") (12) (13) (14! ROOM 70 FAHR., OUTSIDE AIR o FAHR., STEAM PRESSURE o LBS., STEAM" TEMPERATURE 212 FAHR. 90 45 167 167 334 SOi 668 1000 I.Q2 0.96 0.64 0.48 0.32 108 216 324 432 648 100 50 162 162 324 486 648 972 *47 o-73 0.49 0.36 0.24 Q4 188 Q2 37 6 5 6 4 no 55 157 157 314 47i 628 042 I.24J0.62 0.41 O 3I'O.2I 88 176 264 3S2 SV8 120 60 IS 2 152 34 456 608 912 1.100.55 0.37 0.28 0.18 73 147 22O 394 44 ROOM 70 FAHR. OUTSIDE AIR o FAHR., STEAM TEMPERATURE 219" FAHR. PRESSURE 5 LBS., STEAM go 45 174 174 348 522 696 1062 1.72 0.86 o.si 0-43 0.28 112 224 336 44 8i 672 loo 50 169 169 338 507 676 1015 1.38 0.69 0.46 0-34 0.23 196 294 392 788 IIO 55 164 164 328 492 056 934 1.18 0.56 0.39 0.29 o. 19 86 173 260 346 S20 120 60 159 159 477 636 954 r.i6 o-53 o-35 0.27 0.17 77 231 3 o8 4 62 ROOM 60 FAHR., OUTSIDE AIR o FAHR., STEAM PRESSURE o LBS., STEAM TEMPERATURE 212 FAHR. 344 334 326 ROOM 70 FAHR., OUTSIDE AIR o FAHR., HOT WATER AT TEMPERATURE 160 FAHR. 80 40 172 172 90 45 167 167 IOO 50 162 162 no 55 157 J57 1 688 1032 668:1020 1.66 i . 16 0.83 0.55 0.41 0.58 0.29 o 29 0.27 o. 19 I2 5 108 250 216 375 3 2 4 500 332 75 64 480 652! 972 o.93 0.46 0.31 0.23 0.15 94 188 282 376 56 461 628 922 0.89 0.42 0.28 0.21 O.I 4 83 166 249 332 49 90 IOO 45 50 "5 IIO 115 IIO 230 345 220 330 4 60 440 690 660 2.8 2.12 1:^6 0.93 0.70 0.7 0.46 0-530.35 74 64 148 128 222 IQ2 206 2 S 6 IIO 55 105 105 2101 315 4 20 630 i.8b 0.93 0.62 0.4610.32 SS no 165, 220 1 20 60 IOO IOO 2OO; 3OO 4OO 600 1.68 0.83 1 1 480 97 MS 194 ROOM 70 C FAHR , OUTSIDE AIR o FAHR., HOT WATER AT TEMPERATURE 180 FAHR. 90 45 135 135 270 405 540 810 2.36 1.18 0.7810.570.39 87 X 74 261 348, 5 2 IOO 50 130 130 2(X> 390 S20 780 T. 78 0.89 0.590.540.29 75 ISO 22S 300! 4S IIO 55 125 I2S 2 SO 37S Soo 75 i-55 0.72 0.52 p.39'o.26 66 132 198 264 3 g 120 60 1 20 1 2O 240 3 6o 480 720JI.4 o-7 o.47Jo.35jo.23 5 116 174 232) 34 difference of temperature per square foot per hour. Coefficients i to 4 corre- spond to ordinary indirect heating. *To find surface of heater multiply loss from room for one degree difference of temperature by the factor for the given condition. Results computed by formula (6). . DESIGN OF STEAM AND HOT-WATER SYSTEMS. 21$ second and third stories the factors are to be found in the column in which the coefficient is 3. The following table gives the number of cubic feet of air required per hour in indirect heating to maintain the proper temperature, as computed by formulae (4), for each heat-unit rlost from walls and windows of room for a temperature of 60 or 70 above outside air. The total air required will be found my multiplying the values, as given in the table, by the total heat lost per degree difference of temperature from the room. iDiis loss is designated by H in formulae (4), and is approxi- mately equal to the glass plus the exposed wall surface ex- pressed in square feet. (See page 59.) CUBIC FEET OF AIR PER HEAT-UNIT FROM WALLS. Temperature of Room, Temperature of Entering Air above that of Degrees Fahr. Room. 60 70 IO 34S 406 2O 174 203 30 116 135 40 3? 103 50 70 Si 60 53 63 70 49 58 80 44 5i 90 36 45 IOO 35 4i Thus to find the number of cubic feet of air required to \ warm a room to 70 in zero weather, in which the glass plus Kone fourth the exposed wall surface equals 128, and air is in- i troduced 30 above that in the room, multiply 135, as given in ; the table, by 128. It is usual to allow 50 per cent more surface for indirect than for direct heating, although some engineers allow only i 25 per cent more. In concluding this subject it may be remarked that the amount of heat which is given off from indirect heating surfaces would seem from the experiments to depend largely 214 HEATING AND VENTILATING BUILDINGS. on construction. With the surface erected closely together the amount is small. By better arrangement of the surfaces, so that all parts are made hot, and an ample opportunity is provided for circulation of the air, the coefficient of heat trans- mission may be much increased. If extended-surface radia- tors are used and the entire surface figured as effective, the coefficient should be taken about 10 per cent less than assumed by the writer in the computation. For forced draft the coef- cient may be safely taken as 4 and 6, or about 100 per cent greater than for natural circulation. The following tables are collected from various authorities, and are of interest as showing character of " rule of thumb " practice in providing indirect heating surface for rooms of various kinds. It will be noted that the amount specified for the same work differs more than 50 per cent, which shows the crudeness of estimates of this character. CRUDE ESTIMATE OF SPACE HEATED BY i SQ. FT. OF INDI- RECT STEAM-HEATING SURFACE. Authority K. A. B. c D DWELLINGS : First floor 20 to "^ 2C to 1=; 40 to 50 4O to co Average . . . 40 4.0 to c,o 1Q Living-rooms . . . One side exposed. . . . Two sides exposed... Three sides exposed . Halls and bath-rooms 50 to 70 50 to 70 Sleeping-rooms PUBLIC BUILDINGS : Offices 60 j 20 to 35 ) 40 to 50 60 Banks 60 \ 40 to 50 j" See DWELLINGS 40 to 50 60 School-rooms See DWELLINGS 4.O tO 5O Factories . . . 50 to 70 50 to 70 Stores, wholesale. . . . TOO 70 70 IOO " retail 80 CQ CQ to 7O 80 " drv-goods. . . . 7 70 " drugs 60 60 80 to i^c, ioo to 140 Auditoriums 80 to 135 ioo to 140 Churches JCQ 80 to i^t; ioo to 140 I CO IOO IOO DESIGN OF STEAM AND HOT-WATER SYSTEMS. 21$ CRUDE ESTIMATE OF SPACE HEATED BY i SQ. FT. OF INDI RECT HOT-WATER HEATING SURFACE. Authority F. A. TJ c DWELLINGS: First floor jc to 2$ j 15 to 30 30 to 60 I 14 to 20 20 to 30 1 15 to 40 2O to 40 f 20 to 30 Third " 20 to 30 Living-rooms ... IS tO 25 One side exposed Two sides exposed Three sides exposed.. .. Hall and bath rooms. . . Sleeping-rooms 10 to 20 PUBLIC BUILDINGS: Offices 25 to 40 j 15 to 30 30 to 60 Banks ( 15 to 40 20 to 40 School-rooms .... 25 to 40 3 15 to 30 30 to 60 Factories 25 to 40 1 15 to 40 j 30 to 45 20 to 40 35 to 75 Stores wholesale. . . 2^ tO 4O t 25 to 50 3 30 to 45 25 to 50 35 to 75 " retail 25 to 40 ( 25 to 50 25 to 50 " dry-goods " diugs Assembly halls Auditoriums 50 to 80 5O to 80 j 30 to 45 / 25 to 50 j 50 to loo 35 to 75 25 to 50 70 to 150 Churches 50 to 80 ( 50 to 100 j 50 to 100 50 to ioo 70 to 150 Large hotels I 50 to ioo 50 to ioo 120. Summary of Approximate Rules for Estimating: Radiating Surface. As the temperature required for build- ings of various classes varies but little, and as the heating sur- face is usually estimated to be sufficient to heat buildings during zero weather to a temperature of 70 degrees, some very simple rules can be given which are founded on a rational basis, and which with certain modifications, as explained (page 57), for those which are especially exposed, will be found to give good results in practice which agree closely with those used by the best heating engineers. They are as follows : First. The amount of heat required to supply that lost from the room per degree difference of temperature is approxi- mately equal to the area of the glass in square feet plus 1/4 the exposed ti'all surface. (See page 59.) 216 HEATING AND VENTILATING BUILDINGS. Second. The heat necessary to supply loss from ventilation for dwelling-houses, first floor, is 2/55 of the cubic contents per hour for living-rooms ; 3/5 5 f the cubic contents for halls ; 1/55 of the cubic contents for upper stories. For churches, auditoriums, the loss to supply ventilation should be t.iken as 3/55 to 6/55 of the cubic contents; for offices, banks, etc., 1/55 to 2/55 of the cubic contents, depending upon circumstances. Third. To find the radiating surface for direct steam-heat- ing, multiply the sum of the numbers as given by rules First and Second by 1/4. Fourth. To obtain the radiating surface for direct hot- water heating, multiply the sum of the numbers as given by rules First and Second by 0.4. These rules may both be summed up in the following concise form : RULE. For heating to 70 degrees in zero weather, direct heating : Radiating- surface is equal to the sum of the glass sur- face plus 1/4 the exposed wall surface plus 1/55 to 3/55 the cubic contents, for rooms as explained, multiplied by 1/4 for low- pressure steam-heating or by 0.4 for hot-water heating. NOTE. When air is introduced at 100 degrees Fahr., 58 should be used instead of 55. This difference is, however, usually negligible. For indirect heating the following rules will give quite satisfactory results when the temperature of the room is to be maintained at 70 with outside air at zero and the heated air brought in at a temperature 30 above that in the room. In this calculation the surface of the steam radiator is sup- posed to be 212, that of the hot-water radiator 170 Fahr. The coefficients are taken from the preceding table. RULE. The radiating surface for indirect heating is equal to the glass surface plus one fourth the exposed wall surface in square feet multiplied by the following factors: Steam-heating. Hot- water Heating. 1st story 0.7 1.05 2d " 0.6 0.9 3d " 0.5 0.8 The total amount of air supplied will be given by the fol- lowing DESIGN OF STEAM AND HOT-WATER SYSTEMS. 2 1/ RULE. The air in cubic feet per hour is found by multi- plying the radiating surface, computed as in above rule, by the following factors : Steam -heating. Hot- water Heating. ist story 200 125 2d *' 250 160 3d " 300 200 If this is insufficient for ventilating purposes more air must introduced, which must be heated to 70 F., and this will require approximately an additional foot of surface for each additional 250 cubic feet of air heated by steam, or for each additional 150 cubic feet heated by hot water. These rules will be found quite simple in application, and they may be easily committed to memory. For rooms which are poorly constructed or especially exposed these results should be increased the same proportional amount as for direct radiating surfaces. For temperatures lower or higher than 70 the table of factors p. 212 may be used with facility. 121. Flow of Water and Steam. It seems necessary to say a few words respecting the general laws which apply be- fore considering the practical application. The velocity with which water flows in a pipe is computed from the same general laws as those applying to the fall of bodies. The velocity is 1 produced, however, not by actually falling through a given distance, but by a difference of pressure, which must be ex- pressed, not in pounds per square inch, but in feet of head. This head is in every case to be found by multiplying the dif- ference of pressure by the height required for the given fluid to make one pound of pressure. If we denote by // the difference of head as described, by^ the force of gravity == 32.16, by v the velocity in feet per second, we would have in case of no friction v \2gh. The quantity discharged per second would be found in every case by multiplying the velocity by the area of the ori- fice in square feet. In the flow of water in pipes there is considerable friction, 218 HEATING AND VENTILATING BUILDINGS. which acts to reduce the velocity and the amount discharged ; this increases with the length and decreases with the diameter of the pipe. For the actual flow we depend upon experi- mental results. An approximate formula, attributed by Robert Briggs* to Prof. Unwin, which is sufficiently accurate for computing the flow of water in pipes is as follows : Let v = the velocity in feet per second, Fthe velocity of feet per minute, q the quantity discharged in cubic feet per second, Q = that discharged per minute, / = the length of pipe in feet, h the head in feet, D the diameter in feet, d = the diameter in inches. = 0.0448 ; . = 4.7233 The friction caused by bends and by passing throng] valves and into entrance of pipes is of considerable amount and often requires consideration. It can be considered a producing the same resistance to flow as though the pipe hac been increased in length certain distances as follows : go-degree elbow is equivalent to increase in length of the pipe 40 diam eters, globe valve 60 diameters, entrance of a pipe in tee o elbow 60 diameters, entrance in straight coupling 20 diameters The flow of steam in pipes presents some problems slightly different from that of flow of air (Articles 31 and 32), but ii many respects the two cases are similar. There is a tendency for the steam to condense, which changes the volume flow ing and affects the results greatly. The effect of condensa tion and friction is to reduce the pressure in the pipe an amount proportional to the velocity and also to the distance and these losses are greater as the pipe is smaller. There * Steam-heating for Buildings, p. 75, by Briggs. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 2IQ seems to be very little exact data regarding the steady flow of steam in pipes, and it has been customary for writers to assume that the same laws which apply to the flow of water hold true in this case, and that the same methods can be used in com- puting quantities. These results are certainly safe, although .no doubt giving sizes somewhat larger than strictly necessary for the purposes required. In estimating the size of steam-pipe for power purposes it is customary to figure the area of cross-section, such as giving m velocity of flow not exceeding 100 feet per second. This ^velocity is generally accompanied by a reduction of pressure ,in a straight pipe of about one pound in 100 feet. For steam- peating purposes the general practice is to use a much larger pipe and lower velocity, so that the total reduction in pressure on the whole system is much less ; the effect of a drop in pres- pure of one pound will cause the water to stand in the return fcipe in a gravity system 2.4 ft. above the water-level in the boiler. The velocity of water and steam in a gravity system of Bleating is due to a different cause from that in the case just considered, for the reason that the pressure upon the heater iacts uniformly in all directions, and exerts the same force to pre- ^vent the flow into the boiler from the return, as to produce the flow into the main. For such cases the sole cause of circula- rtion must be the difference in weight of the heated bodies, hot water, or steam in the ascending column and the cooler and 'heavier body in the descending column. The velocity induced by a given force will be reduced in proportion as the mass Amoved is greater. In the case of steam-heating the difference between the weight in the ascending and descending column is so great that the velocity will not be essentially different ^frorn that of free fall, provided correction is made for loss of head due to friction, etc., as Explained, but in case of hot water the theoretical velocity produced will be found very small. The case is very similar to the well-known problem in mechanics in which two bodies A and B of unequal weights are connected by a cord passing over the frictionless pulley C (Fig. 190). 220 HEATING AND VENTILATING BUILDINGS. The heavier body in its descent draws up the lighter body A. Ir this case the moving force is to the force of gravity as the difference in the weights is to the sum of the weights, ant the velocity is the square root of twice the force into the height. In other words, if/ equals the moving force, we haw- by proportion f\g\\ B A : B + A, from which _ B .~ A f ~ g B + A' which, substituted in place of /in formula v = t/2///, gives the following as the velocity : h being the height fallen through. In applying this to the case of hot-water heating we have, instead of the descent and ascent of two solids of different weights, the descent and ascent of columns of water connected as shown in Fig. 191, the heated water rising in the branch AJ^ and the cooler water descending in the branch BC. The force which produces the motion is the difference in weight of water in the two columns; the quantity moved is the sum of the weight of water in both columns. This is equal to the difference in weight of i cubic foot of the heated and cooled water divided by the sum, multiplied by the total height of water in the system, so that if W\ represents the weight of i cubic foot in the column BC, and W represents the weight of i cubic foot in the column AF, and h represents the total height of the system, then the velocity of circulation will be, in feet per second, (W, + W) FIG. 191. CIRCULATION IN HOT- WATER PIPES! In this formula no allowance whatever is made for frictioil consequently the results obtained by its use will be much in excess of that actually found in pipes. The amount of fric| tion will depend upon the length of pipe and its diameter! As result of experiment the writer found considerable variation DESIGN OF STEAM AND HOT-WATER SYSTEMS. 221 in different measurements of velocity, but in no case did he find a velocity greater than that indicated by the formula. The following table is calculated from the formula without allowance for loss by friction. The computation is made with the colder water at 160 degrees F., although little difference would be found in calculations at other temperatures. VELOCITY IN FEET PER SECOND IN HOT-WATER PIPES. o c "* u Difference of Temperature. 28 2 fl* !- i 5 10 15 20 30 4 o i 8.03 0.107 0.242 0-335 0.412 0.478 0-593 0.672 5 17.9 0.232 0.541 0.750 0.922 1.09 1-33 1.51 10 25-4 0.328 0.765 1. 06 1.32 1-55 1.88 2.14 20 35-9 0.463 1.085 I.Jj 1.85 2.19 2.66 3.01 30 43-9 0.567 i-33 1.8 3 2.26 2.68 3-26 3-71 40 50-7 0.656 i-53 2.12 2.61 3.08 3-76 4.26 50 56.7 0.732 1.71 2-37 2.82 3-47 4.22 4-77 60 62.1 O.8O2 1.88 2-59 3.20 3-79 4.62 5.22 70 67.1 0.866 2.02 2.80 3-45 4.08 4-97 5.65 80 71.8 0.925 2.16 3-o 3-69 4-37 5.32 6.03 90 76.1 0.932 2.27 3.18 3-91 4.64 5-64 6.41 100 80.3 1.037 2.42 3-35 4.13 4.78 5-93 6.72 This table is of interest for the reason that most computa- tions of the velocity of circulation of hot water have entirely neglected the effect that the mass or weight of the water moved has on the velocity, and hence the results as computed have been many times greater than actually found. The method usually employed in computing this velocity has been to consider the denser and lighter fluids occupying the relative positions shown in Fig. 192, the lighter fluid being in one branch of the U tube, the heavier in the other.* If the cock be opened, equilibrium will be established, and the lighter liquid will stand in the branch higher than the heavier a distance sufficient to balance the difference in weight. If we suppose (i) the cock closed and * See Hood's work on " Warming Buildings," page 27. So far as the writer knows, this theory has not before been questioned. 222 HEATING AND VENTILATING BUILDINGS. enough of the heavier material added to the shorter column, that the heights in each are the same ; (2) the cock opene< then the heavier liquid will move downward and drive the lighter liquid upward with a velocity said to be equal to that; which a body would acquire in falling through the distance equal to the difference in heights when the columns were in; equilibrium. This gives too great results, because it neglects- the effect of the mass of the bodies moved. If friction be con- sidered, we should have as a probable expression of velocity^ using the same notation as on page 218, = qo A^- W}hV V W+ W} I ' 122. Size of Pipes to supply Radiating Surfaces. Thef method of computing the size of pipes required for stearrl heating would be as follows : First find the amount of stearrl by dividing the total number of heat-units given out by \\ square foot of radiating surface by the latent heat in I pound? of steam, this will give the weight of steam required per square! foot; this multiplied by the number of cubic feet in I pound] of steam will give the volume which will be required for eachj square foot of radiating surface. Knowing this quantity thel size of pipe may be computed from the considerations already] given, either by formulae of Article 121 or by assuming the! velocity of flow as equal that due to the head, corrected for friction ; 25 to 50 feet per second can in nearly every case be' realized. As an illustration ; compute the size of main steam-j pipe required to supply 1000 feet of radiating surface with: steam at a temperature of 212 degrees when the surrounding^ temperature of the air is 70: For this case I square foot of radiating surface can be assumed ordinarily as giving off| (1.8 times 142) 255 heat-units. To supply 1000 feet of surface! 255,000 heat-units per hour would be required ; as each pound] of steam during condensation (see steam table) will give up! 966 heat-units, we will need for this purpose 264 pounds per] hour; and as each pound of steam at this temperature makes 26.4 cubic feet, we will require 6970 cubic feet of steam per hour, or 1.94 cubic feet per second. If we proportion the pipes so that the velocity shall not] DESIGN OF STEAM AND HOT-WATER SYSTEMS. 22$ exceed 25 feet per second, the area of the pipe must be 0.077 square foot, which equals n.i* square inches. For this we would require a pipe 4 inches in diameter. If we had as- sumed the velocity to be 50 feet per second, the area would Save been 5.6 square inches and the diameter 3 inches ; if we had assumed a velocity of 100 feet per second, the area required fwould have been 2.8 square inches and the diameter of the :pipe required would have been somewhat less than 2 inches. tThe friction in a pipe when steam is moving at a velocity of ^100 feet per second causes a reduction in pressure of about ij ^pounds in 100 feet, a velocity of 50 feet per second causes about J as much, and a velocity of 25 feet about T ^ as much. ^Indirect surfaces of the same extent usually require twice as ? irmch steam and a pipe with area twice as great as that needed for direct radiation. For the single-pipe system of heating an additional amount pf space must be provided in the steam main to permit the freturn of the water of condensation. The actual space occupied by the water is small compared with that taken by the steam, 'but in order to afford room for the free flow of the currents lof water and steam in opposite directions, experience indicates ^that about 50 per cent more area should be provided than is re- jfquired in the separate return or double pipe system of heating. By similar computations we obtain the following factors, which are to be multiplied by the radiating surface to obtain areas and diameters of steam-heating mains in inches : TABLE FOR AREA AND DIAMETER OF STEAM-MAIN. Velocity of steam, feet per second. (i) Multiply each 100 sq. ft. radiating surface for area steam main by () Multiply sq. root radiating surface for diam. by (3) Probable fric- tional resist- ance per ioo ft., inches water. < 4) Required steam pressures. Lbs. (5) 25 37-5 50 62.5 75 100 Double-pipe system. .90 .675 45 375 -30 .225 Single-pipe system. 1-35 1. 01 0.67 0.56 0-45 0-34 Double-pipe system. .107 .052 .075 .069 .062 .054 Single-pipe system. -131 113 .092 .090 075 .066 2.O 6.0 8.0 12.6 18 32.0 * o to i 2 to 3 3 to 4 4 to 5 5 to 6 6 to 40 In all cases if the mains are not covered, its surface is to be estimated as a part of the radiating surface. * This quantity is greater than the area of a 3^-inch pipe, and in such case the safe proceeding is to use the next greater size. 224 HEATING AND VENTILATING BUILDINGS. The table on page 223 gives in the first column the velocity of steam, in the second column the corresponding area of pipe in square inches required for each 100 square feet of radiating surface for the double and single pipe systems of heating, in the third column the diameter of pipe for each square foot of radiating surface for both systems of heating, which latter is to be multiplied by the square root of the given radiating surface, to obtain the diameter required. Column 4 gives the approximate back pressure in inches of water per 100 feet ini length of the main for steam having the same velocity as inj column I. Column 5 suggests steam-pressures which will render any of these values satisfactory in practice. As an example showing use of table, suppose that a main pipe to supply 650 square feet of radiating surface is needed in a single-pipe system in which the back pressure shall be about 12 inches of water-column per 100 ft. of length. The assumed resistance is found in column 4 and corresponds to a velocity of about 62.5 feet per second. Column 2 gives the factor for the area of pipe as 0.56, which, multiplied by 6.50, gives 3.64 sq. in. as the required area. The diameter can be obtained from this result or computed by; multiplying the square root of the radiating surface by the number in column 3. The square root of 650 is 25.4. This multiplied by 0.09 gives the diameter required as 2.3 in. For this case a 2^-inch pipe must be used. For the double-pipe system, the factor for area would be 0.375 and that for diameter would be 0.069. The required pipe for the case considered would have a diameter of 1.75 in. The size next largest, viz., 2.0 in. should be used for the steam-main. For calculating re- turn see Article 123. Most of the rules which have been given for determining sizes of steam-pipe when the radiating surface only is given will be found included in the tabulated values. Thus Mr. George H. Babcock gives a rule for gravity heating-systems with separate returns as follows :* " The diameter of the mains leading from the boiler to the radiating surface should be equal in inches to one tenth the square root of radiating surface, mains included, * Transactions American Society Mechanical Engineers, May, 1885. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 22$ in square feet." This rule is also adopted by William J. Bald- win, and given in his book on " Steam-heating." * By consult- ing the table already given, column 3, this factor would corre- spond to a velocity of steam slightly exceeding 25 feet per second, and would be adapted for low-pressure steam-heating in small plants. One authority f gives the following rules for determining the cross-sections of area of pipes : " For steam-mains and returns it will be ample to allow a constant of 0.375 f a square ;Jnch for each 100 square feet of heating surface in coils and radiators, 0.375 f a square inch when exhaust steam is used, '0.19 of a sq. inch when live steam is used, and 0.09 of a square tfnch for the return. Steam-mains should never be less than ij inches, nor the returns less than three fourths of an inch, in diameter." Mr. Alfred R. Wolff uses a table which is com- puted by formulae similar to those given on page 218 for ob- taining the capacity of steam-mains of a given diameter, the capacity being expressed both in heat-units delivered and in .radiating surface. This table is given on page 2260 and will be found convenient and accurate. The size of main steam-pipe depends on the consideration already given ; the smaller the size the greater the resistance of the steam and the more friction and consequent back pressure on the system ; the larger the pipes that are used the less the resistance, and, in general, the more satisfactory the results, !but economy, of course, forbids the use of pipes beyond a cer- >tain size, and that size should be selected by considerations relating to pressure, velocity of steam, and friction, as ex- plained. The methods of computing sizes of steam-mains which have been given allow sufficiently for friction for cases in which the pipes are not of considerable length, as in residence heating ; r but when steam must be carried a long distance more satis- factory results will be obtained by computing the capacity from the formula given in Article 121, page 218. For this com- putation various cases can be considered respecting both steam-pressure and frictional resistance. The following tables * " Steam-heating for Buildings," Wm. J. Baldwin, f Van Nosirand's Science Series, No. 68. 226 HEATING AND VENTILATING BUILDINGS. INTERNAL DIAMETERS OF STEAM-MAINS FOR A SINGLE-PIPE SYSTEM OF HEATING BY DIRECT RADIATION.* T Steam-pressure 10 Ibs. above atmosphere, frictional resistance 6 in. of water-column."! L 0. 5 " " 12 " " Length of Steam-main in Feet. Radiating Surface, 20 40 80 IOO 2OO 300 400 600 1000 Sq. Ft. Diameter of Pipe in Inches. 20 0-5 0-5 0.6 0.6 o. 7 0.8 0.8 0.9 I .2 40 0.6 0.7 o.S 0.8 .0 i .0 1. 1 1.2 1 .6 60 0.7 0.8 0.9 I.O . i 1.2 1-3 1.4 1,1 80 0.8 0.9 i .0 1. 1 .2 1.4 1.5 1.6 2. I 100 0.9 I.O 1.2 1.2 4 i . 5 1.6 1-7 2-3 2OO . i i-3 1-5 1.6 .8 1.9 2.0 2.2 2-9 300 3 1.8 1.8 2. I 2-3 2.4 2.6 3-5 400 .5 1-7 2.0 2.0 2.4 2.6 2.7 3-0 4.0 500 .6 1.9 2.2 2.2 2.6 2.8 3-0 3-2 4-2 600 .8 2.0 2.4 2-5 2.8 3.0 3-2 3-5 4-5 800 2.0 2-3 2.6 2.7 3-2 3.4 3-6 3-9 5.0 I.OOO 2.2 2 . e, 2. 9 3-0 3.4 3.7 3-9 4-3 5-5 1,400 2-5 2.8 3-3 3-4 3.9 4.2 4-5 4-9 6-5 1, 800 2-7 3-2 3 .6 3.8 4-4 4.7 5-0 5-4 7.0 2.000 2.9 3-3 3-8 3-9 4-5 4.9 5-2 5.6 7-2 3,000 3-4 3-9 4.4 4.6 5-3 5-8 6.1 6.6 3-5 4,000 3.8 4-3 5-0 5-2 6.0 6.5 6.8 7-5 9-7 6,000 4.1 4-7 5-4 5.7 6.5 7-1 7-4 8.2 10.5 8,000 4-4 5-0 5-8 6.0 7.0 7-5 7-9 8.7 "J 10,000 4-7 5-3 6.1 6.4 7-4 8.0 8.4 9.2 11.9 * The table is computed by formulae for d, page 218, in which h 318.6, Q = 9.2, cu. ft. of steam per minute for 100 sq. ft. radiating surface. The table is computed for straight pipes with water-level in returns 6 inches above that in boiler. In case there are bends or obstructions consider the length of pipe increased as follows: Right-angle elbow 40 diameters; globe-valve 125 diameters; entrance to tee 60 diameters, For other resistances and steam- pressures multiply the diameters as given above by the following factors : Water-level in return above boiler 2 in. 12 in. 18 in. Multiply by 1.25 0.88 0.80 Steam-pressure above atmosphere 0.5 Ibs. 2 Ibs. 5 Ibs. Multiply by 1.22 1.16 1.09 For obtaining the diameter of steam-main to be used in case there is a separate return multiply the above results by 0.82. For indirect heating without separate return multiply above results by 1.4, with separate return use the results in the form given. Do not use steam-pipe less than ij inches in diameter. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 226(1 TABLE FOR THE CAPACITY OF STEAM-PIPES 100 FEET IN LENGTH WITH SEPARATE RETURNS. By A. R. WOLFF. 2 Lbs. Pressure. 5 Lbs. Pressure. Diameter of Diameter of Supply. Return. Inches. Inches. Total Heat Transmitted. Radiating Surface. Total Heat Transmitted. Radiating Surface. B. T. U. Square Feet. B. T. U. Square Feet. | f I 9000 36 15000 60 I* I 18000 7 2 30000 1 2O ri 30000 120 50000 200 2 ii 70000 280 I2OOOO 480 2i 2 J32OOO 528 22OOOO 880 3' 2i 225000 GOO 375000 1500 3* 2^ 330000 1320 550000 2200 4 3 480000 I92O 800000 3200 4* 3 690000 2760 II50000 4600 5 3* 930000 3720 1550000 6200 6 3* 1500000 6OOO 25OOOOO IOOOO 7 4 2250000 9OOO 3750000 15000 8 4 3200000 12800 5400000 2I600 9 4* 4450000 17800 7500000 30000 10 5 5800000 23200 9750000 39000 12 6 9250000 37000 15500000 620(X> H 7 13500000 54000 23000000 92000 16 8 I9OOOOOO 76000 32500000 130000 In above table each square foot of radiating surface is >umed to transmit 250 heat-units per hour, a safe and con- irvative estimate, as will be seen by consulting Chapter IV. For pipes of greater length than 100 feet multiply results the above table by the square root of 100 divided by the length. In all cases the length is to be taken as the equivalent length in straight pipe of the pipe, elbows, and valves, as given on page 226. For other lengths multiply above results by following factors : Length of pipe in feet. . 200 300 400 500 600 700 800 900 1000 Factor 0.71 0.58 0.5 0.45 0.41 0.38 0.35 0.33 0.32 For example, the capacity of a pipe 8 inches in diameter and 800 feet long would be 0.35 of 12800 sq. ft. of radiating surface = 4480 sq. ft. It will be noted that the size of return specified by Mr. Wolff is about one pipe-size greater than be- lieved to be necessary by the author, but sizes of main steam- pipe are in substantial agreement with tables on pp. 226and 226^. 226b HEATING AND VENTILATING BUILDINGS. The following table will be found convenient for obtaining the size of a steam-main for low-pressure steam-heating, single- pipe system, for various lengths. The table is computed from same formulae as those on page 226, but for a lower steam- pressure, and results are given in commercial sizes of pipes. COMMERCIAL SIZES OF STEAM-MAINS FOR A SINGLE PIPE. (System of heating by direct radiation; pressure 0.5 Ibs.; friction resistance 6 inches of water for lengths 100 feet and under, 12 inches of water for greater distances.) Length of Steam-main in Feet. Radiating Surface. 80 Square Feet. 20 40 IOO 200 300 400 600 IOOO Diameter of Pipe in Inches 20 I i l\ ,. j! i * 40 !i ii i- T i - I- t| 4 60 80 IOO Jl ii ii i- i- I* I- t] if 4 2 2 200 ij i4 2 2 2 2 2 2 : 3 300 2 2 2 2 2 "' 2^ 3 3j 400 2 2 24 24 24 3 3 3 4 500 2 24 24 3 3 3 3* 3* 4 600 24 24 3 3 34 3 3 3 4* 800 24 3 34 34 3l5 3i 4 4 5" IOOO 3 34 4 4 4 4 6 1400 34 34 4 4 4 4? 4* 5 6 1800 4 4 4 4 4l? 5 5 6 7 2OOO 4 4 4 44 4i 5 5 6 7 3000 44 44 44 5 5 6 6 7 8 4OOO 5 5 5 6 6 7 7 7 9 6000 54 54 6 7 7 7 ' 7 8 10 8000 54 6 7 7 8 8 9 ii 1OOOO 6 6 6 7 8 8 9 10 12 I20CO 6 7 7 7 8 8 10 II 12 I4OOO 7 7 7 8 9 9 10 12 14 16000 7 8 8 9 9 10 ii 12 14 18000 8 8 8 9 10 ii ii 12 M 2OOOO 9 9 9 10 ii ii 12 14 16 In using the above table take the equivalent length as explained on page 226. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 22? for capacity of steam-mains are computed for steam 10 pounds above atmospheric pressure, and the frictional resistance 6 inches of water column. Tables computed from the same formula and covering other conditions will be found in 44 Steam-heating," * by Robert Briggs, and can be consulted when desired. 123. Size of Return-pipes, Steam-heating. The size fcof return-pipes, if figured from the actual volume of water to zbe carried back, would be smaller than is safe to use, largely because of air which is contained in the steam-pipes, and which odoes not change in volume when the steam is condensed. For this reason it is necessary to use dimensions which have been proved by practical experience to be satisfactory. When the steam-main is large, the diameter of the return-pipe will Jprove satisfactory if taken one size less than one half that of the steam-pipe ; but if the steam-main is small, for instance, ,5 inches or less, the return-pipe should be but one or two sizes smaller. The return-pipe should never be less than I inch, in -order to give satisfactory results. The following table suggests sizes of returns which will prove satisfactory for sizes of main steam-pipes as given : Diameter Steam-pipe. Diameter Return-pipe. Diameter Steam- pipe. Diameter Return-pipe. inches. inches. inches. inches. 2 if 5 6 3 3 3l 2 8 9 10 4 4i 4i 4 2 12 5 The size of return-pipes, if computed on basis of reduction in volume due to condensation of the steam, supposing the steam to have a gauge-pressure of 40 pounds and that one half its volume is air, would be, neglecting friction, about one sixth of that of the main steam-pipe, which is much smaller than would be considered safe in practice. * Van Nostrand's Science Series, No. 68. 228 HEATING AND VENTILATING BUILDINGS. Main and Return-pipes for Indirect Heating Surfaces. The indirect heating surfaces require about twice as much heat as the same quantity of direct radiating surface, and hence, for same re- sistance in the pipe, the area should be twice that required in di- rect heating. It will usually be sufficiently accurate to use a pipe 3 whose diameter is 1.4 times greater than that for direct heating. Reliefs and Drip-pipes. The size of drip-pipes necessary to convey the water of condensation from a main steam to a return cannot be obtained by computation, as there is much uncertainty regarding the amount of water that will flowl through. As the flow through the relief tends to increase the press- ure in the return, it may also serve to lessen the velocity of flow beyond the point of junction, provided the size is greater than necessary to carry off the water of condensation from the steam-main. Drip-pipes should be united to the return in such a manner as to re-enforce rather than impede the circula-i tion, which result can usually be attained by joining the pipes with 60 or 45 degree fittings. The writer would recommend the employment of the fol- lowing sizes of drip-pipes as ample for usual conditions : DIAMETER OF DRIP-PIPE FOR STEAM-MAINS OF VARIOUS LENGTHS. Length of Steam-main in Feet. Diameter of Steam-main, o to 100. IOO tO 2OO. 2OO tO 4OQ. 4XX3 to 600. Inches. Diameter of Drip-pipe in Inches. OtO 2 | \ 1 I 3 i f i i 4 f f i i^ 5 f if i^. 6 I I* i* i* 124. Size of Pipes for Hot-water Radiators. Method of computation of the velocity with which circulation will take place in a hot-water heating-system without friction has been considered in Article 121, page 220. In some instances this DESIGN OF STEAM AND HOT-WATER SYSTEMS. velocity is increased by bubbles or particles of steam which pass up the main risers and reduce the specific gravity of the water in the ascending pipes to such an extent that the actual velocity produced is much in excess of what would have been possible had no steam formed. This condition is undesirable, as it is usually accompanied with more or less noise and a very high temperature in the boiler, and should not serve as a basis for designing main-pipes to be used in hot-water heating ap- paratus. It should not be recommended that heaters be run in [such a manner as to produce steam in any part of the circulation. The heat which is given off from radiating surfaces of va- rious kinds has already been considered (page 204), and as each thermal unit given off by the surface is obtained by the cooling of one pound of water one degree in temperature, it is easy ; to compute from the data already given (i) the weight of hvater required, and (2) the number of cubic feet needed to peat each square foot of radiating surface. The following table gives the data necessary for computing [the volume of water required to supply radiating surface for various conditions likely to occur in heating : HOT-WATER HEATING. DATA USED IN COMPUTATION OF TABLES. Temperature outside air o o o o o Temperature water in radiator. . 140 160 180 200 220 : Heat-units per degree diff. tem- perature per square foot per hour 1.4 1.45 1.5 1.6 1.8 .Weight of cu. ft. water, pounds.. 61.37 60.98 60.55 60.07 59-64 Total heat-units per.square foot per hour : Room 60 per sq. ft 113 145 180 224 288 70 " " " 98 130 165 208 270 Cubic feet of water required to supply one sq, ft. per hour. Radiator cooled 5 Room 70 0.316 0.426 0.546 O.6S6 0.902 60 0.396 0.472 0.592 0.740 0.970 70 0.158 0.213 0.273 0.343 0.451 60 0.183 0.236 0.296 0.37 0.483 70 0.138 0.142 0.182 0.228 0.339 60 0.132 0.157 0.131 0.247 0.361 70 0.079 0.107 0.137 0.172 0.226 60 0.091 0.118 0.148 0.175 0.241 By dividing the number of cubic feet to be supplied per hour by the velocity with which the water moves per hour we obtain the area of the pipe in square feet. Radiator cooled 10 Radiator cooled 15 Radiator cooled 20 230 HEATING AND VENTILATING BUILDINGS. The general case from which practical tables may be com- puted can best be considered by the use of formulae, as fol- lows : Let w equal the weight of water per cubic foot, let H equal total heat per square foot per hour from radiator, R total radiating surface, Q number of cubic feet of water per hour, A area of pipe in square feet, a area of pipe in square inches, u velocity in feet per second as given in table, page 221, V equal velocity in feet per hour, TMossof temperature ofj water in radiator. We have the following formulae: (1) a. (2) V , HR i Total heat divided by heat given off by i ^- wT~y\ cu. ft. equals total number of cubic feet. O a _ which (5) Q = 2$av. Equate (3) and (5), and HR By taking special values corresponding to temperatures of water and of surrounding air we can reduce these formulae to simple forms. Thus, if the temperature of the radiator is 180 and of the room 70, the total _ heat-units given off per hour, H, will be 165. If we further assume that the water in the radiator cools during the circulation a certain amount, say 10 degrees, T will equal 10, weight of water w will equal 60.5 pounds, and we shall have formulae 8 and 9 : (8) R = >> (9) *= For the above condition the radiating surface is equal to 92 times the area of the main pipe in square inches times the velocity of the water in feet per second ; and further, the area in square inches is equal to the radiating surface divided by 92 times the velocity. The velocity in feet per second will depend upon the height, the difference of temperature, and amount of friction. The following table gives relations of radiating surfaces to areas of main pipes, friction neglected. For distances less than 200 ft. sufficient allowance for friction will be made by making the main one size larger than required by table. DESIGN OF STEAM AND HOT-WATER SYSTEMS. AREA AND DIAMETER OF HOT-WATER HEATING-MAIN, DIRECT RADIATION.* DIFFERENCE OF TEMPERATURE, 10 DEGREES. (1) (2) (3) (4) (5) Height, Feet. Velocity Water Feet per Second. Multiply each ioo Square Feet Radiating Surface for Area Main by Multiply Square Root Radiating Surface for Diameter by Equivalent Head in Feet. I 0-335 3-26 0.205 0.0015 5 0.750 1-45 0.133 O.ooSl 10 1. 06 1.03 0.113 0.017 15 1.28 0.85 o. 104 0.025 20 15 0.723 0.095 o 035 25 1.6 7 0.65 O.ogi 0.044 30 1.83 0-595 0.087 0.052 40 2.12 0.513 0.081 0.072 50 2-37 0.46 0.076 0.088 60- 2-59 0.42 0.072 o. 105 80 3-00 0.362 0.068 0.142 100 3-35 0.324 0.064 0.176 In the above table column (i) gives the height in feet ; column (2) the velocity corresponding to the head for a reduc- tion in temperature of 10 F.; column (3) is the area in square inches, neglecting friction, for each ioo square feet of radiating surface ; column (4) is the corresponding diameter of pipe required for each square foot of surface, and is to be multiplied by the number of square feet of radiating surface to give the diameter for any given case ; the actual diameter should be one pipe size greater ; column (5) is the equivalent head which would produce the same velocity if falling freely in the air. The preceding table is in the same form as that given for diameters of steam-main. If we consider 10 feet as the aver- age height or head producing circulation for the first floor, it will be seen that we shall need, neglecting friction, one square inch in area in our main pipe for each ioo square feet of radia- tion, or the diameter of our pipe would be found for this case * As illustrating the use of the table, compute the area of main pipe needed to supply 350 square feet of direct radiation situated 25 feet above the heater. The area is obtained by multiplying 3.5 by 0.65, which will equal 2.28 square inches. The diameter can be found from this, or it may be obtained from column (4), by multiplying the square root of 350 by 0.091. The square root of 350 is 18.7, the product is 1.7. The pipe used, if the distance is about 200 feet, should be i\ inches in diameter. 232 HEATING AND VENTILATING BUILDINGS. as equal approximately to \ of the square root of the radiating surface in square feet. If the temperature of the water be supposed to change 20 in passing through the radiators,the required area of the main would be one half of that given by the table ; if 15, two thirds, etc. In hot-water heating the return-pipe must have the same diameter as the supply-pipe, since there is no sensible change in bulk between the hot and cold water. We may take as a practical rule, applicable when less than 200 feet in length : The diameter of main supply- or return-pipe in a system of direct hot-water heating should be one pipe-size greater than the square root of the number of square feet of radiat- ing surface divided by 9 for the first story, by 10 for tJie second story, and by 1 1 for the third story of a building ; for indirect hot-water multiply above results by 1.5. 125. Size of Ducts and Ventilating-flue for Conveying Air. The method of computing the sizes of flues would evi- dently be that of dividing the total amount of air which is required in a given time by that delivered or discharged through a flue one square foot in area. A table has been given for: cubic feet of air delivered in ventilating-pipes, see Chapter I, pages 45 to 52. The air required can be found as explained in Article 119, page 211, formula 4, or by consulting the table, page 213, which gives the factors to be multiplied by the area of glass plus J the exposed wall surface when the air enters at various temperatures above that in the room. As an illustration, consider the same problem as in previous cases, viz., that of a room with 48 square feet of glass surface and 320 square feet of exposed wall surface, and from which the heat loss per degree difference of temperature is 128. Supposing air in room to be 70 F. and that supplied by flue to be 100 F., we see by table page 213, that for every heat-unit as above there will be required 135 cubic feet of air per hour, and for this case we will require 135 X 128 = 17,280 cubic feet per hour. If excess of temperature of air in flue over that outside be considered as 50, and height of flue as 10 feet, the discharge per square foot of flue (see table page 45) will be 242 feet per minute, or 14,520 per hour. Hence the required area of the flue will be 17,280 divided by 14,520= 1.19 square feet DESIGN OF STEAM AND HOT-WATER SYSTEMS. 233 = 171 square inches. In a similar manner areas of flues may be computed for any given case. As the velocity of flow increases with difference of tem- perature between outside air and that in the flue, and is les- sened when this difference is small, it is better to assume a mean difference of temperature so low that the computation will certainly afford plenty of air for ventilation. AREA OF FLUE IN SQUARE INCHES REQUIRED TO SUPPLY GIVEN AMOUNT OF HEAT. (Excess of temperature is 30 ; allowance for friction 5056.) Height or Head of Flue in Feet. Z is* 5 IO 15 20 30 40 50 60 80 IOO H Area of Flue in Square Inches. B.T.U. B. T. U. j 700 IO 24 17 14 II 9.2' 8.2 7-1 6.6 6.1 5.5 1400 20 48 35 28 22 18.4 16.4 13-2 12.2 10.9 2IOO 30 72 52 42 33 28 25 21 19-5 I8.3JI6.3 28OO 40 96 69 56 44 37 33 28 26 24.421.8 3500 50 120 87 71 55 46 41 35 32.6 30 . 5 j 2 7 . 3 525O 75 1 80 129 116 82 69 61 53 48 45.740.8 7OOO IOO 240 173 141 109 93 82 71 66 61 54-5 8/50 125 300 216 176 136 115 102 87 82 76.568.1 10500 150 3 60 258 212 164 138 122 105 98 I52 l 8i.7 12250: 175 420 302 247 191 162 143 123 114 10795.3 14000 200 480 346 244 218 184 !6 3 141 130 124 109 17500 250 600 432 315 273 231 204 175 163 153 136 2ICOO 300 720 519 423 327 278 245 211 195 183 163 2SOOO 400 960 652 564 436 369 327 28l 261 244 218 35000 500 1200 865 715 545 462 408 352 326 306 273 52500 750 1 800 1290 IO6O 825 693 612 527 457 458 408 7OOOO 1000 24OO 1730 I41O 1090 9 2 5 818 705 655 612) 545 87500 1250 3OOO 2160 1760 1360 150 ;loi8 870 820 7651 681 IO5OOO 1500 3600 2580 2120 1640 1380 1218 1055 980,1520: 817 I4OOOO 2000 4800 3460 2440 2 1 SO 1840 1630 I4IO 1300 1240 1090 i75oooj 2500 6OOO 4320 3150 2730 2310 ,2040 750 1630 1530:1360 2IOOOO 3000 7200 5190 4230 3270 2780 2450 2I1O 1950' 1 830! 1630 Table is computed by finding air required to supply heat by formula 4, page 211, when outside air is o, inside air 70% and heated air 100, and dividing this by the air supplied by a flue one square foot in area for the given height and a difference of temperature of 30, as obtained in table page 45. Ventilat- ing flues for a given height should be taken one quarter larger than the values given in the table. See note on page 246. * See page 57. f Approximately equal to area of glass plus one fourth the exposed wall- surface. See page 59. 234 HEATING AND VENTILATING BUILDINGS. The table on p. 233 is computed by the method explained for different heights of flue and for a difference of temperature of the air in the flue over that in the space into which it discharges of 30 F. For difference of temperature other than 30 multiply results in the table by the following factors to obtain the area of the flue : Difference Temperature, Degrees. Factor. Difference Temperature, Degrees. Factor. IO 2O 40 1-74 1.22 0.87 50 60 70 0-775 0.71 0.655 For usual conditions of residence heating in which the air in the supply-flue is 30 above the temperature of the air in: the room, and that in the ventilating-flue 20, we may compute the approximate area in square inches of the supply- and venti-^ lating-duct, by multiplying each heat-unit per degree difference of temperature lost from the walls by a series of simple factors, which are easily memorized. TABLE OF FACTORS FOR AREA OF AIR-FLUES. suppiy-auct ve ntnating-au :t. Story of Building. Approxi- mate Head in feet. Velocity in feet per sec. Factor for Area, sq. in. Approxi- mate Distance to Roof. Velocity in feet per sec. Factor for Area, sq. in. First Floor Second " (1) 5 28 (2) 2.8 6 8 (3) 2.40 (4) 47 (5) 5-5 (6) O.Q3 Third " JO 8 i o 82 j" 4 20 o 6 Fourth " 50 9- 0.71 IO 2.6 2.17 As an example, find the required area of heat- and venti- lating-ducts for a room with 200 square feet of exposed wall- surface and 30 square feet of glass : 30 plus one fourth of 200 is 80, the approximate building loss per degree. This quantity multiplied by factors in columns (3) and (5) gives respective areas of flues in square inches with sufficient exactness for ordinary requirements. The factors afford a ready means of computation in the absence of an extended table, similar to that on page 233. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 235 In some instances the amount of air can be computed as a function of the cubic contents of the room, especially when required for ventilation alone. For ventilation purposes the problem of proportioning the air-passages is solved simply by computing, first, the air required, on the basis of 1800 cubic feet per hour for each person who will occupy the room ; second, -the number of times the air will be changed per hour, by dividing this result by the volume of the room. This method is considered fully in Article 38, page 53, and a table is given for computing the area of the flue in square inches for different velocities of the moving air. In applying this method to practical problems, it is best to ^proportion the ducts so that in no case will the required ^velocity of the air in the flue exceed 12 feet per second or 43,200 feet per hour, an amount not likely to be reached without a fan or blower, and one which corresponds to a 'pressure of nearly o.i inch of water (pages 42 to 53). 126. Dimensions of Registers. The registers should be so proportioned that the velocity of the entering air will not be sufficient to produce a sensible draft ; that is, the area must pe such that the velocity shall not exceed 3 to 5 feet per second or 10,800 to 18,000 lineal feet per hour. The writer thinks that very excellent results are obtained by proportion- ing the registers* for first floor so as to give velocity of 2^ feet per second, and those of higher floors and at entrance to ventilating-shafts 3 feet per second.* The results above, ex- Pcept for entrances to ventilating-shafts on the top floor, are less than is usually produced by natural draft, so that the area computed by dividing the total amount of air required by the number which expresses the velocity gives satisfactory results. The above rules are for effective or clear opening, and this will be found in each case to be about two thirds of the nomi- ;nal or rated size of the register as shown in the table given in Article 144. By computing, from the data given, the number of changes ?of air per hour in room, the table page 53 can be used as explained to determine the effective area in square inches required for each 1000 cubic feet of space. * See page 52, Article 38. 236 HEATING AND VENTILATING BUILDINGS. As an example illustrating use of this table, suppose, in a room containing 2500 cubic feet, air to be changed four times\ per hour, and that velocity in air-flue be 6 feet per second, in ventilating-shaft 4 feet, through fresh-air register 2.5 feet, through ventilating-register 3 feet. The table on page 53 gives the net area for each IOOO' cubic feet of space, so that for above conditions the results as found in the table must be multiplied by 2.5. We should have, taking 2.5 times the tabulated values, the following results : Net area supply-flue 67.5 sq. in.; ventilating-shaft 100 sq. in.; fresh-air register 166 sq. in.; ventilating-register 136.5 sq. in. The nominal area of the register to be used should be about 50 per cent greater than the net area ; it may be taken- from the table given in Article 144. The velocity correspond-? ing to 2.5 feet per second is taken as the mean of that given., in the table for 2 and 3. It is best to make flue dimensions about one inch greater! than obtained by calculation, to allow for surface friction. 127. Summary of Various Methods of Computing Quan- tities Required for Heating. The following table giveJ the required size of steam-pipes and of steam-boiler or hot-watefl heater, for various amounts of radiating surface. The proporl tions given will apply to residence heating or where the length of main pipe is not over 200 feet. The value given for the steam-main is that for the single-pipe system when no return is needed. For the system of separate steam- and return-pipes? the diameter of the steam-main should be taken f of that givenl that of the return as in table page 227. The cubic spaed heated is given if the ratio to radiating surface be known ; this$ is an approximation only, although it may often serve a use*: ful purpose when experience has been gained of heat required^ in constructions of similar nature in the same locality. About two thirds as much air is warmed by hot-water as by steam radiators, and flues should be about two thirds as large! as given in the table on page 238. 128. Heating of Greenhouses. Greenhouses and con- servatories are heated in some cases by steam and in othea cases by hot water, and there is quite a difference of opinion! held by florists respecting the relative merits of these tw r^^ill -O PI oo v 2 2 8 , x. N , 800 882 8 m^-8 88 q\ q^ 5> 888 m in m >n r ^1l! r^e^HI 'I- 0000*000022 O N co Q Q ^cf " 8^8 VO moo^ in in in A m N m m m co " " u 8 2> S N N f-. 00 " S"c? | o" O m 8 >- w o O O 4m moo q X %~ M 888 o co o c q^ O >O z* 5fr < o^^oog mOO ro Q vo >o m*o o oo o O P.T \o & M M * t^ O *. a. c'o. I * * 2*1 N III J S J^ 5 iH^ 5 H ^ ! m q m M Cfi ^vS'oo' N" tC o o o u^ *S, = :? 5 " 8 3 o c/~. ? () ^',8 O 00 O O 00 OOvOWMOOOO S.C r- m O* z O m o ON e> W 5 mvo co m m in s| & & r-2 a ^ ^ K m o u 3 CA; 2 coco -c 2 2 2 2 ^ "22 5 q 8 8 X u mom co 4- 4- cooo * N 2 2 o : "888 8cU F- o o_ moo oo tx o o o q\ t- M q o 8 '3 tin ti t- ; 1 O 00 O d |I Oi <^ 'A *Vfif H o O m O \O O^^-c^co^coo ||| ^ S CO O "r-"!tt fi O m o ? . ? goo y 2 g ^ ^ V. CS -*n y C _ """I'll u 10 m o" ^ c "> t M 0" m 0' ::::;::: :::::::: li K ^ Radiating surface, square feet Diameter steam-main, inches*.. . Heating-surface boiler, square feet Grate-area boiler, square feet Diameter smoke-flue, inches Cubic feet heated, 40 to i 50 to i 7$toi Radiating surlace, square feet Diameter pipe, inches ist story*... 2d story " 3d siory Heating-surface heater, square feet Grate-area heater, square feet. . Diameter smoke-flue, inches Cubic feet heated, 20 to i 30 to i 40 to i Square feet radiation Cubic leet air heated per minute.. Diameter main steam-pipe* Heating-surface boiler, square feet Grate-area boiler, square feet Diameter smoke-flue, inches Cubic feet heated, 20 to i 30 to i 40 to i Square feet radiation Cubic feet air heated per minute. . Diameter supply- and return-pipe*. Heating-surface in boiler, square fe Grate-area in boiler, square feet . . Diameter smoke flue, inches Cubic feet heated, 15101 " 25 to i 35 to i o OS o b. 1 238 HEATING AND VENTILATING BUILDINGS. HOT-AIR AND VENTILATING FLUES. INDIRECT RADIATION STEAM CIRCULATION. Square feet radiation 2C CQ 7c IOO 12Z I^O 17 = 2OO 2O Cubic feet air per minute . 122 244 062 j86 f)O2 72Q 846 Q72 I22O Area hot-air flue, square feet : 1st story O 72 I 4^ 2 16 2 87 o cT 4q c o 57 7 ^ 2d story O 2Q O <^Q o 88 I Q I 47 I 78 2 06 2 7^ 2 CK qd story . . O 2.1 O 4Q O 7i O Q7 I 22 I 46 1 7 I Q^ 2.4^ Area ventilating flue, square feet : 1st story . O ^7 O 74 j j I 46 I 8l 2 2 2 ^1 2 Q^ a 7 2d story . o 48 87 I 44 I Q2 2 -37 2.8 -3 . -2C -} 84 4 8 3d story Oe c j j I 64 2 2 2 71 3<3 * 8^ 4 A 5j Actual area register, square feet : I 22 2 4 ^ 6 1 Q 6 7 . ^ 8 4 Q. 7 12 .2 2d and above I O 2 6 7 8 o IO O Ventilating register, square feet. . . 0.6 1.2 1.8 2.4 3 3-6 4.2 4.8 6.1 methods of heating. The fact, however, that either system when properly proportioned and well constructed gives satisfac- tory results indicates that the difference is not great, and that the relative value may depend entirely on local conditions. The methods of piping employed may in a general way be like those described, and the pipes may be located so as to run underneath the beds of growing plants, or in the air above, as bottom or top heat is preferred. In many cases large cast-iron pipes, the method of erection of which is described in Article 58, page 88, are used in hot-water heating of greenhouses, These are generally located beneath the beds of growing plants ; the main flow- and return-pipes are laid in parallel lines, with an up- ward pitch from the boiler to the farthest extremity of the house. Recently small wrought-iron pipes, Article 59, page 89, have been used extensively for greenhouse heating. In this case the main pipe has generally been run near the upper part of the greenhouse and to the farthest extremity in one or more branches, with a pitch upward from the heater for hot- water heating and with a pitch downward for steam-heating. The principal radiating surface is made of parallel lines of i^-inch, or larger, pipe, placed under the benches and sup- plied by the return current; this has in all cases a pitch toward the heater. An illustration of the method of piping as de- signed by A. H. Dudley of the Herendeen Mfg. Co. is shown in Figs. 193, 194, and 195 so clearly as to require no special explanation. DESIG-N OF STEAM AND HOT-WATER SYSTEMS. 239 Any system of piping which gives free circulation and which is adapted to the local conditions will give satisfactory results. The directions for erecting and taking off branches are the same as in residence heating (see page 191). Proportioning Radiating Surface. The loss of heat from a greenhouse or conservatory is due principally to the extent of glass surface ; hence the amount of radiating surface is to be FIG. 193. PLAN AND ELEVATION OF PIPING. taken proportional to the equivalent glass surface, which in every case is to be considered as the actual glass surface plus the exposed wall surface. From this surface about I heat-unit will be transmitted from each square foot for each degree difference of temperature between that inside and outside per hour; that is, if the difference of temperature is 70 degrees, each square 240 HEATING AND VENTILATING BUILDINGS. foot of glass surface would transmit 70 heat-units per hour. The radiating surface usually employed for this purpose is horizontal pipe, and hence is of the most efficient kind. From a surface of this nature we can consider without sensible error that 2.2 heat-units are given off from each square foot for each A FIG. 194.- PIPING FOR OUTSIDE BENCH. FIG. 195. PIPING FOR INSIDE BENCH. degree difference of temperature between the radiator and the air of the room per hour. From this data a table can be computed which gives the ratio of equivalent glass surface to radiating surface, in which the results will be found to agree well with average practice ; the results are to be in- creased or diminished 10 to 20 per cent, according as the cir- DESIG-N OF STEAM AND HOT-WATER SYSTEMS. 24! cumstances of exposure or the quality of the building vary more or less from the average condition. TABLE SHOWING AMOUNT OF GLASS SURFACE OR ITS EQUIVA- LENT WHICH MAY BE HEATED BY i SQUARE FOOT OF RADIATING SURFACE IN GOOD BUILDINGS. Hot Water. Steam. Temp, of Radiating Surface, Deg. F. 160 1 80 200 5 Ibs. 227 10 Ibs. 240 Square Feet of Glass for i Square Foot of Radiating Surface Temp, of surrounding air, 90 F. .. 1.9 2-3 2.8 3-3 3-S 80 F. . . 2-3 2.9 3-5 4.0 46 " ' " 70 F. . . 3-o 3-6 4-2 5-o 5-7 ** * " 60 F. 4.0 4.6 5.25 6.0 7.0 4 ' * * * ^ o' J F 5-0 6.0 6.8 8.0 9.0 .," ' " * 40 F... 6.9 8.0 8.2 IO.O ii. 5 From the data above the following table is computed, which gives the radiation in square feet required for green- louses or conservatories with different amounts of glass sur- : aces. It also gives divisors from which the heating-surfaces or grate-surfaces in the boilers may be computed by dividing the given amount of radiation. Thus for a greenhouse with 1000 feet of glass surface, which is to be kept at 70 degrees in the coldest weather, we note in the table that 200 square feet of radiation will be required ; the heating-surface in the boiler will be 200 divided by 5.6 (= 36) square feet, and the area of grate will be (200 divided by 156 =) 1.28 square feet. GREENHOUSE HEATING WITH STEAM. Square feet of glass . Radiation required, sq. ft., tempt. 40. ! . 1 9 250 25 500 50 75 75 IOOO IOO 1500 J 5o 2OOO 200 2500 250 3000 300 4000 j 5000 400 500 10.000 1,000 " " " 50- I ; 33 62 82 125 188 250 3'3 375 500 625 1,250 " " '* " 60. tc 43 84 I 2 5 167 250 333 416 500 660 830 1, 660 " " *' " 70. ad 50 100 ISO 200 300 400 500 600 800 IOOO 2,000 ** " " " 80. S 64 125 1 88 25 35 500 625 75 IOOO 1250 2,500 Divisor of Radiation. r or heating surface in boiler 4 4-5 5-i 5-4 5.6 6.0 6.2 6-5 6.7 6.9 7.0 7 "or area of grate , 25 1^2 138 144 156 160 1 80 190 192 204 216 240 GREENHOUSE HEATING WITH HOT WATER. Square feet of glass Water 160. Radiation sq. ft. tempt. 40 \\ 5 60 - ' '' E"..-.: Divisors of Radiation. r or heating surface r or grate surface '. . 15 25 62 83 37 6.5 6.8 1901 193 no! 145 i r o 200 187! 250 250 333 333 :-i- r.- 7.6 8.i 8.4 9.0 9.3 10.0 10.4 10.5 207 216 232 252 270 288 306 324 2500 3000 4000 r 625 833 looo 1330 -- 330 [660 l66o 2100 3-333 IO.5 12. [42 360 242 HEATING AND VENTILATING BUILDINGS. The sizes of main pipes should be the same as those which are used for direct heating, page 237. Relative Tests of Hot-water and Steam Heating Plants. Several tests have been made to determine the relative efficiency and economy of steam and hot-water heating plants. The first test so recorded was made at the Massachusetts Agricultural College by Professor S. T. Maynard, the results of which are given in Bulletins 4, 6, and 8, issued by the Mass. Exp. Station, 1889 and 1890. In this test two houses were used which were located as nearly as possible with equal exposure, and the tests were made with great care and by entirely disin- terested observers. The following is a summary of the results and conclusions as taken from the bulletins : STEAM-HEAT VERSUS HOT WATER. [From Bulletin No. 4.] In order to get at some facts in regard to this subject, so important to the grower of plants under glass, and gain some positive knowledge as to the relative value of the two systems, two houses were constructed during the summer of 1888, 75 X 18 feet, as nearly alike as possible in every particular. Two boilers of the same pattern and make were put in, one fitted for steam and one for hot water; the steam for heating the east house, and the hot water for the west and most exposed one. The boilers were completed and ready for work in November and were used until January 9, 1889, when these experiments began. Records of temperature of each house were made at 7.30 and 9 A.M., and 3, 6, and 9 P.M. Sufficient coal was weighed out each morning for the day's consumption and the balance not consumed deducted the next morn- ing. " The two boilers and fittings were put in so as to cost the same sum and were warranted to heat the rooms satisfactorily in the coldest weather." These experiments were repeated during the months of January and February, 1889, and in summarizing the results it was found that the steam- boiler consumed during the two months referred to 6582 Ibs. of coal, while the hot-water boiler consumed in the same time only 5174 Ibs., a saving in favor of the latter of nearly 20 per cent. At the same time the temperature of the room heated by hot water averaged 1.7 higher than that heated by steam. The temperature was more even where heated by hot water, and con- sequently there was less danger from sudden cold weather. This was strikingly shown on the night of February 22. The average outside temperature for the day was 34. At 9 P.M. it was above 32, and proper precautions not having been taken for so sudden a change as followed (the average temperature during the j 23d of February was 2), at 6 o'clock on the morning of the 23d the tem- DESIGN OF STEAM AND HOT-WATER SYSTEMS. 243 perature of the room heated by steam was 29, while in that heated by hot water it was 35. . . . [From Bulletin No. 6.] The boilers used were built of cast-iron sections. In the hot-water boiler five sections are used, the area of heating surface exposed to the fire being 74.5 feet. The steam-boiler consists of eight sections, the total heating surface of which is 85.12 feet. The experiments reported in the April Bulletin were continued during the two following months of March and April, and from the tables show- ing the comparative results the following summary is appended: SUMMARY FOR HOT-WATER BOILER. Total coal consumed by hot-water boiler from December 23, 1888, to [April 24, 1889, 4 tons 1155 Ibs. Average daily temperature for the four months, 53.5. SUMMARY FOR STEAM-BOILER. Total coal consumed by steam-boiler from December 23, 1888, to April \, 1889, 5 tons 1261 Ibs. Average daily temperature for the four months, ,1.2. It will be seen by the above that the average temperature of the house icated by hot water was 2.3 higher than that heated by steam, and that ic amount of coal consumed was 2106 Ibs. less in the former than in the itter. [From Bulletin No. 8, April, 1890.] Much discussion having been provoked relative to the accuracy of the isults of experiments with steam and hot water for heating greenhouses, sported in Bulletins No. 4 and 6, we have the past winter made a care- ful repetition of the experiments to correct any errors that might be found md to verify previous results. The boilers having been run with the greatest care possible from )ecember i, 1889, to the present date, March 18, 1890, and every precaution laving been taken that no error should occur, we give the results in the following table: HOT WATER. STEAM. Lettuce and Carnation Room. Lettuce and Carnation Room. Month. ill d ill sll sl *f! V u 6 3 O 4) j 11 *j fcWC 4> 3 n a "2'S a o-q S "2 rt"o. Jl* O--; c o. "2'S c. n be 4) C rt Q. loyed for heating without materially affecting the power >f the engine. The systems of steam-heating which have been lescribed are those in which the water of condensation flows lirectly into the boiler by gravity. In other systems in use ugh-pressure steam is carried in the boilers, high- or low- >ressure steam in the heating-mains and radiators, and the ;turn-water of condensation is received by a trap and de- livered either into a tank from which it is pumped into the boiler or in some instances wasted. The exhaust steam lay need to be supplemented by live steam taken directly rom the boiler, which may be reduced in pressure either by issing, through a valve partly open, or a reducing-valve, as described in Article 137. It will often be found that little attempt is made to utilize :the heat escaping in the exhaust steam from non-condensing engines, and consequently a good opportunity exists for con- struction of systems which will save annually many times their first cost. 131. Systems of Exhaust Heating. The exhaust steam discharged from non-condensing engines contains from 20 to 30 per cent of water, and considerable oil or greasy matter which has been employed in lubricating. When the engine is freely exhausting into the air, the pressure in the exhaust-pipe is, or should be, but slightly in excess of that due to the atmos- 247 248 HEATING AND VENTILATING BUILDINGS. phre. The effect of passing exhaust steam through heating- pipes is likely to increase the resistance and cause back press- ure which will reduce the effective work of the engine. The engine delivers steam discontinuously, but at regular intervals at the end of each stroke. The amount is likely to vary with the work done by the engine, since the engine-governor is always adjusted to admit steam in such amount as is required^ to preserve uniform speed; if the work is light very little steam will be admitted to the engine. For this reason the supply available for heating varies within wide limits. The general requirements for a successful system of exhaust- steam heating must be, first, the arrangement of a system of piping having such proportions as will make little or no- increase in back pressure on the engine and will provide for^ using an intermittent supply of steam ; second, provision for removing the oil from the exhaust, since this will interfere materially with the heating capacity of the radiating surfaces ; third, provision against accidents by use of a safety or back- pressure valve so arranged as to prevent damage to the engine by sudden increase in back pressure. These requirements can be met in various ways. To pren vent sudden change in back pressure due to irregular supply of steam the exhaust-pipe from the engine should be carried : directly to a closed tank whose cubic contents should be at least 30 times that of the engine and as much larger as practi- cable. This tank can be provided with diaphragms or baffle- plates arranged so as to throw all or nearly all the grease and oil in the steam into a drip-pipe, from which it is removed by] means of a steam-trap, as described in Article 98, page 164,] To this tank may be connected a relief-pipe leading to the back- pressure valve, and also a supplementary pipe for supplying live steam. The supply of steam for heating should be drawn from the top of the tank. Any system of piping may be adopted, but extreme care should be taken that as little resistance as possible is introduced j at bends or fittings. The radiating surface employed should] be such as will give the freest possible circulation. In general, that system will be preferable in which the main steam-pipe is] carried directly to the top of the building, the distributing- HEATING WITH EXHAUST STEAM. 249 pipes run from that point, and the radiating surface is supplied by the down-flowing current of steam (Fig. 173). It is desir- able to have a closed tank at the highest point of the system, from which the distributing-pipes are taken, and provided with drips leading to a trap so as to remove, before it can reach the radiating surface, any water of condensation or oil which has been carried to the top of the building. 132. Proportions of Radiating Surface and Main Pipes Required in Exhaust Heating. The size of exhaust pipe required for an engine of given power, in order that the back ^pressure shall not exceed a certain amount, may be computed, She only data required in addition to that already given for heating with live steam, being that relating to the steam re- Quired by engines. The amount of steam used by engines will depend upon the workmanship and class to which they belong, but we can assume with little error that non-con- densing engines will require the following weights of steam per horse-power per hour : simple with throttling-governor 40 pounds, with automatic governor 35 pounds, with Corliss valves 30 pounds ; compound using high-pressure steam 25 pounds. In order that the pipes may be sufficiently large it is better to proportion the systems for the more uneconomical type. TABLE OF DATA FOR COMPUTATION. Absolute M-7 16.7 18.7 24.7 12.7 97 216 Temperature of air 70 70 70 70 70 Heat per min. from 100 sq. ft. radia'ion in ' B. T. U. equal 3 times difference 426 438 447 4<>6 57 402 366 966 067 067 067 062 Latent heat steam B T U 966 963 * 960 946 978 -.6 ! 16.2 Cubic feet steam to weigh % Ib . ... 17.6 16.4 14.0 10.8 20.2 26.0 Cubic feet steam required each min. to supply ii 6 8 8 12.6 Weight of T cubic foot steam Ibs. 0.0379 .O4O3 .0640 .0326 ("Throttling Radiating surface per H. P { Qortiss* ' 152 114 146 129 no 143 127 107 139 122 104 126 112 95 162 I 4 6 122 179 158 [Compound 95 9 1 9 8 7 79 IO2 112 Head of steam in feet equal i foot water of water column . 1669 1585 U55 1317 IOIO 1902 2440 In the following discussion the dimensions of piping are computed for an engine using 40 pounds of steam per horse-power per hour (f pound per minute), and exhausting 250 HEATING AND VENTILATING BUILDINGS. against a back pressure above or below atmosphere as stated.* The preceding table gives properties of steam, also radiating surface supplied per horse-power by engines of various classes. The computation of the size of exhaust-pipes can be made by the following algebraic process : Let V equal velocity of the steam in feet per second ; v, velocity in feet per minute; /, length of pipe in feet; D, diameter of pipe in feet; d, diameter in inches; A, area of pipe in square feet; Q, cubic feet of steam discharged per minute ; h, back pressure above atmosphere ex- pressed in feet of steam ; p, back pressure expressed in pounds per square inch ; HP, horse-power of engine ; c, number of cubic feet in one pound I of steam. From the formulae, page 218, we have, for velocity in feet per second 7 /> ; , . . . . d from which by reduction the velocity in feet per minute The discharge in cubic feet per minute Q = Av = 3000.4 V^-D = 4723 \ -jd\ . . . . (3) Since f pound of steam is used per horse-power per minute, Q= IcHP. ...... ....... (4) From above by reduction ^ = 0.537^ = o.457l/f^ r ; '. .... (5) HP = 7.'35V /! 5f ' ' ....... (6) In case the back pressure is equal to one foot of water column (0.433 pound per square inch) above atmosphere, h = 1598, <: = 25.7, and we have For one pound back pressure HP= i.i It is advisable to make the diameter one inch greater to overcome additional resistances. (See table.) * Radiating surface 25 per cent less. See Article 121, page 218. HEATING WITH EXHAUST STEAM. 251 RADIATING SURFACE AND HORSE-POWER OF ENGINE FOR A GIVEN DIAMETER OF EXHAUST-PIPE. Diam. Exhaust- steam Pipe ioo Ft. Long. Back Pressure not to Exceed 0.4 Lb. Correspond- ing H. P. of Engine. Radiating Sur- face in Sq. Ft. Supplied by AutotnaticType of Engine. Diam. Kxhaust- steam Pipe ioo Ft. Long. Back Pressure not to Exceed 0.4 Lb. Correspond- ing H. P. of Engine. Radiating Su;- face in Sq. Ft. Supplied by AutomaticType of Engine. Inches. Inches. 2 1. 12 no 6 63 6,2OO a| 3-J 300 7 99-3 9.500 3 6.4 605 9 304 19,500 3i n. i 1.050 12 356 34,000 4 17-5 1,650 14 562 54,000 4* 22-9 2,2OO 16 825 89.000 5 36.6 3.400 18 M5o 110,000 The foregoing table is computed for steam having a pressure of 0.43 pound above the atmosphere. For other pressures of exhaust multiply the results given in the table by the following factors (for other distances multiply by 0.1 ^ l)\ Pressure. Factor. Atmospheric 2 pounds below . . 5 pounds below. . 2 pounds above.. . 3 pounds above.. . 10 pounds above. . 1.05 1.125 1.27 0.98 0.895 0.79 As an example ; find, the size of exhaust-pipe and amount of radiating surface supplied by the exhaust of a 50 horse- I power engine of the automatic type, working against a back *' pressure of 0.43 pound. For this condition, the exhaust from one horse-power will supply 25 per cent less than 131 square feet of radiation (see table page 249), or 4900 square feet. From the table at top of page we see that a 6-inch pipe will be some- what larger than required, but should be used. The amount of | radiating surface needed to warm a given building will depend I on pressure of the steam, exposure, and class of building, as explained on page 55. 133. Systems of Exhaust-heating with Less than At mospheric Pressure. If a system of exhaust-heating dis- charge the water of condensation directly into the atmosphere, the pressure must be slightly above atmospheric ; but systems 252 HEATING AND VENTILATING BUILDINGS. DISCHARGE j FIG. 196. SIPHON CONDENSER. have been used with success in which the back-pressure was less than atmospheric, and in the table of proportions which has been given such cases are considered. Such a system can be constructed by connecting the dis- charge from the system to an air-pump which will remove the water of con- densation and to a great extent the atmospheric pressure ; the heating sur- face will act as a con- denser for the engine, and j in case it is insufficient for this purpose a jet or 1 surface - condenser, sup- ' plied with cold water may j be used to supplement it. ' Instead of an air-pump and j condenser, a siphon con- ,j denser, Fig. 196, may be used. This latter instru- ment is regularly on the || market, and consists of a chamber above a conver- gent tube which receives jj| the exhaust steam and a ! jet of water. This con- | denser depends for its action upon the fact that a column of water 34 feet in height will balance and overcome the atmospheric pressure. For its successful use it must be set so that the top of the condenser is at least 34 feet higher than the end of the discharge-tube, the bottom of which is to be submerged. In a .system of exhaust heating by-pass connections to the j condenser should be provided, so that the heating surface would not need to be used in warm weather. Besides the general system which has been described, other systems of great merit have been devised and put on HEATING WITH EXHAUST STEAM, 253 the market with many special and patented features. Of these we may mention first the Willames system, which is shown in Fig. 197, with details of construction. It will be seen that the exhaust from the engine is received into a large upright stand-pipe with back-pressure valve at top, and that the steam is drawn from near the top, and after passing through the radiating system, is received into a large branch-tee, which is supplied with injection-water and serves as a condenser. The suction-pipe of the air-pump is connected to the branch-tee and acts to remove the atmospheric pressure from the entire system. A by-pass for summer use is shown. Water is heated 254 HEATING AND VENTILATING BUILDINGS. in the closed hot-water tank by a portion of the return, and may be used for any purpose needed, as, for instance, feed- water for boilers, heating by hot-water circulation, etc. Another system of this kind which, by increasing the effi- ciency of surface, has met with much favor is that invented by Andrew G. Paul. This differs in construction and principle of operation from that described, in that instead of using an air-^ pump which receives all the exhaust, a small tank is connected with an induction condenser called an exhauster, which is con- nected to all the drips and to the air-valves of the radiators. An automatic device stops the operation of the exhauster as soon as the air is removed. The advantages of this system depend principally upon the quick removal of air from the various radiators and pipes, which constitutes the principal obstruction to circulation ; the inductive action in many cases is sufficient to cause the system to operate at a pressure slightly below the .' atmosphere. Fig. 198 is a diagram * showing an application FIG. 198. PAUL SYSTEM. of the Paul system to the exhaust-piping of a steam-engine. The connections of two radiators are shown, one of which is of the single-pipe, the other of the two-pipe, system. The ex- hauster, shown in the lower left-hand corner, receives all the * Heating and Ventilation, November 15, 1894. 'HEATING WITH EXHAUST STEAM. 255 drips from the piping and radiators, and is connected with the air-valve of each radiator. 134. Combined High- and Low-pressure Heating-sys- tems. In nearly all systems of heating with exhaust steam it is necessary to arrange the piping so that at times live steam may be admitted in any amount required, as substantially described in Article 130. In some instances high-pressure steam is carried in the boiler and may possibly be used in a few radiators, while the principal part of the building is heated with low-pressure steam HEATING AND VENTILATING BUILDINGS. which is drawn directly from the boiler, and is reduced in press- ure by passing through a reducing-valve. In this case the return-water of condensation passes to a tank or chamber at the lowest portion of the system, and is fed into the boiler by means of a return-trap or steam-pump. The principal elements of such a system is shown in Fig. 199, as designed by the Albany Steam Trap Company, and forms a useful illustration of the method of piping essential. To start the pump automatically and to keep it moving at the proper speed a pump-governor (Article 135) is used. 135. Pump-governors. In non-gravity systems of heating the water of condensation is returned to the boiler by return- traps, as described in Article 99, page 167, or by steam-pumps. The trap is automatic, and when in good order will operate without attention, but the ordinary steam-pump needs to be started and stopped, as required, to remove the water. To render the pump automatic a device termed a pump-governor is often employed. Many forms are used, but they con- sist in nearly every case of a tank containing a float or equiv- alent device, connecting with levers to the valve which admits steam for operating the pump. The tank is connected to the suction and located above the pump. When the tank is full of water, the steam-pump is put in operation by the rising of the float, which opens the steam-valve. When the tank is empty, the float falls, closing the steam-valve and thus stopping the pump. A pump governor consist- ing of a float-trap with outside connections to a steam-valve, as described by F. Barren,* is shown in Fig. 200. A steam-pump with attached governor is shown partly in section Fig. 201. In this case the float is of the bucket form, the valve for supplying steam to the pump is flat with a single FIG. 200 PUMP-GOVERNOR WITH OUTSIDE LEVERS. * Pleating and Ventilation, March, 1894. HEATING WITH EXHAUST STEAM. 2$? port, and is connected by an internal lever to the bucket in such a manner that when the tank is filled the valve will be opened and the pump will operate, and when the tank is empty the valve will be closed, and the pump will stop. The pump-governors are frequently set some little distance FIG. 2OT. INTERNAL CONNECTED PUMP-GOVF.RNOR. from the pump, but attached in every case so as to produce the results described. 136. The Steam-loop. A device which has been used quite extensively for returning water of condensation to the boiler when the pressure has been reduced only a few pounds is called a steam-loop, the construction and principle of operation of which, as described by Walter C. Kerr, is as follows : The figure shows the loop returning the water, from a separator attached to an engine-main, to a boiler above the separator level. " From the separator drain leads the pipe called the ' riser,' which at a suitable height empties into the horizontal. This runs back to the drop-leg, connecting to the boiler anywhere under the water-line. The riser, horizontal, and drop-leg form the loop, and usually consist of pipes varying in size from three quarters of an inch to two inches, and are wholly free from valves, the loop being simply an open pipe, HEATING AND VENTILATING BUILDINGS. giving free communication from separator to boiler. (Stop- and check-valves are inserted for convenience, but take no part in the loop's action.) " Supposing, for example, the boiler- pressure to be 100 pounds and the pressure at the separator reduced to 95. " The pressure of 95 pounds at the separator extends (with even further reduction) back through the loop, f Jff FIG. 202. THE STEAM-LOOP. but in the drop-leg meets a column of water (indicated by the broken line) which has risen from the boiler, where the pressure is 100 pounds, to a height of about 19 feet, that is, to the hydro- static head equivalent to the 5 pounds difference in pressure. Thus the system is placed in equilibrium. Now the steam in the horizontal condenses, lowering slightly the pressure to 94 pounds, and the column in the drop-leg rises two feet to balance it ; but meanwhile the riser contains a column of mixed vapor, spray, and water, which also tends to rise to supply the horizontal, as its steam condenses, and being lighter than the solid water of the drop-leg it rises much faster. By this proc- ess the riser will empty its contents into the horizontal, whence there is a free run to the drop-leg and thence to the boiler." 137. Reducing-valves. The reducing-valve is a throttling- valve arranged to be operated automatically so as to reduce the pressure and also to maintain a constant pressure on the steam-mains. A great many forms of these valves are in common use. In one a diaphragm of metal or rubber is em- ployed, as in Fig. 203. The low-pressure steam acts on one side of the diaphragm, a weight or spring which may be set at any desired pressure on the other side. This diaphragm is HEATING WITH EXHAUST STEAM. 26 1 The three important requisites in the construction of such plants are, first, a removal of all surface-water so that it cannot possibly come in contact with the steam-pipe ; second, provision for taking up expansion of pipe and keeping it in proper alignment ; and, third, insulation of the pipe from heat losses. The first condition, which is the most important of all, is also the most likely to be overlooked, and many failures to secure economic transmission have been caused by allowing the surface-water to come in contact with the heated pipes. This water can be removed by the construction of a drain beneath or by the side of the pipe-system, provided with proper outlets. A perfect drainage-system for the soil is in every case an essential requisite for success. Provision for expansion may be made by the use of expan- sion-joints, as already described in Article 62, page 105, or by the use of elbows and right-angled offsets arranged to partly turn as the line expands. The writer has had experience with various forms of these joints, and found nothing equal to the straight expansion-joint, Fig. 90, which should, however, be constructed so that it cannot by any possible accident be pulled apart ; this may be done either by use of an internal lug or external brace. These joints should be thoroughly anchored, so that they will stay in position, and should be placed suf- ficiently close together to take up all expansion without strain on the pipe-line. If the ordinary slip-joints are used, they will need to be placed at distances of about 120 feet apart. The pipe between the joints should rest on rollers or connect- ing hangers which permit its free motion. If elbows and off- sets are employed to take up expansion, there will be an abrupt change in grade, and if any part dips below the main steam-line it should be drained by a pipe connecting to a trap or to the return. If bends convex upward are necessary, means must be provided for removing the air. In general, in systems where the steam is transmited long distances the best results will be possible only when the boiler- plant can be located on lower ground than the buildings to be heated, so that the water of condensation may be returned by gravity. This cannot always be done, and in many cases it will only be possible to return the water of condensation by HEATING AND VENTILATING BUILDINGS. giving free communication from separator to boiler. (Stop- and check-valves are inserted for convenience, but take no part in the loop's action.) " Supposing, for example, the boiler- pressure to be 100 pounds and the pressure at the separator reduced to 95. " The pressure of 95 pounds at the separator extends (with even further reduction) back through the loop, FIG. 202. THE STEAM-LOOP. but in the drop-leg meets a column of water (indicated by the broken line) which has risen from the boiler, where the pressure is 100 pounds, to a height of about 19 feet, that is, to the hydro- static head equivalent to the 5 pounds difference in pressure. Thus the system is placed in equilibrium. Now the steam in the horizontal condenses, lowering slightly the pressure to pounds, and the column in the drop-leg rises two feet to balance it ; but meanwhile the riser contains a column of mixed vapor, spray, and water, which also tends to rise to supply the horizontal, as its steam condenses, and being lighter than the solid water of the drop-leg it rises much faster. By this proc- ess the riser will empty its contents into the horizontal, whence there is a free run to the drop-leg and thence to the boiler." 137. Reducing-valves. The reducing-valve is a throttling- valve arranged to be operated automatically so as to reduce the pressure and also to maintain a constant pressure on the steam-mains. A great many forms of these valves are in common use. In one a diaphragm of metal or rubber is em- ployed, as in Fig. 203. The low-pressure steam acts on one side of the diaphragm, a weight or spring which may be set at any desired pressure on the other side. This diaphragm is . HE A TING WITH EXHAUST STEAM. 26 1 The three important requisites in the construction of such plants are, first, a removal of all surface-water so that it cannot possibly come in contact with the steam-pipe ; second, provision for taking up expansion of pipe and keeping it in proper alignment ; and, third, insulation of the pipe from heat losses. The first condition, which is the most important of all, is also the most likely to be overlooked, and many failures to secure economic transmission have been caused by allowing the surface-water to come in contact with the heated pipes. This water can be removed by the construction of a drain beneath or by the side of the pipe-system, provided with proper outlets. A perfect drainage-system for the soil is in every case an essential requisite for success. Provision for expansion may be made by the use of expan- sion-joints, as already described in Article 62, page 105, or by the use of elbows and right-angled offsets arranged to partly turn as the line expands. The writer has had experience with various forms of these joints, and found nothing equal to the straight expansion-joint, Fig. 90, which should, however, be constructed so that it cannot by any possible accident be pulled apart ; this may be done either by use of an internal lug or external brace. These joints should be thoroughly anchored, so that they will stay in position, and should be placed suf- ficiently close together to take up all expansion without strain on the pipe-line. If the ordinary slip-joints are used, they will need to be placed at distances of about 120 feet apart. The pipe between the joints should rest on rollers or connect- ing hangers which permit its free motion. If elbows and off- sets are employed to take up expansion, there will be an abrupt change in grade, and if any part dips below the main steam-line it should be drained by a pipe connecting to a trap or to the return. If bends convex upward are necessary, means must be provided for removing the air. In general, in systems where the steam is transmited long distances the best results will be possible only when the boiler- plant can be located on lower ground than the buildings to be heated, so that the water of condensation may be returned by gravity. This cannot always be done, and in many cases it will only be possible to return the water of condensation by 262 HEATING AND VENTILATING BUILDINGS. a pump located in one of the buildings to be heated, and regulated by a pump-governor. This in some cases may in- volve more expense than will be warranted by the saving due to returning the water of condensation. For the insulation of the pipe many methods have been adopted, of which we may mention first the wooden tube and concentric air-space surrounding the pipe, Fig. 205. The FIG. 205. PIPE WITH WOODEN-TUBE INSULATION. tube is usually made by sawing out the interior portion of a log, leaving a shell or wall about two inches thick. Each length is provided with a mortise and tenon joint, and the dif- ferent lengths are joined together by driving. These wooden tubes are slipped over the steam-pipe as it is laid, the pipe being held in a central position by collars, so. as to leave an air- space about one inch thick surrounding the pipe. This pipe is usually strongly banded with hoop-iron, and the joints can be made water-tight when laid, but checks soon form in the wood-pipe and make crevices through which the soil-water can reach the steam-pipe. Recently a form of tube made of two layers of inch board separated by tarred felting has come into use and is in general to be preferred to the solid tube as hav- ing superior insulating qualities. A view of such tubing partly in section is shown in Fig. 206. FIG. 206. WYCKOFF BUILT-UP WOOD TUBING. The wooden-tube system of insulation is objectionable, .principally because it does not protect the pipe from ground- HEATING WITH EXHAUST STEAM, 263 water, its durability, as proved by experience, is not great, and leaks in the steam-pipe are very difficult to locate and repair. [A modified plan of the construction described has been em- [ployed, in which both steam- and return-pipes were covered with asbestos and hair-felt and placed in a box made of 2-inch plank ; the box was laid on a concrete bottom three inches thick, |and after the pipes were laid it was completely surrounded Fwith concrete. This was arranged so that the steam-pipes would not be disturbed by decay of the wood. The concrete would in that event support the steam-pipes and constitute a protecting tube. The heat insulation proved on trial to be much superior to that of the solid wooden tube, while its cost was somewhat less. Similar constructions in which the wooden tube has been replaced by sewer-pipe are in use and are of superior durability. In one case familiar to the writer a wooden tube lined with sewer-pipe was laid outside the steam- pipe, the whole being covered with earth ; such a construction replaced one shown in Fig. 205, but in practice its heat-insula- :tion properties have not proved to be better. The best system of transmitting steam long distances, but probably also the most expensive, is to be obtained by build- ing a conduit lined with brick or masonry laid in cement and sufficiently large for inspection and repairs. The pipe should 'be carried in it on proper hangers and thoroughly wrapped with insulating material, as described in Article 116, page 200. Every required condition can be easily met in this construc- tion. The loss of heat from systems protected by a simple wooden tube is considerable, rising in many cases to from 30 to 40 per cent of that from the bare pipe. This is, however, due to the poor system of insulation used, since it should not exceed in any case 20 per cent of that from naked pipe (see page 199). The loss from the underground system of piping at Cornell University, which is somewhat over one half mile in length, and in which the steam-pipes are laid inside of sewer-pipe, with a wooden tube outside the sewer pipe, the whole covered with about 4 feet of earth, causes the consumption of about two and one half tons of coal per day, which is about 10 per cent of the total coal consumption when the plant is working at normal 264 HEATING AND VENTILATING BUILDINGS. capacity. This heat loss is very nearly a constant amount and cannot be expressed as a fixed percentage of the total steam used, for the reason that when the steam consumption is large this percentage of loss is small and vice versa. High-pressure steam for power purposes is also sometimes transmitted in this manner and engines operated at a great distance from the boiler-plant. The losses from such a system of transmission are often serious, especially if a long pipe-line has to be kept hot, and if the engine is operated only a part of the time or only at partial capacity. Where the engine is worked to its full capacity, the loss is usually less than by any other system of transmission. The following paragraph gives a careful estimate, based on actual experiment, of the loss ex- perienced in transmitting constant power by various methods a distance of 1000 feet. The loss in transmitting power by any system is principally constant, and hence when the power is greatly increased the percentage is correspondingly reduced. The following estimate is based on the transmission of loo horse-power 1000 feet : Percentage Method of Transmission. of Loss. Line shafting : Loss by friction (average 32) 25 to 40 Electricity : Loss in transforming from mechanical to electri- cal, and vice versa 20 to 30 Line loss 2 to 5 Total loss, electrical transmission 22 to 35 Conveying steam : Naked steam-pipe (still air) 37 to 45 Pipe covered with solid wood and earth n to 13 For operating machinery which is required occasionally or at intervals electricity is no doubt the most economical medium, since when the demand for power ceases the expenditure on account of transmission also becomes nothing, which is rarely the case either with line-shafting or steam. The diagram, Fig. 207, gives the summary of the results of a test of the Lehigh Coal-storage Plant, South Plainfield, N. J., HEATING WITH EXHAUST STEAM. 265 made by the writer to determine the heat lost in supplying an engine situated 740 feet from a boiler-house, the connecting 2 4 6 8 10 12 (4 16 18 20 22 24 26 28 FIG. 207. DIAGRAM SHOWING RESULTS OF TEST TO DETERMINE HEAT LOSSES IN UNDERGROUND PIPE. pipe-line consisting of 250 feet of 6-inch, 106 feet of 5-inch, and 391 feet of 4-inch pipe, having a total radiating surtace of 1057.5 square feet. 266 HEATING AND VENTILATING BUILDINGS. The engine was 1 2-inch diameter, i6-inch stroke, running with a piston speed of about 600 feet a minute, thus producing, when cutting off at one third stroke, a velocity of steam of about 60 feet per second in the 4-inch supply-pipe. As this pipe was 391 feet long, more reduction in pressure was antici- pated than was actually found. As shown by the summary which follows, the actual reduction varied from 5 to 7 pounds, averaging 6 pounds. The general method of testing adopted was such as to give information, first, of the amount of water in the steam as it entered the steam-pipe ; second, the amount of water in the steam as it reached the engine ; third, the amount of water collected at intervening drips ; fourth, the total amount of steam used ; fifth, the fall in pressure between the boilers and engine. These determinations were made as follows : The amount of water in the steam was determined by a throttling calorimeter, the sample of steam being drawn in each case from a vertical pipe located close to a bend from a horizontal, and collected by a half-inch nipple extending past the centre of the vertical pipe. The drip was caught at places which had been provided in the pipe, and was weighed from time to time. The barometer readings were taken with an aneroid which had been compared with a mercurial barometer. The cor- rected readings are given in the summary as well as in the dia- gram. Simultaneous observations of the quantities given in the summary were taken every ten minutes. A study of the summary shows that the loss was sensibly constant during the run. This is clearly shown by noting the fact that any increase in the amount of steam flowing through the line had the effect of decreasing the percentage of moisture at the engine. The total heat loss per hour was equivalent to that required to evaporate (36 -f- 45.1 =) 81.1 pounds of water from a tempera- ture of 314 F., to a pressure of 70.1 pounds by gauge. This is equal to (81.1 X 893 ) 72,322 B. T. U. The average steam-pressure was 70.1 pounds by gauge, its temperature 313.6 F., the average outside temperature 16.6 F.; hence the difference of temperature was 297. The loss for each de- gree difference of temperature between that of outside air and that of steam becomes (78,342 -^ 297 = ) 243.7 B. T. U. per -HEATING WITH EXHAUST STEAM. 26? hour. The total radiation surface was 1057.5 square feet; hence the loss in B. T. U. per square foot per hour was 0.229 per degree difference of temperature. This for a difference of temperature of 150 corresponds to 0.17 B. T. U. per degree difference per square foot per hour, an amount about 10 per cent of that which would have been given off from a naked pipe. (See page 66.) The loss by condensation varied from 3 to 8 per cent, the loss of pressure and consequent ability to do work about 6 per cent. The total loss was not far from 10 per cent from both these causes ; if this had been proportional to length, it would have been 13.5 per cent for a line 1000 feet in length. The diagram shows variations in the observed quantities as they occurred from time to time. It is to be noted that as the demand for steam at the engine was large the moisture in the steam delivered was correspondingly reduced. CHAPTER XII. HEATING WITH JOT 139. General Principles. The general laws which apply to hot-air heating have already been considered in the articles relating to Ventilation and to the Methods of Indirect Heat- ing with Steam or Hot Water.* The method of heating with hot air, as usually practised, consists in first enclosing a suit- able heater, termed a furnace, in a small chamber with brickj or metallic walls, which is connected to the external air by a flue leading to its lower portion and to the various rooms to be heated by smaller flues leading from the upper part. In ^operation the cold air is drawn from the outside, is warmed by )coming in contact with the heated surfaces of the furnace, and /is discharged through the proper flues or pipes to the various f rooms. The rapidity of circulation depends entirely upon the / temperature to which the air is heated and the height of the flue through which it passes ; the velocity will be in every case essentially as given in the table on page 45. In order that a system of circulation may be complete flues must be pro- vided for the escape of the cooler air from the room to be heated, otherwise the^rirru^gtu^witt be very uncertain and the heating quite unsatisfactory. Registers and flues for the escape of the air from the room are often neglected, although fully equal in importance to those leading to the furnace. Regarding the relative merits of hot-air heating by furnace as described and of the various systems of steam or hot-water heating, little can be said in a general way, since so much de- pends on circumstances and local conditions. It is rarely that these systems come in direct competition. The force which * See pages 52 and 211. 268 HEATING WITH HO 7' AIR. 269 causes the circulation of the heated air is a comparatively feeble one and may be entirely overcome by a heavy wind ; consequently it is generally found that the horizontal distance to which heated air will travel under all conditions is short ; hence the system is in general not well adapted for large buildings. When properly erected and well proportioned, this system gives, in buildings of moderate size, very satisfactory results. It may be said, however, that, in erecting a hot-air system of heating, competition has been in many cases so sharp as to induce cheap,*rather than good, construction. Small fur- naces have been used in which the temperature of the ex- terior shell had to be kept so high, in order to -meet the demands for heat, that the heated air absorbed noxious gases from the furnace and entered the room in such condition as to impair, rather than to improve, the ventilation. Ventilation- ducts for removing the air from the rpoms have often been neglected, and hence the results obtained have been far from satisfactory. Such faults are to be considered, however, as those of design and construction rather than as pertaining to ;the system itself. In order that the hot-air system should be satisfactory in even- respect, the furnace should be sufficiently lajtge, and the ratio of heating surface to grate such that a large quantity of air may be heated a comparatively small amount rather than that a small quantity shall be heated a great amount. As air takes up heat very much more slowly than steam or water, it would seem that the relative ratio of heating surface to grate surface should be more than that commonly employed in steam-heating. By studying the proportions which have already been given for steam-heating boilers (page 125) it will be seen that the ratio of heating surface to grate surface for the steam-boiler varies between 20 and 45, averaging about 32. From a study of the results in catalogues of manufacturers df furnaces the ratio of air-heating surface to grate surface in hot- air furnaces seems to vary from 20 to 50 as extremes. These proportions are essentially the same as used in steam-heating and are much too small for the best results in hot-air heating. It is quite evident that since air cannot be heated by radiation, 27O HEATING AND VENTILATING BUILDINGS. and is warmed only by the contact of its particles against the heated surface, that the exterior form of the furnace should be such as will induce a current of air to impinge in some por- tion of its course directly against the surface. Regarding the economy of this or any other system of indirect heating, it is simply a question of perfect combustion and rela- tive wastes of heat. If the fuel is perfectly burned and all the heat which is given off is usefully applied, the system is per- fect. The waste of heat in any system of combustion is that due to loss in the ashes, to radiation, and to escape of hot gases into the chimney. If the furnace is properly encased and if the hot-air pipes are well covered, there is no reason why losses from imperfect combustion and from radiation should not be a minimum. The chimney loss depends largely upon the temperature of the surface of the heater : if this is high, the loss will be large. In general, it may be said that the larger the heating surface provided the lower may be its temperature, and the greater the economy. It should be noted, however, that this or any system of indirect heatingi requires the consumption of more fuel than when the heating surfaces are placed directly in the room, and for that reason! the operating expense must be considerably greater than that of direct systems of hot-water and steam heating. (See page 202.) Furnaces, or in fact heating-boilers of any kind, are un- economical if operated with a deficient supply of air. In this; case the product of combustion will contain carbon monoxide,*' an extremely poisonous and inflammable gas, which is quite likely to take fire and burn, on coming in contact with air, at the base or top of the chimney. 140. General Form of a Furnace. The principles which apply in furnace construction are not essentially different from those already given in Chapter VII for steam and hot-water boilers. In the case of a hot-air furnace the fire and heated products of combustion are on one side of the shell and the air to be warmed on the other. In^the case of steam or hot- water boilers the water and steam occupy the same relative! * See Article 24, page 26. HEATING WITH HOT AIR. 2JI >sitions as the air in the case of the hot-air furnaces. The rpes and forms of furnaces which are in use may be classified ictly the same as heating-boilers, Articles 77 and 82, as having plain or extended surface, and as being horizontal or vertical, tubular or sectional; it may be said that the forms which are in use are fully as numerous as those described for steam-heating -and hot-water heating. The material which is employed in construction is usually cast iron or steel, and there is a very g*eat difference of opinion as to the relative merits of the two. It seems quite probable that cast iron, because of its rough surface, may be a better medium for giving off heat than wrought iron or steel, but it is quite certain that at a very high temperature, some carbon from the cast iron will unite with the oxygen from the air forming carbonic acid. When very hot it may be slightly permeable to the furnace gases. Such objections are, how- ever, of little practical importance, since the temperature of a furnace never should, and never does if properly proportioned, exceed 300 or 400 degrees Fahr., and for this condition the difference in heating power of cast iron and steel is very slight. It is of great importance that the shell of the furnace be tightj so that smoke and the products of combustion can- not enter the air-passages. Furnaces can be purchased with or without magazine feed, but the demand of late years is principally for those without the magazine, since it has not been proved to present any special advantages. Furnaces are often set in a chamber surrounded with brick walls, as explained for steam-boilers, but they are more fre- quently set inside a metallic casing, this latter being termed a portable setting ; this casing varies somewhat as constructed by different makers, but usually consists of two sheets of metal, the outer of galvanized iron, with intervening air-space empty or filled with asbestos. The casing is placed at such a distance from the furnace as to provide ample room for the passage of air. Some form of dumping or shaking grate which can be readily and quickly cleaned is almost invariably employed. The draft-doors which admit air below the grate and check- dampers in the stovepipe are usually arranged so they can be 2/2 HEATING AND VENTILATING BUILDINGS. opened or closed from some convenient place on the first floo of the house by means of chains passing over guide-pulleys. A pan in which water may be kept is added to every fur- nace for the purpose of increasing the moisture in the air this is of importance, since the heated air requires mor moisture than cold to maintain a comfortable degree of satur tion,as explained in Article 28, page 30. 141. Proportions Required for Furnace Heating. The proportion of the area of heating surface in the furnace to that of the grate cannot be computed from any data accessible to the writer, and the proportions given are assumed to be twice those which have been found to give best results in steam-heat- ing ; these apparently agree well with the best practice. The tables which are given are computed for a maximum tempera- ture of 120 F. for the air leaving the furnace, which is 50 degrees in excess of the ordinary temperature in the house. No doubt better practice might require the introduction of more air at a lower temperature, but considering the fact that this high temperature only has to be maintained when the outside weather is extremely cold, it seems quite doubtful if the expense of a furnace large enough for this additional duty, would be warranted. The ratio which the grate surface of the furnace should bear to the glass and exposed wall surface of the room can be com- puted with sufficient accuracy from known data relating to the heat contained in coal and to the probable efficiency of com- bustion. The heat given off from the walls of a room for each degree difference of temperature between the inside and out- side has been shown on page 59 to be approximately equal to the area of the glass plus one quarter the area of the exposed wall surface, which we will in this place denominate as the equivalent glass surface. One pound of good anthracite coal will give off about 13,000 heat-units in combustion. One pound of soft or bituminous coal will give off in combustion from 10,000 to 15,000 heat-units, depending on the kind and quality. Of this amount a good furnace should utilize 70 per cent.* The amount of coal which is burned per square foot * It is quite probable that the efficiency of combustion in an ordinary fur- nace is much less than the above, often as low as 50 per cent. HEATING WITH HOT AIR. 2/3 of grate surface per hour will depend very much upon the character of attendance ; in ordinary furnaces used in house heating, and where it is expected to replenish the fires only two or three times per day, this amount is low, being not greatly in excess of 3 pounds. If the air is 120 degrees in temperature, nearly 60 cubic feet will be required, when heated one degree, to absorb one heat-unit (see Table VIII), and if such air is delivered 50 degrees above that of the air in the room, each cubic foot will bring in f of one heat-unit. The velocity of air in feet per minute with ample allow- ance for friction is given in a table on page 45, from which it is seen that it will be safe to assume velocities of 4, 5, and 6 feet respectively, per second in the flues or stacks leading to the various floors. The velocity of the air passing the register may be assumed as 3 feet per second in every case ; this lower velocity is obtained by making the area of the register somewhat larger than that of the pipe leading to it. The following mathematical discussion gives these various consid- erations in general and algebraic terms, as follows : Let F = square feet in grate, C = weight of coal burned per square foot of grate per hour, r = heat-units per pound of coal, E = efficiency of furnace, h = heat-units per hour, T = temperature of air leaving fur- nace, /' = temperature outside air, / = temperature of room, G = area of glass in room, W = area of exposed wall surface, H = heat lost by room for one degree difference of temperature, K= cubic feet of air heated by furnace per hour, K' = cubic feet air required to warm room. We have, as explained, // = CFEr = total heat given off by furnace, equal to that re- quired for all the rooms. . ... . . . . . . (i) A' = = cubic feet of air heated per hour by furnace. . . (2) J. / h' = (G + i W)(t /') = total he4lt-units to warm the room. . . (3) K ' = - = cubic feet of air to warm the room. , (4) For average conditions substitute in above, as explained, T= 120, / 70, /' = o, C = .70, r = 13,000, Cr = 9100, and we have h = 9\ovCF=iK. . . . . . . . . . . . (5) K = 4$$oCF = 0.56. . . (6) K' = *4(G + i If) (7) When AT = AT'. CF = G + * W ; when C = 3, F= + *?. (8) 54.2 162.6 iJT) (9) 2/4 HEATING AND VENTILATING BUILDINGS. For computing areas of leader-pipes and stacks, for resi- dence heating, assume velocities which can safely be taken as follows : First floor, 4 feet per second or 240 per minute ; second floor, 5 feet per second or 300 per minute ; third floor, 6 feet per second or 360 per minute. (See table, page 45.) Through a cross-section of the flue equal to one square inch 100 cubic feet will pass in one hour when the velocity is 4 feet per second, 125 when the velocity is 5 feet per second, 150 when the velocity is 6 feet per second, 25?' when the velocity in feet per second is represented by v. Denote area of flue in square inches by L\ then from equa- tion (7) 2$V 257' v. From this, by transposition, we have If for first-floor rooms v = 4. If for second-floor rooms v 5. If for third-floor rooms v = 6. (Also see table on page 53.) The following table gives the relative values of these vari- ous quantities, computed for the conditions as explained : HEATING WITH HOT AIR. 275 PROPORTIONS REQUIRED IN FURNACE HEATING. Equivalent glass surface* .. . ("u. ft. air to be heated per hr. < irate area, square inches . . Equivalent diameter round grate, inches Heating surface, square feet. Diameter smoke-pipe, inches Approximate cubic feet / space ) Area stack ist floor (vel. 4) sq. in. 2 d " (vel. 5) " 3 d " (vel. 6) " Diameter leader-pipe t ist floor. 2 d " .. 3d " -- Net area register, sq. in. ist floor (vel. 3).. . 2d " and above Area ventilating flue 25 2100 22 7-5 ii 50 4200 43 8-5 21 75 f 9-5 32 IOO 8400 85 II.5 42 I2 5 10,500 107 12.5 53 150 12,600 127 5 200 I6.800 170 'i 336 4200 168 i35 112 J 4-7 13-2 12 224 168 168 *35 250 21.000 : 106. 7 4200 5250 2IO 170 I 4 I6. 5 I4. 7 13-4 280 2IO 210 I 7 500 42,000 425 24 212 8 8400 2100 420 345 280 19 21 9 S 60 420 420 345 750 63.000 640 29 320 10 12.600 T5,75<> 630 500 420 23.2 25.2 23.2 840 630 630 500 1000 84,000 850 a II 16.800 21,000 840 6 560 26.7 29.2 26.7 1 120 840 8 4 6 7 420 525 21 17 14 7 7 8 4 1050 42 11 7-5 7 1260 1570 6 3 5i 42 9 8.2 1680 2 IOO a 55 10 5 9-5 2100 2625 105 85 7 11.6 10.5 9-5 210 105 o 5 85 2520 3*50 126 1 02 84 12.7 "5 10.4 1 68 126 126 IO2 28 21 21 7 56 42 42 33 in ON O\ 00 no 84 84 68 Net area ventilating register . * This quantity is (defined page 272). f For pitch of one inch per foot. Use larger pipe for less pitch- NOTE. The proportions in the above table agree very well with those given by the Excelsior Steel Furnace Co. for the condition of changing the air in each room four times per hour, which can be taken as representing the average amount required to bring in the heat. The grate surface is computed for combustion of 3 pounds per square foot per hour, with an efficiency of 70 per cent, or a greater amount at less efficiency. The heating surface given in above table is much larger than ordinarily found in furnaces, but not too large for best results. 142. Air-supply for the Furnace. The air-supply for the furnace is usually obtained by the construction of a passage- way or duct of wood, metal, or masonry leading from a point beneath the furnace casing or near its bottom to the outside \ COLD AIR DUCT If FIG. 208. HOT-AIR FURNACE WITH COLD-AIR Box BELOW CELLAR BOTTOM. air, essentially as shown in section Fig. 208. This duct or pipe is usually termed the cold-air box and is often constructed of 276 HEATING AND VENTILATING BUILDINGS. wood. In all cases there should be a screen over the outer end to keep out vegetable matter or vermin, and doors should be arranged so that it can be cleaned periodically. A damper is usually desirable, arranged so that it can be partly or entirely opened to regulate the admission of the cold air. The cold- air box should be made perfectly tight and in a workmanlike manner, so that air cannot escape 'into or be drawn from the cellar or basement. This should join onto the furnace casing at as Iowa point as the character of the cellar bottom will per- mit. In some instances it is desirable to erect two cold-air boxes, opening to the air on opposite sides of r.he house, so that the supply may be drawn from either direction as re- quired to obtain the help of wind-pressure, to aid in the cir- culation of the air over the furnace. The cross-sectional area of the cold-air box is proportioned, by different authorities, from 66 t^o 100 per cent of the sum, of the areas of all pipes taken from the furnace. If this were proportioned so that its area should be in ratio to the re- spective volume of cold and heated air, the sectional area of the cold-air box should be about 80 per cent, of the sum of the areas of the various stacks. To avoid frictional resistances it would seem to be advisable when practicable to make its area equal to that of the sum of the areas of the stacks. 143. Pipes for Heated Air. The pipes for heated air are of two classes : first, those which are nearly horizontal anol are taken from near the top of the furnace casing these are usually round and made of a single thickness of bright tin, and if possible erected with an ascending pitch of one inch to one foot, and are termed leader-pipes ; second, rectangular verti- cal pipes or risers, termed stacks, made in such dimensions as will fit in the partitions of a building and to which the leader-pipe connects. The bottom of the stack is enlarged into a chamber termed a boot, which is made in various forms and provided with a round collar for connection to the leader-pipe. The top part of the stack may be provided with a similar boot from which horizontal rectangular stacks are taken, or it may be connected to a rectangular chamber into which the register may be fitted and which is known as the register box. The stacks usually pass up or near the woodwork of partitions, HEATING WITH HOT AIR. 277 and for lessening the fire risk as well as preventing loss of heat should be made with double walls separated by an intervening air-space. The register boxes should also in every case have double walls. The general form of a stack in position in a partition, with boot attached at bottom for leader-pipe and with round connection for register box, is shown o in Fig. 209. The leader-pipes and stacks, boots, and ^ register boxes are now a standard article of manufacture by several firms. I am o indebted to the Excelsior Steel Furnace ^ Company of Chicago for the table of < capacity and dimensions of various forms ^ of stacks and leader-pipes, given on page a It will be found profitable in nearly < every case to wrap the leader-pipes with two or more thicknesses of asbestos paper t u FIG. 2 TO. FIRST-FLOOR OUTSIDE REGISTER Box WITH COLLAR AT- TACHED. and mineral wool in order to prevent loss of heat. It is desirable to locate the stacks in the inside partition-walls of the building, or where they will be protected as much as possible from loss of heat, since any loss affects the rapidity of circulation. It is generally necessary to have the leader- pipes not over 15 feet in length, otherwise the circulation will be uncertain in amount and character. 278 HEATING AND VENTILATING BUILDINGS. 144. The Areas of Registers or Openings into Various Rooms. Registers are made regularly in various forms, square or round, and arranged for use either in the floor or side walls * TABLE OF SIZES AND DIMENSIONS OF SAFETY DOUBLE HOT- AIR STACKS. Stack as Listed. (In Inches.) Size of Outside Stack. Size of Inside Stack. f Inside Stack in Inches ty as compared with that ot-air Pipe with Pitch of h to i Foot. "5 3 " C"*-, S -g C - f Round Pipe which Id be ased with each c. f said Round Pipes in ES. Registers and Register :s which should be used each Stack. Feet of Space (approxi- ) that can be Heated each Stack with Pipe Registers of size given. ilent of said Space on r of Rooms 10 Ft. high. i Inches of Registers Space occupied by deducted. 4^ *e3 *rt *O HE r^ ^ -*-> 3y OJ3 O X ** a> r^ > ,~ jq C/5 V 1 3 OJ cL vi - 1 " J3-- O ui O rt ^ 'fe ^ g-r'c .- O rt-^ c5 < * 1 O ^ ?t J5 1" i/5 u w^ < 4 x 8 3%x 7% |3M X 7 23 35 64 7 38 6x 8 500 6x 8 35 4 X 3% x 9% 3Hx 9 29 8 5 8x 10 850 8x 10 45 4 x 3% x 10% 314x10 48 8 8 5 8x 12 IOOO 9x11 55 4 X SZ X T 1^ 3^x11 35 53 8)4 9 63 yx 12 1250 IOX 12^ 60 4 x - 3% x *3% 3^x13 4 1 63 9 9 63 1O X 12 1650 12 X 14 70 6x 5*^ x 9^^ 5^4 x 9 47 71 10 10 78 10 X 14 2000 I2XI 7 80 6x 5% x 11% 5/4 x 1 1 58 87 ii 12 "3 12x15 2300 14X17 TI 5 6x 14 5%xi 3 % 5^4 x 13 68 102 12 12 113 12 X 17 14 x 20 2000 OQOO I5XI8 1 20 Teg 8x18 7% x 17% 7^x17 79 124 1 86 15 16 201 16 x 24 JUOU 4000 20X20 150 210 10 x 20 9% x 19% 9J4 x 19 i 7 6 264 18 18 254 20x24 5400 20 x 27 270 10 X 24 9%X2 3 % 9^x23 213 330 20^ 20 3M 21 X 29 7000 20X 35 340 Stacks for 4 inch studs carried in stock. Other sizes made to order. * This table is copyrighted by Excelsior Steel Furnace Co. as required. These registers are usually supplied with a series of valves which may be readily opened or closed. The FIG. 211. REGISTER BOXES SHOWN IN POSITION. space taken by the screen and valves is usually about J of that of the register, so that the effective or net area is about | of HEATING WITH HOT AIR. 2/9 the nominal size of opening. These registers may be ob- tained finished in black or white japan, or electroplated with nickel, brass, bronze, or copper. The table on page 280 gives the various sizes of registers which are regularly on the market, their effective area in square inches, and diameters of round pipe having the same capacity. The areas of stacks may be considerably less than these of the registers, since it is generally required that the velocity of air entering the room shall not exceed 3 or 4 feet per second, while that passing through pipes and stacks may have ; the highest velocity possible, which for the different floors will not differ greatly from 4 to 6 feet per second, as already ex- \ plained. For methods of proportioning ventilating flues see \ page 233. (Fie. 212. SIDE- WALL REGISTER HEAD OR FLANGE. Considerable difference of opinion exists as to the relative merit of floor and wall registers for heating purposes. It is ! the common practice to use floor registers for most rooms on I the first floor, and wall registers for rooms on the second and I higher floors. The floor register, from its general form and i position, can be supplied with hot air somewhat more readily I than the wall register, and for that reason may induce some- I what stronger circulation, but it is a receptacle for dust and h sweepings of the room and in a position to materially interfere with the carpets. It will be found that the experiments made by Briggs (see page 46) as to diffusion of air hold in the case of furnace heating the same as in that of any other 280 HEATING AND VENTILATING BUILDINGS. system. From these experiments it would seem that the highest efficiency would be attained when the inlet for the heated air was at the side near the top of the room and the outlet for ventilation near the. floor. This distribution is one that, so far as the writer knows, has never been practised in furnace heating of residences, although it is the commonly accepted method in school-house heating, whether with a furnace or an indirect system of steam or hot-water heating. TABLE OF REGISTERS. Size of Opening. Inches. Effective Area. Square Inches. Diameter Round Pipe. Inches. Size of Opening. Inches. Effective Area. Square Inches Diameter Round Pipe. Inches. 4^ X 6* 20 5- ! 10 X 20 132 13.0 4X8' 21 5.2 12 X 12 96 II. I 4 X 10 26 5-8 12 X 14 112 11.9 4 X 13 34 6.6 12 X 15 120 12.4 4 X 15 40 7.2 12 X 16 128 12.8 4 X 18 48 7.8 12 X 17 136 13-2 6X6 24 5-6 12 X 18 144 13 5 6 X 8 32 6.4 12 X 19 152 13.9 6X9 36 6.7 12 X 20 1 60 14-3 6 X 10 40 7-2 12 X 2 4 192 15-6 6 X 14 56 8-5 14 X 14 130 12.8 6 X 16 64 9.1 14 X 16 149 14.8 6 X 18 72 9.6 14 X 18 168 14.7 6 X 24 96 n. i 14 X 20 186 15-5 7X7 32 6.4 14 X 22 205 16.2 7 X 10 52 8.2 15 X 25 250 17.8 8X8 42 7-4 16 X 16 170 14.7 8 X 10 53 8.2 16 X 20 213 16.5 8 X 12 64 9.6 16 X 24 256 iS.i 8 X 15 80 IO. I 18 X 24 288 19.2 8 X 18 96 II .2 20 X 20 267 18.5 9X9 54 8.2 20 X 24 320 20.2 9 X 12 72 9.6 20 X 26 347 21 .O 9 X 13 78 IO.O 21 X 29 406 22.7 9 X 14 84 10.3 24 X 24 384 22.1 10 X 10 66 9.2 24 X 32 512 25-5 10 X 12 80 9.1 27 X 27 486 25.0 10 X 14 93 10.9 27 X 38 684 29-5 10 X 16 107 ii. 7 30 x 30 600 27.7 10 X 18 120 12.4 145. Circulating Systems of Hot Air. -By connecting the cold-air box with the hall floor or the lower portion of a pas- sage communicating with all rooms of the building and clos- ing outside connections a downward current of air will pass from the rooms to the furnace, which, being warmer than the outside air, will aid materially in heating. Such a connection HEATING WITH HOT AIR. 28 1 if properly made and used with judgment may be of great ^service in reducing the cost of operation without seriously ^affecting the ventilation. Such a system if erected, however, should be supplied with devices to prevent overheating and arranged so that cold air can be drawn from outside of the building whenever desired. There is so much danger that ventilation will be poor with this system that it is not recom- mended. 146. Combination Heaters. A combination heater con- sisting of a hot-air furnace, with the addition of a boiler for hot water or steam, is meeting with somewhat extensive use 'and has been described on page 189 so far as relates to the construction of the steam and hot-water appliances. In case a combination heater is used the area of the grate and heating surfaces will need to be proportioned for both systems. A com- bination heater is better suited to large buildings than a hot-air furnace. In practice, however it will be found, diffic. it to so proportion the amount of heating and radiating surface, as to give a perfect distribution of heat in rooms some of which are heated with hot water or steam, and some with hot air, but this difficulty will no doubt be largely overcome by experience. 147. Heating with Stoves and Fireplaces. The manu- facture of stoves for heating purposes is a very great industry in the United States and they are extensively used in the cheaper classes of dwellings. In every case the stove is located directly in the room to be heated and is connected with a chimney by means of several lengths of sheet-iron pipe. Stoves are built in many forms, some of which are very elaborate and highly ornamented, and in many cases they are provided with 1 magazines from which the coal feeds itself automatically as re- quired. The heat, given off from a stove, is generally nearly all utilized in warming, perhaps not over 10 or 15 per cent being carried off by the chimney. Stoves do not, however, present an economical mode of heating, largely because the wastes which occur from the operation of small fires are very great and cannot be avoided. It is doubtful if the efficiency averages much above 25 per cent. In addition, the stove occupies useful room, is the source of very much dirt and litter, and requires a great deal of attention.' 282 HEATING AND VEN7ULATING BUILDINGS. Open fireplaces which were used at one time extensively are very wasteful, as little more than the direct radiant heat from the fire is absorbed in warming. They are also subject to all the wastes which pertain to stoves, and their probable efficiency cannot be considered as over 15 or 20 per cent. They are, however, valuable adjuncts of a system of ventila- tion, since large quantities of air are drawn from the room and discharged into the chimney. In the use, of a stove called a fireplace heater, the heated gases from an open fire pass through a drum or radiating surface in the room above, and the heat which otherwise would be discharged from the chimney and wasted is partly utilized in heating. 148. General Directions for Operating a Furnace. The general directions for operating a furnace so far as regards the care of the fire are the same as those which have been previ- ously given for the operation of steam-heating furnaces, page 169 ; there are, however, no steam-gauges or safety appliances 'needed. In regulating the temperature of the house the drafts of the furnace should be operated rather than the valves of registers leading to various rooms. In some instances if the circulation is strong in certain directions and weak in others so that certain rooms cannot be heated, it may be a good plan to shut all registers except the one to the room where heat is required until circulation is established, after which, circulation will usually continue without further attention. In the opera- tion of a furnace great care should be taken that the metal never becomes red hot or even cherry-red. If it will not warm the building without being excessively hot, the furnace is too small, or else has too little radiating surface in proportion to the fire-pot. The water-pan should be kept filled with water. Thermostats arranged to open or close the drafts when desired are in use in many systems of furnace heating with success. For protection of the furnace during summer months some makers recommend that the fire-pot be filled with lime. For burning soft coal, furnaces of special construction only should be employed. NOTE. Rules for Furnace Heating : First. To find area of grate in square inches: Divide total window surface plus \ total exposed wall surface in square feet by 200. Second. To find area of flue for any room in square inches: Divide window surface plus \ wall surface in square feet by 1.2 for first floor, by 1.5 for second floor, by 1.8 for third floor. CHAPTER XIII. FORCED-BLAST SYSTEMS OF HEATING AND VENTILATING. 149. General Remarks. In the systems of hot-air heat- ing which have been described the circulation of air is caused :>y expansion due to heating, which is a feeble force and is ikely to be overcome by adverse wind currents, by badly pro- portioned pipes, or by friction ; by employing a fan or blower of some character for moving the air the circulation will be rendered positive and so strong as to be unaffected by these causes. This system can be employed where power is available, and n many cases will be found to present an economical and satis- 'actory system of heating, comparing well with any that has jeen devised, especially when the amount of ventilation pro- vided is considered. The cost of heating a large quantity of air is, however, in every case one of considerable amount, so that it is quite probable that in expense of operation no sys- tem of indirect heating, whether by furnace or steam-pipes, can compare with that of direct hot-water or steam radiation. The systems of forced-blast heating are in almost every case employed in connection with steam-heated surfaces, but in some instances the system has been applied successfully with furnace heated surfaces.* 150. Form of Steam-heated Surface. The heating sur- face is generally built of inch pipe, set vertically into a square cast-iron base, connected at top with return-bends, although the box coil, Fig. 94, page 109, or any form of indirect radiat- ing surface could be used. The fan or blower is placed either * The Metal Worker, May 25, 1895, gives an interesting example showing the successful use of a blower and furnace for heating a church. 283 284 HEATING AND VENTILATING BUILDINGS. so as to draw the air by suction over the heated surface and then deliver by pressure into the rooms, or it is placed so as to force the air by pressure over the heating surface and thence into the conduits leading to the various rooms. The heating surface is usually surrounded with metallic walls forming a chamber through which the air is discharged. Fig. 213 shows the arrangement often adopted, in which a pressure fan is directly connected to an engine, and arranged to take air from FIG. 213. BLOWER CONNECTED TO ENGINE. the atmosphere and force it into the chamber in which the heating surface is placed. 151. Ducts or Flues Registers.* The dimensions of the ducts or flues leading from the heater should be such that the required amount of air may be delivered with a low pressure and velocity, so as to avoid excessive resistances due to friction. The velocity which will be produced by various pressures in * General formulae for the motion of air in long pipes is to be found in Weisbach's Mechanics, and in article Hydrodynamics in Encyclopaedia Britan- nica, by Prof. W. C. Umvin. The formula given by Weisbach is elaborated in an article by Carl S. Fogh '^Engineering Record, Feb. 16, 1895, and a graphical diagram given for practical application. The uncertainty which relates to the application of these elaborate formulae is well shown by the fact that a factor of safety of 4 is used by Mr. Fogh, and serves in the writer's opinion to render such estimates as crude as those obtained by the approximate formulae given here. The article is of great value, however, to those desiring to study the theory of motion. FORCED-BLAST SYSTEMS. 285 excess of that of the atmosphere is given in table on page 42, from which it is seen that a pressure sufficient to balance ^ inch of water (0.29 ounce per square inch) will produce a ve- locity of 30 feet per second in a pipe 100 feet long and I foot in diameter ; this is generally considered to be the maximum velocity which should be pemitted in any of the pipes or pas- sages. In proportioning apparatus in this system of heating it is generally required that sufficient air shall be brought in to change the cubic contents of the room four times per hour. By consulting the table on page 53, it will be seen that for this condition, and without allowance for friction, it will require a flue with 5.7 square inches of area for each 1000 cubic feet of space in the room. By adding two inches to the diameter obtained as above, a fair allowance for friction will be made. The pipes are usually made of galvanized iron or bright tin and should have tight joints and be protected from loss of heat by some good covering (see page 197). Flues of brick or masonry cause more friction than those of galvanized iron, and if used should generally be about two inches larger in diameter than provided for by this table. As branch pipes for various apartments are taken off, the main pipe can be reduced in size ; this should never be done abruptly, but only by the use of taper- ing tubes, the angle of whose sides measured from the line of the main pipe should rarely be greater than 15 degrees. The fan can be located in a chamber which is connected with the external air, as in Fig. 214, or it may be placed in a tube or passageway leading from the heating surface .to the out- side. The area of the cold-air duct or passageway leading to the fan should be as great as possible in order to keep the velocity of entering air low ; if the area of cross-section is equal to the sum of the areas of all the ducts leading from the heating surface, i the velocity will probably be about three quarters of that in the hot-air pipes, and may draw in considerable dust and dirt from outside. The flues which convey air to the rooms should discharge near the upper part of the room substantially as described on page 49 and shown in Fig. 21. The friction in small pipes is greater than in large ones, being relatively pro- portional to the circumference or perimeter ; hence the sum 286 HEATING AND VENTILATING BUILDINGS. of the areas of the branch pipes should be considerably greater than that of the main.* The table on opposite page gives the number of small pipes which provide an area equivalent to that of one large pipe of similar cross-section ; in case no table is at hand the same re- sults may be obtained by dividing the larger diameter by the smaller one and taking the square root of the fifth power of the quotient. The following table gives the actual amount discharged with constant resistance, and with pressure equal to one half inch of water column in round pipes, as computed from Unwin's formulae, page 41 : VELOCITY AND QUANTITY OF AIR DELIVERED IN PIPES OF DIFFERENT DIAMETERS, EACH 100 FEET LONG, WITH AN AIR-PRESSURE EQUAL TO \ INCH OF WATER COLUMN. Diameter of Pipe. In. Velocity of Air. Ft. per Sec. Cubic Feet of Air per Min. Diameter of Pipe. In. Velocity of Air. Ft. per Sec. Cubic Feet of Air per Min. I 8.7 2.6 16 35 6 3,024 2 12.4 16 18 36.8 4,032 3 15-0 45 20 3 8.8 5,184 4 17.3 90 22 40.6 6,480 5 19.4 1 60 24 42.4 8,208 6 21.3 253 26 44-2 9y36 7 23 o 380 28 46.0 U,952 8 24-5 5*5 30 47-4 14.256 9 26.1 720 36 52.0 23,040 10 27.4 900 42 56.1 33-120 ir 28.6 1190 4 8 61.0 46,080 12 30.5 1440 54 63.6 61,920 13 31-3 1620 60 67.0 80,640 14 3 2 -4 2160 *The velocity of flow of air is given in formulae on page 41 ; the amount discharged is equal to the area of the pipe multiplied by the velocity, and will be equal in every case to the square root of the fifth power of a constant multi- plied by the diameter of the pipe. If we denote diameter of larger pipe by of smaller pipe by d, and the number of smaller pipes required to make one of area equivalent to that of larger by n, To find diameter of round pipe, d, which shall be equivalent in carrying capacity to a rectangular pipe with dimensions a and b, we would have - I/ 32< V X\a -f b} FORCED-BLAST SYSTEMS. 2&? * = cx com -coo co ~ M* M co k. 'T3 ^rf* r^ ~r* ~ .2 a" W 3 .2 rt 3 i C ! ^ . . . ^* 3 t *4 J '5'o"" u 'y i (N ~ -i p< co top 'O 2cj4)C-fcO j^QPI'^-NCOI^CIr-. ^ |^a'S^ -- ~ : a. v - -= - - S CQ M c c vo oo ica 1 - 1 '* 00 ^ . 9 . *? 1? ' rt ^ t -"o I QO Nc ^ r ^' Hvr); ^ vO . I ^ u ^ Nv g ^ = ^ w I tH^^HJNcicAtn Aoo " * i ^ c* -TO co O N O co r>. <> coco -G j ^ PI rfO _ _ _ "I ^ _ . _, _ N r^co O co o Iv* ~~ : " . ~~. iH M M M ei PI c c co-t-i^ooo M ^ r^. ^ coo CT* r^VL^ r^cxj \j co o>^/ u\o ;.. i-iMpaco-^- . o* co c^o co N coo N co T in )O co C^ ____ ,H W >< O~~C* -i-Oir>^OO O O^O^ ci O"-> cno nO O co co ^ ON -rco PI r^ w co O r^OM-i-i'-i>-"Wccoo co coo "> ^^ ......... <- tno co O O w O^co o co o O -f * - p< PI co -f ino co ^wi-,piae<-)cn-r inco N co -r co r^ M IQ _ I-H COO CO i-" "TCp P - O '-''-''HpjCMC4c'-r u->o t^oo co o co co o co co <-t "* M N no OO ? C^f^O ir>O3O Q -t "> O C^mmr^O ~co "-" Pi cou->co ~ ci C4 coco-rmo r^co O M -Tco O i C>coccoco ^^^ > coo COPI PIO "-"co r>-o^w Oco ^mcoco coir)in-r>- o w coo^ _^_____ S PI co -r >-icor>QO o*O -rr^pi -> cor^oo r^*rio r^-r-t-Tt-r>cococo o^o *" Mco-i-i-iOO'-'cor^piC> r^co s^co c->r^oo cocoo 288 HEATING AND VENTILATING BUILDINGS. Air which is. drawn in from outside at high velocity is often loaded with dust, and for this reason filters made of some tex- tile material,, or baffle-plates which discharge the dust into vessels of water, are sometimes required in the passageway leading to the fan. Where fans are required for ventilation as well as heating, it is an advantage to have by-pass pipes lead- ing from the fan around as well as over the heating surface and provided with proper dampers so that the air can be delivered into the room fully or partly heated as required. Such an arrangement is shown in Fig. 214. FORCED-BLAST SYSTEMS. 289 The net areas of registers should be sufficiently great to prevent the velocity in the entering air becoming so great as to produce a sensible draft. Taking this limiting value at 5 feet per second, the area of the register can be obtained from table on page 53. If the air is to be changed four times per hour, there should be 34 square inches in the register for each 1000 cubic feet of space. The nominal area of the regis- ter should be about 50 per cent greater than given by this computation ; the actual areas of commercial registers is given in table page 280. 152. Blowers or Fans. Blowers or fans are made in a great variety of forms, and there is little reliable data as to the best shape of fan-blades for practical use. It is quite certain that in the centre of the fan there is very little useful work done, and in some cases a back current is produced which reduces the capacity of the fan, although probably not affect- ing to any great extent the power required to drive it. It is quite probable that the workmanship and character of bear- ings have more to do with the efficiency than any theoretical form of blades. The limits of this book do not permit a dis- cussion of the various forms of blowers. The reader is referred for some experiments on this subject to the work on " Warm- ing and Ventilating of Buildings," by J. H. Mills, vol. II, page 559- The motive power employed to drive fans may be obtained from a running countershaft, from an engine either directly connected or belted, or from an electric or water motor. Where the fan is to be used only at intervals, the electric motor will be found more desirable and fully as economical as the engine. The fan should be located in a position where the noise caused by its operation is likely to be of little importance, and it should be arranged so that a portion or all of the blast can be deflected from the heating surface and sent to the rooms without being warmed if so required. This can be done by proper construction of ducts and dampers. The actual power required to drive fans cannot, for the reasons mentioned, be determined from theoretical considera- tions, but must be obtained by actual test for each given make of fan. 2 9 HEATING AND VENTILATING BUILDINGS. The following table gives the sizes, capacity, and power re- quired for various dimensions of the Sturtevant pressure fan- wheels, which are built to be set in wood or brick housing : TABLE OF CAPACITIES, REVOLUTIONS PER MINUTE, AND HORSE-POWER REQUIRED. PRESSURE IN OUNCES PER SQUARE INCH, AND INCHES OF WATER. Size. In. Diameter Fan in inches. O o a Q Width of housing in inches. Pulley. i oz. Pressure. 0.43 in. i oz. Pressure. 0.86 in. J oz. Pressure. 1.3 in. i oz. Pressure. 1.73 n. a 5 cJ U Jfi C _' c "A V3 C ti-S Cu v, c &,' J" c 9'Q n'S cu ffi * I02i 120 I28J 42 48 48 54 60 72 84 90 22 24 28 H 11 & 4 12* 12* 12* 12* 14* 14* 164 150 138 118 103 K 69 59 55 24734 3 l6 94 42167 47486 60992 75816 108703 149840 172740 1.2 2.1 2-3 3-o 3-7 5-3 1:1 212 I 94 166 MS 129 116 Q7 % 34992 44857 67218 86180 107313 ^3850 212070 244487 3-4 44 5-J 0.6 8.4 10.5 15-0 20.7 23-8 259 238 204 178 !59 '43 119 1 02 95 42892 54966 73130 82355 105602 T 3'475 188520 259765 299584 5-6 7- 1 9-5 10.8 17.1 24-5 33-8 39-o 300 206 183 165 3 no 49524 63463 84436 95086 121938 151800 217340 300000 3459oo 9-7 T2.4 18.6 23.8 29.6 42.4 58.4 67-4 The following table gives the capacity and power required for Sturtevant steel-plate exhaust fans : TABLE OF CAPACITIES, REVOLUTIONS PER MINUTE, AND HORSE-POWER REQUIRED. PRESSURE IN OUNCES PER SQUARE INCH AND INCHES OF WATER. J oz. Pressure. * oz. Pressure. i oz. Pressure. i oz. Pressure. 0.43 in. 0.86 in. 1.3 n. 1.73 in. Size. Rev. Cub. ft. Ou Rev. Cub. ft. cu Rev. Cub. ft. DH Rev. Cub. ft. per per per per per per per per. . min. mm. ffi min. min. S* mm. mm. DC mm. min. a 40 in. 412 2,388 .11 582 3,380 32 714 4,141 54 824 4,782 93 50 in. 329 4,396 .20 465 6,220 .60 571 7,623 .98 659 8,802 1.70 60 in. 274 6,458 31 388 9,140 .89 476 11,200 1.49 549 12,932 2 . 52 70 in. 235 8,412 .41 333 1 1 , 906 1.16 407 14,588 1.90 470 16,848 3- 29 80 in. 206 11,234 54 291 15,9001.55 366 19.483 2-53 412 22,495 go in. 183 15,195 74 258 21,507 2.10 317 26,354 3-43 366 30,427 5- 92 100 in. 165 19,646 95 233 27,804 2.71 286 34,070 4.44 329 39,338 7-67 An examination of this table will show the superior economy of moving a given volume of air under low pressure with a large fan as compared with the movement of the same volume under high pressure by a small fan. Thus to move 8400 cubic feet of air we can use (see above table) a fan 70 inches in diameter FORCED-BLAST SYSTEMS. 2QI revolving at 235 revolutions, and requiring 0.41 horse-power to drive it, or we can use a 5o-inch fan moving at 659 revolutions and requiring 1.7 horse-power. It is therefore evident that true economy can be best attained by purchasing a large fan, and thereby saving the running expense necessary for ad- ditional power to drive a smaller fan up to the same capacity. An exhaust fan in the ventilating shaft has been used, in some instances with good results, for removing air from a building and producing circulation over the heater, but there is liability of leakage or infiltration of air into the flues from the outside. In case air enters this without passing over the heat- ing surface, which is likely to reduce its efficiency, so that in practice it has not proved as satisfactory as the pressure-sys- tem. For purposes of ventilation only, or for the removal of foul and noxious gases where the ventilating ducts are tight, or as an accessory to the pressure-system, the exhaust fan is very efficient and often invaluable. 153. Heating Surface Required. The methods of pro- portioning the heating surface, will be the same in every par- ticular as those previously described for indirect heaters, page 211, and for hot-air furnaces, page 278. In this case, however, as the air passes over the heating surfaces with considerable velocity, the amount of heat which is given off is many times more than that from ordinary radiating surfaces in direct heat- ing. Experiments have already been quoted on page 83 which show that the number of heat-units given off per degree differ- ence of temperature per square foot of surface per hour is approximately equal to twice the square root of the velocity of the air in feet per second ; for a velocity of 36 feet per second this would amount to 12 heat-units. For very cold weather the difference of temperature between heating surface and air will be from 160 to 170 degrees, and in this case the total heat given off per square foot will be about 2000 heat-units, or the equivalent of that given off in the condensation of some- what more than 2 pounds of steam. The following general formula will apply to this case : Let T = temperature of heating surface, / that of the air of the room, /' that of outside air, /" that of air leaving heating surface, t\ the mean temperature of air surrounding heating surface = \(t" /'), n = 292 HEATING AND VENTILATING BUILDINGS. number of times air is to be changed per hour in the room, C cubic contents of room, a = coefficient giving number of heat-units per degree difference of temperature per square foot per hour from heating surface. We have, since one heat-unit is capable of heating 56 cubic feet of air one degree : * Cubic feet of air heated per hour = nC\ Heat-units required for warming this air = ~~j^^" ~~ *') Square feet of radiation = _ . If in the above equations outside air is zero and air leaving heating surface is at 120 degrees, and the air in the room is changed 4 times per hour and maintained at 70 degrees, we shall have T 220, t' o, /, = 60, n = 4, a(T /,) = 2000, from which is deduced the following simple rules : First, the heat required expressed in heat-units per hour is equal to 8.6 times the number of cubic feet in the room ; second, the number of square feet of heating surface will be equal to the number of cubic feet in the room multiplied by 0.0041. The amount of heat given off per square foot of surface is about 6 times that in direct heating ; hence the areas of main steam- and return-pipes should be 6 times greater than those given by the table on page 237. 154. Size of Boiler Required. From the preceding state- ment and by reference to page 124 it is seen that one square foot of heating surface in hot-blast heating will condense from 0.7 to 0.9 the amount of steam that can be produced by one square foot of heating surface in the boiler. Hence there should be from 0.7 to 0.9 as much area of heating surface in the boiler as in the indirect heater, or in other words there should be one boiler horse-power for every 15 to 18 square feet in the heater. The proportions of grate surface, chimney, etc., will be found by consulting Article 74, page 124. 155. Practical Construction of the Hot-blast System of Heating. The following matter regarding the construction of hot-blast heating plants has been kindly furnished for this book by Mr. F. R. Still of Detroit, who has had an extensive engineering experience in this particular kind of work : * See Table VIII, temp, at 70 F. FORCED-BLAST SYSTEMS. 293 "Air Required. The following is intended to give the basis of calculation for different parts of a plant of the so-called hot- blast system. The first thing to consider with this system usually is the amount of air to be delivered and warmed per minute. Experience has proved that the delivery of an amount of air into a building or apartment equal to its cubic contents every 15 minutes, will warm it under average conditions of con- struction to 70 degrees F. when the outside temperature is zero. This amount of air will accomplish like results in some buildings when the outside temperature is 10 or even 20 degrees below zero, and in other cases this amount will be found insufficient ; the variation being due to construction, glass surface, and con- ditions which have been previously mentioned on page 58. In some classes of buildings, for instance, churches, school- houses, theatres, and hospitals, a change of air may be required every 10 minutes. Amount of Heating Surface. Having determined the amount of air required, the next consideration is the amount of heating surface to be used in the indirect heater. This can be treated better by taking a specific example, for instance, suppose that 20,000 cubic feet of air to be delivered into the building every minute (1,200,000 cubic feet per hour) at a temperature of 120 degrees, when air outside is zero, that the steam-pressure on the coils or heating surface is 10 pounds per square inch, and that the temperature of the water of condensa- tion is 213 degrees. In one pound of steam at a pressure of 10 pounds above the atmosphere there is 1186.5 units of heat, while in one pound of water of condensation there is 213 units, leaving 973.5 units, which is given off by the heating surface. By consulting Table VIII it will be seen that at tem- perature of 70 F. one heat-unit will warm 56 cubic feet of air one degree, and hence to heat one cubic foot 120 degrees will require 2.15 heat-units: each pound of steam gives off 973.5 heat-units and will heat 452 cubic feet of air from zero to 1 20 degree. To heat 1,200,000 cubic feet of air to 120 degrees will require 2660 pounds of steam. The indirect heater provided with blower will condense under average conditions 2 pounds of water per square foot of surface per hour, and hence we should require as many square feet of 2Q4 HEATING AND. VENTILATING BUILDINGS. surface as the quotient of 2660 divided by 2, or 1330 square feet.* Size of Boiler. To find the size of boiler needed, divide the total steam required per hour, in the example 2660, by that re- quired for one boiler horse-power; this, when water of conden- sation is all returned to boiler, is 34.5 pounds (see page 122), and we obtain 77 horse-power. This computation gives a larger boiler than would generally be installed for work of this magnitude. The rated horse-power of a boiler is capable of considerable increase in times of necessity and for short periods. It can hardly be considered good practice to overwork a boiler, but as extremely severe weather is usually of very short duration and the balance of the season mild, there is good reason, on the score of economy in first cost, for this practice. The boiler is usually rated on the supposition that it will need to supply 1.5 pounds of steam for each square foot of surface in the radiator per hour, in which case 23 square feet of surface would be supplied by one boiler horse-power. This estimate would require the normal rating of the boiler to be developed during the average stress of weather; this method would require a boiler of about 60 horse-power for the plant considered in the example. Such a method of pro- portioning has proved quite satisfactory in actual practice, although greater economy could, no doubt, be obtained by using a larger boiler. Size of Blower. We are next to determine the size of blower required, which in some respects is the most difficult part relating to the design, as much depends on the location of the fan and the various uses to which the building is to be put. Noise is an objection in any kind of a building except perhaps one devoted to manufacturing. A good basis from which to determine the velocity of the air is that relating to the highest speed at which the blower can be driven without making a serious noise. This limit of speed is found to be about 250 revolutions per minute, but except in rare cases the blower should run at from 180 to 200 revolutions. We do not advo- * Some manufacturers claim 5 pounds of condensation at zero weather ; highest results obtained by Mr. Still were 3.5 pounds. FORCED-BLAST SYSTEMS. 295 ircate a linear velocity of the air through the discharge of a blower in excess of 2400 feet per minute, and it will be found to give better economy and more satisfactory results if the velocity does not exceed 1500 or 1800 feet ; though in some in- stances this low velocity may require a large and unsightly fan. Assuming, as in the example, that the blower is to deliver 20,000 cubic feet of air per minute at a velocity not exceeding 2000 feet per minute, the following considerations must receive attention : A blower standing in an open room and having a free inlet and outlet will discharge air at a velocity nearly 10 [per cent greater than the peripheral velocity of the fan-blades, but attach this blower to a bank of heating coils and a system of conduits and the resistance due to friction becomes so great that it reduces this velocity nearly 50 per cent. To allow for this loss and retain a factor of safety it is customary to call the periph- |eral velocity of the fan-blades equal to the linear velocity of the air, and to figure on the efficiency of delivery in actual work as 50 per cent of this amount. On this basis a velocity of 2000 feet through the discharge of the blower will be main- tained when the peripheral velocity of the fan is about 4000 feet. Having determined that the blower is not to run over 200 revolutions per minute, it will be necessary to have fan- wheels for this peripheral speed 6.4 feet in diameter. A fan 6 feet in diameter running 200 revolutions has a peripheral velocity of 3770 feet per minute, so that the air delivered, with 50 per cent allowance for friction will move at the rate of 85 feet per minute. A blower of any standard make, having a wheel 6 feet in diameter, would be provided with a discharge- opening at least 11.5 square feet in area. The product of this area by 1885 gives a discharge of 21,677 cubic feet per minute, which is slightly more than is required in the example con- sidered. Power Required. The next consideration is the amount of power required to drive the blower, regarding which we will say that we know of no formula which has sufficient elasticity to apply alike to large and small blowers at high and low speeds. The following tables give the results of the actual power, as obtained by testing, required to operate various sizes of Smith fans when delivering a specified amount of air: 296 HEATING AND VENTILATING BUILDINGS. TABLE OF CAPACITY AND POWER FOR STEEL-PLATE BLOWERS OF VARIOUS SIZES. Size. o . % Oz. Pres. Y% Oz. Pres. % Oz Pres. i Oz. Pres. 2 Oz. Pres. In. J3 | .5 - - -' s *^. > cu > pu > . ^ P- ^ OH > S A Q ul re K 3 uS. 3& E 04 3 i u & K C* 3 I rt V i In. iamet c Scr Cv) Size. In. C ^ ~u jU be c S Fan | 1 Only. Single Engine. Double Engine. c7J Q Q Q < < t/J Q 70 42 2 T ^ 14 x 8j>*j 26 530 24 X24 576 4x4 3 X 3 1000 1290 1330 80 48 2 T 6 S i6x 8>^ 3 706 26^x26^ 702 4x4 3 X 3 1300 1590 1630 9 54 2 T 5 g 1 8 X 10 Vt 34 907 30 x 3 o 900 5 X 5;4 X 4 1650 2150 2190 100 60 2 ^ 20 X 10^ 38 "34 34 x 34 ' 1156 6x6 5 X 5 2000 2640 2850 no 66 2-^j 22 X 10^ 42 1385 37 X 37 1369 6x6 5 X 5 2500 3 HO 3350 120 72 2ll 2 4 XI2J4 46 1661 41 x 4 i 1681 7x7 6x6 3 000 3870 4300 140 84 3^S 28 x 12^6 53 2206 47^x47^ 2256 .... 7x7 4OOO 5600 5700 160 96 3 T ^ 32 x 12^ 60 12827 53^X53^ 2862 7x7 5200 6800 6900 * Catalogue American Blower Co. Capacity of Blower. The 120-inch fan has a wheel 6 feet in diameter, as shown by the table of dimensions. By consult- ing the table of powers it will be seen that this fan, running with a speed of 200 revolutions per minute, requires less than 7 horse-power to drive the blower. The capacity, as given under the same head, is that for a fan working with free inlet and outlet, and, as before remarked, is about 10 per cent greater than the capacity when delivering into conduits. To totally close off either inlet or discharge of the blower causes the air to move around with the fan ; this removes so much load FORCED-BLAST SYSTEMS. from the engine that unless it, is provided with an excellent governor it will speed up to a very great rate and may run away. This fact that an increase of resistance diminishes the power required at different speeds is not considered in the tables given ; consequently these powers are somewhat in ex- cess of those actually required. The excess of power would depend upon friction and other resistances ; consequently no allowan.ce can be made which would be accurate for all con- ditions. Dimensions of Horizontal Conduits. We now come to the question regarding dimensions of horizontal conduits that con- vey the air from the blower to various parts of the building. There is a great difference of opinion as to the proper velocity of the air through such conduits, and circumstances have a great deal to do with this question. In my opinion the easier you make it for the air to travel the more successful will be the plant. In no plants, in public-buildings, do we advocate a velocity of air that exceeds 15 feet per second, or 900 feet per minute ; 600 feet, or even 400 feet, is better, although in an extensive plant the conduits might be so large as to be un- sightly and interfere with the convenience of the building. Vertical flues in the walls leading to the various apartments should be so large that the velocity of the air will not exceed 10 feet per second, or 600 feet per minute. Maximum Velocity of Air. From an economical and efficient standpoint air should never enter a room through a register, screen, or grille at a velocity exceeding 400 feet per minute (6.6 feet per second). A greater velocity is liable to create such a rapid movement of the air as will stir up the dust in the room and create serious throat affections. Again, air coming in contact with the screen at a very high velocity will cause a low whirr or whistle often proving very annoying. Better ventilation, or perhaps we should say better circulation of the air, takes place when introduced at a moderate velocity than at a high velocity, because in that case the air enters gently and is distributed by gravitation, due to the cooling of the air in contact with cold walls, and the whole body of air is thus kept in slight motion and the entering air is more evenly distributed. If the air is forced in at high velocity, it creates swift currents 298 HEATING AND VENTILATING BUILDINGS. and counter-currents, which will completely prevent the equitable distribution of the fresh air. Introduction of Air. My method of introducing air into a room is from a register about 8 feet above the floor, connected with a flue located in an inside wall, and discharging the cur- rent of air in the direction of an outside wall. The vent regis- ter should be located in the same wall as the fresh-air register, but at the opposite side and in the warmest corner of the room.* General Remarks. Architects very often combat such ar- rangements on the ground of interfering with their plans or of taking up too much room, and very often seriously object to making even the slightest alteration. This often leads to sorry arrangements for heating and ventilating plants, which will probably always continue so long as competiting manufacturers design those to be installed in certain buildings. It may be said generally that while the method of design- ing, followed by different manufacturers, may be essentially different from that given here, yet the experience of the writer has shown that the quantities, as computed by various manu- facturers when 1 submitting plans in competition for the same building, are essentially the same as those stated here. 156. Systems of Ventilation without Heating. Where large quantities of air are required, especially in seasons when heat is not needed, systems of ventilation may be constructed which are independent from the systems of heating. The cir- culation of the air through the building may be produced either by exhausting or rarefying the air in the discharge-ducts, or by delivering fresh air to the rooms under pressure, as described for hot-blast heating. The air may be rarefied in the discharge-flue by heating either with steam or hot-water radiators, with an open fire- place or a stove. When circulation is produced by heat, the amount of air moved will depend upon the height of the chim- ney or discharge-duct and its temperature, and will be essen- tially as that given in the table on page 45. The air may also * The above opinion gives the practice of Mr. Still, and is different from lhat of many engineers. See a full discussion of the matter on pages 44 to 49. FORCED-BLAST SYSTEMS. 299 be exhausted from the building by induction, for which may be used a jet of steam, water, or compressed air which is de livered from a nozzle into a convergent pipe of somewhat larger diameter and with both ends open. A very strong draft can be ; produced in this way, although at the expense of more energy than that required to operate exhaust fans or blowers. The ; air may also be exhausted by means of a fan located in the main flue. In case any of these means for producing drafts ;by exhausting or rarefying the air in the discharge-ducts is employed, every precaution that has been mentioned in regard to chimney-tops (page 162) should be observed, otherwise a considerable portion of the force may be required to over- come adverse wind currents. The general remarks regarding hot-blast heating-systems and also the tables of dimensions apply equally well to this case. The tables on page 52 will be useful in proportioning areas of flues and registers for the discharge of a given amount of air ; as an allowance for friction add one inch to each lineal dimension. The blower system of ventilation has been fully described in connection with the hot-blast system of heating, and tables of capacities of various fans given which are applicable to this case. In this system as well as in the hot-blast system of heating especial care should be taken that the resistances in pipes and flues are as small as can be made, that bends are made with a long radius, and that the reduction in size in pass- ing from one pipe to another is as gradual as possible. 157. Heating with Refrigerating Machines. The refrig- erating machine is virtually a pump which removes heat from a body at one temperature and discharges it at a higher tem- perature. Reckoned on the basis of heat transmitted, it is a very efficient machine, as it may move from a lower to a higher temperature 10 to 20 times as much heat as the mechanical equivalent of the work performed ; in all respects this machine is the converse of the steam-engine. By utilizing the heat which is discharged from a machine of this character in warm- ing a building, and also that in the exhaust steam from the engine working the compressor pump, there is a possible effi- ciency many times greater than that which can be obtained by burning the coal directly. 300 HEATING AND VENTILATING BUILDINGS. The practical arrangement of such a machine, if using air as the working fluid, would be such as to draw in air from the outside, compress it to such a point that its temperature would be very high, pass it through circulating pipes and radiating surfaces when still under pressure, and discharge into a cham- ber from which the pressure has been removed, or in the out- side air after being cooled. If the exhaust steam could be used for heating, such a system would be very economical, although it would be costly and take up considerable room. An ammonia refrigerating machine might be used, in which case the heat in the compressed ammonia could be removed by water, which would thus become heated and could be circulated for the purpose of warming. The scheme of using the re- versed heat-engine or refrigerating machine as a warming machine was pointed out first by Lord Kelvin in 1852,* and although it presents great advantages economically, the writer has no data showing that it has ever been put to practical use. 158. Cooling of Rooms. The converse operation of cool- ing rooms, although at the present not undertaken except in the case of cold-storage plants and warehouses, bids fair to be at some time an industry of considerable importance. Rooms may be artificially cooled by a system constructed similar to that described for hot-blast heating. The coils or radiating surface, however, would need to be replaced by ice or con- structed in such a manner that ammonia or some liquid at a very low temperature could be circulated. Over these the air could be driven, its heat would be absorbed, and it could be reduced in temperature to any point desired. In lowering the temperature of the air, a considerable amount of moisture might be precipitated, and some means should be provided for artificially removing it without heating, otherwise the rooms would be made damp. It may be remarked that ordinary pipe-fittings cannot be used with safety for ammonia circula- ; tion, and that special fittings are manufactured for this purpose. * Proc. of the Phil. Soc. of Glasgow, Vol. Ill, p. 269. CHAPTER XIV. HEATING WITH ELECTRICITY. 159. Equivalents of Electrical and Heat Energy. Electrical energy can all be transformed into heat, and as there are certain advantages pertaining to its ready distribution, it s likely to come into more and more extended use for heat- ng, especially where the cost is not of prime importance. The value of mechanical and electrical units has been given on >age 5, from which it will be seen that one watt for one hour, vhich is the ordinary commercial unit for electricity, is equal o 3.41 heat-units ; for one minute it is 1/60 and for one, second t is 1/3600 this amount. Electricity is usually sold on the )asis of IOOO* watt-hours as a unit of measurement, the watts >eing the product obtained by multiplying the amount of cur- rent estimated in amperes by the pressure or intensity esti- mated in volts ; on this basis 1000 watt-hours is the equivalent of 3410 heat-units. We have considered in Chapter III the amount of heat required per hour for the purpose of warming. This amount divided by 3410 will give the equivalent value in dlowatt-hours which would need to be supplied for the re- quired amount of heat. 160. Expense of Heating by Electricity. The expense of electric heating must in every case be very great, unless the electricity can be supplied at an exceedingly low price. Much data exists regarding the cost of electrical energy when it is obtained from steam-power. Estimated f on the basis of * One thousand watts is called a kilowatt. \ The mechanical energy in one horse-power is equivalent to 0.707 B. T. U. per second or 2545 per hour. One pound of pure carbon will give oft 14,500 heat-units by combustion, which if all utilized would produce 5.7 horse-power 301 302 HEATING AND VENTILATING BUILDINGS. present practice, the average transformation into electricity, does not account for more than 4 per cent of the energy in the fuel which is burned in the furnace ; although under best conditions 15 per cent has been realized, it would not be safe to assume that in commercial enterprises more than 5 per cent could be transformed into electrical energy. In transmit- ting this to a point where it could be applied losses will take place amounting to from 10 to 20 per cent, so that the amount of electrical energy which can be usefully applied for heating would probably not average over 4 per cent of that in the fuel. In heating with steam or hot water or hot air the average amount utilized will probably be about 60 per cent, so that the expense of electrical heating is approxi- mately as much greater than that of heating with coal as 60 is greater than 4, or about 15 times. If the electrical current can be furnished by water-power which otherwise would not be usefully applied, these figures can be very much reduced. The above figures are made on the basis of. fuel cost of the electrical current, and do not provide for operating, profit, interest, etc., which aggregate many times that of the fuel. With coal at $3.30 per ton this cost on above basis is about .97 cent per thousand watt-hours. The lowest commercial price quoted, known to the writer, for the electric current was 3 cents ; per thousand watt-hours the ordinary price for lighting current varies from 10 to 20 cents. It may be said that for lighting purposes 10 cents per thousand watt-hours is con- sidered approximately the equivalent of gas at $1.25 per thou- sand cubic feet. It may be a matter of some interest to consider the method of computation employed for some of these quantities. The ordinary steam-engine requires about 4 pounds of coal for each horse-power developed ; on account of friction and other losses about 1.5 horse-power are required per kilowatt, or in other for one hour, in which case one horse power could be produced by the combus- tion of 0.175 Ib. of carbon. The best authenticated actual performance is one horse-power for 1.2 Ib., corresponding to 14.6 per cent efficiency. The usual consumption is not less than 4 to 6 pounds per indicated horse-power, or from 3 to 5 times the above. A kilowatt is very nearly \\ horse-power, but because of friction and other losses requires an engine of 1.5 indicated horse-power. HEATING WITH ELECTRICITY. 303 words 6 pounds of coal are required for each thousand watts of electrical energy. In the very best plants where the output is large and steady this amount is frequently reduced 20 to 30 per cent from the above figures in cost. The cost of 6 pounds of coal at $3.33 per ton is one cent. To this we must add transmission loss about 10 per cent, attendance and interest 20 per cent, making the actual cost per kilowatt 1.3 cents per hour. As one pound of coal represents from 13,000 to 15,000 heat-units, depending upon its quality, and one kilowatt-hour is equivalent to 3415 heat-units, if there were no loss whatever tin connection with transformation of heat into electricity, one pound of coal should produce 4 to 5 kilowatts per hour of electrical energy. This discussion is sufficient to show that at [cost prices electrical heating obtained from coal will amount under ordinary conditions to 15 to 20 times that of heating :with steam or hot water, and at commercial prices which are likely to be charged for current its cost will be from 2 to 10 times this amount. The following table gives the cost of a given amount of heat, COST OF HEAT OBTAINED FROM ELECTRICITY. Cost per kilowatt hour, cents. Heat- units. i 2 | 3 4 5 6 7 8 9 10 B. T. U. 1 Cost of heat obtained, cents. IO.OOO 2.93 S.86 8.78 11.71 14.64 17-57 20.50 23.42 26.35 29.28 20.000 5.85 11.68 17.57 23.42 29.28 35.13 40.99 46.84 52.70 58.56 30,000 8.78 17-57 26.35 35-M 43.92 52.70 61.49 70.28 79.06 87-84 4O,OOO 11.71 22.42 35-14 46.84 58.56 70.28 81.98 93-68 105.40 117.12 50,000 14.64 29.28 43-92 58.56 73-20 87.84 102.48 117.12 131.86 146.40 6o,OOO 17-57 35-14 52-70 70.28 87.84 105.40 122.98 140.56 158.12 175.68 7O,OOO 20.50 40.99 61.49 81.98 102.48 122.98 M3.47 163.96 184.46 204.96 So,ooo 23.42 46.84 70.28 93-68 117.12 140-56 163.97 187.36 210.80 234-24 qO,000 ! 26.35 52.70 79.06 105.42 131-76 158. 10 184.46 210.84 237.17 263 52 100,000 29.28 58.56 87-84 117.12 146.40 175.68 204.96 234.24 263.52 292 . 8O i NOTE. 10,000 heat-units is equal to two thirds the heat contained in one pound of the best coal, and is very near the average amount that can be realized per pound in steam or hot-water heating, hence the table can also be considered as showing the relative price of electricity and coal for the same amount of heating. For instance, if 5 cents per kilowatt hour is charged for electric current, the expense would be the same as that of good coal at 14.64 cents per pound, which is at rate of $392.80 per ton. 304 HEATING AND VENTILATING BUILDINGS, if obtained from the electric current, furnished at different] prices. Thus 30,000 heat-units if obtained from electric current! furnished at 8 cents per kilowatt hour would cost 70.28 cents per hour. The amount of heat needed for various buildings can be determined by methods stated in Chap. III. There are some conditions where the cost is not of moment^ and where other advantages are such as to make its use desir- able. In such cases electricity will be extensively used for] heating. For the purposes of cooking it will be found in many cases that electrical heat, despite its great first cost, is more econom-' ical than that obtained directly from coal. This is due to the fact that of the total amount of heat, which is given off fromj the fuel burned in a cook stove very little, perhaps less than] one per cent, is applied usefully in cooking: the principal pard is radiated into the room and diffused, being of no use what- ever for cooking, while the heat from the electric current can be utilized with scarcely any loss. 161. Formulae and General Considerations. The fol- lowing formulae express the fundamental conditions relating to the transformation of the electric current into heat : W=CE=C*K. / . , .... (2) . - (3) H=o.2iC*R. . . . ... . . (4) >fci = .00000009 5 C"*R. (5) hi = 3.415 W ~ 3.41 5 C 8 A' = 34I5CZT. (6 In which the symbols represent the following quantities: E, electro motive force in volts ; C, intensity of current in amperes ; R, resistanc of conductor in ohms ; /, the length in metres ; w, the area of cross-sec tion in square centimetres; k, coefficient of specific resistance; W, kilo watts ; H, the heat in minor calories, and h\ in B. T. U. per second, h the heat in B. T. U. per hour. The amount of heat given off per hour is given in equatioi (6), and is seen to be dependent upon both the resistance an< the current, and apparently would be increased by increase ii either of these quantities. The effect, however, of increasing the resistance as seen by equation (i) will be to reduce th amount of current flowing, so that the total heat suppliec HEATING WITH ELECTRICITY. 305 would be reduced by this change. On the other hand, if there were no resistance no heat would be given off, for to make R = o in equation (6) would result in making // 2 = o. From these considerations it is seen that in order to obtain the maximum amount of heat, the resistance must have a certain mean value dependent upon the character of material used for 'the conductor in the heater, its length and diameter. For purposes of heating, a constant electromotive force or voltage is maintained in the main wire leading to the heater. A very much less voltage is maintained on the return wire, and [the current in passing through the heater from the main to the [return drops in voltage or pressure. This drop provides the energy which is transformed into heat. The principle of electric heating is much the same as that involved in the non-gravity return system of steam-heating. In that system the pressure on the main steam-pipes is essen- tially that at the boiler, that on the return is much less, the reduction of pressure occurring in the passage of the steam through the radiators ; the water of condensation is received into a tank and returned to the boiler by a steam-pump. In a system of electric heating the main wires must be sufficiently large, to prevent a sensible reduction in voltage or pressure between the dynamo and the heater, so that the pressure in them shall be substantially that in the dynamo. The pressure or voltage in the main return wire is also constant but very low, and the dynamo has an office similar to that of the steam- pump in the system described, viz., that of raising the pressure of the return current up to that in the main. The power which drives the dynamo can be considered synonymous with the boiler in the other case. All the current which passes from the main to the return current must flow through the heater, and in so doing its pressure or voltage falls from that of the main to that of the return. Thus in Fig. 215 a dynamo is located at D, from which main and return wires are run, much as in the two-pipe system of heating, and these are so proportioned as to carry the re- quired current without sensible drop or loss of pressure. Between these wires are placed the various heaters ; these are arranged so that when electric connection is made, they 306 HEATING AND VENTILATING BUILDINGS. draw current from the main and discharge into the return wire. Connections which are made and broken by switches take the FIG. 215. DIAGRAM OF ELECTRIC HEATING. place of valves in steam-heating, no current flowing when the switches are open. The heating effect is proportional to the current flowing, and this in turn is affected by the length, cross-section, and relative resistance of the ma- terial in the heater. The resist- ance is generally proportioned such as to maintain a constant temperature with the electro- motive force available, and the amount of heat is regulated by increasing the number of con- ductors in the heater. 162. Construction of Elec- trical Heaters. Various forms of heaters have been employed. Some of the simplest consist FIG. 2i6.-ELECTRic HEATER AT THE merely of coils or loops of iron VAUDEVILLE THEATRE, LONDON. w j re arranged in parallel rows so that the current can be passed through as many wires as are needed to provide the heat required. In other forms of HEATING WITH ELECTRICITY. these heaters the heating material has been surrounded with fire-clay, enamel, or some relatively poor conductor, and in other cases the material itself has been such as to give consid- erable resistance to the current. It is generally conceded that __ >-i J FIG. 217. OFFICE OR HOUSE HEATER. the most satisfactory results are obtained with electrical as with other heaters by regulating the resistance, by change of length and cross-section of the conductor, to such an extent as to keep the heating coils at a moderately low temperature. Some of 308 HEATING AND VENTILATING BUILDINGS. the various forms which have been used are shown in the cuts. Fig. 216 represents a portable form of electrical heater used in the Vaudeville Theatre, London. Fig. 217 shows the interior of an office or house heater made by the Consolidated Car Heating Co., of Albany. The electrical heating surface is made in the latter by a coil of wire wound spirally about an incom- bustible clay core. The casing is like that for an ordinary UU FIG. 218. CAR HEATER OF CONSOLIDATED Co. FIG. 2TQ. AMERICAN CAR HEATER. stove, and is built so that air will draw in at the bottom and pass out at the top. * The electrical heaters at the present time are used almost exclusively in heating electrical cars, where current is available and room is of considerable value. These heaters are generally located in an inconspicuous place beneath the seats, their gen- eral form being shown in Figs. 218 and 219. HEATING WITH ELECTRICITY. 509 163. Connections for Electrical Heaters. The method of wiring for electrical heaters must be essentially the same as for lights which require the same amount of current. The details of this work pertain rather to the province of the electrician than to that of the steam-fitter or mechanic usually employed for installing heating apparatus. These wires must be run in accordance with the underwriters' specifications, so as not, under any conditions, to endanger the safety of the building from fire. CHAPTER XV. TEMPERATURE REGULATORS. 164. General Remarks. A temperature regulator is an automatic device which will open or close, as required to pro- duce a uniform temperature, the valves which control the supply of heat to the various rooms. Although these regula- tors are often constructed so as to operate the dampers of the heater, they differ from damper-regulators for steam-boilers, as described in Article 91, by the fact that the latter are un- affected by the temperature of the surrounding air* although acting to maintain a uniform pressure and temperature within the boiler, while the former are put in operation by changes of temperature in the rooms heated. The temperature regulator, in general, consists of three parts, as follows : First, a thermostat which is so constructed that some of its parts will move because of change of tempera- ture in the surrounding ,air, the motion so produced being used either directly or indirectly to open dampers or valves, and thus to control the supply of heat. Second, means of transmitting and often of multiplying the slight motion of the parts of the thermostat produced by change of temperature in the room, to the valves or dampers controlling the supply of heat. Third, a motor or mechanism for opening the valves or dampers, which may or may not be independent from the thermostat. In some systems the thermostat is directly connected to the valves or dampers, and no independent motor or mechanism is employed ; in this case the power which is used to open or close the valves regulating the heat-supply is generated within the thermostat, and is obtained either from the expansion or contraction of metallic bodies, or by the change in pressure 310 TEMPERATURE REGULATORS. 311 caused by the vaporizing of some liquid which boils at a low temperature. The force generated by slight changes in tem- perature is comparatively feeble, and the motion produced is generally very slight, so that when no auxiliary motor is em- ployed it is necessary to have the regulating valves constructed so as to move very easily and not be liable to stick or get out of order. In most systems, however, a motor operated by clock- work, water, or compressed air is employed, and the thermostat is required simply to furnish power sufficient to start or stop this motor. The limits of this work do not permit an extended historical sketch of many of the forms which have been tried. The reader is referred to Knight's Mechanical Dictionary, article " Thermostats," and to Peclet's " Traite du la Chaleur," Vol. II, for a description of many of the early forms used. Those which are in use may be classified either according to the general character of the thermostat or the construction of the motor employed to operate the heat-regulating valves as follows : f Moved by f N auxili f Expansion or expansion or ^ contraction. change of M I Water. pressure. \ Compressed L air. 165. Regulators Acting by Change of Pressure. A change of temperature acting on any liquid or gaseous body causes a change in volume, which in some instances has been utilized to move the heat-regulating valves so as to maintain a constant temperature. Fig. 220 represents a regulator in which the expansion or contraction of a body of confined air is utilized to control the motion of the dampers to a hot-water heater. It consists of a vessel containing in its lower portion a jacketed chamber connected to the hot-water heater at points of different elevation so as to secure a circulation from the heater through the lower portion or jacket of the vessel from 2 to 3. Above this is a second chamber which is covered on top with a rubber diaphragm, and which contains a funnel- shaped corrugated brass cup. The opening to the cup is in 312 HEATING AND VENTILATING BUILDINGS. the lower portion of the chamber, the top and larger surface resting against the rubber diaphragm. Enough water at atmospheric pressure or alcohol is poured into the upper chamber through the opening marked I to seal the orifice in FIG. 220. LAWLER HOT-WATER DAMPER-REGULATOR. the inverted cup and confine the air it contains. The reg- ulator acts as follows : The warm water from the heater mov- ing through the lower chamber communicates heat to the water or alcohol in the upper chamber, which in turn warms the air in the inverted cup, causing it to expand. This moves the rubber diaphragm and connected levers leading to the dampers substantially as in the damper-regulator for steam- heaters, already described. The Powers regulator for hot-water heaters (see Fig. 221) is somewhat similar in construction to the one described, but acts on a different principle. A liquid which will vaporize at a lower temperature than that of the water in the heater is placed in the vessel communicating with the diaphragm, in which case considerable pressure is generated before the water in the heater reaches the boiling-point. As the water in the heater is usually under a pressure of 5 to 10 pounds per square inch, its boiling temperature is from 225 to 240 degrees, water of at- mospheric pressure which boils at 212 can be used in the closed vessel, and will generate considerable pressure before that ip the heater boils. TEMPERATURE REGULATORS. 313 The method of construction is shown at the right, in Fig. 22 1 , as applied to a hot-water heater. The diaphragm employed consists of two layers of elastic material with compartments be- tween and beneath ; the lower one is connected to the chamber i 2 3 FIG. 221. THE POWERS THERMOSTAT FOR HOT- WATER HEATERS. A, which is filled with water at atmospheric pressure and is sur- rounded by the hot water flowing from the heater. The water in chamber A, being under less pressure, will boil before that in the heater, and will produce sufficient pressure to move the diaphragm and levers so as to close the dampers, before the water in the heater reaches the boiling-point. The compart- ment between the two diaphragms f, f is in communication with a vessel D, which in turn is connected by a closed pipe E with a thermostat, which may be placed at any point in the house and so arranged that if the temperature becomes too high in that room, the dampers of the heater will be closed. With this apparatus the dampers are closed either by excessive temperature of water at the heater or too great a heat in any room. The intermediate compartment is only required when the dampers are to be operated by change of temperature in the rooms. The thermostat employed in this apparatus consists of a vessel 2, Fig. 221, separated into two chambers by a diaphragm ; one of these chambers, B, is filled with a liquid which will boil at a temperature below that at which the room is to be maintained ; the other chamber, A, is filled with a liquid which HEATING AND VENTILATING BUILDINGS. FIG. 222. ELEVATION OF THERMOSTAT- does not boil, and is connected by a tube to a diaphragm damper-regulator which moves the dampers through the me- dium of a series of levers. Fig. 221, 2, shows a transverse section and I an elevation with parts broken away of a thermostat, and Fig. 222 an ele- vation with attached ther- mometer. The vapor of the liquid in the chamber B pro- duces considerable pressure at the normal temperature of the room, and a slight increase of heat crowds the diaphragm over and forces the liquid in the chamber A outward through a con- necting tube which leads to the damper - regulator, one form of which has been described. The damper-regulator as applied to a steam-heater is pro- vided with a single rubber diaphragm with the parts arranged as shown in the sec- tional view Fig. 223. In this case the liquid pressure is applied above the diaphragm, its weight being coun- terbalanced by springs and weights, attached to the levers. The liquid used in the thermostat may be any which has a boiling temperature somewhat below that at which the room is to be kept. Many liquids are known which fulfil this condition, of which we may mention etheline, bromine, various petroleum distillates, anhy- drous ammonia, and liquid carbonic acid. The liquids em- ployed in the Powers thermostat are said to give pressures as follows at the given temperatures : FlG> M DIAPHRAGM DAMPER-REGULATOR. TEMPERATURE REGULATORS. 31$ At 6o c ...... ...... I pound to the square inch. 70 ............ 4 " " " 90 .......... 10 " " " " " 100 ........... 13 " " " 166. Regulators Operated by Direct Expansion. VIetals of various kinds expand when heated and contract vhen cooled, and this fact has often been utilized in the con- struction of temperature regulators. A single bar of metal expands so small an amount that it is of little value for this purpose unless very long, or unless its expansion is multiplied by a series of levers. Several forms lave been used, of which may be mentioned : a bent rod with ts ends confined so that expansion tends to change its curva- ture ; a series of bent rods of oval form resting on each other with the ends confined between two fixed bars ; two metallic Dars, having different rates of expansion arranged parallel and the variation in length multiplied by a series of connecting evers an amount sufficient to be available in moving dampers ; two strips of metal of different kinds bent into the form of an arc and fastened together so as to form a curved bar, with the metal which expands at the greater rate on the inside, so that expansion tends to straighten it when heated ; the differ- ence in expansion between an iron rod which is not heated and the flow-pipe of a hot-water heater multiplied by means of a series of levers. The constructions described above lave all been tried for the purpose of moving the dampers of icaters or for opening and closing valves. In general, how- ever, they have not proved satisfactory, because of the slight motion caused by expansion, and the uncertainty of operation obtained with multiplying devices. Certain organic materials have the property of bending or curling when heated, and this has been utilized in the construction of the Howard regulator. This regulator consists of a ther- nostat in the form of a plaque of triangular form n inches ong and 9 inches wide (Fig. 224), which is located in any 316 HEATING AND VENTILATING BUILDINGS. living-room. As the temperature of the room increases the plaque bends. It is connected by means of cords running over pulleys to a very light and easily moved cylinder damper arranged so as to regulate both fire and check drafts. The] damper used in connection with this thermostat consists of a slotted cylinder rotating on the inside of a tube which leads in one direction to the ash-pit and in the other to the smoke-pipe. A parti- tion separates the two parts of the tube, and the slots in the cylindric damper are so arranged that when the connection for' air to the furnace is open the other is closed, and vice versa, a very slight motion serving to completely open or close the damper. The cylinder damper is con- nected to the plaque by a cord, and is so arranged that the drafts are opened by FIG. 224. HOWARD the motion of the thermostat and closed THERMOSTATIC PLAQUE. , by gravity. The direct expansion of a liquid or of a gas in a confined vessel has also been utilized to move a diaphragm or piston which is connected by levers to the dampers of heaters, in a manner similar to that described in the preceding article. The writer at one time constructed a regulator for a hot-water system in which the expansion of water in a closed vessel sur- rounding the return-pipe was employed to operate a damper- regulator similar to those used in steam-heating, page 156. Peclet describes, regulators in which the expansion of air was employed to move a piston connected by cords and pulleys to the dampers. 167. Regulators Operated with Motor General Types. The regulators which have been described in the preceding articles operate the regulating valves with a feeble force acting through a considerable range, or with a considerable force act- ing through a short distance. They are consequently liable to be rendered inoperative by any accident to the levers or connecting tubes, or by any cause which renders the valves difficult to operate. To overcome such difficulties several TEMPERATURE REGULATORS. 3 IJ systems have been devised in which the power for operating the dampers should be obtained from an independent source, and in which the work required of the thermostat would be simply that of starting and stopping an auxiliary motor. In the first systems of this kind the motor employed was a system of clockwork which had to be wound at stated intervals in order to supply the force required for moving the dampers. In recent systems electricity, water, or compressed air is employed to generate the power required, and in some instances regulators are arranged to operate not only the valves which supply heat to the rooms, but also the various dampers for sup- plying hot or cold air in the ventilating system. In all of the early forms of this kind of regulator the thermostat consisted of a tube of mercury or a curved strip, made of two metals of different kinds soldered together and arranged so that a given change of temperature would pro- duce sufficient motion to make or break electric contact. A current was obtained from a battery, and connecting wires led to the motor and to the various terminals. When electric con- tact was made at a position corresponding to the highest temperature, the current would flow in a certain direction and cause a magnet to release a pawl which would start a motor revolving in the proper direction for closing the valves. When the temperature fell below a certain point, the thermo- stat would make electric connections so that the current would flow in the opposite direction and cause the motor to reverse its motion, thus opening the valve. If the motor was operated by water, the electric current would open and close a valve in the supply-pipe ; if the motor was operated by electricity, the current from the battery would move a switch on the wires leading to the motor. The valves for regulating the heat-supply are made in a great variety of ways. Dampers for regulating the flow in chimneys or flues are generally plain disks, balanced and mounted on a pivot, so that they may be turned very easily; globe- or gate-valves are usually employed in steam-pipes and must, to give satisfactory service, either be closed tight or opened wide. A system in which steam-valves are oper- ated requires much more power than one in which dampers only are moved. HEATING AND VENTILATING BUILDINGS. Many systems of heat-regulation employing motors are in use and are doubtless worthy an extended notice, but space will only permit a short description of the one in most ex- tensive use in the larger buildings of this country, namely, the Johnson system of temperature regulation. 168. Pneumatic Motor System. In the Johnson system of heat-regulation the motive force for opening or closing the valves which regulate the heat-supply is obtained from com- pressed air which is stored in a reservoir by the action of an automatic motor. The thermostat acts with change of tem- perature to turn off or on the supply of compressed air. When the air-pressure is on, the valves supplying heat are closed; when off, they are opened by strong springs. The detailed construction of the parts are as follows : The compressed air is supplied by an automatic air-com- pressor which is operated in small plants by water-pressure and acts only when the supply of compressed air has fallen be- low the limit of pressure. The external form of the air-com- pressor is shown in Fig. 225. It consists of a vessel divided into two chambers by a diaphragm ; one chamber is connected to the water-supply, the other to the atmosphere. The water enter- ing' on one side crowds the dia- phragm over until a certain position is reached when the supply-valve is closed and a discharge-valve is opened, after which the diaphragm returns to its original place. The motion of the diaphragm backward and forward serves to draw in and discharge air from the other chamber in a manner similar to the operation of a piston-pump, valves being provided on both inlet- and discharge-pipes. FIG. 225. EXTERNAL VIEW SMALL AIR-COMPRESSOR. OF TEMPERATURE REGULATORS. 319 When the air-pressure reaches\a certain amount, the pump ceases its operation. An air-pipe leads from the air-compressor to the thermostat, and another from the thermostat to the diaphragms in con- nection with valves or dampers. The action of the thermo- stat, as already explained, is simply to operate a minute valve for supplying or wasting, as necessary, compressed air in the pipe leading from the thermostat to the diaphragm-valves. Fig. 226 is a sectional view of the diaphragm-valve, the FIG. 226. SECTIONAL VIEW OF DIAPHRAM- VALVE. FIG. 227. DAMPER FOR HOT- AND COLD-AIR FLUE. compressed air being admitted above the valve and acting merely to close it. It can also be closed if necessary by hand. The compressed air can also be made to operate dampers of which various styles are used, and these may be placed in ven- tilating flues, hot-air pipes, or smoke-flues, and so arranged as to admit either warm or cold air alternately to a room, as may be required to maintain a uniform temperature. Fig. 227 shows a damper for two round flues, one for cold air, the other 320 HEATING AND VENTILATING BUILDINGS. for hot, connected to a diaphragm and arranged so that when one is open the other will be closed. This system of heat-regulation has been brought to a very high degree of perfection, and if sufficient heat is supplied the temperature of a room is maintained with certainty within one degree of any required point. Farther than that, the system is so arranged that after all the rooms of the house reach the desired temperature the heat-regulator then acts to close the furnace-dampers. The apparatus is in extensive use for regulating temperature in the hot-blast system of heating. Fig. 228 shows the method adopted of applying a damper- regulator to a stack for indirect heating which is so arranged as to admit either warm or cool air as necessary to maintain a uniform temperature. FIG. 228. DOUBLE DAMPER IN BRICK DUCT. 169. Saving Due to Temperature Regulation. The ex- .pense of constructing a perfect system of heat-regulation is imet in a short time by the saving in fuel bills. The writer recently examined the records of the fuel consumed in a build- ing when heated for a series of years without, and afterwards with, the heat-regulating system. He also examined the records showing the coal consumed in two buildings of exactly the same size and class, in the same city, and as nearly as possible with the same exposure. In both these cases the saving was somewhat over 35 per cent annually of the cost of the regu- lating apparatus. The saving in any given case must, of course, depend upon TEMPERA TURE REG ULA TORS. 321 conditions and how carefully the drafts are regulated under ordinary systems of operation. Usually, when the temperature is regulated by hand, the rooms are allowed to become alter- nately hot and cool, but a greater portion of the time they are much warmer than is necessary, and frequently windows are opened for the escape of the extra heat. The maintenance of a uniform temperature for such cases means a saving of fuel by utilizing the heat better, and usually, also, by a more perfect combustion of fuel. It would seem from these considerations that a reasonable estimate of the saving obtained by the use of a perfect temperature regulator, as compared with ordinary regulation, would run from 15 to 35 per cent of the fuel bills per year. Construction of Pneumatic Thermostat. The following diagram and explanation will render the principle of action of RESERVOIR a THERMOSTAT b FIG. 229. DIAGRAM ILLUSTRATING THE PNEUMATIC THERMOSTAT. the pneumatic thermostat as employed in the Johnson system of heat regulation intelligible. Fig. 229 shows to different scales the reservoir for com- pressed air, a diagram of the thermostat and of a diaphragm 3 2 1 a HE A TING A ND VEN TIL A TING B UIL D ING S. for operating dampers. The thermostat is drawn relatively to a very large scale. The temperature regulator as a whole con- sists first of an air compressor, as shown in Fig. 225, or one of similar construction, and arranged so as to maintain a constant pressure in air reservoir R or in the pipes of the building. The principle of operation of the thermostat is illustrated by the diagram, although the details of construction of the act- ual instrument are quite different. Compressed air from the reservoir or air-pump passes through the pipe A to the cham- ber B, thence, if the double valve ab is open, it will pass out through the pipe C to the chamber V above the diaphragm. Its pressure then causes the end X' of the lever X' X to move downward. This lever is connected to the damper in such a manner as to close off the supply of heat when in the lowest position. If the room becomes too cold, mechanism to be hereafter described moves the valve ab into such a position as to close the communication to the compressed air in the cham- ber B and open communication with the atmosphere at b. This permits the air to escape from the chamber V, through the pipe C and opening b, into the air, the diaphragm in the lower part of the chamber V being moved upward by a spring or weight not shown in the sketch. Thus it is seen that by mov- ing the double valve ab the chamber Fisput in communication with the compressed air and the damper moved to close off the heat, or with the outside air, in which case the pressure in the chamber Fis lessened and the damper is moved by action of a weight or a spring so as to admit the warm air. The mechanism for moving the valve ab consists of a thermostat T, which may be made of any two materials having a different rate of expansion, as rubber and brass, zinc and brass, etc. Connected to the thermostatic strip is a small valve Kj so adjusted that when the room is too warm the valve will be opened and when too cold it will be closed by the ex- pansion and contraction of the thermostatic strip. Suppose the room too warm and the valve K open, air then flows through the chamber B, through the filtering cotton in the lower part of B' , thence through the small tube OO 68 W. 36 . 24" 68 S. 20 . 38" 65 Third. W. 24 38" 65 S. 16 38" 65 Q INDIRECT RADIATION. (NOTE. Omitted on specifications when heating system is all direct.) The indirect radiators shall consist of stacks or clusters of prime surfaces connected together with tight joints, and firmly suspended from ceiling by suitable wrought-iron hangers, as directed by radiator makers, or by other methods equally- good. (There shall be a difference of level of not less than eighteen inches between lowest point of all indirect radiation and the water-line of boiler.) All stacks shall be so piped and hung as to permit a quick, noiseless, and constant flow throughout of (steam and all water of condensation) [the heated water]. COLD-AIR DUCTS, CASINGS, ETC. (NOTE. Omitted on specifications when heating system is all direct.) The area of internal cross-section of fresh-air inlet and duct, as well as registers and warm-air outlet, shall never be less than standards of measurements laid down in Carpenter's " Heating and Ventilating Buildings." Fresh-air inlet shall be of 600 square inches area, and shall be provided with substantial iron wire-gauze screen. Connecting cold-air duct and casing of indirects shall be made of galvanized iron (No. 20 or heavier), provided with door for clean-out and inspection all joints being made permanently air-tight. Cross-section of duct throughout its length to be as nearly uniform, circular SPECIFICATION PROPOSALS SUGGESTIONS. 333 or square, as conditions of building permit. Casing of indirects shall be so erected that all entering air must pass through each stack, and be warmed, before passing to its respective outlet register. Stacks shall be so hung and encased that the full area of inlet and outlet ducts shall be maintained above and below the stack, which space shall in no case be less than ten inches in height, by the length and breadth of stack, and casing shall be so arranged that all inflowing fresh air shall be heated and conveyed to destination without loss through tin warm-air ducts, of areas as above provided for, same to be furnished by owner, and set in walls or floors by owner, as directed by ar- chitects. Each cold-air inlet shall be provided with one con- trolled damper, fitted with iron handle. REGISTERS AND REGISTER-BOXES. (NOTE. Omitted on specifications when heating system is all direct.) All registers shall be of Jones design. The sum of areas of openings in same never to be less than area of warm-air outlet. Registers to be set flush with, and firmly fastened in, openings in floor or wall provided by owner, and to be located to best advantage according as conditions of building permit. Proper register-boxes made of /. X. tin shall be provided by contractor for reception of registers. CUTTING, PAINTING, BRONZING, ETC. All cutting and carpenter work shall be done by owner as directed by contractor. All uncovered exposed piping in boiler- room shall receive two coats of best or drying Japan paint. All exposed piping and radiation above boiler-room to receive one coat of priming and one coat of pale-gold bronze. EXTRAS. It is understood and agreed, upon the acceptance of the Proposal accompanying this Specification, that any and all verbal or other agreements, statements, or representations made by any person or persons, for or on behalf of the con- tractor, shall be considered as absolutely merged in the Pro- 334 HEATING AND VENTILATING BUILDINGS. posal and Specification, and that the contract then existing shall be taken and held to be fully set forth and expressed therein. If any deviation in system, material, or mode of installation is to be made, such change shall be considered an " extra," and must be provided for by a special agreement. COMPLETION AND TESTING. If this Specification with accompanying Proposal be accepted notice of date when work may begin shall be given contractor, and same shall be prosecuted with due despatch, and shall be completed on or before , whereupon notice to that effect shall be served on architect. Should any unforeseen or unavoidable delay occur, same shall not constitute a breach of contract on the part of contractor. Upon notification that work as herein provided for has been completed, same shall be promptly inspected, and "accepted" or " rejected," and notice thereof served on the contractor. Acceptance shall in no event waive the guarantee herein below given. Failure to promptly inspect and accept or reject work shall be considered as accept- ance, and shall entitle undersigned to payments as provided for. " Testing " shall consist of firing boiler all fuel for which shall be delivered in boiler-room, and furnished by owner, and the developing of a (steam-pressure not exceeding fifteen pounds to the square inch) [flow-temperature not less than degrees Fahrenheit without boiling over] and the making tight of all joints in system. Determination of fulfilment of guarantee shall be gauged by standards set down in Carpenter's " Heating and Ventilat- ing Buildings," page 86. If the condition of building is such that work cannot be completed without delay, and that delay requires running of all or part of apparatus for use or con- venience of any one other than the contractor, it will only be so run at the risk and expense of owner, and apparatus must be delivered again in as good condition as when taken. A payment of five (5) dollars shall be due for each radiator dis- connected and reconnected. SPECIFICATION PROPOSALS SUGGESTIONS. 335 IN GENERAL. Estimates for capacity of within apparatus, as well as this Specification and accompanying Proposal, are ail based on dimensions, information, etc., concerning construction of build- ing furnished by architects; and if such dimensions, information, etc., are erroneous, or if changes shall be made in construction of building, then in so far as such deviations detract from effi- ciency of apparatus, the guarantee as to the efficiency thereof which is herein given shall be deemed cancelled. Instructions as to conduct of work must be made to the contractor and not to employees, and all instructions from architects shall be con- sidered as final, unless otherwise advised by owner. GUARANTEE. When the apparatus as herein proposed to be furnished shall be completed, the same is guaranteed to be capable of warming the rooms entered on schedule, to the temperatures specified therein, when apparatus is run as directed, and under the con- ditions which would maintain in the finished building. Any failure to fulfill this guarantee by reason of any defect of work- manship, material, or efficiency within a period of one year will be made good by contractor within a reasonable time after receiving notice of such defect. N. B. The term " defect " as above used, shall not be con- strued to cover such imperfections as result from accident, de- sign, or the natural wear and tear of use. The contractor shall have and retain, until the final payment in full shall have been made, a first and valid lien upon all materials (including pipe, fittings, valves, covering, radiators, registers, ducts, boilers, etc.) furnished by contractor under terms of this specification and accompanying proposal, and shall have the right at all times prior to such final payment, upon failure on part of owner, to make all payments as provided for, to take possession of and remove the said materials, and to retain the possession of same and every part thereof, and also to retain all payments that have been made on account thereof as liquidated damages for non-fulfilment of contract. 336 HEATING AND VENTILATING BUILDINGS. SPECIAL NOTE. This Specification with accompanying Proposal shall be ac- cepted or rejected on or before inst., and notice thereof be served on contractor. Respectfully submitted, JOHN G. DOE Co. October i, 1895. 173. Form of Uniform Contract. UNIFORM CONTRACT FOR THE CONSTRUCTION OF HEAT- ING APPARATUS (TO BE) ADOPTED FOR USE BY THE MASTER STEAM AND HOT-WATER FITTERS' ASSOCIA- TION OF THE UNITED STATES.* (Copyright, 1895, by the Master Steam and Hot-Water Fitters' Association of the United States.) THIS AGREEMENT, made and concluded at Kalamazoo, State of Michigan, the first day of January, in the year one thousand eight hundred and ninety-yfo^, by and between Jones & Brown, of Chicago, State of Illinois, for themselves and their legal representatives, parties of the first part (hereinafter desig- nated the Contractor), and R. /. Peters, of Kalamazoo, State of Michigan, for himself and his legal representatives, party of the second part (hereinafter designated the Owner). WITNESSETH, That the Contractor, in consideration of the fulfilment of the agreements herein made by the Owner, agrees with the said Owner, as follows: ARTICLE I. The Contractor, for the consideration herein- after provided, covenants and agrees, with the Owner, that the Contractor shall and will, within the space of three months next, after the date hereof, in a good and workmanlike manner, and at his own proper charge and expense, well and substantially build, furnish, and erect a certain Steam Heating Apparatus, at 444 4th Avenue, City of Kalamazoo, according to the Specifi- cations, Drawings, and Plans designed by Thomas Robinson, Architect, which Specifications, Drawings, and Plans are made a part of this Contract and are identified by the signatures of the parties hereto. * Printed words in italics to be supplied in each contract. SPECIFIC A riON PROPOSA LSS UGGES TIONS. 337 ARTICLE II. No alterations shall be made in the work shown or described by the drawings and specifications, except upon a written order of the Architects, and when so made, the value of the work added or omitted shall be computed by the Architects, and the amount so ascertained shall be added to or deducted from the contract price. In the case of dissent from such award by either party hereto, the valuation of the work added or omitted shall be referred to three (3) disinterested arbitrators, one to be appointed by each of the parties to this Contract, and the third by the two thus chosen ; the decision of any two of whom shall be final and binding, and each of the parties hereto shall pay one-half of the expenses of such ref- erence. ARTICLE III. Should any difference arise in interpreting the Plans or Specifications, involving or assuming additional compensation, the Contractor shall, upon written notice from the Owner, immediately execute such interpretation, the ques- tion of compensation to be determined on completion by arbitrators, as provided in Article II. ARTICLE IV. All of the materials and workmanship of the apparatus to be of the quality as expressed in said Specifica- tions, Drawings, and Plans ; said Owner to reserve the right to reject, through himself or his authorized agent, all material or workmanship of an inferior quality, which said Contractor may attempt to use in the erection of said Heating Apparatus, and if the said Contractor, after being notified, neglects or refuses to do the work, or furnish the materials as called for in the Specifications, Drawings, and Plans, then, acd in that case, said Owner shall give notice in writing to the Contractor, which notice is to set forth in full the cause or causes of complaint. If the Contractor demurs and refuses to do the work or furnish the materials as directed in the notice of complaint, within three days from the date of said notice, resort to arbitration shall be had as provided in Article II. ARTICLE V. The Owner shall not, in any manner, be answerable or accountable for any loss or damage that shall or may happen to the said works, or any parts thereof respectively, or for any of the materials or other things used and employed in finishing and completing the same, loss or damage by fire HEATING AND VENTILATING BUILDINGS. excepted. The Contractor shall be responsible for all damage to the building and adjoining premises, and to individuals, caused by himself or his employees in the course of their employment. ARTICLE VI. It is hereby mutually agreed between the parties hereto, that the sum to be paid by the Owner to the Contractor for said work and materials shall be Seven Thousand Dollars ($7,000), subject to additions and deductions as herein- before provided, and that such sum shall be paid in current funds by the Owner to the Contractor, in monthly payments, to the amount of oo per cent of the value of materials delivered to and labor performed in the said building during the preced- ing month ; and the remaining 10 per cent shall be paid as a final payment within 30 days after this contract is fulfilled. All payments shall be made upon written certificates of the Architects to the effect that such payments have become due. ARTICLE VII. It is mutually agreed that payments for all additional work shall be made at the same time and in the same manner as contract payments, Article VI. ARTICLE VIII. It is mutually agreed that should default be made in any of the payments as herein provided, the Con- tractor shall have the right to stop work and withdraw all un- used materials until such payment is properly made, or may at his option cancel the contract. ARTICLE IX. It is further mutually agreed that the essence of this Agreement is that the Owner purchasing this apparatus and paying therefor will receive full value to the extent that it will warm the subdivisions of the building indicated on the plans to 70 degrees Fahrenheit in the coldest weather ; but nothing herein contained, or in the Specification accompanying the same, shall prevent the Contractor from receiving from the Owner a final payment for the work herein and at the time stipulated. ARTICLE X. The Contractor guarantees his workmanship and materials, the capacity of the boiler, the circulation of the system and the efficiency of the heating surfaces, all as called for in the Specifications hereto attached, and should any de- fects or deficiencies occur, other than from neglect on the part of the Owner or his employees, within the term of one year SPECIFIC A TION PROPOSA LSS UG GESTIONS. 3 39- from the above date, the Contractor agrees to make good the same upon a written notice from the Owner at the Contractor's expense. ARTICLE XI. If at any time there shall be evidence of any lien or claim for which, if established, the Owner of the said premises might become liable, and which is chargeable to the Contractor, the Owner shall have the right to retain out of any payment then due, or thereafter to become due, an amount sufficient to completely indemnify himself against such lien or claim. Should there prove to be any such claim after all pay- ments are made, the Contractor shall refund to the Owner all moneys that the latter may be compelled to pay in discharging any lien on said premises made obligatory in consequence of the Contractor's default. ARTICLE XII. It is further mutually agreed, between the parties hereto, that no certificate given or payment made under this Contract, except the final certificate or final payment, shall be conclusive evidence of the performance of this Contract, either wholly or in part, and that no partial payment shall be construed to be an acceptance of defective work or improper materials. ARTICLE XIII. The said parties for themselves, their heirs, executors, administrators, and assigns, do hereby agree to the full performance of the covenants herein contained. IN WITNESS WHEREOF, the parties to these presents have hereunto set their hands and seals, the day and year first above written. In presence of /. B. Sax* Jones & Brown (SEAL) R. J. Peters (SEAL) (SEAL) (SEAL) ALTERNATE FOR ARTICLE VI. It is hereby mutually agreed, between the parties hereto, that the sum to be paid by the Owner to the Contractor for said work and materials shall be Seven Thousand Dollars ($7.000} sub- ject to additions and deductions as hereinbefore provided, and 340 HEATING AND VENTILATING BUILDINGS. that such sum shall be paid in current funds by the Owner to the Contractor in instalments, as follows : When The Boilers are delivered and set, $1,500 When Steam Mains and Risers are in place, $1.500 When The Radiators are delivered, $1,500 When The Radiators are connected, $1,500 And the balance of $ 1,000 as a final payment to be made within 30 days after this contract is fulfilled. All payments shall be made upon written certificates of the Architects to the effect that such payments have become due. 174. Specifica.tions for Plain Tubular and Water-tube Boilers. This boiler is employed extensively for heating large buildings. The boiler is described on page 130, and several methods of setting are shown on page 145. The following specifications represent the best practice of to-day in the con- struction of plain tubular boilers employed for heating. They are in each case to be set in brickwork, substantially as de- scribed on page 143. SPECIFICA TION PROPOSALS SUGGESTIONS. O CO O M vo O \\"C.\\\\\ *< * O ^^x. tf> t-. fn ri ti t^ - Ov - ooo - -co i* - 1 1 t_ "u B - D yj VO ^^O^O ^vo ^vo ^^ rt "o 1 c course N vovovovo VOO ^ c T3 S Ist^fS-SS^^-s-s-S-l 3 | > g a c I 1 1 > * "* z en ^oo* moi^QO^ oo * 2 S m ^%>>^^^>^v2 ^ m 2 >> 5" c ? a r 4> "5 cu MM U!fs!s! a $s 1 go j: W) c - E S cu 1 o rt IT s < 5 01 i "3 i-f^ -^OO OO>- OO *o ^= 4-> tfl = u "33 c c c rt - ^ < S k VO 00*2(30*2 oo^ U) JO V O) -^ PI n c ~ "7. t_ ci F essrs. F D en OQ OQ D J 1 VO OO^OO- ^00*2 en 53 cd E T3 C D - pi a co 73 3 to - 1 ' & - u ^ 3 ^ - c s '^J r. _- y. : . . . . . . ; : B ^ 4J ^ V u. X s - 3 i * 3 '^ ^ "o U S "S ] $ i 58 .CIFICAT1Q] : w= s : -. t = r 3* i" :l c 8. ?) ctf 8 in C U X Z T3 g s O.U2 1 " J^- oal iron or s refined iron. 3referably m E s 5 - s rt c Wi cu to S3 :"gj?8-8J?8S >: : 'll'.o 1 on a g - ^ r- CU S ~ rt LNDARD Materials.- *o cd "o r cd 8 a sl s 0. o- 2 ^ *- "o t/) il s H 23 to r seams or i but one p C/) Illll Illss 3 u cd r U 34 2 HEATING AND VENTILATING BUILDINGS. Riveting for a Working Pressure of 100 Ibs. Horizontal seams double- staggered riveted, lap-joint ; pitch of rivets 3" longitudinally and T.\" diagonally. Circular seams single-riveted, lap-joint ; pitch of rivets 2%". Flange seam and vertical seam of dome double-staggered riveted ; pitch of rivets 3" longitudinally and 2j" diagonally. Circular seam at dome head single-riveted ; pitch of rivets 2^-". For a Working Pressure of 125 Ibs. Horizontal seams triple-riveted ; lap-joints required except for boilers exceeding 66" diameter, when hori- zontal seams shall be made with butt-joint, with inside and outside lap strips covering the joint, these strips same thickness as plate in shell of boilers ; three rows of rivets each side of joint; pitch of rivets on triple lap-joints 3^" longitudinally, 2" diagonally, 2-f'' transversely. Pitch of rivets on butt- strapped joints 3^" and 6" longitudinally, 2" diagonally, and 2-f" transversely. Circular seams single-riveting, lap-joint; pitch of rivets i\" . Flange seam, od, dome triple-riveting staggered ; pitch of rivets 3" longitudinally and 2" diagonally ; vertical seam of dome double-staggered riveting ; pitch of rivets 3" longitudinally and 2\" diagonally. Circular seam at dome head single-riveting ; pitch of rivets 2j". Bracing. All braces to have a sectional area of \\ square inches and to be of the solid crowfoot style, and riveted to heads and shell with two rivets in each end ; pitch of rivets 4". On heads of boiler these braces to be set radially and spaced about 7" centres, and to lead from head to shell and to be at least 3 ft. in length and preferably longer. Braces in dome to lead from shell of dome to shell of boiler, spaced about 18" centres, two rivets in each end spaced 4" centres ; braces as long as height of dome will permit. Head of dome may be convex and without braces. Tube Setting. Tubes to be set in straight horizontal and vertical rows, one inch apart each way, and no tube nearer shell than three inches. Distance from top of upper row of tubes to shell not less than one third the diameter of boiler. Tubes to extend through heads, and be carefully expanded and beaded to the heads. Calking. Calking edges of each seam to be bevelled by machine be- fore plates are put together, and calking tool driven straight. Manholes. A suitable manhole in top of shell, having an internal opening ii"xi5", reinforced with strong internal frame of forged iron. Manhole to be provided with suitable plate, bolt, guard, and gasket. For large boilers a manhole shall be left in front head beneath the tubes. Hand-holes. A suitable hand-hole, 4^" x 6", in each head under tubes, provided with suitable plate, bolt, guard, and gasket. Outlets. Outlet for steam should be on top of the dome, the opening into dome to be reinforced with wrought-iron flange properly threaded and riveted to the head ; the safety-valve to be attached to this opening. The opening for blow-off should be in the back head at the side of hand-hole. The opening for surface blow shall be in the top of the shell, SPECIFICATION PROPOSALS SUGGESTIONS. 343 and provided with pipe having a trumpet shaped mouth ending at water- line. The opening for feed connection should be in the top of shell and reinforced. The feed-pipe is to be extended downward below the water- line, and at least four feet horizontally. The upper connection for water-column should be in front head near top. The lower connection for water-column should be in front head, about on the centre line of the boiler. Wall-brackets. There should be two heavy cast-iron wall -brackets riveted to each side of shell for supporting boiler on masonry. These brackets should be at least 9 inches wide with foot 12 inches long, and 14 inches on the boiler and \\ inches thick, with heavy rib through the centre. These, and all other castings riveted to the shell, to conform to the shape of same and fit accurately without linings of any kind. Testing. For a working pressure of 100 Ibs.' the boiler should be tested to a hydrostatic pressure of 150 Ibs. per square inch, and for a working pressure of 125 Ibs. it should be tested to a hydrostatic pressure of 200 Ibs. per square inch, and should be perfectly tight under each test. Castings. The boiler should be provided with a cast-iron front at least ' thick, with double flue, fire and ash-pit doors swinging right and left. Fire-doors should be provided with perforated liners and air-reg- isters. Provide heavy cast-iron dead-plate, arch-plate over fire-door, and cast-iron plates at each side of fire-door opening, to protect the fire-brick- The grates* should equal in width the full diameter of the boiler, and should be in two lengths, with necessary bearing bars ; the entire length of the grate surface should equal about one third the length of the tubes. The air-space in the grates for soft coal should be from " to ", and for hard coal from ' 'to ''. Two heavy cast-iron arch bars for supporting brick at rear of boiler. One back door and frame of cast iron, to provide access to rear of the setting. All necessary anchor-bolts for holding front and back doors in posi- tion, and at least four long tie-bolts extending full length of the setting ( with cast-iron washers for rear end. Four heavy cast-iron buck-stays with rods, extending crosswise of the setting, for supporting side walls. Four cast-iron wall-plates with rollers for supporting brackets to rest upon. Fittings. One steam-gauge inches diameter. One lever safety- valve. One water-gauge fitted to cast-iron water-column, with three gauge-cocks. One steam-cock for blow-off. One globe-valve, and one check-valve for feed-pipe connections. One set of fire tools, slice- bar, and rake. One damper with, suitable handles and with auto- matic regulator. * If rocking gates are desired, name of manufacturer should be specified. 344 HEATING AND VENTILATING BUILDINGS ' It is generally desirable to provide two independent methods of feeding, so that an accident will not affect the supply of feed- water , but specifications for the feed-pumps are not often in- cluded with those for the boiler. 175. Protection from Fire Hot Air and Steam Heating. Where hot-air stacks or steam-pipes pass up through parti- tions near woodwork there is considerable danger of fire, and for this reason certain requirements have been made both as to the position of hot-air pipes in furnace-heating and steam pipes in steam-heating. The following digest, compiled by H. A. Phillips, of the municipal laws relating to hot pipes in buildings, in force in some of the principal cities of the United States, appeared in the American Architect and Building News, Feb. 1893, and is useful in preparing specifications. They are as follows : Boston. i. Hot-air pipes shall be at least i inch from woodwork. (This may be modified by inspector in first-class buildings.) 2. Any metal pipe conveying heated air or steam shall be kept i inch from any woodwork, unless pipe is protected by soapstone or earthen tube or ring, or metal casing, Baltimore. i. Metal flue for hot air may be of one thickness of metal, if built into stone or brick wall. 2. Otherwise it must be double, the two pipes separated by i inch air-space. 3. No woodwork shall be placed against any flue or metal pipe used for conveying hot air. Chicago. i. Hot-air conductors placed within 10 inches of wood- work shall be made double, one within the other, with at least inch air-space between the two. 2. All hot-air flues and appendages shall be made of 1C or IX bright tin. 3. Steam-pipes shall be kept at least 2 inches from woodwork, unless protected by soapstone, earthen ring or tube, or rest on iron supports. Cincinnati. No pipes conveying heated air or steam shall be placed nearer than 6 inches to any unprotected combustible material. All subject to approval of inspector. Cleveland. i. Hot-air conductors placed within 10 inches of wood- work shall be .made double, one within the other, with at least | inch air-space between the two. 2, No pipes conveying heated air or steam shall be placed nearer than 6 inches to any unprotected combustible material. Denver. Metal flue for hot air may be of one thickness of metal, if SPECIFICATION PROPOSALS SUGGESTIONS. 345 built into stone or brick wall ; otherwise it shall be made double or wrapped in incombustible material. Detroit. No metal pipe for conveying hot air shall be placed nearer than 3 inches to any woodwork. Such pipes over 15 feet long shall be safely stayed by wire or metal rods. District of Columbia. i. Hot-air pipes shall be at least i inch from woodwork. 2. Pipes passing through stud or wooden partitions shall be guarded by double collar of metal, "giving at least 2 inches air-space, having holes for ventilation, or other device equally secure, "to be approved by inspector." 3. Metal pipe double, with the space filled with i inch of non-com- bustible, non-conducting material, or a single pipe surrounded by i inch of plaster of Paris or other non-conducting material between pipe and timber. Kansas City.i. Any metal pipe conveying heated air or steam shall be kept i inch from any woodwork, unless pipe is protected by soap- stone or earthen tube or ring, or metal casing, or otherwise protected to satisfaction of superintendent. 2. No wooden flue or air-duct for heating or ventilation shall be placed in any building. Memphis. i. All stone or brick hot-air 'flues and shafts shall be lined with tin pipes. 2. No wooden casing, furring, or lath shall be placed against or over any smoke-flue or metal pipe used to convey hot air or steam. 3. No metal flues or pipes to convey heated air shall be allowed unless inclosed with 4 inches thickness of hard, incombustible material, except horizontal pipes in stud partitions, which shall be built in the following manner: The pipes shall be double, one inside the other, and inch apart, and with 3 inches space between pipe and stud on each side; the inside faces of said stud well lined with tin plate, and the out- side face with iron lath or slate. Where hot-air pipe passes through partition shall be at least 8 feet from furnace. 4. Horizontal hot-air pipes shall be kept 6 inches below floor-beams or ceiling. If floor-beams or ceiling are plastered or protected by metal shield, then distance shall not be less than 3 inches. 5. Where hot-air pipes pass through wooden or stud partition, they shall be guarded by double collar of metal with 2-inch air-space and holes for ventilation, or by 4 inches of brickwork. 6. No hot-air flues or pipes shall be allowed between any combus- tible floor or ceiling. 7. Steam- pipe shall not be placed less than 2 inches from woodwork unless wood is protected by metal shield, and then distance shall not be less than i inch. 8. Steam-pipes passing through floors and ceilings or lath-and-plaster UNIVERSITY J 34-6 HEATING AND VENTILATING BUILDINGS. partitions shall be protected by metal tube 2 inches larger in diameter than pipe. 9. Wooden boxes or casings inclosing steam-pipes and all covers to recesses shall be lined with iron or tin plate. Milwaukee. i. Hot-air conductors placed within 10 inches of wood- work shall be made double, one within the other, with at least i inch air-space between them. 2. All hot-air flues and appendages shall be made of 1C or IX bright tin. Nashville. I. Sheet-iron flue running through floor or roof shall have a sheet-iron or terra-cotta guard at least 2 inches larger than flue. 2. Steam-pipes shall be kept at least 2 inches from woodwork. 3. All steam and hot-air flues and pipes must be suspended by iron brackets. Newark. i. Hot-air pipes shall be set at least 2 inches from wood- work and the woodwork protected with tin. 2. Such pipes placed in lath-and-plaster partitions must be covered with iron, tin, or other fire-proof material. New York. (Same regulations as noted under heading of " Mem- phis.") No hot-air flue or pipe allowed between combustible floor or ceiling. Omaha. i. Steam-pipe shall not be placed less than 2 inches from woodwork unless wood is protected by metal shield ; and then distance shall not be less than i inch. 2. Steam-pipes passing through floors and ceilings, or lath-and- plaster partitions, shall be protected by metal tube 2 inches larger in diameter than pipe. 3. Wooden boxes or casings inclosing steam-pipes and all covers to recesses shall be lined with iron or tin plate. 4. Stud partitions in which hot-air pipes are placed to be at least 5 inches wide, and the space between studs at least 14 inches. 5. Hot-air pipes shall not be placed between floor-joists unless same are doubled and the joists 14 inches apart. 6. Bright tin shall be used in construction of all hot-air flues and appendages. Providence. i. Hot-air pipes shall be at least i inch from wood- work, unless protected by soapstone or earthen ring, or metal casing permitting circulation of air around pipe. 2. Steam-pipes must be kept at least i inch from woodwork, or sup- ported by incombustible tubes or rest on iron supports. St. Louis. i. Hot-air pipes shall be at least i inch from woodwork, unless protected by soapstone or earthen ring or metal casing permitting circulation of air around pipe. 2. Steam or hot-water pipes carried through wooden partition or between joists, or in other close proximity to woodwork, shall be SPECIFIC A TION PROPOSALS SUGGESTIONS. 347 inclosed in clay pipe or covered with felting or other non-conducting material. San Francisco. i. Metal flue for hot air may be of one thickness of metal, if built into stone or brick wall; otherwise double, one pipe within the other, i inch apart, and space filled with fire-proof material. 2. No woodwork shall be placed against any flue or metal pipe used for conveying hot air. 3. Steam-pipes shall be placed at least 3 inches from woodwork, or protected by ring of soapstone or earthenware. Wilmington. Metal pipes to carry hot air shall be double, one inside the other, inch apart ; or, if single, have a thickness of 2 inches of plaster of Paris between pipe and woodwork adjoining same. 176. Duty of the Architect. The heating system is a essential part of the building in this latitude, and it should be the duty of the architect to provide building designs of such character that it can be readily and economically installed. The architect's specifications for the buildings hould provide for the construction of ventilating, heating, and smoke flues, and his plans should show the location, including pipe-lines, of every essential part of the heating apparatus. All responsibility re- garding flues and the general adaptability of the heating sys- tem to the building should be assumed by the architect, and not shifted to the contractor. If the heating system is designed at the same time as the building, slight changes can be made in arrangements of details, partitions, doors, etc., that will tend to cheapen construction, and will add to the efficiency of opera- tion and the general appearance of the heating apparatus. If steam or water pipes are required to be erected out of sight, conduits should be provided, so that they will be readily accessible for inspection and repairs. 177. Methods of Estimating Cost of Construction. In estimating the cost of construction of any system of heating apparatus the contractor must depend largely upon his own experience and knowledge. No general directions can be given, but a few suggestions are offered which may aid in adopting a systematic method of proceeding. Determine first the amount and character of radiation to be placed in each room by the methods which have already been given fully in Chapter X. Second, determine the position and sizes of pipes leading from HEATING AND VENTILATING BUILDINGS. the heater to the various radiating surfaces by methods given in Chapter XL To facilitate the above work, a set of floor drawings of each story should be obtained, and on these there should be carefully laid out the position of all radiators, flues, pipe-lines, etc. After determining the amount required, a schedule of material should be made and the cost should be computed. The manufacturers have adopted a price, which is changed very rarely, for all standard fittings, pipes, etc., and from which a discount is given which varies with the condition of the market, cost of material, labor, etc. The discount is usually large upon cast-iron fittings and brass goods, being seldom less than 70 per cent, and sometimes 80 per cent and even greater. The discount on piping, especially the smaller sizes, is much less, ordinarily ranging from 40 to 70 per cent. The cost of labor will vary greatly in different localities, so that no general method of estimating can be given. It must be determined largely by experience in each locality and with j a given set of men. The cost of heaters of any given type, with fittings, etc., can only be determined accurately by correspond- ence with manufacturers. Table XXII may frequently be useful, as it gives the list- j price of the principal standard fittings, pipes, and valves (seel appendix to book). 178. Suggestions for Pipe-fitting. Certain suggestions I are here made relating to the actual work of pipe-construction which may be useful to those not having an extended experi- ence. In the actual construction of steam-heating or hot-water] heating systems it is usually customary to send a supply of! pipe and fittings to the building somewhat greater than is required, and the workman, after receiving plans of construction which show the location and sizes of the various pipes to be ; erected, makes his own measurements, cuts the pipes to the i proper length in the building, threads them, and proceeds tol screw them into place. In some rare instances all lengths of j pipe are purchased the proper length, and the workman has j merely to put them in the proper position. The skill required j for pipe-fitting may seem to the novice to be easily acquired : ] SPECIFICATION PROPOSALS-^SUGGESl^IONS. 349 this is not true, as it is a trade requiring as much training and experience as any with which the writer is familiar. The tools belonging to this trade consist of tongs or wrenches for screwing the pipe together, cutters for cutting, taps and dies for threading the pipe, and vises for holding it in position while cutting or threading. A very great variety of tongs and wrenches is to be found on the market, some of which are ad- justable to various sizes of pipe, and others are suited for only one size. For rapid work no tool is perhaps superior to the plain tongs, and one or more sets especially for the smaller sizes of pipes should always be available. For large pipes, chain tongs of some pattern will be found strong and convenient, and can be used with little danger of crushing the pipe. A form of adjustable wrench known from the inventor as the Stilson wrench has proved a very excellent and durable tool, and is well worthy a place in the chest of any fitter. Other wrenches of value are also on the market, one with a triangular head and projecting teeth being especially valuable for small pipes. The wrenches or tongs which are used for turning the pipe in most cases exert more or less lateral pressure, and if too great strength is applied at the handles there is a tendency to split the pipe. It is an advantage to have the tongs or wrenches catch on the outer circumference of the pipe with as little lateral pressure as posible, and to this end the projecting edges should be kept sharp and clean. The cutter ordinarily employed for small pipe consists of one or more sharp-edged steel wheels, which are held in an ad- justable frame, the cutting being performed by applying pres- sure and revolving it around the pipe. With this instrument the cutting is accomplished by simply crowding the metal to one side, and hence burrs of considerable magnitude will be formed both on the outside and inside of the pipe. The outside burr must usually be removed by filing before the pipe can be threaded. The inside burr forms a great obstruction to the flow of steam or water, and should in every case be removed by the use of a reamer. Workmen quite often neglect to remove the inside burr. A cutter consisting of a cape chisel set in a frame is more difficult to use and keep in order, although it makes cleaner cuts ; it can be had in connection with some 350 HEATING AND VENTILATING BUILDINGS. of the adjustable die-stocks, but is rarely used. Pipes, es- pecially the larger sizes, are sometimes cut by expert workmen with diamond-pointed or cape chisels, but this process requires too much time to be applicable to small pipes. The hack-saw is coming into use to some extent for cutting pipes, and is an excellent instrument for this purpose, as it does not tend to burr or crush the pipe, and is quite as rapid as the wheel-cutter. The dies for threading the pipes are of a solid form, each die fitting into a stock or holder with handles, or of an adjust- able form, the dies being made of chasers, which are held where wanted and can be set in various positions by a cam. The adjustable dies can be run over the pipes several times, and hence work easier than solid ones ; but in their use great care should be taken that the exterior diameter of the pipe is not made less than the standard size. The cutting edges of the dies should be kept very sharp and clean, otherwise perfect threads cannot be cut. In the use of the dies some lubricant, as oil or grease, kept on the iron will be found to add materi- ally to the ease with which the work can be done, and will tend to prevent heating and crumbling of the pipe and injury to the threads. Taps are required for cutting threads in openings or coup- lings into which pipes must be screwed an operation which the pipe-fitter seldom has to perform, unless a thread has been in- jured. The vises for holding the pipe should be such as will prevent it from turning without crushing it under any circum- stances. Adjustable vises with triangular-shaped jaws on which teeth are cut are usually employed. In the erection of pipe great care should be taken to pre- serve the proper pitch and alignment, and the pipes should, to appear well, be screwed together until no threads are in sight. Every joint should be screwed six to eight complete turns for the smaller sizes, 2" and under, and eight to twelve turns for the larger sizes, otherwise there will be danger of leakage. It is a good plan to test the threads on all pipes before erection by unscrewing the coupling and screwing it back with the ends reversed. It is also advisable to look through each length of pipe and see if it is clear before erect- SPECIFIC A TION PROPOSA LSS UGGES TIONS. 3 5 I ing in place ; serious trouble has. been caused by dirt or waste in pipes, which would have been removed had this precaution been taken. In screwing pipes together, red or white lead is often used ; the writer believes this practice to be generally objectionable, and to be of no especial benefit in preventing leaks. The lead acts as a lubricant, and consequently aids by reducing the force required to turn the pipe. It will generally be found, however, that linseed or some good lubricating oil will be equally valuable in that respect, and will have the advantage of not discoloring the work. If possible, arrange the work so that it can " be made up " with right and left elbows, or right and left couplings. Packed joints, especially unions, are objectionable, and likely to leak after use. Flange-unions, packed with copper gaskets, should be used on heavy work. Good workmanship in pipe-fitting is shown by the perfec- tion with which small details are executed, and it should be remembered that bad workmanship in any of the particulars mentioned may defeat the perfect operation of the best-de- signed plant. APPENDIX CONTAINING REFERENCES AND TABLES. LITERATURE AND REFERENCES. The literature devoted to the subject of warming and ven- tilation is quite extensive, dating back to a treatise on the economy of fuel and management of heat by Buchanan in 1815. A most excellent compilation of this literature was made by Hugh J. Barron of New York, in a paper presented to the American Society of Heating and Ventilating Engineers at its first meeting in January, 1895, from which the following list of books has been copied : A Treatise on the Economy of Fuel and Management of Heat. Robertson Buchanan, C.E. Glasgow, 1815. Conducting of Air by Forced Ventilation. Marquis de Chabannes. London, 1818. The Principles of Warming and Ventilating Public Buildings, Dwell- ing-houses, etc. Thos. Tredgold, C.E. London, 1824. Warming, Ventilation, and Sound. W. S. Inman. London, 1836. The Principles of Warming and Ventilating, by Thos. Tredgold, with an appendix. T. Bramah, C.E. London, 1836. Heating by the Perkins System. C. J. Richardson. London, 1840. Illustrations of the Theory and Practice of Ventilation, with Re- marks on Warming. David Boswell Reid, M.D. London, 1844. A Practical Treatise on Warming by Hot Water. Chas. Hood, F.R.S. London, 1844. History and Art of Warming and Ventilating. Walter Bernan, C.E, London, 1845. Warming and Ventilation. Chas. Tomlinson. London, 1844. Walker's Hints on Ventilation. London, 1845. Practical Treatise on Ventilation. Morrill Wyman. Boston, 1846. Traite de la Chaleur. E. Peclet. Paris. First edition, 1848; sec- ond edition, 3 vols, 1859. 353 354 APPENDIX CONTAINING REFERENCES AND TABLES. Practical Method of Ventilating Buildings, with an appendix on Heating by Steam and Water. Dr. Luther V. Bell. Boston, 1848. Warming and Ventilation. Chas. Tomlinson. London, 1850. Practical Ventilation. Robert Scott Burns. Edinburgh, 1850. Ventilation and Warming. Henry Ruttan. New York, 1862. A Treatise on Ventilation. Robert Richey. London, 1862. American edition of Dr. Reid's Ventilation as Applied to American Houses, edited by Dr. Harris. New York, 1864. A Treatise on Ventilation. Lewis W. Leeds. Philadelphia, 1868; New York, 1871. Observations on the Construction of Healthy Dwellings. Capt. Douglas Galton. Oxford, 1875. Practical Ventilating and Warming. Jos. Constantine. London, 1875. Warming and Ventilation. Chas. Tomlinson. London, 1876. Sixth edition. Mechanics of Ventilating. Geo. W. Rafter, C.E. New York, 1878. Ventilation. H. A. Gouge. New York, 1881. Ventilation. R. S. Burns. Edinburgh, 1882. American Practice in Warming Buildings by Steam. Robert Briggs. Edited by A. R. Wolf, with additions. New York, 1882. Steam-heating for Buildings. W. J. Baldwin. New York, 1883. Thirteenth edition published in 1893. The Principles of Ventilation and Heating. John S. Billings, M.D. New York, 1884. Heating by Hot Water. Walter Jones. London, 1884. A Manual of Heating and Ventilation. F. Schuman. New York, 1886. Ventilation. W. Butler. Edited by Greenleaf. New York, 1888. Steam-heating Problems from the Sanitary Engineer. New York, 1888. Metal Worker Essays on House Heating. New York, 1890. Heat Its Application to the Warming and Ventilation of Buildings. John H. Mills. Boston, 1890. Ventilation and Heating. T. Edwards. London, 1890. Ventilation A Text-book to the Art of Ventilating Buildings. Wm. Paton Buchan. London, 1891. The Ventilating and Warming of School Buildings. Gilbert B. Mor- rison. New York, 1892. Hot-water Heating. Wm. J. Baldwin. New York, 1893. Ventilation and Heating. John S. Billings, M.D. New York, 1893. Warming by Hot Water, Chas. Hood, C.E. Edited by F. Dye. London, 1894. In addition to this list of books a large number of pam- phlets have been printed containing valuable articles on spe- cial subjects. The scope of this work does not permit any APPENDIX CONTAINING REFERENCES AND TABLES. 355 historical review of the literature or of progress and improve- ments in the art of heating. CURRENT LITERATURE OF THE DAY. The current literature of the day relating to this subject is very extensive and is mainly found in magazines or papers published either weekly or monthly and devoted to the whole or special portions of this industry. In these are to be found the best available descriptions of plants, of new and improved methods and appliances, and in general all that relates to the best systems of construction. The journals devoted to this industry provide an invaluable literature to those engaged in the art of constructing heating and ventilating apparatus. REFERENCES. Information which has been obtained from other works has generally been credited in the body of the book. The writer wishes, however, to express special thanks for substantial assistance to the publishers of the various papers, and to. J. J. Blackmore and J. G. Dudley, members of the Committee of the Boiler Manufacturers' Association, as well as to other engineers who have given cordial help in the preparation of the work. It may be stated that Messrs. Blackmore and Dudley read and revised all proofs and contributed considerable matter of prac- tical and general interest. LIST OF TABLES IN BODY OF BOOK. Air delivered in pipes of different diameters 286 Air discharged at different heights and temperatures 45 Air discharged under pressure.. . . 42 Air-flues, area of, residence heating 234 Air-pipes, various diameters, ca- pacity of 286 Air required per person for various standards of purity. . , 32 Blowers or fans, capacity of 296 Boiler explosions 174 Boilers, steam, proportion of parts 125 Boiling-point, different pressures. 159 Boiling temperature of water 22 Building loss 56 Chimney, diameter of 162 Conduction of heat, absolute 18 Conduction of heat, relative 18 Drip-pipe, diameter 228 Electrical heat, expense of 303 Equalization of pipe areas for air 287 Exhaust-steam heating 251 Flue for indirect heating, area of. 233 Flues, area of 53 Forced-blast heating surface, heat emitted 84 Forced-blast test 80 Greenhouse heating 241 Heat emitted, Peclet's table. . . .64-66 Heat emitted, Tredgold's experi- ments 76 Heat transmitted, different media. 69 Hot-air heating 275 Hot- water heaters, proportion of parts 125 Hot-water heating, data 229 Hot-water heating, main-pipe diameter. 231 Hot-water heating, proportions. . 237 356 APPENDIX CONTAINING REFERENCES AND TABLES. 'Hot- water pipes, velocity in feet per second 221 Indirect radiators, air heated 213 Indirectjradiators.cubic feet heated 214 Indirect radiator tests 81, 82 Indirect radiators, heat emitted. . 84 Moisture in air 30 Pipe-coverings, tests of. 199 Pipe diameter for great lengths. . 226 Power-transmission, loss in 264 Radiant heat, amount transmitted. 17 Radiant heat, diffusion of 17 Radiant heat, relative emissive powers 16 Radiant heat, relative reflecting powers 16 Radiator tests 77~79 Radiators, cubic feet of space heated 208, 209 Radiators, diameter of openings.. 119 Radiators, direct proportioning of 205 Radiators, indirect, factors for ... 211 Registers, areas of 53 Registers, commercial sizes 280 Relation between velocity and pressure of air 45 Relation between temperature and color 12 Return-pipe, diameter 227 Size of room influence on ventila- tion 34 Stacks, area of, hot-air heating. . . 278 Steam-boiler, energy in 173 Steam-heating, proportions of. ... 237 Steam-heating boilers, proportions in use 136 Steam-heating boilers, proportions of parts 125 Steam-pipe, area and diameter.. . 223 Steam-pipe, diameter for different lengths 226 Temperature produced by radiation in warm weather 86 Thermometric scales 8J Tubular boiler, dimensions of... . 131 Ventilation-flues, indirect heating 238 Windows 54 Wrought-iron pipe 91 LIST OF TABLES IN APPENDIX. Table No. I. United States standard weights and measures. II. The equivalent value of units in British and metric sys- tem, and (IlA) of properties of gases. III. Table of circles, squares, and cubes. IV. Circumferences and areas of circles. V. Logarithms of numbers. VI. Important properties of familiar substances. VII. Coefficients, strength of materials. VIII. Properties of air. IX. Moisture absorbed by air. X. Relative humidity of the air. XI. Properties of saturated steam. XII. Composition and value of various fuels of the United States XIII. Reducing barometric observations to the freezing-point. XIV. Thermal conductivities. XV. Dimensions of wrought-iron, steam, gas, and water pipe. XVI. Weight of water per cubic foot. XVII. Pressure of water per square inch per different heights in feet. XVIII. Contents of pipes in cubic feet and gallons. XIX. Equalization of pipe areas. XX. Temperatures of various localities. XXI. Price of pipe and fittings. APPENDIX CONTAINING REFERENCES AND TABLES. 357 EXPLANATION OF TABLES. Of the tables which have been given a few only need special explanation in order to fully understand their use. These are as follows: Table No. V, Logarithms of numbers. This table will be found of very great convenience in facilitating any operation involving multiplication and division. Thus it will be found in every case that the sum of two logarithms is the logarithm of a number equal to the product of the two num- bers whose sum was taken, and the difference of two logarithms is the logarithm of the quotient obtained by dividing one by the other. Every logarithm consists of two parts : a decimal part, which is given in the table, and an index or characteristic, which must be prefixed. The index or characteristic is a whole number and is one less than the number of integral places ; for a decimal number it is negative and one more than the number of ciphers between the decimal point and the first significant figure. Thus, to find the logarithm of 254, a number containing 3 integral places, the index is 2, the decimal part of this logarithm found opposite 25 and under 4 in the table is 4048, making the full logarithm 2.4048. If the number had been 25.4 the index would have been I, the decimal part as be- fore. If the number had been 0.0254, the index would have been minus 2, the decimal part the same as before. As an illustration showing how to multiply by logarithms, multiply 254 by 2.48. We have : The logarithm of 254 = 2.4048 " 2.48 = 0.3945 Log. of product = 2.7993 The sum of these two logarithms, which is the logarithm of the product, is equal to 2.7993. The index, or number 2, is of use in showing that there are three figures or integral places in the result. To find the logarithm, look in the table for the number next smaller than 7993 ; in this case the result is exact and is found opposite 63 in the column marked zero, indicating that the product is 630; the actual product of these numbers is slightly less than this, the difference, however, being scarcely ever of any practical importance. Had our number been 7994, it would have been one greater than 7993 and 6 less than the logarithm of the next number. In that case our number would 358 APPENDIX CONTAINING REFERENCES AND TABLES. have been 630^-, which, reduced to a decimal, would have been the number to consider as the product. The logarithm of a power can be found by multiplying the logarithm by the num- ber which represents the power and the logarithm of a root by dividing by the index of the root. Thus, to raise 368 to the fifth power, we have : Log. 368 = 2.5658 Multiply by 5 Log. 5th power = 12.8290 No. = 674^- expanded to 13 places = 6745000000000. To extract 5th root : 368 : Log. 368 = 2.5658 Divide by 5 = 0.51316 = log. of root Root 3.259 In general the table will be found to afford an easy method of dividing or multiplying, and it will be well worth while to become master of its use. The table which is printed in the book is correct for 4 places of figures only, but tables of 7 and even 13 places have been printed. The four-place table can be used with confidence for all operations not requiring extreme accuracy. It will in almost every case be found sufficiently accurate for all practical prob- lems of designing. The method of using Tables Nos. IX and X to determine the amount of moisture in the air has been quite fully explained on page 30. The method of using Table No. XI. (properties of saturated steam) has been fully explained on page 120. The reader should note that the steam-pressure tabulated is that above a vacuum, and not the reading of a pressure-gauge. The pressure-gauge reads from the atmosphere, which is generally 14.7 pounds above zero ; hence, in order to use the table, add 14.7 pounds to the steam-gauge reading for the pressure above zero. The other quantities will be quite readily understood. The table for equalization of pipe areas has been quite fully explained on page 287. The number of pipes of the size, as shown in the side column, required to give an equivalent area to the one in the top column is given by the numbers. Thus 14.7 pipes i inch in diameter have a carrying capacity equfva- 'lent to that of one pipe 3 inches in diameter. APPENDIX CONTAINING REFERENCES AND TABLES. 359 X U - _] PQ < ii a CUBIC Bushels to Hecto- litres. M in r^* o I-H T o co - Too NO ** m O enco o< T r^ o M TO o i- m O m O O O i-if^ r^I^O T t^ - TOO 1-1 OOi-ii-<>*CttMcn tn w w en t oj s ssi tl EE 2 r 2 E e ! EE --E> ^ in i^. fcfi e Coast Survey office, whose length at 59. 62 British yard. 5 of brass of unknown density, and therefore direct comparison. The British Avoirdupois se in the United Slates is equal to the British Cubic Yards to Cubic Metres. in o Too en r^ N o O N Oinctoo vni-ioo r^mw o mcn^oo ^ OS TcTlS -i o r^.oo c\ - co o T \r> SO en o en M ir> r> ,0 N *2 si" 1 " II II II II t || || C "' . 4vt i agg Jfl^Ja Hi HIS O M w to n T nO O Cubic Keel to Cubic Metres. c en m r^oo O N T m cnO O^ N mow moo GO O T n i-i CT^OO O T N moo TO O^cim OOO>--ws COOOOOOOO . if r^ T a^o en a r- T oo r^-o -t- en ci o^oo cni^" in<^cnr^o n^ OC C^>n>-iQO^-i-'r~ -H en TO oo a* i- en -r 11 II II II II II II II II w c enTmO i~^'~a O WEIGHT. Troy Ounces to Grammes. ooo TM o Oilmen T O T O TOO cnoo en eno O en r^. o T i^- IH O o M - M040-i T t^ ^ W _,_i ON C>l OO'-'-'CiciNencn ii D ; o c< oo Tf-i-i r~* en o m h M 5 W en t^ O TOO 1-1 in CO M w^rtu ooO in en i-i O oo O m r o* Is C* *i 6 M en T m in O t* Avoirdu- pois Pounds to Kilo- pnunmes. s Ocx) f^ O O in T en mi-i r^cnc>mi-i r^en en r^- o ^1* r^ moo N inOO O OJr^NQO T O enco N i^ w o O 6oM*HCMNenenT mary length is the Troughton scale i in use in the United States is therefo mary weight is the Troy pound of t d from the British standard Troy pou is 7000 grains Troy. ?rain Avoirdupois, and the pound A^ litres. The British bushel = 36.3477 U O | - - '-i~MMOlenen * rt.^ oco r^o m T en M - JJ 3 U ^ M una ** 1" ^ ^^ 3 '-ft C Q Oao r^f^O m m T en o> o e i-i w en T mo r^ao Avoirdu- pois Ounces to Grammes. O OoO CO t^ t^O O n TOTOTOTOT eno O en t^ o T ! M ooo neni-i Oooo u> M moo i-> T t-^ O M in _ _ K, _ C l Cl . Menini^-aoG>-enm x inOmOmi-iO*-O ^^ cr w j; 1 -j. ^ crj co N ri-i\o O ,O w 'O oi Oin o< co in M co J^Ug ~~enenTmin Grains to Milli- grammes. 1 O">co oo r^o m T T en oo t-^o inTcnM - O r~.men Ot^men>-i T O T O enoo enco en Oo; OinMcoin>-ico -* t-i 01 cnenTmm II II II II II II II II II i N enTmo r^oo O* II II II II II II II II II M 01 en T mo r-^oo s LINEAR. Miles to Kilometres m ^ -^- O^ TOO enuo W cno O en r^ o T f^ foo oo r-^O O m T T c> en T mo r^oo C^CO TOO MOO T 1-1 en TO 06 O> >-i N T The only authorized material standard of custr Fahr. conforms to the British standard. The yard The only authorized material standard of custo not suitable for a standard of mass. It was derive pound was also derived from the latter, and contaii The grain Troy is therefore the same as the pound Avoirdupois. The British gallon = 4-54346 CAPACITY. Gallons to Litres. TOO 01 O O TOO 01 O TOO en r^ M O O in O ir> O O i-" r~ M oo enco co 1^-mTM i-i OQOO r^-meni-i or^TM O Yards to Metres. M Tmr^Oi-i enmo TOO Ci O O TOO CJ \X5 Too en r^ o O O m c> i o T >n r^oo O > W Oco r^-O m T T en IN O N en T mo r-oo en r^ i-* moo 01 O O T HI i-i H- 01 M en en 2 M 2H 6 2 O Mco TOO MOO T eni^O TOO " >nco 01 O M O m CO TO !" TO en oo enr^M r^- O^oooo r^r-~oo mm Feet to Metres. -~-i -r r^ O - OJ en T mo r-oo ll|i ^QO^ r^ m o< O i** T 01 oo in M r~ enco sj- O m -i O oco oo r r> r-o o c u>co w T r> O no M M M ct CQ^ C4 OOO-">-'"-'oiCM Inches to milli- metres. w -~oioienen-r OOOOOOOOC ooooooooc. TOO CM O O TOO 04 O inoo' M r^oi r^-^no oj mr-o cs inr^O f ' H- - ^- _ ci e-i _2Sgg Ji^ is^ue cs s - OOO Oco co co I>OO r^enOt^T^co me? eni^M *1-oo 01 mOcn M M i-i N M 01 en 1 II II II II II II II II II IM en T o f*oo oi II II II II II . coo a cs inco w T r^ mO mwo M r^N r>. CO t^. O T 1^ i TCX3 -H >-i i-i i-i N o eot^O cor^o T r^ Q* i-i TO co M ONCO TO o r>- O CN CM coTmO r^co o CMCO TOO CMCO T co co T T co m M Q^O co T O TOO coco a r- a O W CO T O O CM O Oco co co r- T r^o o co m r^ T O r^ oo CM m o co r^> <-> T Omi-cco T** r^ ci Oco incOMOO M PJ co T mO I^co OOOOOOMMM II II II II M CM co T Metres t Yards. Metre Inche ^O co oco ^ O CM M CM. CO TO f^OO i-c c O M CM CO T ino t^ao O in co HI Ocoo in i-i CM co -t m mo r* coo TCM OcoO T c* CM mco M TO O CM in COO OcoO O CM O O M IH i-i M CM CM 888888888 r^> T i-i co m CM O^O co co r~ M TOO CM m O* co o o n T T r^w in CM CO CO Milliers Tonne to Poun Av. 55^ C OH mO u"Q ir>O WMvO 1-1 co TO r^ o O e o- N TO CO O CM m i^ o COO O CM O O CM moo OOO*-"Mi-iCMeMCM OOOOOOOOO O CMCO TOO CMCO T O COOO CO I s * CM O M TO CO O CM TO CO TO co M co in r^. o OMWCMCMCOCOT TO CO O N TO CO TO CO i-i CO ir> r*. CT> II II II II II II II COT ino r^co O M *' w* 0^< . Mes [5*111 5 J gra gra Ou N TO O> fi CO in t>- O O N co T 1-1 r^ co CMn T c coco co r^ CM o I-H OO>- | '- TCO WOO TOO W O r>i T N O\ t^* T G^O N vnco O COO O\ 1-1 T cor-O w TCO Kilo- grammes to Grains. ram to Grai M T l- O^ M rj-O co i COO C7^ M O O^ N vo O Too c< I^M vnQ TOO m o O w r^. c^ co coco M co TO r* O O CN co coo O coo O coo & Too co r^ <-i u~> o TCO u->oo i-i rMco coco M co TO r- G O M co OOOOOOH.W,-, OOOOOOOOO II II II II II II II II II M cj COTU">O r^co c Hekto litres t Bushel Deka- litres to Gallons. Litres to Quarts. O 111! r->. T HI co in M OO co M co>ooco O 1-1 co r> TCO NO O -M ir>o\MO O T coo O coo O co r^ O iss II II CO rj- cipal governments nternational Coma e of these a certain ere intercompared t to the different g fice. e United States in derived from the posited at the Inte me is a mass of pla re of water, and a vacuum, the vok prin he In one we y lo is offi n the is r dep ram imetr in a pilSS^Si? si :=^lo|si3,:| -Iiii-Slillll .2 ^S"^-T-o-g:3 sr^^^cSs^s^i^ S^llllliiil f|<4 H hKS"|] *tiu]Wy Sisis S 5 II APPENDIX CONTAINING REFERENCES AND TABLES. 361 TABLE No. II. EQUIVALENT VALUE OF UNITS IN BRITISH AND METRIC SYSTEMS. One foot = 12 inches = 30.48 centimetres = 0.3048 metre. One metre = 100 centimetres = 3.2808 ft. = 1.936 yd. One mile 5280 ft. 1750 yd. = 1609.3 metre. One foot = 144 sq. in. = 1/9 sq. yd. = 929 sq. centimetres .0929 sq. metre. One sq. metre = 10000 sq. centimetres = 1.1960 sq. yds. = 10.764 sq. ft. One cubic foot = 1728 sq. in. = 2832 cu. centimetres = 0.02832 cu. metres. One cubic metre = 35.314 cu. ft. = 1.3079 cu. yds. One pound adv. = 7000 grains = 16 oz. 453.59 grains 0-45359 kilograms. One kilogram = 1000 grams = 2.2046 Ibs. = 15432 grains = 35.27 oz. adv. COMPOUND UNITS. One foot-pound = 0.13826 kg.-mt. = 1,3826 gr.-c. = 1/778 B. T. U. One horse-power = 33000 ft. -pound per minute = 746 Watts. One kilogram-metre = 7.233 ft.-lb = 723.300 gr.-c. = 1/426 calorie. One gram-centimetre = i/iooooo kg.-mt. = .00007233 ft.-lb. One calorie =426.10 kg.-mt. = 3.9672 B. T. U. = 42000 million ergs per second = 42 Watts. One B. T. U. = 778 ft.-lbs. = 0.2521 cal. = 10820 mil. ergs. = 107.37 kg.-m. One calorie per sq. metre = 0.3686 B. T. U. per sq. ft. C. G. S. SYSTEM. One dyne = one gram /98i = 0.00215 Ib. One erg. = I dyne X I cent. = 0.0000707 ft.-lb. One Watt = 10 mil. ergs, per sec. 0738 ft.-lbs. per sec. = h. p. 7746. One h. p. =- 746 Watts. 362 APPENDIX CONTAINING REFERENCES AND TABLES, TABLE No. HA. TABLE OF PROPERTIES OF GASES. Element or Compound. Symbol by Volume. Atomic Weights. Cubic feet per Ib. at 62. Weight per. cu. ft. at 62. Lbs. Specific Gravity at 62. Water = i Relative Density. O N H C P S Si 79N+2iO H 2 O NH 3 CO C0 2 CH 2 CH 4 S0 2 SH 2 S 2 C Oa 16 14 I 19 12 31 32 14 18 17 28 44 14 16 64 34 76 24 11.88 13-54 189.7 15.84 6.119 5-932 13.55* I3-I4 2I.O7 22.3 13-6 8.64 13.587 23.757 6.463 5.582 2.487 7-97 0.0814 0.0738 0.00527 0.63131 0.16337 o. 16861 0.07378 0.0761 0.04745 0.0448 0.07364 0.11631 0.0736 0.04209 0.15536 0.17918 0.40052 0.12648 0.001350 O.OOII85 0.0000846 0.001607 O.OOIOI3 O.OO2622I o 002705 0.001184 O.OOI22I 0.0007613 O.OOII8 0.002369 O.OOI87 0.001181 O.OOO675 0.002493 O.002877 0.00643 O.OO2O3 1.10563 0.97137 0.06926 I.3II8 0.82323 2.1877 2.2150 1.01032 1. 0000 0.6253 0.5892 0.9674 1.52901 0.96710.4 0.55306 1.54143 2.3943 5.3007 1.64656 Hydrogen Carbon Phosphorus . . .... Air W^ater vapor Ammonia Carbon monoxide. . . . (Carbonic oxide) (Carbonic acid) Olefiant gas Marsh gas Sulphurous acid Sulphuretted hydrogen Bisulphuret of carbon. * By this table there would be 12.75 cubic feet of air at 32 per pound. APPENDIX CONTAINING REFERENCES AND TABLES. 363 TABLE No. III. TABLE OF CIRCLES, SQUARES, AND CUBES. n Diam. fur Circumf. ir n*~ 4 Area. Square. Cube. v Sq. Root. V* Cub. Rt. .O 3.142 0.7854 .000 I .OOO .0000 I. 0000 .1 3-456 0.9503 .210 I-33I .0488 1.0323 .2 3-770 I.I3IO .440 1.728 -0955 I .0627 3 4.084 I 3273 .690 2.197 .1402 1.0914 4 4.398 1-5394 .960 2-744 .1832 I.II87 5 4.712 1.7672 2.250 3-375 2247 I.I447 .6 5-027 2.0106 2.560 4.096 .2649 1.1696 -7 5-341 2.2698 2.890 4.913 .3038 I - I 935 .8 5.655 2-5447 3.240 5-832 .3416 1.2164 9 5.969 2-8353 3.610 6.859 .3784 1.2386 2.0 6.283 3.T4I6 4-000 8.000 .4142 1.2599 2.1 6-597 3-4636 4.410 9.261 .4491 1.2806 2.2 6.912 3-8013 4.840 10.648 .4832 1.3006 2-3 7.226 4.1543 5-290 12. 167 .5166 1.3200 2. 4 7-540 4-5239 5.760 13.824 .5492 1.3389 2.? 7-854 4.9087 6.2=;o 15.625 .5811 1.3572 2.6 8.168 5.3093 6.760 17.576 .6125 I-375I 2.7 8.482 5.7256 7.290 19.683 -6432 1.3925 2.b 8.797 6.1575 7.840 21.952 .6733 1.4095 2.9 9.111 6.6052 8.410 24.389 .7029 1.4260 3.0 9-425 7.0686 9.00 27.000 -7321 1.4422 3-i 9-739 7-5477 9.61 29.791 7607 1.4581 3-2 10.053 8.0425 10.24 32.768 .7889 1-4736 3-3 10.367 8.5530 10.89 35-937 .8166 1.4888 3-4 10.681 9.0792 11.56 39-304 8439 1.5037 3-5 10.996 9.6211 12.25 42.875 .8708 1.5183 3-6 11.310 10.179 12.96 46.656 .8974 1.5326 3-7 11.624 10.752 13.69 50-653 9235 i . 5467 3-8 n.938 U-34I 14.44 54-872 9494 1.5605 3-9 12.252 11.946 15.21 59-3I9 -9748 i. 5741 4.0 12.566 12.566 16.00 64.000 2.OOOO 1.5874 4.1 12.881 13.203 16.81 68.921 2.0249 1.6005 4.2 13-195 13-854 17.64 74.088 2.0494 1-6134 4-3 4-4 13 509 13-823 14-522 15-205 18.49 19.36 79-507 85 - 184 2.0736 2.0976 1.6261 1.6386 4-5 14-137 15.904 20.25 91.125 2.I2I3 1.6510 4.6 14.451 16.619 21. 16 97.336 2 . 1448 1.6631 4-7 14.765 17-349 22.09 103.823 2.1680 i 6751 3^4 APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND CUBES Continued. n Diam. nit Circumf. *; Area. " Square. [ Cube. v Sq. Root. s Y'n Cub. Rt. 4.8 15.080 18.096 23.04 110.592 2.1909 .6869 4-9 15-394 18.857 24.01 117.649 2.2136 .6985 5-0 15.708 19-635 25.00 125.000 2.2361 7100 5-i 16.022 20.428 26.OI 132-651 2.2583 7213 5-2 16.336 21.237 27.04 140.608 2 . 2804 7325 5-3 16.650 22.062 28.09 148.877 2.3022 7435 5-4 16.965 22.902 29.16 157.464 2.3238 7544 5-5 17.279 23.758 30.25 166.375 2.3452 .7652 5;6 17-593 24.630 31-36 I75.6I6 2.3664 .7758 5*7 17.907 25.518 32-49 185.193 2.3875 .7863 5-8 18.221 26.421 33-64 I95.II2 2.4083 .7967 5-9 18.535 27.340 34.81 205.379 2.4290 .8070 6.0 18.850 28.274 36.00 2X6.000 2.4495 .8171 6.1 19.164 29.225 37-21 226.981 2.4698 .8272 6.2 19.478 30.191 38-44 238.328 2.4900 8371 6.3 19.792 31.173 39-69 250.047 2.5100 .8469 6.4 20.106 32.170 40.96 262.144 2.5298 .8566 6.5 20.420 33.183 42.25 274-625 2-5495 .8663 6.6 20-735 34-212 43.56 287.496 2.5691 .8758 6.7 21.049 35.257 44.89 300.763 2.5884 .8852 6.8 21.363 36.317 46.24 314.432 2.6077 .8945 6.9 21.677 37.393 47-6i 328.509 2.6268 .9038 7.0 21.991 38.485 49.00 343.000 2.6458 .9129 7-i 22.305 39-592 50.41 357-9" 2.6646 .9220 7.2 22.619 40.715 51.84 373-248 2.6833 .9310 7-3 22.934 41.854 53-29 389-017 2.7019 9399 7-4 23-248 43.008 54.76 405 224 2.7203 .9487 7-5 23.562 44.179 56.25 421.875 2.7386 -9574 7.6 23.876 45-365 57.76 438.976 2.7568 .9661 7-7 24.190 46.566 59-29 456.533 2-7749 9747 7.8 24-504 47.784 60.84 474-552 2.7929 1.9832 7-9 24.819 49.017 62.41 493-039 2.8107 1.9916 8.0 25.133 50.266 64.00 512.000 2.8284 2.OOOO 8.1 25-447 51.530 65.61 53I-44I 2.8461 2.0083 8.2 25-761 52.810 67.24 55L468 2.8636 2.0165 8.3 26.075 54-106 68.89 57L787 2.8810 2.0247 8.4 26.389 55.418 70.56 592 704 2.8983 2.0328 8-5 26.704 56.745 72.25 614.125 2-9155 2.0408 8.6 27.018 58.088 73.96 636.056 2.9326 2.0488 8.7 27.332 59-447 75.69 658.503 2.9496 2.0567 8.8 27.646 60.821 77-44 681.473 2.9665 2.0646 8.9 27.960 62.211 79-21 704.969 2.9833 2.0724 APPENDIX CONTAINING REFERENCES AND TABLES. 365 CIRCLES, SQUARES, AND CUBES Continued. n Diam. tat Circumf. *4 Area. 2 Square. 3 Cube. *Tn Sq. Root. V; Cub. Rt. 9 23.274 63.617 Sl.OO 729.000 3.0000 2.0801 Q.I 28.588 65-039 82.81 753.571 3.0166 2.0878 9.2 28.903 66.476 84.64 778.688 3 0332 2.0954 9-3 29.217 67.929 86.49 804.357 3-0496 2.1029 9-4 29-53I 69.398 88.36 830.584 3.0659 2.II05 9-5 29.845 70.882 90.25 857.375 3.0822 2.1179 9.6 30.159 72.382 92.16 884.736 3.0984 2.1253 9-7 30.473 73.898 94.09 912.673 3-"45 2.1327 9.8 30.788 75-430 96.04 941.192 3.1305 2.1400 9-9 31.102 76.977 98.01 970.299 3.1464 2.1472 IO.O 3i-4r6 78 . 540 IOO.OO lOOO.OOO 3.1623 2-1544 10. I 3I-730 80.119 102.01 1030 . 301 3.1780 2.1616 10.2 32.044 81.713 104.04 1061.208 3-1937 2.1687 10.3 32.358 83.323 106.09 1092.727 3.2094 2.1757 10.4 32.673 84.949 108.16 1124.863 3.2249 2.1828 10.5 32.987 86.590 110.25 1157.625 3.2404 2.1897 10.6 33-301 88.247 112.36 1191.016 3-2558 2.1967 10.7 33.6I5 89.920 114.49 1225.043 3.27II 2.2036 10.8 33-929 91.609 116.64 1259.712 3.2863 2.2104 10.9 34-243 93.313 118.81 1295.029 3.3015 2.2172 II. 34-558 95-033 121.00 1331.000 3.3166 2.223Q li. i 34.872 96.769 123.21 1367.631 3.3317 2.2307 II. 2 35-186 98.520 125.44 1404.928 3.3466 2.2374 II- 3 35-500 100.29 127.69 1442.897 3.3615 2 . 2441 11.4 35.814 102.07 129.96 1481.544 3.3/64 2.25O6 n. 5 36.128 103.87 132.25 1520.875 3-3912 2.2572 li. 6 36.442 105.68 134.56 1560.896 3-4059 2.2637 li. 7 36.757 107.51 136.89 1601.613 3.4205 2 . 27O2 II. 8 37-071 109.36 139.24 1643.032 3.4351 2.2766 11.9 37.385 '111.22 141.61 1685.159 3.4496 2.2831 12.0 37.699 113. 10 144.00 1728.000 3.4641 2.2894 12. 1 38.013 "4-99 146.41 1771.561 3.4785 2.2957 12.2 38.327 116.90 148.84 1815.848 3.4928 2.3O2I 12.3 38.642 118.82 151.29 1860.867 3 5071 2.3084 12.4 38.956 120.76 153.76 1906.624 3-5214 2.3146 12-5 39.270 122.72 156.25 1953.125 3-5355 2.3208 12.6 39.584 124.69 158.76 2000.376 3.5496 2.3270 12.7 39-898 126.68 161.29 2048.383 3.5637 2.3331 12.8 40.212 128.68 163.84 2097.152 3-5777 2.3392 12.9 40.527 130.70 166.41 2146.689 3.59I7 2.3453 13.0 40.841 132.73 169.00 2197.000 3-6056 2.3513 13-1 41-155 134-78 171.61 2248.091 3.6194 2-3573 ,43-2 41.469 136.85 174.24 2299.968 3-6332 2.3633 366 APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND CUBES Continued. n Diam. rnr Circumf. 7T - 4 Area. Square. 3 Cube. v Sq. Root. 3 K Cub. Rt. 13-3 4L783 138.93 176.89 2352.637 3 6469 2.3693 13-4 42.097 141.03 I79-56 2406 . 104 3.6606 2.3752 13-5 42.412 143.14 182.25 2460.375 3.6742 2.3811 13-6 42.726 145.27 184.96 2515.456 3-6878 2.3870 13-7 43.040 147.41 187.69 257L353 3.7013 2.3928 13-8 43-?54 149-57 190.44 2628.072 3.7148 2.3986 13-9 43 . 668 I5I-75 193.21 2685.619 3.7283 2.4044 14.0 43.982 153-94 196.00 2744.000 3.7417 2.4101 14.1 44.296 156.15 198.81 2803.221 3.7550 2 .4I59 14.2 44.611 158.37 201.64 2863.288 3.7683 2.4216 14-3 44-9 2 5 160.61 204.49 2924.207 3.7oI5 2.4272 14.4 45-239 162.86 207.36 2985.984 3-7947 2.4329 14.5 45-553 165.13 210.25 3048.625 3.8079 2.4385 14.6 45.867 167.42 213. 16 3112. 136 3.82IO 2.4441 14-7 46.181 169.72 216.09 3176.523 3.8341 2-4497 14.8 46.496 172.03 219.04 3241.792 3.847I 2-4552 14.9 46.810 174-37 222. OI 3307-949 3 . 8600 2.4607 15-0 47-124 176.72 225.00 3375-000 3-8730 2 . 4662 I5-I 47.438 179.08 228.01 3442.951 3-8859 2.4717 15.2 47-752 181.46 231.04 3511.808 3.8987 2.4772 15-3 48.066 183.85 234.09 3581.577 3-9II5 2.4825 15-4 48.381 186.27 237.16 3652.264 3.9243 2.4879 15-5 48.695 188.69 240 25 3723.875 3-9370 2-4933 15.6 49-009 191.13 243.36 3796.416 3-9497 2.4986 15-7 49-323 193-59 246.49 3869.893 3.9623 2.5039 15-8 49-637 196.07 249.64 3944.312 3-9749 2.5092 15-9 49-951 198.56 252.81 4019.679 3-9875 2.5146 16.0 50.265 201.06 256.00 4096 . ooo 4.0000 2.5198 16.1 50.580 203.58 259.21 4173.281 4-0125 2.5251 16.2 50.894 206.12 262.44 4251.528 4.0249 2.5303 16.3 51.208 208.67 265.69 4330.747 4.0373 2.5355 16.4 51-522 211.24 268 . 96 4410.944 4 - 0497 2.5406 16.5 51.836 213-83 272.25 4492.125 4.0620 2.5458 16.6 52.150 216.42 275-56 4574.296 4-0743 2.5509 16.7 52.465 219.04 278.89 4657.463 4.0866 2.5561 16.8 52.779 221.67 282.24 4741.632 4.0988 2.5612 16.9 53-093 224.32 285.61 4826 . 809 4.1110 2.5663 17- o 53-407 226 98 289.00 4913.000 4.1231 2.5713 17.1 53.721 229.66 292.41 5000.211 4.1352 2.5763 17.2 54.035 132.35 295-84 5088.448 4-H73 2.5813 17-3 54-350 235-06 299.29 5177.717 4-1593 2.5863 17-4 54-664 237-79 302.76 5268.024 4.I7I3 2.5913 APPENDIX CONTAINING REFERENCES AND TABLES. 367 CIRCLES, SQUARES, AND CUBES n Diam. nir Circumf. *- 4 Area. 2 Square. 3 Cube. f~n Sq. Root. 3 Vm ! Cub.Rt. 17-5 54-978 240.53 306.25 5359.375 4.1833 2.5963 17-6 55.292 243.29 309.76 5451.776 4.1952 2.6012 17.7 55-606 246.06 3I3.29 5545.233 4.2071 2. 6o6l 17-8 55-920 248.85 316.84 5639.752 4.2190 2.6109 17-9 56.235 251.65 320.41 5735-339 4-2308 2.6158 18.0 56.549 254-47 324.00 5832.000 4.2426 2 . 6207 18.1 56.863 257.30 327.61 5929.741 4.2544 2.6256 18.2 57-177 260.16 33L24 6028.568 4.2661 2.6304 18.3 57.491 263.02 334.89 6128.487 4.2778 2.6352 18.4 57.805 265.90 338.56 6229.504 4.2895 2 . 6401 18.5 58.119 268.80 342.25 6331-625 4-3012 2.6448 18.6 58.434 271.72 345.96 6434.856 4.3I2S 2.6495 18.7 58.748 274.65 349.69 6539-203 4.3243 2.6543 18.8 59.062 277-59 353.44 6644.672 4-3359 ! 2.6590 18.9 59-376 280.55 357-21 6751.269 4.3474 2.6637 19.0 59-690 283.53 361.00 6859.000 4.3589 2.6684 19.1 60.004 286.52 364-81 6967.871 4-3703 2.6731 19-2 60.319 289.53 368.64 7077.888 4.3818 2.6777 19-3 60.633 292.55 372-49 7189.057 4-3932 2.6824 19-4 60.947 295.59 376.36 7301.384 4.4045 2.6869 19.5 61.261 298.65 380.25 7414.875 4.4I59 2.6916 I9- 6 61.575 301 . 72 384.16 7529-536 4.4272 2.6962 19.7 61.889 304.31 388.09 7645-373 4.4385 2.7008 19.8 62.204 307.91 392.04 7762.392 4.4497 2.7053 19-9 62.518 3".03 396.01 7880.599 4.4609 2.7098 20.0 62.832 314.16 400.00 8000.000 4-4721 2.7144 20.1 63.146 317.31 404.01 8I2O.6OI 4.4833 2.7189 20.2 63.460 320.47 408.04 8242.408 4-4944 2.7234 20.3 63.774 323.66 412.09 8365-427 4.5055 2.7279 20.4 64.088 326 85 416.16 8489.664 4.5I66 2.7324 20.5 64.403 330.06 420.25 8615. 12^ 4.5277 2.7368 20.6 64.717 333-29 424.36 8741.816 4.5387 2.7413 20.7 65.031 336.54 428.49 8869.743 4-5497 2-7457 20.8 65.345 339-80 432.64 8989.912 4.5607 2.7502 20.9 05.659 343.07 436.81 9129.329 4.5716 2-7545 21.0 6 5-973 346.36 441.00 9261 .OOO 4-5826 2.7589 21. 1 66.288 349.67 445.21 9393.931 4-5935 2.7633 21.2 66.602 352.99 449.44 9528.128 4-6043 2.7676 21.3 66.916 356.33 453-69 9663.597 4-6152 2.7720 21.4 67.230 359-68 457.96 9800.344 4.6260 2.7763 21-5 67.544 363-05 462.25 9938.375 4.6368 2.7806 21.6 67.858 366.44 466.56 10077.696 4.6476 2.7849 21.7 1 68.173 369.84 470.89 I02I8.3I3 4.6583 2.7893 APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND CUBES Continued. n Diam. HIT Circumf. JT - 4 Area. n* Square. n 3 Cube. v Sq. Root. a *H Cub. Rt. 21.8 68.487 373-25 475-24 10360.232 4 . 6690 2-7935 21-9 68.801 376.69 479-61 10503.459 4.6797 2.7978 22.0 69.115 380.13 484.00 10648.000 4.6904 2 . 8021 22-1 69.429 383-60 488.41 10793.861 4-70II 2 . 8063 22.2 69.743 387.08 492.84 10941.048 4.7117 2.8105 22-3 70.058 390.57 497 - 29 11089.567 4.7223 2.8147 22.4 70.372 394.08 501.76 11239.424 4.7329 2.8189 22.5 70.686 397.61 506.25 11390.625 4-7434 2.8231 22.6 71.000 401.15 510.76 11543.176 4-7539 2.8273 22.7 71.314 404-71 515-29 11697.083 4.7644 2.8314 22.8 71.268 408 . 28 519.84 11852.352 4-7749 2.8356 22.Q 71.942 411.87 524.41 12008.989 4.7854 2.8397 23.O 72.257 4I5.48 529.00 12167.000 4-7958 2.8438 23-1 72-571 419. 10 533-6i 12326.391 4.8062 2.8479 23-2 72.885 422.73 538.24 12487.168 4.8166 2.8521 23-3 73.199 426.39 542.80 12649.337 4-8270 2.8562 23-4 73-5I3 430.05 547-56 12812.904 4-8373 2.8603 23-5 73.827 433-74 552.25 12977.875 4.8477 2 . 8643 23.6 74.142 437-44 556.96 13144.256 4-8580 2.8684 23-7 74.456 441.15 561.69 13312.053 4.8683 2.8724 2 3 .8 74-770 444.88 566.44 13481.272 4.8785 2.8765 23-9 75.084 448.63 571.21 13651.919 4.8888 2 . 8805 24.0 75.398 452 39 576.00 13824.000 4.8990 2.8845 24-1 75-712 456.17 580.81 13997.521 4 . 9092 2.8885 24-2 76.027 459.96 585.64 14172.488 4-9 J 93 2.8925 24-3 76.341 463.77 590.49 14348.907 4.9295 2.8965 24.4 76.655 467 . 60 595.36 14526.784 4.9396 2 . 9004 24-5 76.969 471.44 600.25 14706.125 4-9497 2 . 9044 24.6 77.283 475-29 605.16 14886.936 4.9598 2.9083 24.7 77.597 479.16 610.09 15069.223 4.9699 2.9123 24-8 77.911 483-05 615.04 15252.992 4.9799 2.9162 24-9 78.226 486.96 620.01 15438.249 4.9899 2.92OI 25.0 78.540 490.87 625.00 15625.000 5.0000 2.9241 25.1 78.854 494.81 630.01 15813-251 5-0099 2.9279 25.2 79-168 498.76 635-04 16003.008 5.0199 2.9318 25-3 79.482 502.73 640.09 16194.277 5.0299 2-9356 25-4 79.796 506.71 645.16 16387.064 5-0398 2-9395 25-5 80. Ill 510.71 650.25 16581.375 5-0497 2-9434 25.6 80.425 5H.72 655-36 16777.216 5-0596 2.9472 25-7 80.739 518.75 660.49 16974.593 5.0695 2.9510 25.8 81.053 522.79 665.64 17173.512 5-0793 2-9549 25-9 81.367 526.85 670.81 17373.979 5.0892 2.9586 APPENDIX CONTAINING REFERENCES AND TABLES. 369 CIRCLES, SQUARES, AND CUBES Continued. n Diam. 7T Circumf. IT *- 4 Area. ' Square. Cube. ^n \n Sq. Root. : Cub. Rt. 26.0 81.681 530-93 676.00 17576.000 5.0990 2.9624 26.1 81.996 535-02 68I.2I I7779-58I 5.1088 2.9662 26.2 82.310 539.13 686.44 17984-728 5.II85 2.9701 26.3 82.624 543-25 691.69 18191.447 5.1283 2.9738 26.4 82.938 547-39 696.96 18399.744 5.I2SO 2.9776 26.5 83.252 55L55 702.25 18609.625 5.1478 2.9814 26.6 83.566 555.72 707.56 18821.096 5.1575 2.9851 26.7 83.881 559.90 712.89 19034.163 5.1672 2.9888 26.8 84.195 564-10 718.24 19248.832 f-1768 2 . 9926 26.9 84.509 568.32 723-61 19465 . 109 5.1865 2.9963 27.0 84-823 572.56 729.00 19683.000 5.1962 3-0000 27.1 85-I37 576.80 734-41 19902.511 5-2057 3-0037 27.2 85.451 581.07 739-84 20123.648 5-2153 3.0074 27-3 85-765 585.35 745.29 20346.417 5.2249 3.OIII 27.4 86.080 589.65 750.76 20570.824 5.2345 3-0147 27-5 86.394 593-96 756.25 2070.875 5.2440 3.0184 27.6 86.708 598-29 761.76 21024.576 5-2535 3.0221 27.7 87.022 602.63 767.29 21253-933 5.2630 i 3.0257 27.8 87 336 606.99 772-84 21484.952 5.2725 3.0293 27.9 87.650 611.36 778.41 21717.639 5.2820 3-0330 28.0 87-965 615-75 784.00 21952.000 5.2915 3.0366 28.1 88.279 620. 16 789.61 22188.041 5.3009 3.0402 28.2 88.593 624.58 795-24 2242^.768 5-3103 3-0438 28.3 88.907 629.02 800.89 22 65.187 5-3I97 3-0474 28. 4 89.221 633-47 806.56 22906.304 5.3291 3.0510 28.5 89.535 637-94 812.25 23149.125 5.3385 3.0546 28.6 89.850 642.42 817.96 23393.656 5.3478 3-058I 28.7 90 164 646.93 823.69 23639.903 5-3572 3.0617 28.8 90.478 651.44 829.44 23887.872 5.3665 3.0652 28.9 90.792 655.97 835-21 24137.569 5.3758 3.0688 29.0 91.106* 660.52 841.00 24389.000 5.3852 3.0723 29.1 91.420 665.08 846.81 24642.171 5-3944 3.0758 29.2 91-735 669.66 852.64 24897.088 5.4037 3-0794 29-3 92.049 674.26 858.49 25153.757 5.4129 3-0829 29.4 92.363 678.87 864.36 25412.184 5-4221 3.0864 29 5 92.677 683.49 870.25 25672.375 5-4313 3-0899 29.6 92.991 688.13 876.16 25934.336 5-4405 3-0934 29.7 93.305 692.79 882.09 26198.073 5-4497 3.0968 29.8 93.619 697.47 888.04 26463.592 5.4589 3-1003 29.9 93-934 702.15 894.01 26730'. 899 5.4680 3-1038 30.0 94.248 706.86 900.00 27000.000 5-4772 3-1072 30.1 94.562 711.58 906.01 27270.901 5.4863 3.1107 _30.2 94.876 716.32 912.04 27543.608 5-4954 3.1141 37 APPENDIX CONTAINING REFERENCES AND TABLES CIRCLES, SQUARES, AND CUBES Continued. n Diam. mr Circumf. 77 -4 Area. n i Square. 3 Cube. y~ Sq. Root. 3 *u Cub. Rt. 30.3 95.190 721.07 918.09 27818. 127 5 - 5045 3.H76 30.4 95.505 725-83 924.16 28094.464 5-5I36 3.I2IO 30.5 95.819 730.62 930.25 28372.625 5.5226 3-1244 30.6 96.133 735-42 936.36 28652.616 5.5317 3.1278 30-7 96.447 740.23 942.49 28934.443 5 . 5407 3.I3I2 30.8 96.761 745.06 948 . 64 292I8.II2 5 5497 3.1346 30.9 97-075 749.91 954.81 29503.629 5.5587 3.1380 31.0 97.389 754.77 961.00 297QI.OOO 5-5678 3.I4I4 3I-I 97.704 759. 6 5 967.21 30080.231 5.5767 3.1448 31.2 98.018 764.54 973-44 30371.328 5-5857 3.I48I 31-3 98.332 769.45 979.69 30664.297 5.5946 3.I5I5 31-4 98 . 646 774-37 985.96 30959.144 5-6035 3.I548 31-5 98.960 779-31 992.25 31255.875 5-6124 3.1582 31.6 99.274 784.27 998.56 31554.496 5.6213 3-1615 31-7 99.588 789.24 1004.89 31855.013 5.6302 3.1648 31-8 99.903 794.23 1011.24 32157.432 5.6391 3.1681 31-9 100.22 799-23 1017-61 32461.759 5.6480 3.1715 32.0 ioo. S3 804.25 1024.00 32768.000 5-6569 3.1748 32.1 100.85 809.28 1030.41 33076.161 5-6656 3.1781 32.2 101.16 814.33 1036.84 33386.248' 5.6745 3-1814 32.3 101.47 819.40 1043.29 33698.267 5-6833 3-I847 32-4 101.79 824.48 1049.76 34012.224 5.6921 3.1880 32-5 IO2. IO 829.58 1056.25 34328.125 5-7008 s-ig^ 32.6 102.42 834-69 1062.76 34645.976 5.7096 3-1945 32.7 102.73 839.82 1069.29 34965.783 5.7183 3.197* 32.8 103.04 844.96 1075-84 35287.552 5.7271 3.2010 32-9 103 . 36 850.12 1082.41 35611.289 5.7358 3.2043 33'0 103.67 855.30 1089.00 35937.000 5.7446 3-2075 33-1 103.99 860.49 1095.61 36264.691 5.7532 3.2108 33-2 104.30 865.70 1102.24 36594.368 5.7619 3.2140 33-3 104.62 870.92 1108.89 36926.037 5-7706 3.2172 33-4 104.93 876.16 1115.56 37259.704 5.7792 3.2204 33-5 105.24 881.41 1122.25 37595-375 5.7S79 3.2237 33-6 105 . 56 886.68 1128.96 37933.056 5.7965 3.2269 33-7 105.87 891.97 1135-69 38272.753 5-8051 3.2301 33-8 IO6.I9 897.27 1142.44 38614.472 5.8137 3-2332 33-9 106.50 902.59 1149.21 38958.219 5-8223 3.2364 34-o 106.81 907-92 1156.00 39304.000 5.8310 3-2396 34-1 107.13 913.27 1162.81 39651.821 5.8395 3.2428 34-2 107.44 918.63 1169.64 40001 .688 5 . 8480 3.2460 34-3 107.76 924.01 1176.49 40353.607 5-8566 3.2491 34-4 108.07 929.41 1183.36 40707.584 5-8651 3-2522 4PPENDIX CONTAINING REFERENCES AND TABLES. 37 r CIRCLES, SQUARES, AND CUBES Continued. n Diam. HIT Circumf. .? Area. w 2 Square. t' Cube. Sq. Root. V Cub. Rt. 34-5 108.38 934-82 IigO.25 41063.625 5.8730 3-2554 34-6 108.70 940.25 II97.:6 41421.736 5.8821 3.2586 34-7 lOg.OI 945.69 1204.09 41781.923 5.8906 3.2617 3-4-8 109-33 951.15 1211.04 42144.192 5.8991 3 2648 34-9 109.64 956.62 I2I8.0I 42508.549 5.9076 3-2679 35-o 109.96 962.11 1225.00 42875.000 5.9161 3.2710 35-1 110.27 967.62 1232.01 43243.551 5.9245 3.2742 35-2 110.58 973-14 1239.04 43614.208 5.9329 3-2773 35-3 IlO.gO 978.68 1246.09 43986.977 5-9413 3 2804 35-4 III .21 984.23 1253.16 44361.864 5-9497 3-2835 35-5 "I- 53 989 . 80 1260.25 44738.875 5.9581 3.2866 35.6 111.84 995.38 1267.36 45118.016 5.9665 3-2897 35-7 112.15 1000.98 1274.49 45499.293 5-9749 3-2927 35-8 112.47 I006.60 1281.64 45882.712 5.9833 3-2958 35-9 112.78 1012.23 I288.8I 46268.279 5.9916 3-2989 36.0 113.10 1017-88 1296.00 46656 ooo 6.0000 3.3019 36-1 113.41 1023.54 1303.21 47045.881 6.0083 3 3050 36.2 "3-73 1020.22 1310.44 47437.928 6.0166 3-3080 36.3 114.04 1034.91 1317.69 47832.147 6.0249 3.3"i 36.4 114.35 1040.62 I324-96 48228.544 6.0332 3.3I4I 39-5 114.67 1046.35 1332.25 48627.125 6.0415 3.3I7I 36.6 114.98 1052.09 I339.56 49027.896 6.0497 3-3202 367 115.30 1057.84 1346.89 49430.863 6.0^80 3-3232 36.8 115-61 1063.62 1354.24 49836.032 6.0663 3-3262 36.9 115.92 1069.41 1361.61 50243.409 6-0745 3.3292 37-0 116.24 1075.21 1369.00 50653.000 6.0827 3-3322 37-1 "6.55 loSi .03 1376.41 51064.811 6.0909 3-3352 37-2 116.87 1086.87 1383.84 51478.848 1 6.0991 3-3382 37-3 117-18 1092.72 1391.29 51895.117 6.1073 3-3412 37-4 117.50 1098.58 1398.76 52313.624 6.1155 3-3442 37-5 117.81 1104.47 1406.25 52734.375 6.1237 3.3472 37-6 118.12 1110.36 1413.76 53157-376 6.1318 3-3501 37.7 118.44 1116.28 i 1421.29 53582.633 6.1400 3-3531 37-8 118.75 1122.21 1428.84 54010.152 6.1481 3.350r 37-9 119.07 1128.15 1436.41 54439.939 6.1563 3-3590 38.0 119-38 II34-" 1444.00 54872.000 6.1644 3-3620 38.1 119.69 ! 1140.09 M5I.6I 55306.341 6.1725 3 3649 38.2 120.01 1146.08 1459.24 55742.968 6.1806 3-3679 38.3 I2O.32 1152.09 1466.89 56181.887 6.1887 3.3703 38.4 120.64 1158.12 1474.56 56623 . 104 6.1967 3-3737 38-5 120.95 1164.16 1482.25 57066.625 6 , 2048 3.376.7 38.6 121.27 II7O.2I 1489.96 57512.456 6.2129 3.3796 J>8. 7 121.58 ' 1176.28 1497.69 57960.603 6.2209 3-3^25 37 2 APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND CUBES Continued. n Diam. W7T Circumf. "; Area. ni Square. n* Cube. VH Sq. Root. 3 \'n Cub. Rt. 38.8 121.89 "82.37 1505.44 58411.072 6.2289 3.3854 38.9 122.21 1188.47 1513.21 58863.869 6.2370 3-3883 39.0 122.52 1194.59 1521.00 59319.000 6.2450 3-39^2 39-i 122.84 1200.72 I528.8I 59776.471 6.2530 3.3941 39-2 123.15 1206.87 1536.64 60236.288 6.26lO 3.3970 39-3 123.46 1213.04 1544.49 60698.457 6.2689 3-3999 39-4 123.78 1219.22 1552.36 61162.984 6.2769 3.4028 39-5 124.09 1225.42 1560.25 61629.875 6.2849 3-4056 39.6 124.41 1231.63 1568.16 62099.136 6.2928 3-4085 39-7 124.72 1237.86 1576.09 62570.773 6 . 3008 3.4II4 J 7 ' 39.8 125.04 1244. 10 1584.04 63044.792 6.3087 3.4142 39-9 125-35 1250.36 1592.01 63521.199 6.3166 3.4I7I 40.0 125.66 1256.64 I6OO.OO 64000 . ooo 6.3245 3-4200 40.1 125.98 1262.93 1608. oi 64481.201 6.3325 3-4228 40.2 126.29 1269.23 1616.04 64964.808 6 . 3404 3-4256 40.3 I26.6I 1275.56 1624.09 65450.827 6.3482 3.4285 40.4 126-92 1281.90 1632.16 65939.264 6.3561 3.4313 40-5 127.23 1288.25 1640.25 66430.125 6.3639 3-4341 40.6 127-55 1294.62 1648.36 66923.416 6.3718 3-4370 40.7 127.86 I3OI.OO 1656.49 67419.143 6.3796 3-4398 40.8 I28.I8 1307.41 1664.64 67911.312 6.3875 3.4426 40.9 128.49 I3I3.82 I672.8I 68417.929 6-3953 3.4454 41.0 I28.8I 1320.25 1681.00 68921.000 6.4031 3.4482 41.1 129.12 1326.70 1689.21 69426.531 6.4109 3-4510 41.2 129.43 1333.17 1697.44 69934.528 6.4187 3-4538 4i-3 129-75 I339.65 1705-69 70444.997 6.4265 3.4566 41.4 130.06 1346.14 1713.96 70957.944 6-4343 3-4594 41-5 130.38 1352.65 1722.25 71473.375 6.4421 3.4622 41.6 130-69 1359. J 8 1730-56 71991.296 6.4498 3-4650 41.7 131.00 1365.72 1738.89 72511.713 6-4575 3-4677 41.8 I3L32 1372 ,28 1747.24 73034.632 6.4653 3.4705 41.9 131.63 1378-85 I755.6i 73560.059 6.4730 3-4733 42.0 I3L95 1385.44 1764.00 74088.000 6.4807 3.4760 42.1 132.26 1392.05 1772.41 74618.461 6.4884 3.4788 42.2 132.58 1398.67 1780.84 75151.448 6.4961 3-4815 42.3 132.89 1405-31 1789.29 75686.967 6.5038 3.4843 42.4 133-20 1411 .96 1797.76 76225.024 6.5H5 3.4870 42.5 I33.52 1418.63 1806.25 76765.625 6.5192 3-4898 42.6 133.83 1425-31 1814.76 77308.776 6.5268 3.4925 42.7 134.15 1432.01 1823.29 77854.483 6-5345 3-4952 42.8 134.46 1438.72 1831.84 78102.752 6.5422 3.4980 42.9 134-77 1445.45 1840.41 78953.55*9 6.5498 3.5007 APPENDIX CONTAINING REFERENCES AND TABLES. 373 CIRCLES, SQUARES, AND CUBES Continued. n Diam. nir Circumf. "'; Area. 2 Square. 3 Cube. ' V Sq. Root. Cub. Rt. 43-0 I35-09 1452.20 1849.00 79507.000 6-5574 3 5034 43-1 135-40 1458.96 1857.61 80062.991 6.5651 3.<;o6i 43- 2 135-72 I465.74 1866.24 80621.568 6.5727 3.5088 43-3 136.03 1472.54 1874.89 81182.737 6 . 5803 3.5II5 43-4 136.35 1479.34 1883.56 81746.504 6.5879 3.5I42 43-5 136.66 1486.17 1892.25 82312.875 6-5954 3.516-9 43-6 136.97 1493-01 1900.96 82881.856 6 . 6030 3.5io6 43-7 137.29 1499.87 1909.69 83453.453 6.6ic6 3.5223 43-3 137.60 1506.74 1918.44 84027.672 6.6182 3.5250 43-9 I37-9 2 1513-63 1927.21 84604.519 6.6257 3o277 44.0 138-23 1520.53 1936.00 85184.000 6.6333 3o303 44.1 138.54 I527.45 1944.81 85766.121 6.6408 3-5330 44-2 138.86 1534-39 1953 64 86350.888 6.6483 3-5357 44-3 139-17 I54r.34 1962.49 86938.307 6.6558 3.53S4 44-4 139-49 1548.30 1971-36 87528.384 6.6633 3-5410 44-5 139-80 1555-28 1980.25 88I2I.I25 6.6708 3-5437 44.6 140. 12 1562.28 1989.16 88716.536 6.6783 3-5463 44-7 140.43 1569-30 1998.09 89314.623 6.6858 3-5490 44.8 140.74 1576.33 2007.04 89915.392 6.6933 3-55i6 44-9 141.06 1583.37 2OI6.OI 90518.849 6.7007 3-5543 45-0 I4L37 1590.43 2025.00 91125.000 6.7082 3.5569 45-1 141.69 I597-5I 2034.01 91733.851 6.7156 3-5595 45-2 142.00 1604.60 2043-04 | 92345.408 6.7231 3-5621 45-3 142.31 1611.71 2052.09 92959.677 6-7305 3-5648 45-4 142.63 1618.83 2061. 16 93576.664 6-7379 3-5674 45-5 142.94 1625.97 2070.25 94196.375 6-7454 3-5700 45-6 143 . 26 1633.13 2079.36 94818.816 6.7528 3-5726 45-7 143-57 1640.30 2088.49 95443 . 993 6 . 7602 3-5752 45-3 143.88 1647.48 2097.64 96071.912 6.7676 3o778 45-9 144.20 1654.68 2106.81 96702.579 6-7749 3-5305 46.0 144-51 1661.90 2116.00 97336.000 6.7823 3-5330 46.1 144.83 1669.14 2125.21 97972.181 6.7897 3.5356 46.2 145-14 1676.39 2134.44 98611.128 6.7971 3o332 46.3 145.46 1683.65 2143.69 99252.847 6.8044 3-5908 46.4 145-77 1690.93 2152.96 99897.344 6.8117 3-5934 46.5 146.08 1698 . 23 2162.25 100544.625 6.8191 3.5960 46.6 146.40 1705.54 2171.56 101194.696 6.8264 3.5986 46.7 146.71 1712.87 2180.89 101847.563 6.8337 3.6011 46.8 I47.03 1720.21 2190.24 102503.232 6.8410 3-6037 46.9 147-34 1727.57 2199.61 103161.709 6.8484 3.6063 47.0 M7.65 1734-94 2209.00 103823.000 6.8556 3.6088 47.1 147-97 1742.34 2218.41 104487.111 6.8629 3 6114 47.2 148 . 28 1749.74 2227.84 105154.048 6.8702 3-6139 374 APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND CUBES Continued. n Diam. nir Circumf. +z 4 Area. 11* Square. 3 Cube. *5 Sq. Root. V; Cub. Rt. 47-3 148 . 60 I757.I6 2237.29 105823.817 6-8775 3.6165 47-4 148.91 1764.60 2246 .76 I 06496 . 424 6.8847 3-6I90 47-5 149.23 1772.05 2256.25 107171.875 6.8920 3.6216 47.6 M9-54 1779.52 2265.76 107850. 176 6.8993 3-6241 47-7 149.85 1787.01 2275.29 108531.333 6.9065 3.6267 47-8 150.17 1794-51 2284.84 109215.352 6.9137 3.6292 47-9 150.48 1802.03 2294.41 109902.239 6 . 9209 3.6317 48.0 150.80 1809.56 2304.00 IIO592.OOO 6.9282 3 6342 48.1 151 .11 1817.11 2313-61 111284.641 6-9354 3-6368 48.2 151.42 1824.67 2323.24 111980.168 6.9426 3.6303 48.3 I5L74 1832.25 2332.89 112678.587 6.9498 3.6418 48-4 152.05 1839.84 2342.56 II3379-9 4 6.9570 3.6443 48.5 152.37 I847.45 2352.25 114084.125 6 . 9642 3.6468 48.6 152.68 1855.08 2361.96 114791.256 6.9714 3.6493 48.7 153-00 1862.72 2371.69 II550I.303 6.9785 3-6518 48.8 153.31 1870.38 2581.44 116214.272 6.9857 3-6543 48.9 153.62 1878.05 2391.21 116930.169 6.9928 3-6568 49.0 153-94 1885.74 2401 .OO 117649.000 7.0000 3.6593 49.1 I54.25 1893-45 2410.81 118370.771 7.0071 3.6618 49.2 154.57 1901 . 17 2420.64 119095.488 7-0143 3 6643 49-3 154.88 1908 . 90 2430.49 119823.157 7.0214 3.6668 49-4 I55-I9 1916.65 2440.36 120553.784 7.0285 3.6692 49-5 155-51 1924.42 2450.25 121287.375 7-0356 3-6717 49.6 155.82 1932.21 2460.16 122023.936 7 0427 3-6742 49-7 156.14 1940.00 2470.09 122763.473 7 . 0498 3-6767 49-8 156.45 1947.82 2480.04 123505.992 7.0569 3.6791 49-9 156.77 I955-65 2490.01 124251.499 7 . 0640 3.6816 50.0 157-08 1963.50 2500.00 I25OOO.OOO 7.0711 3.6840 51-0 160.22 2042 . 82 2601.00 132651.000 7.1414 3.7084 52.0 163.36 2123.72 2704.00 140608.000 7.2111 3.7325 53-o 166.50 2206.19 2809 . oo 148877.000 7.2801 3-7563 54-o 169.64 2290.22 2916.00 157464.000 7.3485 3.779S 55-0 172.78 2375.83 3025 . oo 166375.000 7.4162 3.8030 56.0 175-93 2463.01 3136.00 I756l6.000 7.4833 3.8250 57-0 179.07 255I-76 3249.00 185193.000 7.5498 3-8485 58.0 182.21 2642.08 3364.00 I95II2.OCO 7-6158 3.8700 59-o 185.35 2733-^7 3481.00 205379.000 7.6811 3.8930 60.0 188.49 2827.44 3600 . oo 2I6OOO.OOO 7.746o 3-9MC, 61.0 I9L63 2922.47 3721.00 226981.000 7.8102 3.93 fl 5 62.0 194-77 3019.07 3844.00 238328. ooo 7-8740 3-957Q 63.0 197.92 3II7.25 3969 . oo 250047.000 7-9373 3.9791 64.0 2OI.O6 3216.99 4096 . oo 262144.000 8 . oooo 4 . oooo 65.0 204 . 20 3318.31 4225.00 274625.000 8.0623 4.0207 66.0 207 . 34 3421.20 4356-00 287496.000 8. 1240 4.0412 APPENDIX CONTAINING REFERENCES AND TABLES. 375 CIRCLES, SQUARES, AND CUBES Continued. n Diatn. WIT Circumf. - * a 4 Area. Square. Cube. ^ v Sq. Root, ! Cub. Rt. 67.0 210.48 3525.66 4489-00 300763.000 8.1854 4.0615 68.0 213.63 3631-69 4624.00 314432.000 8.2462 4-0817 69.0 216.77 3739-29 4761 .OO 328509.000 8.3066 4.1016 70.0 219.91 3848.46 49OO.OO 343000.000 8.3666 4.1213 71.0 223.05 3959.20 5041.00 357911.000 8.4261 4.1408 72.0 226.19 4071.51 5184.00 373248.000 8.4853 4 . 1602 73-o 229.33 4185.39 5329.00 389017.000 8.5440 4.1793 74.0 232.47 4300.85 5476.00 405224.000 i 8.6023 4.1983 75-o 235.62 4417.67 5625.00 421875.000 8.6603 4.2172 76.0 238.76 4536.47 5776.00 438976.000 8.7178 4-2358 77.0 241.90 4656.63 5929 oo 456533.000 8.7750 4-2543 78.0 245.04 4778.37 6084.00 474552.000 8. 318 4-2727 79.0 248.18 4901.68 6241 .OO 493039.000 8.8S82 4-2908 80.0 25L32 5026.56 64OO.OO 512000.000 8-9443 4-3089 81.0 254-47 5153.01 6561.00 531441.000 9.0000 4-3267 82.0 257.61 5281.03 6724.00 551368.000 9-0554 4.3445 83.0 260.75 5410.62 6889.00 571787.000 9.1104 4.3621 84.0 263 . 89 554L78 7056.00 592704.000 9.1652 4-3795 85.0 267.03 5674.50 7225.00 614125.000 9. -195 4-3968 86.0 270.17 5808.81 7396.00 636056.000 9.2736 : 4.4140 87.0 273.32 5944.69 7569.00 658503.000 9.3274 ! 4.4310 88.0 276.46 6082.13 7744.00 681472.000 9.3808 4.4480 89.0 279.6C 6221.13 792I.OO 704969.000 9.4340 4.4647 90.0 282.74 6361.74 SlOO.OO 729000.000 9.4868 4.4814 91.0 285.88 6503.89 | 8281.00 753571.000 9-5394 4-4979 92.0 289.02 6647.62 8464.00 778688.000 9-59*7 4-5144 93-0 292.17 6792.92 8649 . oo 804357.000 9-6437 4.5307 94.0 295.31 6939.78 8836.00 830584.000 9.6954 4.5468 95-0 298.45 7088.23 9025.00 857375.000 9.7468 4.5629 96.0 301.59 7238.24 9216.00 884736.000 9.7980 4-5789 97.0 304.73 7389.83 9409.00 912673.000 9.8489 4-5947 98.0 307.87 7542.98 9604.00 941192.000 9.8995 4.6104 99.0 311.02 7697-68 9801 .00 970299 . ooo 9-9499 4.6261 100. 314.16 7854.00 10000.00 lOOOOOO.OOO 10.0000 4.6416 3/6 APPENDIX CONTAINING REFERENCES AND TABLES. TABLE No. IV. CIRCUMFERENCES AND AREAS OF CIRCLES.* Diam. Circum. Area. Diam. Circum. Area. Diam. Circum. Area. i 3.1416 0.7854 65 204 . 20 33*8 3i 129 405-27 13069.81 2 6.2832 3.1416 66 207.34 3421.19 130 408.41 13273.23 3 9.4248 7.0686 67 210.49 3525-65 I 3 I 41 i .55 13478.22 4 12.5664 12.5664 68 213.63 3631.68 132 414.69 13684.78 5 15.7080 19-635 69 216.77 3739-28 133 417-83 13892.91 6 18.850 28.274 70 219.91 3848.45 T 34 420.97 14102.61 7 21.991 38.485 7 1 223.05 3959-19 135 424.12 14313.88 8 25-133 50.266 72 226.19 4071.50 136 427.26 14526.72 9 28.274 63.617 73 229.34 4185.39 137 430.40 14741.14 10 31.416 78-540 74 232.48 4300.84 138 433-54 14957.12 II 34-558 95-033 235-62 4417.86 436.68 15174.68 12 37-699 113.10 76 238.76 4536.46 140 439.82 15393.80 Z 3 40.841 1^2.73 77 241.90 4656.63 141 442.96 15614.50 '4 43.982 153-94 78 245.04 4778.36 142 446.11 15836.77 IS 47.124 176.71 79 248.19 4901.67 143 449-25 16060.61 16 50.265 201.06 80 251-33 5026.55 144 452.39 16286.02 *7 53-407 226.98 81 254.47 5i53-oO MS 455-53 16513.00 18 56-549 254.47 82 257.61 5281.02 146 458.67 16741.55 19 59.690 283.53 83 260.75 5410.61 147 461.81 16971.67 20 21 22 62.832 65-973 69.115 314.16 346.36 380.13 84 ii 263.89 267.04 270.18 5541-77 5674-5 5808.80 148 149 150 464.96 468.10 471.24 17203.36 17436.62 17671.46 23 72.257 415-48 87 273-32 5944-68 151 474-38 17907.86 24 75-398 452.39 88 276.46 6082.12 152 477-52 18145.84 2 5 78.540 490.87 89 279.60 6221 .14 480.66 18385.39 26 81.681 530.93 90 282.74 6361.73 154 483-81 18626.50 27 84.823 572.56 gi 285.88 6503.88 i55 486.95 18869.19 28 87.965 92 2*9-03 6647.61 156 490.09 19113.45 29 91.106 660.52 93 292.17 6792.91 157 493-23 19359.28 30 94.248 706.86 94 295-31 6939.78 158 496.37 19606.68 31 3 2 97-3.89 100.53 754-77 804.25 95 96 298.45 301-59 7088.22 7238.23 159 160 499-51 502 65 19855-65 20106.19 33 103.67 855-30 97 304.73 7389.81 161 505-80 20358.31 34 106.81 907.92 98 307-88 7542.96 162 508.94 20611.99 109 . 96 962.11 99 311.02 7697-69 163 512.08 20867.24 36 113. 10 1017.88 100 314.16 7853.98 164 515.22 21124.07 37 116.24 1075.21 IOI 3 I 7-30 8011.85 165 518.36 21382.46 38 119-38 1134.11 IO2 320.44 8171.28 1 66 521.50 ^1642.43 a 122.52 125.66 1194.59 1256.64 103 104 323-58 326.73 8332.29 8494.87 167 1 68 524 65 527.79 21903.97 22167.08 41 128.81 1320.25 105 329-87 8659.01 169 530.93 22431.76 42 131.95 1385.44 106 333-01 8824.73 170 534 07 22698.01 43 1^5.09 1452.20 107 336.15 8992 . 02 171 537-21 22965.83 44 138-23 1520.53 108 339-29 9100.88 172 540.35 23235.22 45 Mi-37 1590.43 109 342-43 933L32 543-50 23506. 18 46 I44-5I 1661 .90 110 345-58 9503 S 2 T 74 546.64 23778.71 47 147-65 1734-94 ii i 348.72 9676.89 24052.82 48 150.80 1809.56 112 351.86 9852.03 176 552.92 24328 49 153-94 1885.74 "3 355-oo 10028.75 177 556.06 24605.74 50 157-08 1963.50 114 358.14 IO2O7.O3 178 559.20 24884.56 52 160.22 163.36 2042 . 82 2123.72 "5 116 361.28 364-42 10386.89 10568.32 179 180 562.35 565-49 25164.94 25446.90 53 166.50 2206.18 117 367.57 10751.32 181 568.63 25730-43 54 169.65 2290.22 118 370.71 10935.88 182 57 1 - 77 26015.53 55 172.79 3375.83 119 373-85 III22.O2 183 574-9 1 26302 . 20 56 I75.93 2463.01 120 376.99 11309.73 184 578-05 26590.44 179.07 182.21 2551.76 2642.08 121 122 380.13 383 27 11499.01 11689.87 185 186 581.19 584-34 26880.25 27171.63 59 185 35 2733-97 I2 3 386.42 Il882.29 187 587.48 27464.59 60 188.50 2827.43 124 389-56 12076.28 1 88 590.62 27759.11 61 191.64 2922.47 I2 5 392.70 12271.85 189 593-76 28055.21 62 194.78 3019.07 126 395-84 12468.98 190 596.90 28352.87 63 197.92 3117.25 127 398.98 12667.69 191 600.04 28652.11 64 2OI .06 3216.99 128 402.12 12867.96 192 603.19 28952.92 * From Kent's Pocket-book for Mechanical Engineers. APPENDIX CONTAINING REFERENCES AND TABLES. 37? TABLE No. V. LOGARITHMS OF NUMBERS. No, 1 2 3 4 5 6 7 8 5 10 oooo 0043 0086 0128 0170 O2I2 0253 0294 334 0374 ii 12 0414 0792 0453 0828 0492 0864 0899 0569 0934 0607 0969 0645 1004 0682 1038 0719 1072 0755 1106 13 "39 '"73 1206 1239 1271 '303 1335 1367 1399 '43 14 1461 1492 1523 1553 1584 1614 1644 1673 1732 15 /i 76 1 1790 i8i8 1847 1875 1903 1931 1959 1987 2014 16 2041 2068 2095 2122 2148 2175 2201 2227 2253 2279 jjy 2304 233 2355 2380 2405 2430 2455 2480 2504 2529 18 2553 2577 2601 2625 2648 2672 2695 2718 2742 2765 19 2788 2810 2833 2856 2878 2900 2923 2945 2967 2989 2O 3010 3032 3054 3075 3096 3"8 3139 3160 3181 3201 21 3222 3243 3263 3284 3304 3324 3345 3365 3385 3404 22 3424 3444 3464 3483 3502 3522 3541 3560 3579 3598 23 3617 3636 3655 3674 3692 37" 3729 3747 3/66 3784 24 3802 3820 3838 3856 3874 3892 3909 3927 3945 3962 25 26 3979 415 3997 4166 4014 4183 4031 42 .0006 87 i .000 .922 .00122 .00127 .000089 .00198 .212 .0508 .0308 0939 .092 .1298 .1138 0324 0314 0333 .1086 .0324 .056 .1165 .0562 0953 .2149 .2174 .2 .2694 -2I 5 8 57 65 .2415 .2411 -203 .1977 .2026 .6588 :fi, .416 1. 000 .504 .238 .2412 3.2936 .2210 Per cu. in. 0.0956 0.2428 o-3533 0.2930 0.3179 0.2707 0.2801 0.6965 0.4106 0.4918 0.3183 0-5787 0.3788 0.2916 0.2637 0.26 Per cu. ft. 174.0 197.0 140.0 168.0 165.0 IX I* 62.5 180.7 127.0 57-5 55-o .050 54-37 62.35 57-5 .0807 .0892 .00559 .1234 810 476 1692 1996 2250 !37oo 2590 608 ~ 39 3700 2OOO 4000 446 680 Antimony Bismuth Brass .049 .0327 .648 .566 .1329 5i5-o 103.0 103.0 Copper . Iron, cast Iron, wrought Gold .. . Lead Mercury at 32 Nickel 50.0 Platinum Silver. .0265 Steel , Tin 0439 .049 .6786 735 735 735 735 73 73 IO2.O Zinc Stones- Chalk Limestone Masonry Marble, gray Marble, white Woods- Oak 5-6 4-4 0.4 7 Pine white Mineral substances- Charcoal, pine Coal, anthracite Coke Glass, white .. 5948 !-S Liquids Alcohol, mean Oil, petroleum Steam at 212 Turpentine 1.480 1.0853 Water at 62. . . Solid Ice at 32 Gases- Air at 32 Oxygen Hydrogen 38G APPENDIX CONTAINING REFERENCES AND TABLES. TABLE No. VII. COEFFICIENTS, STRENGTH OF MATERIALS. Ultimate Strength. Tons per Square Inch. Moduli. Tons per Sq. Inch. Tension. Com- pression. Shearing. Elasticity. Rig. T c s E Es 54-io4 7 14 15-20 27-29 24 22 IQ 27-29 25 19-24 25-50 26-32 30-45 40-65 So 72 70 150 10-14 15-16 28 8-13 22 11-23 15-26 2-3 7-IO 2 0. 9 3-7 ii-34 4 4-7 . 4-6 4-7 25-65 42 36-58 60-75 20 35 5 3 4 24 2-4 34 24-5 14-24 14-3 i-6 9-13 II - 18-22 ] a - $ M o" 3 10-14 I 4 5000 \ t0 6000 112,000 to 13,000 12,000 \ t0 j 13,000 I3,OOO 7000 8000 5500 6400 45OO-6OOO 6OOO 5500 IOOO 800 600 950 750 650 1300 to 2500 5000 5000 to 5200 2800 1500 22OO I700- 2400. Repeatedly melted . . ... Wrought-iron Finest Low- j with grain., moor plates: \ across " .. Bridge-iron:]^ ". Bars finest Bars soft Swedish . . Wire Steel Mild-*teel plates Axle and rail steel Tungsten " . Steel wire. . Piano- wire. Copper Cast Rolled ^Vire hard drawn Brass Wire Phosphor bronze .Zinc cast Zinc, rolled Tin . Lead Timber- Oak Pitch-pine . Ash.. Beech Mahogany Stone Sandstone Brick From Vol. XXII. , Encyc. Britannica. APPENDIX CONTAINING REFERENCES AND TABLES. 381 TABLE No. VIII. PROPERTIES OF AIR. OF THE WEIGHTS OF AIR, VAPOR OF WATER, AND SATURATED MIXTURES OF AIR AND VAPOR OF DIFFERENT TEMPERATURES, UNDER THE ORDI- NARY ATMOSPHERIC PRESSURE OF 29.921 INCHES OF MERCURY. =5- 5i .St* 6 !~ Mixtures of Air saturated with Vapor. ~ u *" C u u 3 S& !x* *>> 4) O "'5 c ^ 3 W Elastic Weight of a cubic foot of the mixture. rt *j "" C 3 p o S Dl I, ' "*"'' a fa Is "3 C U oa H at w " UT3 ^1< - rt"' |1S H at u P3 n U u 1 9 10 1 1 12 13 14 15 .00092 1092.4 .02056 .02054 48.5 48.7 12 .00115 646.1 .... .02004 .02006 50.1 50.0 22 .00245 406.4 .... .01961 .01963 51-0 32 .00379 263.81 3289 .01921 .01924 52.0 51-8 42 .00561 178.18 2252 .01882 .01884 53-2 52.8 52 . 008 i 9 122.17 J595 .01847 .01848 54-0 53-8 60 .01251 92.27 1227 .01818 .01822 55-0 54-9 62 .01179 84-79 .01811 .01812 56.2 55-7 70 .01780 64.59 882 .01777 .01794 57-3 56-5 72 .01680 59-54 819 .01777 .01790 58.5 56.8 82 .02361 42.35 600 .01744 .01770 57-2 56.5 92 .03289 30.40 444 .01710 .01751 58.5 57-1 TOO 04495 23.66 356 .01690 01735 59- 1 57-8 102 04547 21.98 334 .01682 .01731 59-5 57-8 112 .06253 15-99 253 .01651 .01711 60.6 58.5 122 .08584 11.65 194 .01623 .01691 61.7 59- * 132 .11771 8.49 .01596 .01670 62.5 59-9 142 . 16170 6.18 118 .01571 .01652 63.7 60.6 152 .22465 4-45 93-3 01544 .01654 65.0 60. 5 162 .31713 3.15 74-5 .01518 .01656 62.2 60.4 172 46338 2.16 59-2 .01494 .01658 67.1 60. 3 182 .71300 1.402 48.6 .01471 .01687 68.0 59' 5 192 1.22643 .815 39-8 .01449 68.9 .... 202 2.80230 357 32.7 .01466 .... 68.5 ... 212 Infinite .000 27.1 .01406 71.4 APPENDIX CONTAINING REFERENCES AND TABLES. 383 TABLE No. IX. MOISTURE ABSORBED BY AIR. THE QUANTITY OF WATER WHICH AIR is CAPABLE OF ABSORBING TO THE POINT OF MAXIMUM SATURATION, IN GRAINS PER CUBIC FOOT FOR VARIOUS TEMPERATURES. Degrees Fahr. Grains in a Cubic Foot. Degrees Fahr. Grains in a Cubic Foot. IO I . I 85 12.43 15 I-3I 90 14.38 2O 1.56 95 16.60 25 1.8 5 100 19.12 30 2.1 9 105 22.0 32 2-35 no 25-5 35 2-59 115 3O.O 40 3.06 130 42-5 45 3.6! 141 58.0 50 4.24 157 85.0 55 4-97 170 112. 5 60 5-82 179 138.0 65 6.81 1 88 166.0 70 7-94 195 194.0 75 9.24 212 265.0 80 10.73 TABLE No. X. RELATIVE HUMIDITY OF THE AIR. Difference of Temperature of the Air and Dew-point. Temperature of Air. 32 Fahr. Temperature of Air. 70 Fahr. Temperature of Air. 95 Fahr. O IOO IOO IOO I 96 97 97 2 92 93 94 3 88 90 91 4 85 87 88 5 81 - 84 86 6 78 81 83 7 74 78 80 8 7i 76 78 9 68 73 75 10 65 7T 73 12 60 66 68 14 54 61 64 16 50 57 60 18 45 53 56 20 41 49 53 22 38 46 49 24 34 43 46 384 APPENDIX CONTAINING REFERENCES AND TABLES. TABLE No. XL PROPERTIES OF SATURATED STEAM. [From Charles T. Porter's treatise on The Richards Steam-engine Indicator^ Press- ure above zero. Temperature. Sensible Heat above zero Fahr. Latent Heat. Total Heat above zero Fahr. Weight of One Cubic Foot. Lbs. per sq. in. Fahr. Deg. B.T.U. B.T.U. B.T.U. Lbs. 1 102.00 102.08 1042.96 1145.05 .0030 2 126.26 126.44 i.026.01 1152.45 .0058 i8 141.62 141.87 1015.25 1157.13 .0085 4 153.07 153.39 1007.22 1160.63 .Oil? 5 162.33 162.72 1000.72 1163.44 .01 37' 6 170.12 170.57 995.24 1165.82 :0163 7 176.91 177.42 990 47 1167.89 .0189 8 1$2.91 183.48 986.24 1169.72 .0^14 9 188.31 188.94 982.43 1171.37 .0239 10 193.24 193.91 978.95 1172.87 .0264. 11 197.76 198.49 975.76 1174.25 .0289 12 201.96 202.73 972.80 1175.53 .0313 13 205.88 206.70 970.02 1176.73 .0337 \\ 209.56 213.02 210.42 213.93 967.42 964.97 1177.85 1178.91 .036,3 .0387 16 216 29 217.25 962.65 1179.90 .0413 17 219.41 220.40 960.45 1180.85 .0437 18 222.37 223.41 958.34 1181.76 .0462 19 225. 2a 226.28 956.34 1182.62 .0487 20 227.91 229.03 954.41 1183.45 .0511 J31 230.51 231.67 952.57 1184.24 .0536 22 233.01 234.21 950.79 1185% 00 .0561 23 2S5.43 236.67 949.07 1185.74 .0585 24 237.75 239.02 947.42 1186.45 .0610 25 240.00 241.31 945.82 1187.13 .0634 26 242.17 243.52 944.27 1187.80 .0653 27 244.28 245.67 942.77 1188.44 MS3 28 246.32 247.74 941.32 1189.06 .0707 29 248.31 249.76 939.90 1189.67 .0731 30 250.24 251.73 938.92 1190.26 .0755 31 252.12 253.64 937.18 1190.83 .0779 32 253.95 255.51 935.88 1191.39 .0803 33 255.73 257.32 934-. 60 1191.93 .0827 34 257.47 259.10 933.36 1192. 4G .0851 35 259.17 260.83 932.15 1192,98 .0875 36 260.83 262.52 930.96 1193.49 .0899 87 262.45 264.18 929.80 1193.98 :0922 38 264.04 265.80 928.67 1194.47 .0946 39 265. 5"9 267.38 927.56 1194.94 .0970 40 267.12 268.93 926.47 1195.41 .0994 41 268.61 270.46 925.40 1195.86 1017 42 270.07 271.95 924.35 1196.31 1041 43 271.50 273.41 923.33 1196.74 1064 "44 272.91 274.85 922.33 1.197.17 .1088 45 274.29 276.26 921.33 1197.60 .1111 46 275.65- 277.65 920.36 1198.01 .1134 APPENDIX CONTAINING REFERENCES AND TABLES. 385 PROPERTIES OF SATURATED STEAM Continued. Press- ure above zero. Temperature. Sensible Heat above zero Fahr. Latent Heat. Total Heat above zero Fahr. Weight oi One Cubic Fool. Lba.per sq. in. Fahr. Deg. B.T.U. B.T.U. B.T.U. Lbe. 47 276.98 279.01 919.40 1198.42 .1158 48 278.29 280.35 918.46 1198.82 .1181 49 279.58 281.67 917.54 1199.21 .1204 50 280.85 282.96 916.63 1199.60 .1227 51 28^.09 284.24 915.73 1199.98 .1251 52 583.32" 285.49 914.85 1200.35 .1274 53 284.53 286.73 912. 9S 1200.73 .1297 54 285'. 72 287,95 913.13 1201.08 .1320 55 286 89 289.15 912.29 1201.44 .1343 56 288.05 290.33 911.46 1201.79 .1366 57 289.11 291.50 910.64 1202.14 .1388 58 290.31 292.65 909.83 1202.48 .1411 59 291.42 293.79 909.03 1202.82 .1434 60 292.52 294.91 908.24 1203.15 .1457 61 293.59 296.01 907.47 1203.48 .147D 294.66 297.10 906.70 1203.81 .1503 63 295.71 298.18 905 94 1204.15 .1524 64 296.75 299 .-24 905 20 1204.44 .1547 65 297.77 300.30 904.46 1204.76 .1569 66 298.78 301.33 903.73 1205.07 .1593 7 299.78 302.36 903.01 1205.37 .1614 8 300.77 303.37 902.29 1205.67 il637 69 301.75 304.88 901.59 1205.97 .1659 70 302.71 305.37 900.89 1206,26 .1681 71 303.67 306. a-> 900.21 1206.56 .1703 72 304.61 307.32 899.52 1206.84 .1725 73 305.55 308.27 893.85 1207.13 .1748 74 306.47 809.22 898.18 1207.41 .1770 75 307.38 310.16 897.52 1207.69 .1792 76 308.29 311.09 896.87 1207.90 .1814 77 309.18 312.01 89Q.23 1208.24 .1836 78 810.06 312.92 895.59 1208.51 .1857 79 310.94 313.82 894.95 1208.77 .1879 80 311.81 314.71 894.33 1209.04 .1901 81 312.67 315.59 893.70 1209.30 .1923 82 313.52 316.46 893.09 1209.56 .1935' 83 314.36 317.33 892.48 1209.82 .1967 84 315.19 318. 1*9 891.88 1210.07 .1988 85 316.02 319.04 891.28 1210.32 .2010 86 316.83 319.8? 890.69 1210.57 .2033 87 317.65 320.71 890:10 . 1210.82 .2053 88 318.45 321.54 889.52 1211.06 .20T5 89 319.24 322.36 838.94 1211.31 .2097 90 320.03 323.17 888.37 1211.55 .2118 91 92 93 94 320.82 321.59 322.36 323.12 323.98 324.78 325.57 326.35 887.80 887.24 S86.68 885.13 1211.79 1212.02 1212.26 1212.49 .213?. .2160 .2183 .2204 95 323.88 327.13 885.53 1212.72 .2224 APPENDIX CONTAINING REFERENCES AND TABLES. PROPERTIES OF SATURATED STEAM Continued. Press- ure above zero. Lbs.per $q. in. Temperature. Sensible Heat above zem Fahr. Latent Heat. Total Heat above zero Fahr. Weight of One Cubic Foot. Lbs" Fahr. Deg. B.T.U. B.T.U. B.T.U. 96 324.63 327.90 885.04 1212.95 .2245 97 325.37 328.67 884.50 1213.18 .2266 98 326.11 329.43 $83 97 1213.40 .2288 99 326.84 330.18 883 ."44 1213.62 .2309 100 327.57 330.93 882.91 1213.84 .2330 101 328.29 331.67 882.39 1214.06 .2351 102 329.00 332.41 881.87 3214.28 .2371 103 329.71 333.14 881.35 1214.50- .2392 104 330.41 333.86 880.84 1214.71 .2413" 105 331.11 334.58 880.34 1214.92 .2434 106 331.80 335.30 879.84 1215.14 .2454 107 332.49 336.00 879.34 1215.35 .2475 108 333.17 336.71 878.84 1215.55 .2496 109 333.85 337.41 878.35 1215.76 .2516 110 334.52 838.10 877.86 1215.97 .2537 111 335.19 838.79 877.37 1216.17 .2558 112 335.85 339.47 876.89 1216.37 .2578 113 336.51 340.15 876.41 1216.57 .2599 114 337.16 340.83 875.94 1216.77 .2619 115 337.81 341.50 875.47 1216.97 .2640 116 338.45 342.16 875.00 1217.17 .2661 117 339.10 342.83 874.53 1217.36 ,2681. 118 339.78 343.48 874.07 1217.56 .2702 119 340.36 344.14 873.61 1217.75 .2722 120 340.99 344.78 873.15 1217.94 .2742 121 341.61 345.43 872.70 1218.13 .2762 122 342.23 346.07 872.25 1218.32 .2782 123 342.85 346.70 871.80 1218.51 .2802 1.24 343.46 347.34 871.35 1218.69 .2822 125 844.07 347.97 870.91 1218.88 .2842 126 344.67 348.59 870.47 1219.06 .2832 127 345.27 349.21 870.03 1219.25 .2882 128 345.87 349.83 869.59 1219.43 .2902 129 346.45 350.44 869.16 1219.61 .2922 130 347.05 351.05 868.73 1219.79 .2943 131 347.64 351.66 868.30 1219.97 .2961 132 348.22 352.26 867.88 1220.15 .2981 133 348.80 352.86 867.46 1220.33 .3001 134 349.38 353.46 867.03 1220.50 .3020 135 349.95 354.05 866.62 1220.67 .3040 136 / 350.52 354.64 866.20 1220.85 .3060 137 351.08 355.23 866.79 1221.02 .3079 138 351.75 355.81 865.38 1221.19 .3099 139 352.21 356.39 864.97 1221.36 .3118 /I40 352.76 356.96 864.56 1221.53 .3188 141 353.31 357.54 864.16 1221.70 .3158 142 353.86 358.11 863.76 1221.87 .3178 143 854.41 358.67 863.36 1222.03 .3199 144 354.96 359.24 862.96 1222.20 .3219 APPENDIX CONTAINING REFERENCES AND TABLES. 387 PROPERTIES OF SATURATED STEAM Continued. Free*- ure above zero Temperature. Seneible Heat above zero Fahr. Latent Heat. Total Heat above zero Fahr. Weight of One Cubic .Foot. Lbs.pcr sq. in. Fahr. Deg. B.T.U. B.T.U. B.T.U. Lbs. 145 355.50 359.80 862.56 1222.36 .3239 146 356.03 360.85 862.17 1222.53 .3259 iH 356.57 860.91 861.78 1222.69 .3279. 148 357.10 861.46 861.39 1222.85 .3299 149 357.63 362.01 861.00 12S3.01 .3319 150 358.16 362.55 860.62 1223.18 .3340 151 358.68 363.10 860.23 1223.33 .3358 152 359. 20 363 64 859.85 1223.49 .3576 153 359.72 364.17 859.47 1223.65 .3394 154 360.23 364.71 859.10 1223.81 .3412 155 360.74 365.24 858.72 1223.97 .3430 156 361.26 365.77 858.35 1224.12 .3448 157 361.76 366.30 857.98 1224.28 .3466 158 362.27 366.82 857.61 1224.43 .3484 159 362.77 367.34 857.24 1224.58 .3502 160 363.27 367.86 856.87 1224.74 .3520 161 363.77 368.38 856.50 1224.89 .3539 162 364.27 368.89 856.14 1225.04 .3558 163 364.76 869.41 855.78 1225.19 .3577 164 365.25 369.92 855.42 1225.34 .3596 165 865.74 37042 855.06 1225.49 .3614 166 366.23 370.93 854.70 1225.64 .3633 167 366.71 371.43 854.35 1225.78 .3652 158 367.19 371.93 853.99 1225.93 .3671 169 367.68 372.43 853.64 1226.08 .3690 170 368.13 372.93 853.29 1226.22 .3709 171 368.63 373.43 852.94 1226.37 .3727 172 369.10 373.91 852.59 1226.51 .3745 173 369.57 374.40 852.25 1226.66 .3763 174 370.04 374.89 851.90 1226.80 .3781 175 370.51 375.38 851.56 1226.94 .3799 176 370.97 375.86 851.22 1227.08 .3817 177 371.44 376.34 850.88 1227.23 .3835 173 371.90 -376. 82 850.54 1227.37 .3853 179 372.36 $77.30 850.20 1227.51 .3871 m 372.82 377.78 49.86 1227.65 .3889 181 373.27 378.25 849.53 1227.78 .3907 1S2 373.73 378.72 849.20 1227.92 .3925; 183 374.18 379.19 848.86 1228.06' .3944^ 184 374.63 379.66 848-. 53 1228.20 .3962 ia r > 375.08 380.13 848.20 1228.33 .3980 1S6 375.52 380.59 847.88 1228.47 .3999 187 375.97 381.05 847.55 1223.61 .4017 188 376.41 381.51 847.22 1228.74 .4035 189 376 85 381.97 846.90 1228.87 .4053 190 377.29 382.42 846.58 1229.01 .4072 191 377.72 382.88 846.26 1229.14 .4089 192 378.16 383.33 845.94 1229.27 .4107 193 378.59 383. r <8 845.62 1S29.41 .4125 388 APPENDIX CONTAINING REFERENCES AND TABLES. PROPERTIES OF SATURATED STEAM Continued. Pressure above Zero. Temperature. Sensible Heat above Zero Fahr. Latent Heat. Total Heat above Zero Fahr. Weight of One Cubic Foot, Lbs. per sq. in. Fahr. Deg. B.T.U. B.T.U. B.T.U. Lbs. 194 379.02 384.23 845.30 1229.54 .4143 195 379.45 384.67 844.99 1229.67 .4160 196 379.97 385.12 844.68 12:29.80 .4178 197 380.30 385.56 844.36 1229.93 .4196 198 380.72 386.00 844.05 1230.06 .4214 199 381.15 386.44 843.74 1230.19 .4231 200 381.57 386.88 843.43 1230.31 .4249 201 381 99 387.32 843.12 1230.44 .4266 202 382.41 387.76 842.81 K'30.57 .4283 203 382.82 388.19 842.50 1230.70 .4300 204 383.24 388.62 842.20 1230.82 .4318 205 383.65 389.05 841.89 J 230. 95 .4335 206 384 06 389.48 841.59 1*81.07 .4352 207 384.47 389.91 841.29 1231.20 .4369 208 384.88 390.33 840.99 itti. ae .4386 209 385.28 390.75 840.69 1231.45 .4403 210 385.67 391.17 840.39 1231.57 .4421 QUANTITIES OF HEAT CONTAINED IN ONE POUND OF WATER AT VARIOUS TEMPERATURES, RECKONED FROM ZERO, FAHRENHEIT. [From Charles T. Porter's treatise on The Richards' Steam-Engine Indicator.} Tempera- ture. Heat con- tained above Zero. Tempera- ture. Heat con- tained above Zero. Tempera- ture. Heat con- tained above Zero. Fahr. Deg. B.T.U. Fahr. Deg. B.T.U. Fahr. Deg. B.T.U. 35 35.00 155 155.33 275 276.98 40 40.00 160 160.37 280 282.09 45 45.00 165 165.41 285 287.21 50 50.00 170 170.45 290 292.32 55 55.00 175 175.49 295 297.45 60 60.00 180 180.54 300 302.58 65 65.01 185 185.59 305 307.71 70 70.02 190 190.64 310 312.84 75 75.02 195 195.69 315 317.98 80 80.08 200 200.75 320 323.13 85 85.04 205 205.81 325 328.28 90 90.05 210 210.87 330 333.43 95 95.06 215 215.93 335 338.59 100 100.08 220 221 .00 340 343.75 105 105.09 225 226.07 345 348.92 110 110.11 230 231.15 350 354.10 115 115.12 235 236.23 355 359.28 120 120.14 240 241.31 360 364.46 125 125.16 245 246.39 365 369.65 130 130.19 250 251.48 370 374.84 135 135.21 255 256.57 375 380.04 140 140.24 260 261.67 380 385.24 145 145.27 265 266.77 385 390.45 150 150.30 270 271.87 390 395.67 APPENDIX CONTAINING REFERENCES AND TABLES. 389 TABLB No. XII. COMPOSITION OF VARIOUS FUELS OF THE UNITED STATES. C. H. 0. N. s. Mois- ture. Ash. Spec. Grav. 78.6 8s- 8 2-5 i-7 0.8 o-4 1.2 148 i 45 \% 1.40 i-33 1 32 1.30 1.24 Rhode Island " 10.5 Massachusetts " 92 o 83 i 6.0 7-8 North Carolina " .... 9-i Welsh *' Maryland Semi-bituminous 80.5 75-8 59-4 70.0 52.0 62.6 58.2 59-5 48.4 71.0 4527 20.2 3 8.8 28.0 39-0 35-5 P:5 48.8 17.0 n 1.2 *-7 8-3 4.0 1.8 2.0 1.9 1.30 * 4 (Block) Bituminous Illinois and Indiana (Cannel) Bituminous Kentucky (Cannel) Bituminous 39 2.8 12.0 1.27 1-25 i-45 Tennessee Bituminous Alabama " 4i.5 56.5 42 6 2-5 18 6 California and Oregon Lignite 50.1 0.9 i-5 16.7 13.2 i-3* 3-9 13-7 STATE. COAL. KIND OF COAL. Per Cent, of Ash. THEORETICAL VALUE. In Heat Units. In Pounds of Water Evaporated. Pennsylvania 44 44 M 44 44 Kentucky Anthracite 3-49 6.13 2.90 15.02 6.50 10.77 5.00 5-60 9-50 2.75 2.00 14-80 7.00 5-20 5.60 5-50 2.50 5.66 6.00 3-98 S-oo 9.25 4-50 4.50 3-40 i4,i<39 13,535 14,221 i3,*43 13,368 13.155 14,021 14,265 ia,3 2 4 H,39i 15,198 13,360 9,326 1 3. 02 5 13,123 12,659 13,588 14,146 13,097 12,226 9,215 '3,562 13,866 12,962 ,55i 20,746 14.70 14. ot 14-72 13.60 13.84 13.62 '451 14.76 12-75 14.89 16.76 13.84 9.65 13-48 13 58 13.10 14.64 13-56 12.65 9-54 14.04 14-35 13-41 11.96 21-47 H Cannel .. . . . Semi-bituminous . Stone's Gas Youfirhiojrheny. Brown Caking t Cannel 44 Illinois . . Bureau County 44 , Mercer County 44 Indiana M Block Caking Arkansas Colorado . . 44 Texas M V'aahington. Pennsylvania 44 Petroleum 3QO APPENDIX CONTAINING REFERENCES AND TABLES. TABLE No. XI L Continued. DRY ANTHRACITE COAL AVERAGE TABLE OF RESULTS.* Mine. Locality. Volatile Matter. 4 Fixed Carbon. z O I* (A u x O. u 'CT3 3 C_- ^ 3 rt |S u rt g |l ^So' Jfils ,J L. V. Buckwheat W.-Barre, Pa. . . Unknown 6.21 6.8 15-5 76.94 80.2 i-3 11,959 12.38 it 14 5 14 81 1 1, 800 D L. & W M 84 Jermyn Stove Woodward Schuy. Co.. Pa... 6.08 4 06 1 1. 02 82.90 81 87 T -4 2 5 12,316 13-05 84 38 Mt Pleasant . ti o 10.78 gj 59 12 A-8 L. V. Pea Forty-foot L. V. region Scranton, Pa 7-49 16.23 76 28 8U 02 -52 11,920 12-37 Manville Shaft . . . 7 ^3 86 =; It H r 7 g 5-78 6ie Avondale Oxford Avondale, Pa 6 49 6.QI 87.78 44 I3,2l8 I3-7I Mammoth(Buckwh't) -j Dnfton, Pa. / (Slate removed) f Cross Creek.Pa j_ 2.44 6.97 90-59 1-55 i c;6 r 3,72o 14.20 (Slate removed) ) BITUMINOUS COAL AVERAGE TABLE OF RESULTS.-' 3 d I I* % rt -cjj rt | 2*O ? -"2 w s'^ s Mine. Locality. 6 o 'CTJ ^ o rf ^J^CJ - o i 3 T5 O 9" g C Q ^ O V . > o w *o | X o/~ So^u u < fa * K ^ Gillespie '. Gillespie 111 36.26 12.33 5* *4* 1.26 IO,GO2 11.28 o ^6 Auburn Screenings. Sugar Creek, 111 37.5 15.2 47-3 11,200 ii. 6 VJ.^U LittlePittsburg,Va. Morgantown, W. Va. 37-5 6.6 559 I2,8OO ^3*3 Bernmont Monongahela R.. Pa. 32 8.04 jo *y 59-96 '275 1 3,424 13-9 1.04 Antrim New Blossburg, Pa.. 18.54 II .30 70. 16 1.42 13,695 14 18 0.27 Eureka . Cleartield Co., Pa . 23-79 :? 5-82 7-39 1.32 o, v yo J 3,897 -43 Turtle Creek Monongahela R., Pa. 34-95 4-33 60.72 1.28 I 4,45 14.96 0.30 Nova Scotia Reynoldsville Leisenring No. 2 Slope, U. S Reynoldsville, Pa Connellsville. Pa. . . . 32-38 24.67 29.26 4.11 5-37 6.25 63-61 69.96 64.49 1 -34 15,285 15.86 15-67 15.82 0.27 o-33 0.92 Pocahontas New River, Va 17.84 3-72 78.45 *o *->* 15.82 0.2 Cooperstown Nova Scotia 30-75 4.09 65-16 !-345 15,435 15.98 0-5 * From experiments made by Flory and Gilbert at Sibley College, Cornell University. The heat-units are given per pound of dry coal. Coal in ordi- nary conditions contains from 3 to 10 per cent of moisture, and the results must be reduced accordingly. Seventy per cent of the theoretical heating value represents the average results obtained in practice. APPENDIX CONTAINING REFERENCES AND TABLES. 39 1 TABLE No> XIl. Continued. ANALYSES OF ASH. Specific Grav. Color of Ash. Silica. Alum- itia. Oxide Iron. Lime. Mp. nesia. Loss. Acids S.&P. Pennsylvania Anthracite Bituminous 559 372 Reddish Buff. Gray. 45-6 76.0 42-75 21.00 44 8 9-43 2.60 1.41 0-33 trace 0.48 0.40 Scotch Bituminous z 37-6 52.0 3-7 i.i * oa .27 IQ.7 n. 6 5.8 23.7 2.6 .8 TABLE No. XIII. FOR REDUCING BAROMETRIC OBSERVATIONS TO THE FREEZING-POINT. Reading of Ba- rometer. Correction at 10 Fahr. Correction at 40 Fahr. Correction at 70 Fahr. Correction at 90 Fahr. Inches. Inches. Inches. Inches. Inches. 27 0.045 O.O28 0.100 0.148 27-5 0.046 0.028 O. IO2 O.I5I 28.0 0.047 0.029 0.104 0.153 28.5 0.048 0.029 0.106 0.156 29 0.049 o 030 0.108 0.159 29-5 0.050 0.030 0.109 0.162 30.0 0.051 0.031 O. Ill 0.164 30-5 0.052 0.032 0.113 0.167 31-0 0.053 0.032 0.115 0.170 39 2 APPENDIX CONTAINING REFERENCES AND TABLES. TABLE No. XIV. THERMAL CONDUCTIVITIES. PER DEGREE DIFFERENCE OF THE SUBSTANCE. Substances. Thickness, one metre. Calories per sq. metre. Thickness, one foot. B. T. U. per sq. ft. per hr. Authority. ?26 594 57.5 104 Zinc 56 1 02 Lead 28 50.5 Air, ] Oxygen, Nitrogen, Carbonic oxide, J u.ui/y 0.0137 *j*j 0.0249 ing to kinetic theory. Do. do. do. O.OI25 0.0227 Do. do. do. Glass O.82 1.40 Peclet. Porphyritic trachyte 2.12 3.86 Aryton & Perry, Phil. Mag., Marble J.I-7 5.67 1878, first half year, p. 241. Peclet. Underground strata. ..... 1.8 1.82 3-29 3.31 Forbes and Wm. Thomson. Sandstone of Craig- } leith Quarry f ' ' Trap-rock of Calton Hill.. Sand of experimen- ) tal garden \ ' ' Water 3-84 1-5 0.94 0.72 7.0 2-73 1.72 1.82 Do. do. do. Do. do. do. Do. do. do. J. P. Bottomley. Fir across fibres . o ocn o 169 P6clet in Everett's Units and " along fibres O.I 60 o 308 Physical Constants. Do. do do. W^alnut across fibres o 105 o 192 Do do do " along fibres. . . . . O 173 O 71 C Do do do O 212 o ^87 Do. do. do. Cork .. O. IOC, O IQ2 Do. do. do. Hempen cloth nevv . . . o 052 O OQ 1 ^ Do do do " old o 043 o 078 Do do do Writing paper, white Gray paper unsized .... 0.043 O.O337 0.078 O O^I^ Do. do. do. Do do do Calico, new, of ) all densities f Wool, carded, of ) all densities f ' ' Finely carded cotton-wool Eider-down 0.044 0.04 O O3Q 0.08 0.073 0017 Do. do. do. Do. do. do. Do do do Indian rubber O 17 o 308 Brick dust. . . . OT C O 272 o 06 o 109 Coke 406 9OI APPENDIX CONTAINING REFERENCES AND TABLES. 393, > < X . Q < g H o .g M rZ H g. " 15 - m 'I'C "I y 5- Kw = 58 ?>? K8Smm v R'&1>8 c ocjvJr::o? Z^ -X MfmiotxoOf joo moo m o^ m m tx. rs. w 5 1 * o.- S ns 55-8 ****{& >o 3 o a m t S>?.Rv v sg.q. M 2'2-S 0vtx * fOCINM " MM -J ; 3 a M -" ^ i 8 m moo oo tx m tx ooo tx ^-oo tx N t^ ooo oo oo f*~ 5 O si fcu M - OM I Is U ~ V *Sms3t*gK$E*i5i;!g???S? 2 w a^ . 0> s cr l?ffl^^ffrf|f||?l|||?|8 X < M "rt c w c " 5- J^5- m^S vc oo vo -4-00 tx. - oo oo o moo r^ in in O O O mo o f" moo oo oo mvo ooo m -^ m m cr ooo oo -^ -^ - minoo mi- moo t^ o* o-oo t^ o r-oo o O oo * o w i > W .--pi.m t- JT -''S N m |4 1 c ?n^H < S?IHJH5^5l :l SS'88 r_. 2 >< cr C/l N N -\o O M m- o -^ * moo N O oo rx mvo - vo * cd W u g" I oo * CX.ON m- < mvo vo oo ts o <* mvo vo r-oo vo oo ^- * in moo o mvO o m m ** -^vo -f mvo t r r in vooow _ Id M c j= -m*mvo t xO-CJjmo ? jmo3-^tv-*oo- z s 3 D U c u S J3 t-'o (M m o m - vS"vc m oo m o_ r-_^ m o m t-- -_ m,t vo m U s O c i A j i te I y oo oo o m ^- m-^-^t- tvo t vo o MCI -^vo m m in m ** vooo OO M m^^mjO w r^-^- moo O 01 -^-vo t* r^ i t oo m C il "3 1 u n:iF5i*i r.iiHsigr. o 999 , m < c i u 5 1"! OS 4 u t3 1*?^ r ?!^^!!!!!n^ aj s O 00 Q H 11 S xsxxsr sx x x s; 11 Z.~ 5 M M M M M M H " 394 APPENDIX CONTAINING REFERENCES AND TABLES. TABLE No. XVI. WEIGHT OF WATER PER CUBIC FOOT FOR VARIOUS TEM- PERATURES.* WEIGHT OF WATER PER CUBIC FOOT, FROM 32 TO 212 F., AND HEAT- UNITS PER POUND, RECKONED ABOVE 32 F. oT 3 5 a JS , 3 1 c , ^,3 J 51 "Z' ^ w -3 '5 ttj . >) .J 3 ^ * r-; C.J *-* 3 C^ s/t Q O *-* 3 4> ~ L * S^S 3 is cg.1 i S 2Q Sgjj i 30 ?SJ 0) EJ2Q 3r M 9 40.269 36.372 40.702 36.805 4i-i35 37-238 41-568 37-67I 42.001 38.104 42.436 38.537 42.867 HEAD IN FEET OF WATER, CORRESPONDING TO PRESSURES IN POUNDS PER SQUARE INCH. i lb. per square inch = 2.30947 feet head, i atmosphere - 14-7 Ibs. per square inch = 33.95 feet head. Press- ure. t 2 3 4 5 6 7 8 9 | o 10 20 3 40 SO 23.0947 46.189* 69 2841 115.4735 2.309 25.404 48.499 71-594 94.688 117.78 4.619 50! 808 73-903 96.998 I2O.O9 6.928 30.023 53 "8 76.213 99.307 122.40 9.238 32-333 55-427 78.522 101.62 124.71 "547 34-642 57-737 80 831 IC3-93 126.02 13-857 36-952 60.046 83.14- 106.24 129.33 16.166 ^9.261 62.356 ?S 450 108.55 131.64 18.476 41.570 64.665 87-760 110.85 '33-95 20.785 43.880 66.975 90.069 113.16 136.26 60 70 138.5682:140 88 161 .6620 163.97 143.19 'HS.SO 166.28 168.59 147.81 170.90 150.12 152.42 T 54-73 177-83 180.14 J 59-35 182.45 80 184.7576 187.07 189.38 191.69 194.00 196.31 198.61 200.92 203.23 1205.54 90 207.8523 210.16 212-47 214.78 217.09 219.40 221.71 224.02 226.33 228.04 * Kent's " Pocket-book." 396 APPENDIX CONTAINING REFERENCES AND TABLES. TABLE No. XVIII. CONTENTS IN CUBIC FEET AND U. S. GALLONS OF PIPES AND CYLINDERS OF VARIOUS DIAMETERS AND i FOOT IN LENGTH.* i gallon = 231 cubic inches, i cubic foot = 7.4805 gallons. Diamtter in Inches. For i Foot in Length. Diameter in Inches. For i Foot in Length. Diameter in Inches. For i Foot in Length. Cu. Ft , also Area in Sq. Ft. U.S. Gals.. 231 Cu. In. Cu. Ft., also Area in Sq. Ft. U. S. Gals.. 231 Cu. In. Cu. Ft., also Area in Sq. Ft. U. S. Gals., 231 Cu. In. A .0003 .0005 .0025 .004 6% 7 .2485 1.859 .2673 1.999 %H 1.960 2.074 H-73 i .0008 .0057 7*4 .2867 2.145 20 2.18-; 16.32 A .001 .0078 7*18 3068 2.295 20^ 2 .292 T .0014 .0102 7H 3276 2-45 21 2.405 17.99 t .0017 .0021 .0129 8 3491 -3712 2.611 2-777 21*13 22 2.521 2.640 18.86 J9-75 A .OO26 .0193 8* 3941 2.948 22* 2.761 20.66 i .0031 .0230 8^4 4-76 3- I2 5 2 3 2.885 21.58 H .0036 .0269 9 .4418 3-305 23*6 3.012 22-53 I .0042 .0312 9*4 4667 3-491 24 3.I42 23.50 & .0048 '55 -0359 .0408 9% .4922 5185 3.682 3-879 25 26 3.409 3.68 7 25-50 27-58 ^ .0085 .0123 .0638 .0918 10 10*4 5454 5730 4.08 4.286 27 28 4.276 29.74 31-99 i% .0167 .1249 Io *4 .6013 4.498 29 4.587 34-31 2 .0218 .1632 Io 94 .6303 4.715 3 4.909 36.72 2*4 .0276 .2066 ii 66 ! 4.937 31 5.241 39-2t 2>4 .0341 .2550 "*4 -6903 5.164 32 41.78 2% .0412 3085 nj| .7213 5-396 33 5-940 44-43 3 .0491 .3672 "94 -7530 5 633 34 6.305 47.16 .0576 .4309 12 -7854 5-875 35 6.681 49.98 .ji2 .0668 -4998 I2 *12 .8522 6-375 36 7.069 52.88 3*4 .0767 5738 13 .9218 6.895 37 7.46 7 55-86 4 .0873 6528 994 7-436 38 7.876 58.92 4*4 0985 7369 14 .069 7-997 39 8.296 62.06 4* II34 .8263 I?** .147 8.578 40 8.727 65.28 5 1231 .1364 .9206 ( .O2O .227 .3:0 0.180 9.801 4 1 42 9.168 9.621 68.58 7' 97 1503 '.I2 5 16 396 10.44 43 10.085 75-44 5* 1650 234 1 6*4 .485 ii . ii 44 10-559 78.99 sM .1803 349 17 .576 11.79 45 11.045 82.62 6 .1963 469 i7)4 .670 12.49 46 11.541 86-33 6*4 .2131 594 18 .768 13.22 47 12.048 90.13 6*1 2304 7*4 18* .867 13.96 48 12.566 94.00 To find the capacity of pipes greater than the largest given in the table look in the table for a pipe of one half the given size, and multiply its capacity by 4; or one of one third its size, and multiply its capacity by 9, etc. To find the weight of water in any of the given sizes multiply the capacity in cubic feet by 62*4 or the gallons by 8^6, or, if a closer approximation is required, by the weight of a cubic foot of water at the actual temperature in the pipe. Given the dimensions of a cylinder in inches to find its capacity in U. S. gallons : square the diameter, multiply by the length and by .0034. If d = diam. / = length, gallons = * Kent's " Pocket-book. APPENDIX CONTAINING REFERENCES AND TABLES. 397 TABLE No. XIX. EQUALIZATION OF PIPE AREAS.* Sizes of Pipe. r-. h %" %:" 3*4 " 4^ " 5 6 7 8 " Nu-'ber of small pipes required to make area equivalent to one larger pipe, with allowance for friction. & % in. I in. H in. ?K in. 2 in. *X in. 3 in. & in. 4 in. & in. 5 in. 6 in. 7 in. 8 in. ..!. 2.O 3-7 1.8 i 7.6 3-7 2.0 i "3 5-4 3-i i-5 1 19 9-2 1.1 8., 9-3 4-5 55 25-5 14-7 7-3 80 39 2 i .6 108 53 30 4-7 9.8 5-8 3-5 2-4 1.4 i 146 70 39 19-5 3-4 7.8 4-7 2-7 1.8 1 3 i 1 88 90 53 3.. 9-9 5-9 3-5 290 $ 16 9-3 5-4 427 210 117 g 23 3-7 $ 595 295 6 5 80 54 32 19 ii i x.83 i 2.Q *-7 -5 5 1.7 1.25 2.7 2 1.6 4-i 3-3 2-5 i-5 i 5-5 4.1 3-2 2 1/4 i * Especially computed. 39 8 APPENDIX CONTAINING REFERENCES AND TABLES. TABLE No. XX. TEMPERATURES OF VARIOUS LOCALITIES. COMPILED FROM OBSERVATIONS OF THE SIGNAL SERVICE, U. S. A., AND BLODGETT'S "CLIMATOLOGY OF THE UNITED STATES." NOTE. In the United States the comfortable temperature of the air in occupied rooms is generally 70 degrees when walls have the same temperature. Station. No. of months fire s required. Mean temp, of cold months. Av. No. ofj deg. temp, to be raised. Max. No. deg. temp, to be raised. Minimum tempera- ture F. Albany NY . 1 3^ 3" 87 17 Baltimore, Md Boston, Mass Buffalo NY 6 8 39 37 qc 3i 3^ qc, 72 8l 8? 2 II iq Burlington Vt 7 q2 38 qo 2O Chicago 111 7 35 3^ 9 20 Charleston, S. C Cincinnati O 3 7 52 42 18 2^ 47 77 + 23 7 Cleveland O 7 18 3 iq Detroit Mich .... 7 qc q^ QO 2O Duluth Minn . . 8 28 4- ioS 38 Indianapolis, Ind Key West, Fla Leavenworth, Kan 7 6 6 41 O 37 42 2o o 33 28 88 26 90 80 - 18 + 44 20 IO Memphis, Tenn Milwaukee Wis . . .. 8 39 ^7 3' q 5 68 QC + 2 2 5 New Orleans, La New York, N. Y Philadelphia, Pa 7 7 7 o 40 40 30 i ) 30 3" qr 44 76 75 82 + 26 6 - 5 12 Portland Me 8 qq q7 82 12 Portland Ore 6 4"3 2" 67 4- 3 San Francisco, Cal. ...... St. Louis, Mo 4 c 53 57 I? 33 34 86 + 36 16 St Paul Minn 7 2^ 4c, IO2 32 Washington, D. C Wilmington N C 5 40 CQ 3" 20 73 CC + 3 4- 1^ APPENDIX CONTAINING REFERENCES AND TABLES, 399 : : : : :888885,88 : : : : :*$SnW$3S 8 -8 8 8 & 8 S *fi 8 88888888 pOf^iw n ^uic*it>. 888888 : 00 W 6 -9-VC N 8888888S N- M U H W u$ u u X ^ X cr; o w z X: H < S 10 t>0 jnjj!^ 1 "i vooo t^ 10 M oo irioo OOWOOOO -*->o i-wciwei-OMnM u-,oo Ovo c> COO O m O*O O c*l\O O- O >O NnMcocomin^-rMMN-ow -*-o . S. : "S-d : : : S :*&:: :: : C c : : : E| aioJJJ 2. - . c s - * : S 400 APPENDIX CONTAINING REFERENCES AND TABLES. TABLE XXI. Continued. PRICE-LIST OF PIPE, ADOPTED JAN. 29, 1895. Diameter, inches \& H % ^ % jl/f Butt-weld, black .Each $005$ $0.05$ $o.o 5 i $0.07 $0.08^ $0.1 if $0 iqi 41 galvanized. 08 7$ ,07$ ooi -ni 16 Diameter, inches tH 2 2^ 3 3tf 4 4^ 5 6 Lap- weld, black Each $0 26 So ^ So =J2 So 68 4 81 Si 2c; Si 42 $i 8^ galvanized '" 62 80 08 i 16 For selected pipe, or pipe cut to specified lengths, the discount will be five (5) per cent less in the gross (i.e., 5 per cent higher in gross list discount) than on regular pipe. On pipe lighter than standards, or without threads or sockets, no extra allowance will be made. INDEX A PAGE Absolute pressure, defined 120 zero 6 Air, analysis of 27 , change of, in a room 51 delivered in pipes, table ; 286 , discharge, different temperatures, table of 45 , discharge, different pressures 42 , flues, indirect heating 232 , force required for moving 35 , humidity of 29 , inlet, location of 46 , measurement of velocity 37 , microbe organisms in , 23 , properties of, table 381 , relation between velocity and force, table 45 required for ventilation 31, 202 -supply for furnace 272 -trap 1 80 -valves 102 , velocity of, how computed 39 , weight of 22 Anemometer, description of 37 Angle-valves 100 Area of main pipe 192 of pipes, hot-water heating 229 of safety-valve 1 50 of steam-pipes 222, 226 of ventilating-flues ., 52 Areas and circumferences of circles 376 Argon 27 Atmosphere, composition and pressure of 21 B Bacteria in air 23 Bailey, L. H., tests.... 245 Barometer 21 Blower, capacity of 292 401 402 INDEX. VA.GE Blow-off cocks and valves. 157 Boiler explosions 172 Boiler horse-power, standard established 122 Boiler-setting, depth of foundation for . . . 145 Boiler, size of, hot-blast heating, practical construction 292-4 Boiler specifications 326 Boilers, appliances for 147 , brick settings for 143 , fire-tube 128 , heating, classes of 1 30 , forms of 129 , for soft coal 142 , setting of 147 , horizontal tubular 130 , locomotive and marine 131 , portable settings for 147 , power 128 , sectional 140 , steam-heating, care of 169 , steam, requisites of 127 , tubular 138 , types of 128 , water-tube 133, 138 Boiling-points, gases 9 Books, list of, on heating 353 Bourdon pressure-gauge 154 Branch tees 97 Breeching 145 Brick settings for boilers 143 Bucket traps 165 Buildings, loss of heat from 54 C Calorie, defined . . . 4 Capacity of boiler 122 Capital invested in manufacture 2 Carbonic acid, CO 2 , or carbon dioxide 24 Carbonic oxide, CO 26 Ceiling and floor plates 98 Check-valves 102 Chimneys, form of -. 160 , size of 161 Chimney-tops 162 Coal, soft, kind of heater for 142 Cocks and valves 98 Cocks, blow-off 157 , try 152 INDEX. 403 PAGE Combination heaters : 188 Conduction of heat 188 Connection to radiators in hot-water heating systems 195 Contents of pipe in gallons 396 Convected heat 60 Convection iq , formula for 63 Cooling of rooms 300 Couplings, right and left 93 , union 93 Coverings for pipes 198 D Damper-regulators - 156 Dead-weight safety-valve 149 Density and weight per cubic foot of water 394 Diagram of heat from radiating surfaces 204 Diathermancy, denned 16 Diffusion, amount of 35 of gases 24 of radiant heat 17 Dimensions of steam, gas, and water pipe, table 399 Direct and indirect heating 60 Drip-pipes 228 Drop tubes for boilers. ... 139 E Elbows and bends 94 Electrical and heat equivalents 301 heaters 306 heating 301 expense 303 units, value of 5 Equalization of pipe-areas, use of table . . - 286 table for air 287 for steam 397 Equalizing valve i63 Exhaust-steam heating 247 , table of dimensions 249 Expansion of pipes 260 Expansion-joints 106 -tank 158 -traps * 166 Explosions, boiler 172 Explosions of hot- water heaters 1 76 Extended-surface heaters 139 404 INDEX. F PAGE Factory and workshop heating 245 Fans and blowers 289 Field tube 1 39 Fittings, miscellaneous 96 pipe 92 Flange-union, joint 94 Float traps , 165 Flues, dimensions of 52 for forced-blast system 284 , indirect heating, table 233 , ventilation, size of 49 Forced-blast systems of heating 283 Foot-pound, defined 3 Foundation, depth of, for boiler-setting 145 Fuels of the United States, table . . . . : 389 Furnace, form of 270 , heating, formula for dimensions 274 , proportions of 272 Furnaces, directions for operating 118 G Gases and air, flow of 40 , diffusion of 24 Gate-valve 100 Gauge-pressure 153 Gauges, Bourdon 1 54 , U-shaped, water 38 , vacuum 155 Globe valve 99 Governor for pump 255 Grates, kind of 163 Gravity circulating system 178 Green-house heating , 236 H Heat, bodily sensation of jg , conduction of 1 8 , demand for i , flow through metals . 61 , latent 15, 121 \ loss of, from buildings . . 54 , measurement of, in test 71 , mechanical equivalent . . 3 , nature of 2 , radiant 15, 61 INDEX. 405 PACK Heat, radiant, diffusion of ij , transmitted, table of ij , relation to electricity and work 2 removed by convection ij t 53 required for ventilation 58 , specific 14 supplied by radiating surfaces .... 60 , total, emitted from radiating surfaces, diagram 203 transformation 4 transmission, table of 69 , test of 264 -unit '4- Heaters, extended surface 136 , hot- water 135 , care of 171 , explosions of 1 76 , setting of 148 , indirect, setting of 1 18 Heating-boilers, classification of 130 , for soft coal 142 , setting of 147 with magazines 141 Heating, indirect, amount of surface required for 209 -surfaces, indirect, tests of 79 , systems of 20 , with fan 283 H igh-pressure system 178, 254 Hot air and steam, combination of 190 heating 268 formula for 273 Hot-blast heating, radiating surface required 291 system, air heated 293 , heating surface 293 , size of blower 294 Hot-water and steam heating, tests 242^ heaters 135 , care of 171 , explosions of 176 , setting of 148 heating, general table, proportions 237 , rule for pipes 232 , table of data 229 of pipes 231 radiators 112 Howard regulator 3 J 6 Humidity of air 29, 363 Hygrometer, description of 29 406 INDEX. I PAGR Indirect heating, air-flues 232 , dimensions of registers 235 , factors for flues 234 , surface required, table for 84 , table of proportions 238 , tests of surfaces 79 radiators 116 , efficiency of 84 , experiments on 81 Industry, magnitude of i Insulating substance, best known 198 J Johnson system of heat regulation 318 Joint, lead, how formed 87 , rust, how made 88 Joints, flange-union. 94 L Lap-welding, process of 89 Latent heat 15 Lawler regulator 312 Lead joint, how formed 87 Leader-pipe , 276 Lever safety-valve 149 Literature and references 353 Logarithms, how to use 357 of numbers, table of 377 Loss in transmitting steam 260 M Main pipes, exhaust-steam 249 , hot- water heating 231 , steam-heating table 226 , steam and hot-water 237 Manometer 153 Marine boilers 132 Mason reducing valve 260 Maynard (S. T.) greenhouse test 242 Melting-points, table of 12 Mill's experiments on steam-heated surfaces 77 system of piping 181 INDEX. 4O7 N PAGE Nipples, hooks, etc 97 Nitrogen 27 O Oxygen 25 Ozone 25 P Papers devoted to heating 355 Paul system 254 Pettersson's apparatus for determining CO 2 28 Petticoat-pipe 131 Pipe-boilers 138 -connections, hot- water heating systems 193 , steam-heating systems ........ 191 -fittings 92 , radiating surface of 107 , return .... 1 79 , steel 91 Pipe systems, comparisons of 197 , table of dimensions 399 , wrought-iron 89 , thickness and size of 89 Pipes, method of computing area . 222 Piping for indirect heaters 196 , method of, in greenhouses 239 , in hot- water heating , . 185 , systems of 180 Pitch, defined 179 Pilot's tube, description of 38 Plain-surface boilers 136 Plates, ceiling and floor 98 Pop-valve 150 Portable setting for boilers 147 Power's regulator 3*3 Pressure-gauge . 153 , Bourdon 154 Pressure, methods of measuring 153 systems of hot- water heating 159 Properties of air, table of ... 381 of steam, table of 384 Proportions, hot-air heating 275 Protection of main pipe from lose of heat 197 of pipes ^6 1 Pump-governor - - 255 Strength of materials, table 379 408 INDEX. PAGE Pyrometers 1 1 , calorimetric 12 R Radiint heat, defined 60 , diffusion of . . 17 , emissive power, table of , 16 , transmission of 17 Radiating surface, exhaust-steam heating 249 for greenhouses 241 , hot-blast heating. 291 , measurement of 73 of pipe 107 , proportioning of 201 , results of tests. 75 , rules for 215 surfaces, effect of painting 74 Radiation 15 , amount of f 61 , direct , 60 , indirect 60 Radiators, contents of, how determined 74 , direct indirect 1 16 , effect of grouping surfaces 67 , extended surface 79 , flue 112 , heat from 60 , hot-water , 112 , testing 72 , indirect 116 , efficiency of 84 , experiments on 81 , material of 67 , method of testing 69 , proportion of parts of 119 .sectional no , tests 78-83 , valves 101 , vertical-pipe 109 Reducing-valves 258 Reflection and transmission of radiant heat 16 power, table of 16 Refrigerating machines, heating with 299 Registers, area of, hot-air heating 274 , dimensions of 52, 235 for forced-blast system , 200 , table of 280 , table of dimensions 275 INDEX. 409 Regulator for temperature ....... v . ..................................... P ^* Regulators, damper .......... ..................................... I56 Relations of units for measuring pressures ......................... ! ee Relay, term denned ................................................ , 7 Relief- or drip-pipe .................................................. I7 Reliefs ................................. ......................... 22g Return pipes ........................................ , ............... ljg > lable V' ............................................... 227 steam-traps .................................................. j^ Risers .............................................................. r - 9 Rules, approximate, for estimating radiating surface ..................... 215 , hot-water mains ............................................. 232 , steam-mains ............ , ..................................... 224 Rust-joint, how made ........... .. ..................................... 88 S Safety-valve ........................................................ 149 , area of .................................................. 150 Setting of heating-boilers .............................. .............. 147 of hot- water heaters ........................................... 148 of indirect heaters ............................................ 118 Settings, brick, for boilers ............................................. 143 Single-pipe system for hot-water heating. .-. ............................. 188 Siphon, term defined .................................................. 179 -trap ..................................... .................... !64 Specific heat ............................ ............................. 14 Specifications, heating apparatus ....................................... 322 , tubular boiler ........................................... 34 1 Stacks, table for ..................................................... 278 Standard forms, hot water and steam specifications ....................... 323 Steam and water, flow of .............................................. 217 , circulation, comparisons of ........................... 82 Steam-boiler, requisites of .......................................... 121-127 -fitter's tools .................................................... 349 -heating, general table of proportions ... .......................... 237 -loop ............................. . ............................. 257 radiators, cast-iron ............................................ no , vertical-pipe .......................................... 109 tables, explanation of ........................................... 120 -thermometer ................................................... 13 transmission ...... . ........................................... 260 -traps .................................... .................. 164, 180 Steel pipe ..................................................... ...... 91 T Tables, see list on page ................................................ 35 Taft, L. R , tests .................... ........................... ..... 244 4IO INDEX. PAGE Tank, expansion 158 Tees, Y's, pipe-junction, etc 95 Temperature, boiling, table of 22 in various localities of the United States, table 398 , melting-points 12 , measured by color . . 12 produced by given amount of surface 85 regulators 310 , saving due to 320 required i Test of loss in steam-transmission = 265 Thermal conductivity, table of 392 Thermometer, air and mercurial 10 -cup 13 , Fahrenheit and centigrade 7 , maxima and minima 12 , steam 13, 1 56 , use of .... 13 Thermostat.. . t 310 Tools, steam-fitter's 349 Transmission of steam 260 Traps, bucket 165 , counterweighted , 165 , expansion 166 , float 165 , gravitating- return 169 , siphon 164 , steam 164-180 , steam-return 167 Tredgold's experiments, summary of 76 Try-cocks t 152 Tubular boilers 138 , horizontal 130 , specifications for 341 Two-pipe system of steam-heating 184 Types of boilers 128 U Underground pipe systems 261 Unit of heat 4 V Vacuum- gauges 155 Valves, air 102 , angle 100 , check ..... . 102 INDEX. 41 1 PAGE Valves, corner and cross .' 101 , equalizing 168 , gate loo , globe 99 , pop 150 , position of, in pipes 195 , radiator , 101 , safety 149 Velocity of air due to heat 43 of water and steam 219 of water, hot- water heating 220 Ventilation, air required 31 by heat 35 by suction 42 ducts 269 -flues, size of 49 , table of 238 , influence of size of room , 34 inlet for air 44 , mechanical 36 , principles of , 21 , relation to heating 21 space for each person 52 , summary of problems 50 , systems of 298 Vertical boilers 132 W Warming, systems of 20 Water and steam circulation, comparison of 82 , flow of 217 Water-columns 153 -hammer . . . . 180 -surface, steam and water space 126 -tube boilers 133, 138 Watts 5 Welding-lap, process of 89 Willame's system 253 Windows, loss of heat from 54 Wolff's rule for steam- mains 225 Workshop and factory heating 245 Wrought-iron pipe 89 UNIVEESITY -OF CALIFORNIA LIBRARY BERKELEY THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW Books not returned on time are subject to a fine of 50c per volume after the third day overdue, increasing to $1.00 p'er volume after the sixth day. Books not in demand may be renewed if application is made before expiration of loan period. SEP 25 1929 NOV 1G MAR II 1822 50m-7,'16 YC 12839 7m* "** I UNIVERSITY OF CALIFORNIA LIBRARY