HEATING AND VENTILATION % Qraw-MlRock & 7m PUBLISHERS OF BOOKS Coal Age v Electric Railway Journal Electrical World v Engineering News-Record American Machinist v Ingenieria Internacional Engineering 8 Mining Journal ^ Power Chemical & Metallurgical Engineering Electrical Merchandising .HEATING AND VENTILATION BY THE LATE JOHN ft. ALLEN Gre. DIRECTOR OP RESEARCH LABORATORY OP AMERICAN SOCIETY OF HEATING AND VENTILATING ENGINEERS; FORMERLY DEAN OF ENGINEERING AND ARCHITECTURE, UNIVERSITY OP MINNESOTA; PAST PRESIDENT AMERICAN SOCIETY OP HEATING AND VENTI- LATING ENGINEERS; MEMBER AMERICAN SOCIETY OP MECHANICAL ENGINEERS AND J. H. WALKER SUPERINTENDENT OF CENTRAL HEATING, THE DETROIT EDISON COMPANY; MEMBER AMERICAN SOCIETY OF HEATING AND VENTILATING ENGINEERS; PRESIDENT NATIONAL DISTRICT HEATING ASSOCIATION 1922 SECOND EDITION McGRAW-HILL BOOK COMPANY, INC. NEW YORK: 370 SEVENTH AVENUE LONDON: 6 & 8 BOUVERIE ST., E. C, 4 1922 COPYRIGHT, 1918, 1922, BY THE McGRAW-HiLL BOOK COMPANY, INC. THE MAPLE FKESS T O H K PREFACE TO SECOND EDITION A second edition of this book has become desirable because of the advances in the art which have been made during the last few years, such as the establishment of ventilation standards and the work of the Research Laboratory of the American Society of Heating and Ventilating Engineers. Much of the new material is taken directly from Professor Allen's writings while Director of the Laboratory during the last year of his life. Several of the chapters have been entirely rewritten and a more logical arrangement has been adopted. The entire book has been thoroughly revised and slightly enlarged. The aim has been to increase in every possible way its value as a college text book, in which field it has come to be widely used. Acknowledgment is made to Prof. H. C. Anderson of the University of Michigan for his valuable advice and criticism and to the many others who have contributed various material, credit for which is given throughout the book. September, 1921. J. H. W. PREFACE TO FIRST EDITION This book is offered as a text-book upon the subject of heating and ventilation for use in the engineering and architectural schools. It is also believed that the development of working methods of design and the including of the various tables and charts make the book of some value as a handbook for the practicing engineer and architect. Calculus has been employed to some extent in the develop- ment of certain expressions, this having been deemed desirable for the sake of completeness. For architectural students and others not equipped with higher mathematics, such parts may be omitted, however, without destroying the structure of the book. Problems have been included at the end of many of the chapters in order to illustrate the principles involved, but it is felt that they can be profitably supplemented by the actual designing by the student of complete heating and ventilating systems for representative buildings of various types. Acknowledgment is made to the American Blower Company and the Buffalo Forge Company for the use of various charts and tables. Information as to the typographical errors which are doubtless present in this initial edition will be gratefully received. J. R. A. March, 1918. J. H. W. CONTENTS PAGE PREFACE TO SECOND EDITION ................... v PREFACE TO FIRST EDITION ................... vii CHAPTER I HEAT* Measurement of Heat ...................... 1 Measurement of Temperature .................. 2 Unit of Heat .......................... 4 CHAPTER II V HEAT LOSSES FROM BUILDINGS Radiation ........................... 9 Conduction .......................... 10 Convection .......................... 11 Loss of Heat from Buildings ................... 12 Heat Lost Due to Infiltration ................... 19 Calculation of Heat Loss ..................... 21 CHAPTER III DIFFERENT METHODS OF HEATING Grates ............................. 25 Stoves ............................. 26 Hot-air Furnaces ........................ 27 Direct Steam Heating ...................... 28 Direct Heating by Hot Water .................. 28 Indirect Heating ........................ 30 Economy of Heating Systems .................. 32 CHAPTER IV HOT-AIR FURNACE HEATING / Furnaces ............................ 35 Cold-air Pipe .......................... 39 Hot-air Pipes . ......................... 40 Pipeless Furnaces ........................ 46 ix x CONTENTS CHAPTER V PROPERTIES OF STEAM PAGE The Formation of Steam. 49 Properties of Steam 50 Steam Tables 52 Mechanical Mixtures 54 CHAPTER VI RADIATORS Direct Cast-iron Radiators 61 Pressed Metal Radiators 65 Heat Transmission from Radiators 67 Location of Radiators 78 Proportioning Radiation 81 Indirect Radiators 83 CHAPTER VII / STEAM BOILERS < Fuel 92 Combustion 95 Smoke 95 Types of Boilers 98 The Downdraft Boiler . . V 101 Boiler Rating - . . . 105 Draft and Chimney Construction 110 CHAPTER VIII STEAM HEATING SYSTEMS v Single-pipe Systems 113 Two-pipe Systems . 115 Overhead System 117 Vapor System 119 Vacuum Return Line System . . . ... . 125 CHAPTER IX PIPE, FITTINGS, VALVES, AND ACCESSORIES Pipe 127 Fittings 129 Valves 132 Pipe Covering 134 Air-valves 137 Traps 138 Reducing Valves 141 CONTENTS xi CHAPTER X STEAM PIPING PAGE Principles Involved in Piping Design 145 Expansion 145 Drainage 146 Mains and Branches 147 Risers 149 Pipe Hangers 150 Radiator Connections 154 Flow of Steam in Pipes 157 Selection of Pipe Sizes 160 CHAPTER XI HOT-WATER SYSTEMS Theory of Flow in a Gravity System 168 Types of Gravity Systems 172 Method of Computing Pipe Sizes : 177 Forced Circulation 184 Pumpage, Friction, and Temperature Drop 185 Calculation of Pipe Sizes 185 CHAPTER XII TEMPERATURE CONTROL Manual Control 189 Automatic Control Applied to Boiler 190 Automatic Control of Radiators 192 Advantages of Automatic Control 194 CHAPTER XIII AIR AND ITS PROPERTIES Composition of Air 196 Water Vapor 197 Measurement of Humidity 200 , Psychrometric Chart 202 CHAPTER XIV VENTILATION Ventilation Standards 206 Amount of Air Required 209 Methods of Measuring Air Supply 209 Temperature and Humidity 211 Air Movement . . 213 xii CONTENTS PAGE Odors 214 Dust and Bacteria 215 Ventilation Tests 215 Synthetic Air Chart. . y < ...... 216 CHAPTER XV FAN SYSTEMS FOR VARIOUS TYPES OF BUILDINGS Office Building Systems 226 School Building Systems. 226 Factory Heating 231 Unit Ventilators 234 CHAPTER XVI DESIGN OF FAN SYSTEMS Calculation of Air Quantities 237 Flow of Air in Ducts . 239 Proportioning Duct Systems 247 Theory of the Centrifugal Fan 253 Fan Performance 256 Selection of a Fan 258 Heaters 263 Transmission of Heat from Fan Coils 266 CHAPTER XVII AIR-WASHERS AND AIR CONDITIONING The Air-washer 274 Air Conditioning 276 Humidity Control 278 Cooling and De-humidification 281 CHAPTER XVIII CENTRAL HEATING Location of Power Plant 283 Systems of Distribution 285 Methods of Carrying Pipes 287 Expansion Fittings 289 Tunnels 291 Commercial District Heating 293 INDEX. . 327 HEATING AND VENTILATION CHAPTER I HEAT 1. Heat. Heat has long been known to be a form of energy. Modern theories as to the exact nature of heat conceive it to be a motion or agitation of the molecules, or extremely small particles, of which every substance is composed. The intensity of the heat in a body is believed to be dependent upon the violence of this molecular disturbance. Every substance on the earth contains some heat and to say that a body is "cold," means simply that it contains a relatively small amount of molecular motion. Heat and many other forms of energy are mutually convertible. For example, heat energy is converted into electrical energy in a generating plant and electric energy is re-converted into heat energy in an electric stove. Heat energy is converted into mechanical energy in a steam locomotive and some of this mechanical energy is re-converted into heat energy by the friction of the locomotive brakes. 2. Measurement of Heat. In measuring heat there are two quantities to be considered : the intensity of heat and the amount of heat. A small piece of white-hot metal may not contain as great a quantity of heat as a pail of warm water, but the intensity of the heat in the former is much greater. The intensity -m* heat is denoted by the word temperature. The temperature Ir^ of a body is most easily measured by noting its effect upon some other substance. One measure of the iiitensity of heat in a body is its ability to transmit heat to a body of loweTTelnpefature. Heat will flow from a body "of higher temperature to one of lower temperature but will never flow, of itself, from one body into another of higher temperature. When two bodies of different temperatures are placed in contact a heat exchange takes place until the two bodies are at the same temperature and thermal equilibrium is reached. We may, therefore, state that two bodies are at the "H&ATING AND VENTILATION same temperature when there is no tendency for heat to flow from the one to the other. 3. Measurement of Temperature. The measurement of tem- perature is usually based upon some arbitrary scale which is standardized by comparison with some well-established ^phys- ical, fixed points. In mechanical engineering most measure- ments of temperature are made on the Fahrenheit scale. On this scale the freezing point of water is taken at 32 and the boiling point at sea level barometer at 212, the tube of the thermometer between these points being divided into 180 equal parts or degrees. There is, however, an increasing use of the Centigrade scale among engineers. In the Centigrade scale the distance between the freezing point and the boiling point is divided into 100 equal parts. The freezing point on the scale is marked and the boiling point is marked 100. If the temperature Fahrenheit is denoted by tj and the tempera- ture Centigrade by t c , then the conversion from one scale to the other may be made by the following equations: t c = ~ (t f - 32) The most common instrument for measuring temperature is the mercury thermometer. Mercury like most other substances undergoes an increase in volume when heated, and is particularly useful because the amount of its expansion for equal increments in temperature is nearly constant over a wide range in tempera- ture. The thermometer is a glass tube of very fine bore with a bulb blown on one end and filled with mercury, as shown in Fig. 1. The air is expelled from the tube by boiling the mercury and the tube is sealed. The space above the mercury then con- tains mercury vapor at a very low pressure. The 32 9 and the 212 points of the Fahrenheit scale are located on the stem by immersing the bulb in a freezing mixture and in boiling water. The distance between these points is then divided into 180 equal parts. To do accurate work with the thermometer is much more difficult than is generally supposed. The mercury of the ordi- nary glass thermometer does not expand in exactly equal amounts for equal increments of temperature and the bore of the ther- mometer is never absolutely uniform throughout the length of the tube. All of these irregularities produce errors. When measur- HEAT 3 ing the temperature of liquids the depth to which the thermom- eter is immersed affects the reading and the thermometer should be calibrated at the depth at which it is to be used. It is really its own temperature that the thermometer ^ indicates and the accuracy with which the temperature of a substance is measured depends upon the complete- ness with which its temperature is reached by the thermometer. The thermometer must therefore be brought into intimate contact with the substance to be measured. In measuring the temperature of fluids in pipes, a brass or steel well is inserted into the pipe and filled with some liquid such as oil or mercury, in which the thermometer is immersed. If the thermometer is used to measure the temperature of the air in the room in which there are objects of a higher temperature than the thermometer, its bulb must be protected from the radiant heat of these hot bodies; otherwise the ther- mometer will not read the temperature of the air sur- rounding it but will be affected by the radiant heat absorbed by it. When accurate temperature measure- ments are desired a careful study should be made of the thermometer and its errors and all inaccuracies should be allowed for by careful calibration. The mercury thermometer can be used up to tem- peratures of 500F. and for temperatures as low as 40. Where lower temperatures must be measured it is customary to use thermometers filled with alcohol, and for temperatures higher than 500F. some form of pyrometer must be used. The most common form of pyrometer is the thermo- couple, whose operation depends on the fact that when two different metals are brought into contact and the point of junctipn heated above the remainder of their length, an electromotive force is produced. If the un- heated ends of the two elements are connected by a Fl0 ' 1> metallic conductor this electromotive force will produce a flow of current through the circuit. The electromotive force will vary according to the temperature of the junction and is measured by means of a sensitive galvanometer which may be calibrated to read directly in 1 } degrees of temperature. Thermocouples may be made of a pair of rare metals such as platinum and a platinum- HEATING AND VENTILATION rhodium alloy, or of base metals, such as a nickelsteel alloy and copper. High temperatures may be determined approximately by color. For each temperature there is a corresponding color and an approximation to the actual temperature can be made by an observation of the color of the heated substance. Table I gives the temperature colors. TABLE I. TEMPERATURE COLORS Color Temp. C. Temp. F. Faint red 525 977 Dark red 700 1 292 Faint cherry 800 1 472 Cherry. . . . 900 1 652 Bright cherry 1 000 1 832 Dark orange . ... 1 100 2012 Bright orange 1 200 2 192 White heat 1,300 2372 Bright white 1 400 2552 Dazzling white 1,500-1,600 2,732-2,912 4. Absolute Temperature. In any theoretical consideration of heat it is necessary to have some absolute scale of temperature. The point at which the molecules of a substance would have no motion is considered to be the absolute zero point. According to Marks and Davis this point is theoretically at 491.64 below the freezing point of water on the Fahrenheit scale, or 459.64 below the Fahrenheit zero. On the Centigrade scale the absolute zero is at 273.1. To convert any temperature on the Fahren- heit or Centigrade scale to absolute temperature the following formulae are used: T f = t f + 459.6 T c = t c + 273.1 in which the absolute temperatures on the Fahrenheit and Cen- tigrade scales are represented by Tf and T c . No one has as yet been able to produce a temperature as low as the absolute zero. The lowest temperatures ever attained have been produced in the heat laboratory at Leyden, Holland, at which there has been produced a temperature of 49 below the Fahrenheit freezing point. ?* * 5. Unit of Heat. Heat must be measured by the effect which it produces upon some substance. The unit of heat used HEAT 5 in mechanical engineering is the heat required to raise the tem- perature of a pound of water one degree Fahrenheit. This is called the British thermal unit and is denoted by B.t.u. As this quantity is not exactly the same at all temperatures it is necessary to specify further a definite temperature at which the unit is to be established. The practice of different authorities varies in this regard, but the mean B.t.u. established by Marks and Davis is becoming generally used. This is defined as the one hundred and eightieth part of the heat necessary to raise the temperature of one pound of water from 32 to 212F. 6. Specific Heat. Specific heat may be defined as the heat necessary to raise the temperature of a unit weight of a sub- stance through one degree. It represents the specific thermal capacity of a body. In English units the specific heat is the quantity of heat necessary to raise a pound of a substance one degree Fahrenheit, expressed in British thermal units. Since the British thermal unit is the quantity of heat necessary to raise aTpounbro^water one degree Fahrenheit, we may say that the specific heat represents thejratio between the heat necessary to raise a unit weight of a body one degree and the heat neces- sary to raise the same weight of water one degree. When a substance is heated at constant pressure its volume increases against that pressure and external work is done as a consequence. The exterrjal work may be computed by multiply- ing the pressure by the change in volume. When heated at constant volume no external work is. done as no movement is made against an external resistance. In any substance, such as a gas, which has a large coefficient of thermal expansion, the specific heat of constant volume will have a different value from the specific heat of constant pressure, the latter being the greater. The difference between the two specific heats in any particular gas must be equal to the heat equivalent of the exter- nal work done when a unit weight of the .gas is raised one degree at a constant pressure.-- The quantity of heat added to or removed from a body is equal to in which W = weight of the body* in pounds. C = specific heat of the material. ti = lower temperature Fahrenheit. t = higher temperature Fahrenheit. HEATING AND VENTILATION TABLE II. SPECIFIC HEATS Substance Specific heat Liguidt: Water 1.0000 Alcohol 0.6220 Turpentine 0.4720 Petroleum 0.4340 Olive oil . 3090 Metals: Cast iron 0. 1298 Wrought iron 0. 1138 Softsteel 0.1165 Copper 0.0951 Brass.... 0.0939 Tin 0.0569 Lead 0.0314 Aluminum 0.2185 Zinc 0.0953 Mercury 0.0333 Minerals: Coal 0.2777 Marble 0.2159 Chalk 0.2149 Stones generally 0.2100 Limestone . 2170 Building Materials: Brickwork 0. 1950 Masonry . 2000 Plaster 0.2000 Pine wood 0.4670 Oak wood 0.5700 Birch 0.4800 Glass.. . 0.1977 SPECIFIC HEAT OF GASES Constant Constant Substance pressure volume Air 0.2415 0.1729 Oxygen 0.2175 0.1550 Hydrogen 3.4090 2.4122 Nitrogen 0.2438 0. 1727 Steam 0.5000 0.3500 Carbonic acid, CO 2 0.2479 0.1758 Ammonia . 5080 . 2990 Example. It is required to raise the temperature of a cast-iron"radiator ^ weighing 300 pounds from 70 to 212. The temperature through which the iron would be raised would be 212 minus 70 or 142. From Table HEAT II we see that to raise 1 pound of cast iron JL would require 0.1298 "units. To raise 1 pound 142 would require 142 times 0.1298 or 18.43 heat units, and to raise 300 pounds 1 would require^ 300 times this amount or 5529 B.t.u., the heat required to heat the radiator. "^ Example. A church 80 by 100 feet inside and 30 feet high, to the eaves has stone walls 2^ feet thick for 10 feet above the ground and for the remaining distance 2 feet thick. The roof has a slope of 45 degrees and is made of 2 by 8-inch oak rafters, 16 inches on centers, covered with 1 inch of oak boarding, tar paper and slate Y inch thick. Main floor composed of two 1-inch thicknesses of boards laid on 2 by 12-inch joists, 16-inch centers. Ceiling is of plaster % inch thick. The church has 20 windows, 6 feet wide and 15 feet high, 12 windows 4 feet wide and 6 feet high, and 2 doors, 8 feet wide and 12 feet high. Allowing an addition of 15 per cent, for furnishings, find the heat required to raise the temperature of the structure from to 50. Weight of stonework, stone weighing 160 pounds per cubic foot: * 370 X 10 X 2K = 9,250 cubic feet 368 X 20 X 2 = 14,720 cubic feet 84^2X40X2X2 = 6,720 cubic feet *** 30,690 cubic feet Deduction for windows and doors: 20 X 6 X 15 X 2 = 3,600 12 X 4 X 6 X 2 = 576 2 X 8 X 12 X 2H = 480 4,656 4,656 26,034 X 160 = 4,165,440 pounds. Weight of woodwork, weight per cubic foot taken as 40 pounds : o vx o ^f~ X 56.2 X 75 X 2 X 40 = 37,500 pounds of rafters. -L4' 56.2 X 104 X 2 X Y\i X 40 = 39,000 pounds of roof boards. 80 X 100 X % 2 X 40 . = 53,300 pounds of floor boards. * X 80 X 75 X 40 = 40,000 pounds of floor joists. Total weight of woodwork = 169,800 pounds. Slate, weight per cubic foot taken as 170 pounds: 56.5 X 104 X 2 X Y% X 170 = 41,600 pounds. Plaster, weight per cubic foot taken as 90 pounds : (360X30+80X40 + 100X56.5 X2)MXK2X90 = 142,300 pounds. Air, weight per cubic foot taken as 0.08 pounds: (80 X 30 X 100 + M X 80 X 40 X 100) 0.08 = 32,000 pounds. Heat required : HEATING AND VENTILATION 4,165,440 X 50 X 0.2100 = 43,737,000 B.t.u. 169,800 X 50 X 0.5700 = 4,839,000 B.t.u. 41,600 X 50 X 0.2159 = 449,000 B.t.u. 142,300 X 50 X 0.2000 = 1,423,000 B.t.u. 32,000 X 50 X 0.2415 = 386,000 B.t.u. 50,834,000 B.t.u. Adding 15 per cent, for furnishings 7,625,000 B.t.u. Total to raise to 50 58,459,000 B.t.u. The heating of the building structure may be very important in determining the size of the heating plant when a building is intermittently heated. 7. First Law of Thermodynamics. When mechanical energy is produced from heat a definite quantity of heat is used up for every unit of work done and, conversely, when heat is pro- duced by the expenditure of mechanical energy the same definite quantity of heat is produced for every unit of work spent. This first law of thermodynamics might also be called the law of the Conservation of Energy. The relation between work and heat has recently been determined with great accuracy and the results show that one British thermal unit is equivalent to 778 foot-pounds. This factor is called the mechanical equivalent of heat or Joule's equivalent. Problems 1. Convert 50F. to degrees Centigrade. Convert 150C. to degrees Fahrenheit. Convert 219F. to degrees Centigrade. Convert 225F. to absolute temperature on the Fahrenheit scale. 2. A copper ball weighing 10 pounds is heated in a fire and immediately placed in a vessel of water having an equivalent water weight of 10 pounds. The water is raised in temperature from 50 to 100. What was the temperature of the ball when it was removed from the fire? 3. A bar of cast iron weighing 5 pounds and at a temperature of 250F. and a bar of lead weighing 10 pounds and at a temperature of 300 are put into a tub of water which is at 120. The water is heated to 123. Neglect- ing the effect of the tub itself and the heat lost during the process, how much water is in the tub? 4. A piece of limestone weighing 10 pounds and at a temperature of 150F. and a piece of wrought iron weighing 20 pounds and at a temperature of 70 are put into a tank and a sufficient quantity of water at 88 is added to bring the temperature of the water, stone, and iron to 90. How much water is required, neglecting the heat lost during the process? CHAPTER II HEAT LOSSES FROM BUILDINGS 8. Sources of Heat Loss. When the interior of any building is maintained at a temperature higher than that of the outside air there is a continual loss of heat from the building. The functions of a heating system are, first, to raise the temperature of the interior of the building to the point desired and, second, to maintain this temperature by supplying sufficient heat to replace that lost from the building. The determination of the amount of heat lost from the building under maximum condi- tions is the first step in designing the heating system. Before taking up the methods of calculating heat loss it is necessary to consider first the manner in which heat may be given up by any body. There are three ways in which heat can be transmitted from a solid body: byjajiiatioj^ by conduction, and by convection. Each of these will be discussed separately. 9. Radiation. Heat is transmitted, or radiated, through space by what is supposed to be a motion or vibration of the ether which is believed to pervade all space. Radiant heat follows the same physical laws as radiant light, being radiated, like light, in straight lines. We may have heat "shadows" just as we have light 'shadows and as with light the intensity of radiant heat is inversely proportional to the square of the distance from the source. Some substances are transparent to heat rays and others absorb them. Gases are almost perfectly transparent to radiant heat while such substances as wood, hair felt, and mineral wool are almost perfectly opaque to it. Radiant heat does not affect the medium through which it passes. When heat is radiated fErough the atmosphere for example, the atmosphere is not perceptibly warmed by it. The rate at which heat is radiated increases as the absolute tem- perature of its source is_.,raised. It has been determined experi- mentally that the amount of heat radiated from a body varies as the 4th power of the absolute temperature, or 1.1 10 HEATING AND VENTILATION in which Q r is the quantity of heat radiated, T the absolute tem- perature of the body, and K a constant depending upon the nature of the substance composing it. Radiant heat is given off by all bodies, the net amount of heat radiated by a body being the difference between the total amount radiated from it and the amount radiated from other bodies which is absorbed by it. If one body of absolute temperature T^ is surrounded by another < body of the same material at temperature T 2 , then the heat which 1 will pass between them is Q r = This is known as Stefan's law. - TV) FIG. 2. 10. Conduction. As has already been stated, heat will pass from any body to a body at a lower temperature which is brought into contact with it. It is further true that if one part of a body is at a higher temperature than an- other part there will be a flow of heat through the body. The transmission of heat in this manner is known as conduction, A familiar ex- ample of this phenomenon is the flow of heat along an iron bar, one end of which is heated in a fire. The ability of different materials to conduct heat differs considerably. Metals are the best conductors of heat, while such materials as wood, felt, asbestos, etc., are very poor conductors. The specific conductivity of a material is the amount of heat which would be conducted through a plate of the material of unit area and unit thickness with a unit difference in temperature between the two sides of the plate. The conduction of heat which takes place through the walls of a building may be best understood from Fig. 2 in which PP is a plate, one side of which is enclosed by the walls Tf W. Let the temperature of the outside of the plate be 59 and let 60 be the temperature of the inside of the plate,, of the inside walls TFTF, and of the inside air. Then all the heat that is lost^y the room must be lost by conduction through the plate PP.r The amount HEAT LOSSES FROM BUILDINGS 11 of heat lost will be dependent upon the material of the plate PP, upon the difference in temperature of its two sides, and upon its thickness. Let e = the specific conductivity of the material in B.t.u. per__ hour, pej^qjiarejoot of area, pejjn^^injy^^ne^pej: ti = tne temperature of the warmer side of the plate, in degrees F. t z = the temperature of the cooler side of the plate, in degrees F. A = the area of surface in square feet. I = the thickness of plate in inches. Q the total quantity of heat transmitted in B.t.u. per hour. Then Q = Ae the conductivity of the heat path is then -y- and the resistance of the heat path is its reciprocal . . Example. Suppose a boiler plate, 5 feet square, and % inch thick, to have a temperature of 70 on one side and 200 on the other side. Assume the specific conductivity of the metal to be 240 B.t.u. per hour per square foot of area per inch in thickness per degree difference in temperature. The total heat transmitted per hour is then Q ,JXMO(200-70) _ ij560)0oo fi t ^ per ^^^ 11. Convection. When a body is in contact with a fluid at a lower temperature, the envelope of fluid surrounding it becomes heated by conduction of heat from the body. As this fluid envelope is heated its density decreases and it is forced to rise, giving place to the colder fluid from below. A continuous current is thus created and maintained over the surface of the body.- This process of heat transfer is called convection. It should be noted that the heat actually leaves the hot body by con- duction from its surface to the fluid in contact with it. The essential characteristic of the process of convection is the con- tinuous renewal of the fluid layer at the surface of contact. The loss of heat from a body by convection is independent of the material composing it, but is greatly affected by the form of the body, a cylinder and a sphere, .for example, transmitting different amounts of heat by convection per square foot of sur- 12 HEATING AND VENTILATION face. The velocity of the fluid over the surface also affects the rate of heat transmission. In the case of convection by air the air movement is often produced by some external force, as when the wind blows against a building or when a fan in an indirect heating system forces air over the surface of steam coils. An increase in the velocity produces a more frequent renewal of the layer of air in contact with the body and augments the rate of heat transmission. Heat may also be transmitted from a fluid to a solid by con- vection as well as from a solid to a fluid. An example of this process is the transfer of heat from the warm air of a room to the cold outside walls. The air, upon giving up its heat, increases in density and falls, giving place to warmer air from above and producing a continuous downward current. 12. Loss of Heat from Buildings. The heat which is lost /from a building may be divided into two parts : (a) the heat which / passes by conduction through the building structure; and (6) the heat which is lost due to air passing into and out of the building. The latter may consist merely of the natural in- filtration through the building structure, or may be partly due to air supplied for ventilation. The heat which flows by conduction through the walls, floors, roof, etc. is transmitted from the outer surfaces which are exposed to air partly by radiation and partly by convection. From the surfaces buried in the ground the basement walls and floors it is dissipated by conduction into the earth. The calculation of the heat lost by convection is very difficult. Methods of arriving at the loss by convection from bodies of various shapes were developed by Peclet and are given in Box's " Treatise on Heat," but these methods cannot, as a rule, be applied to the loss of heat from buildings. They assume, for example, that the air surround- ing the object is, except for the influence of the heat from the body itself, in a perfectly quiescent state. In the case of buildings this is far from true, for the air surrounding a building is always circulated more or less rapidly by the winds. Because of the necessity of taking into account variable factors of this nature, the heat loss from a building could not be stated in any simple expression and the practical rules that are used for such calcula- tions are therefore largely empirical. The common method of treating the loss of heat through building walls as given in th following pages was translated by J. H. Kinealy from the work of Rietschel and published in the Metal Worker. HEAT LOSSES FROM BUILDINGS 13 In the simplest form of building the walls consist of one solid piece of a single material and the transmission of heat takes place from the air of the room to the inner surface of the wall by convection, through the wall by conduction, and from the outer surface of the wall by convection and by radiation. Such a wall is shown in Fig. 3. In order that heat may flow through the wall it is necessary that the room temperature t\ be higher than the temperature of the inside of the wall ti, that the temperature of the outside of the wall to' be lower than t\\ and that the tem- perature of the outside air to be lower than t f . The amount of heat which will be transferred from the air of the room to a unit Fig .3 x^xSsxvi/v' *$ Fig.4 /o *>. Fig.5 area of the wall will be a\ (ti t\) in which a\ is a constant. The amount of heat flowing through a unit area of the wall will be - (ti'-to') in which e\ is a constant which represents the specific conductivity of the material composing the wall. Simi- larly the heat transfer from a unit area of the outside wall surface is do (to' to). When the rate of heat flow through the wall has reached a stable condition the quantity of heat flowing through successive points of the walls thickness must be the same and we have therefore, oi(Q And for Fig. 5: i+j+i+i+j+i /> For thin glass or thin metal walls - is a very small quantity and 6 may often be neglected. The values of a and e must be known before k can be deter- mined. The value of the convection factor, a, is determined by Grashof by the following equation: a = c + d+ 10,000 in which c is a factor depending on the condition of the air, whether at rest or in motion. Rietschel gives the following values for c: TABLE III. VALUES OF c c Air at rest, air in rooms . 82 Air with slow motion, air in rooms in contact with windows 1 . 03 Air with quick motion, air outside of a building 1 . 23 The factor d depends upon the material composing the wall and on the con- dition of the surface. The values for d may be taken as follows: TABLE III. VALUES OF d Substance d Substance d Brickwork 0.740 Sheet iron 0.570 Mortar and similar materials . 740 Sheet iron polished . 092 Wood 0.740 Brass polished 0.053 Glass 0.600 Copper 0.033 Cast iron. . . v 0.650 Tin 0.045 Paper .' 0.780 Zinc 0-049 T is the difference between the temperature of the air and that of the surface of the wall. For walls composed of materials of low conductivity or very thick walls it may be taken as zero. In approximate calculations it is usually taken as zero. 16 HEATING AND VENTILATION The following values of T are given by Rietschel: TABLE IV. VALUES OF T Brickwork 5 inches thick .......... ..... 14 . 4 Brickwork 10 inches thick ........................... 12 . 6 Brickwork 15 inches thick .......... .... 10 . 8 Brickwork 20 inches thick ........... ---- 9.0 Brickwork 25 inches thick ........................... 7.2 Brickwork 30 inches thick ........................... 5.4 Brickwork 40 inches thick. ; ......... 1.8 For single windows ..................... ... 36 . For double windows ............................. 18 . For wooden doors .................. 1.8 Table V gives values of e. These values, as given by different authorities, vary considerably. TABLE V. VALUES OF e e Brickwork ....................................... 5. 60 Mortar, plaster ................................... 5 . 60 Rubble masonry .................................. 14 . 00 Limestone ........................................ 15 . 00 Marble, fine-grained ............................... 28 . 00 Marble, coarse-grained .......... '. ........ - ......... 22 . 00 Oak across the grain .............................. 1-71 Pine, with the grain ............................. 1 . 40 Pine, across the grain .............................. . 76 Sandstone ........................................ 10.00 Glass ........................................... 6.60 Paper ........................................... 0.27 For example, assume a brick wall as shown in Fig. 6. There are four air contact surfaces and two walls through which conduc- tion takes place, then: k is the same as in equation (2) . Rietschel assumes 01, a 2 , and a 3 equal and he uses the same value of T as for a solid of thickness equal to the brickwork with- out the air space. ai = a2 = 03 = 0.82 + 0.74 + (40X0.82 + 30X0.74)10 = ^ lU,uul) o. = 1.23 + 0.74 + MX-23 + 30X0.74)10 l(j,uuU HEAT LOSSES FROM BUILDINGS Since both walls are of brickwork xi 4.75 17 5.6 = 0.85 8.25 " 5.6 = 1.47 Substituting in equation (2) f _ __ _ 0.62 + 0.85 + 0.62 + 0.62 + 1.47 + 0.49 Making this same calculation, assuming T = 0, gives k = 0.210 014 13. Experimental Determination of Coefficients. The method outlined in the preceding paragraph is useful in computing the heat loss for unusual types of walls. The value of the coefficient k has been determined for most of the ordinary types of wall construction by experiment. The method most commonly used in making such determina- tions is to employ a cubical box, having five faces made of a material of low conductivity, the sixth side being constructed of the material to be tested. The temperature inside of the box is maintained constant and above that of the surrounding air, by supplying a measured amount of heat, usually electrically, to the interior. 'With the proper corrections made for the loss through the other five sides, the heat transfer through the mate- rial under test can be accurately determined. In Table VI are given the values of k for several common types of building construction. 18 HEATING AND VENTILATION TABLE VI. COEFFICIENTS OF HEAT TRANSMISSION FOR VARIOUS MATERIALS k B.t.u. per square foot, per hour per degree difference in Walls: temperature Brick wall 4 inches thick, plain . 52 Brick wall 8^ inches thick, plain . 37 Brick wall 4 inches thick, furred and plastered . 28 Brick wall 8% inches thick, furred and plastered 0.23 Concrete wall 4 inches thick, furred and plastered 0.31 Concrete wall 6 inches thick, furred and plastered . 30 Clapboard wall with paper, sheathing, studding, and lath and plaster 0.23 Ceilings and Roofs: Lath and plaster, no floor above . 32 Lath and plaster, single floor above . 26 Tin or copper roof on 1-inch boards . 45 Shingle roof . 33 Windows, Skylights and Doors: Ordinary windows 1 . 09 Double windows . 45 Single skylight 1 . 50 Pine door % inch thick 0. 47 Oak door % inch thick 0.63 More complete tables are given in the Appendix. 14. Temperatures Assumed in Heating. In determining the heat transmission through the walls of a building, it is necessary to assume certain temperatures for the outside air and for the inside air. In the latitude of New York City it is customary to assume for the outside temperature. In the latitude of Washington it is customary to assume 20 above, and in the latitude of St. Paul 20 below. The assumed outside tempera- ture is ordinarily taken as the temperature which might exist for a period of at least 24 hours. Lower temperatures than these may exist for short periods but the heat stored in the building structure is usually sufficient to counteract this effect. The inside temperature to be assumed depends upon the type of building. The temperature maintained in many classes of buildings is largely a matter of custom. In residences this tem- perature is higher in the United States than in any other country in the world, with the possible exception of Germany. In England and many other countries a temperature of from 55 to 60 is a perfectly proper temperature for a room; while in this country ,the temperature ordinarily ranges from 65 to 70. HEAT LOSSES FROM BUILDINGS 19 The following are the inside temperatures usually assumed: TABLE VII. INSIDE TEMPERATURES Degrees Residences ..................................... 70 Lecture rooms and auditoriums ................... 65 Factories for light work .......................... 65 Factories for heavy work ........................ 60 Offices and schools ....................... / ...... 68 to 70 Stores ......................................... 65 Prisons ........................................ 65 Bathrooms ....................... " .............. 72 Gymnasiums ................................... 55 to 60 Hot houses ..................................... 78 Steam baths ................................... . 110 Warm air baths ................................. 120 The following assumptions are ordinarily made for unheated spaces: Degrees Cellars and closed rooms ......................... 32 Vestibules frequently opened to the outside ........ 32 Attics under a roof with sheathing paper and metal or slate covering .............................. 25 Attics under a roof with paper sheathing and tile covering ..................................... 32 Attics under a roof with composition' covering ...... 40 15. Heat Lost Due to Infiltration. No building is ever air- tight; there is a large amount of leakage through the walls, the windows, and other openings. The amount of this infiltration depends largely upon how well the building 'has been constructed and upon the type of construction. For this reason no definite rule can be given for the determination of infiltration, and the allowance made for this loss must be a matter of judgment and experience. Usually the volume of infiltration is expressed as a certain ratio of the cubic contents, and experiments go to show that the air of the average room is changed about once an hour because of infiltration. In rooms where doors are frequently opened to the outside, or where the windows are loosely fitted "and the construction is faulty, the change of air may be as fre- quent as twice an hour. Strictly speaking the amount of infiltration does not de- pend upon the volume of the room but upon the nature and 20 HEATING AND VENTILATION size of the windows. Experiments 1 have shown that the amount of air leakage varies considerably for different types of windows. Some forms of metal sash allow a large amount of leakage to take place. Weather strips are very effective in reducing air leakage. As the principal source of leakage is around the window sash the amount of leakage may be considered as varying directly with the perimeter of the windows. It is customary to assume a leakage of from 1.0 to 1.5 cubic feet of air per minute per foot of sash perimeter for windows equipped with weather strips. For windows without weather strips a considerably higher factor should be used. In large buildings the amount of infiltration should be computed in this manner, especially in the case of a tall or exposed building. In very tall buildings there is often a pronounced chimney effect in the building itself, especially if there are open elevator shafts or stair wells. The heat required to supply these infiltration losses must be sufficient to warm the air from the temperature of the outside air to that of the room/ If the infiltration is figured on the basis of a certain number of air changes per hour the loss from this source may be expressed as follows: Let H a = heat required per hour to supply loss due to infiltration. C = cubic contents of the room. n = number of changes per hour. t r = temperature of the room. t Q = temperature of the outside air. _ C(t r - t Q )n Ha= 55.2 The factor 55.2 = 9415 X 074Q = number of cubic feet of air which 1 B.t.u. will raise 1 where 0.2415 is the specific heat of air at constant pressure and 0.0749 is the weight of a cubic foot of air at 70. 16. Heat Required for Ventilation. The heat required for ventilation can easily be computed when the amount of air supplied per hour is known. ^ee "Window Leakage" by S. F. VOOBHEES and H. C. MEYER, Trans. A. S. H. & V. E., 1916. HEAT LOSSES FROM BUILDINGS 21 Let H = heat required for ventilation, B.t.u. per hour. Q = quantity of air supplied in cubic feet per minute. Then, 60 X Q(t r - t ] ~~52~~ Besides supplying heat to replace that lost through the walls and by infiltration of air, a heating system must supply the heat which is stored in the structure and its contents and in the inside air. In heavy buildings the effect of the heat stored in the walls may have a material effect upon the amount of heat which must be supplied to warm the building initially. If the building is intermittently heated the effect is decidedly appreciable. The best illustration is in the cathedrals of Europe in which no heating systems are used and the heat stored in the walls during the summer serves to keep the building warm throughout the year. The heat which is required initially to warm the inside air and the building structure affects the rapidity with which the build- ing can be heated, to the desired temperature. It is often desirable to investigate this question in designing a heating system which is to be operated intermittently and to increase the capacity of the heating system, if necessary, so that the build- ing can be warmed within a reasonable time. 17. Calculation of Heat Loss from a Building. In deter- mining the heat loss from a room all surfaces should be considered which have on the outside a. lower temperature than the tem- perature to be maintained in the room. If the room is over a portion of the basement which is unheated or below an unheated attic, the loss through the floor or ceiling should be considered. Similarly, if an adjacent room is liable to be unheated at times, the additional heat loss through the wall should be taken into account. Ordinarily it is assumed that there is no loss through inside walls where the surrounding rooms are heated. The conditions under which the room is to be used should be studied in determining the amount of heat necessary. In certain rooms such as restaurants in the basements of buildings, for ex- ample, where there are no outside windows, the problem is often one of cooling rather than heating. In designing any heating system, careful consideration should be given to the conditions existing such as the use, occupancy, and exposure of each room in the building, and the other sources of heat therein, if any. The first step in computing the heat loss is to determine for 22 HEATING AND VENTILATION every room the gross surface of exposed wall, and the window surface, from which the net wall surface is obtained by sub- traction. The heat loss through the walls can then be computed from the expression, H w = Wk(t r - to) in which H w = heat loss in B.t.u. per hour. W = exposed wall surface in square feet. t r = inside temperature. to = outside temperature. k = coefficient of heat transmission. A similar expression must be worked out for the walls, ceilings and floors next to unheated spaces. The value of t r in such cases may be taken from Table VII. The heat loss through the glass surface is computed from the expression, H g = GK(t r - to) in which G is the area of the entire window opening in square feet and k is the coefficient of heat transmission for glass. The heat lost' due to air infiltration is next determined by one of the methods given on pages 19 and 20. The total heat loss from the room in B.t.u. per hour is then H = HW ~T~ H g ~\~ Ha 18. Correction Factors. The heat losses determined by this method are for rooms not exposed to prevailing winter winds. It is common practice to add certain percentages to the com- puted heat losses on the exposed sides of the building. Also, when a building is intermittently heated, an allowance should be made to insure that the building can be heated within a reason- able time. The correction factors commonly used are given in Table VIII. TABLE VIII. FACTORS FOR EXPOSURE AND INTERMITTENT HEATING Percentage to For exposure in direction of prevailing winter winds / (usually north and northwest) ..................... 15 Same, severe conditions .............................. 20 For west exposure ................................... 10 For building heated during the day only and closed at night ......................................... 10 For buildings heated during the day and open at night .... 1,0-15 For buildings heated intermittently'. .................. 10-15 HEAT LOSSES FROM BUILDINGS 23 19. Heat Given Out by Persons and Processes. In consider- ing the amount of heat necessary to heat a room attention must be given to the amount of heat that will be given off by the occupants of the room or by the processes which go on in it. But these sources of heat cannot always be depended upon, as it may sometimes be necessary to heat a room when there are no people in it or when the processes ordinarily going on are not in opera- tion. On the other hand, it may be necessary to cool the room instead of heat it. Often in large auditoriums the greatest source of hea\ in a room are the people in it. The following table show^the heat given off by the human body under various/ 'conditions in a room at a temperature of 70. TABLE IX Adults at rest Adults at work Adults at violent exercise . . . Children Infants B.t.u. per hour 440 450-600* . 600-1200 240 63 Example 1. Assume a room, as shown in Fig. 7. Let the temperature be maintained in the room at 70, the temperature of the outside air be 0. Let the walls be of brick, 18 inches thick, plastered on the inside, the Note: Windows 2-6'x 6-o' FIG. 7. windows be 2> by 6 feet, the ceiling of the room be 10 feet high. Let the room be on the second floor of the building, the rooms above and below heated. The window openings are 2 X 2>^ X 6 = 30 square feet. The 24 HEATING AND VENTILATION gross wall surface is 20 X 10 = 200 square feet. The net wall surface is 200 - 30 = 170 square feet. The cubic contents is 20 X 14 X 10 = 2800 square feet. Then the heat lost from the room would be determined as follows. H w = 170 X 0.24 (70 - 0) = 2856 H g = 30 X 1.09 (70 - 0) = 2289 . . ^M X 1.0 - 3551 H = 8696 B.t.u. per hour. Problems 1. Compute the value of k for a wall consisting of 2 inch pine boards. Assume T 3. 2. Compute the heat loss per hour, per square foot of area, of a wall consisting of two thicknesses of 1 inch pine boards with an air space of 2 inches between. Room temperature 60, outside temperature 10. Assume T = 1.8. 3. Compute the heat loss for the wall in Prob. 2 assuming a single wall, 2 inches thick. What percentage of the heat loss is saved by the air space when the two 1 inch thicknesses are used. 4. Compute the heat loss per hour, per square foot of area, of a wall consisting of 1 inch oak boards, an air space of 1 inch, and 4 inches of brickwork. 5. In the room of Fig. 7 (Example 1) find the percentage of the heat loss which would be saved during a heating season of 8 months if double windows were used. Assume average temperature of the room and the surrounding rooms to be 65 and the average outside temperature to be 40. 6. Taking the same room as in Example 1, heated to a temperature of 60, with the surrounding rooms at 70 and the air outside at 10, how much heat must be supplied to the room per hour? Inside walls are of lath and plaster. Ceiling is 6f lath and plaster, with single floor above, and the room below has its ceiling plastered. 7. Take the same room as Example 1, except that the room is covered by a flat tin roof. The air space between the ceiling of the room and roof should be assumed to 'be at a temperature of 32. CHAPTER III DIFFERENT METHODS OF HEATING 20. Direct and Indirect Heating Systems. We have seen that to maintain the rooms of a building at a comfortable temperature, it is necessary to supply continuously a definite amount of heat to each room, equal to the amount lost from the room. It is the function of the heating system, taken as a whole, to extract the heat from the fuel (by combustion) and deliver to the rooms where it is needed. In many kinds of buildings, particularly where large numbers of people congregate or where fumes or odors are given off by industrial processes, making artificial ventilation necessary, the warming of the supply of air required for ventilation is, part of the task of the heating system. So closely are the problems of heating and ventilating related that it is imperative that they be. considered together. The heat supplied to the various rooms may be delivered there as radiant heat only, $s is practically the cas$ with a grate fire or by convection onhr as in the cas*e of a hot air furnace, or by a combination of the two methods, as in the case of a steam radiator. In general, a heating system which heats principally or wholly by convection is more satisfactory than one which delivers its heat entirely by radiation; the room heated by convection is usually much more uniformly and comfortably heated. Heating systems may be roughly divided into two classes, depending on the location of the sources of heat. When the source of heat, such as a radiator, stove or grate is located in the room to be heated, this is known as direct heating. In indirect systems the source of heat is located outside of the room and the heat is conveyed to the room by a current of air. Under the head of indirect systems come hot air furnaces and the various types of fan systems. Before studying the design of the various systems of heating, it is desirable to understand in general their advantages and disadvantages. 21. Grates. The most primitive form of heating apparatuses the grate. .In the grate the air which passes through the fire, and is heated by the fire, all passes up the chimney and only the heat given off by radiation to the walls and objects in the room and 25 26 HEATING AND VENTILATION the small amount given off by the chimney walls is effective in heating the room. In grates of better construction this condition is somewhat improved by surrounding the grate with firebrick so arranged that it becomes highly heated and radiates heat to the room. But the fact that all the air heated by the grate passes up the chimney makes the grate a very uneconomical form of heat- ing. In the best forms of open grates only about 20 per cent, of the heat of the fuel is effective in heating the room. This form of heating, however, is highly recommended by many and is a very popular method of heating throughout' England and Scotland. The feeling of a grate-heated room is quite different from that of a room heated by other means. All of the heat is given off by radiation and the air is at a considerably lower temperature than the objects in the room, owing to the fact that the radiated heat does not heat the air through which it passes. The air of the room being at a much lower teniperature, its capacity for moisture is not increased as much as it would be were the air heated to a higher temperature. The result is that the air contains proportionately more moisture than is the case with most other forms of heating, which, no doubt, is an advantage. Also, the undeniably cheerful aspect of an open fire is in its favor. On the other hand, it is impossible to heat the room uniformly and a person is either hot or cold, depending on his distance from the fire. The labor, dust, and dirt attendant upon the main- tenance of grate fires is another disadvantage. Heating by means of grates is practiced only in the more moderate climates. Grates are useful in houses heated by other means, as the open chimney forms a most efficient foul-air flue and greatly improves the ventilation. 22. Stoves. The stove is a marked improvement over the grate, particularly from the standpoint of economy. The modern base-burner stove is one of the most efficient forms of heating apparatus, making use of from 70 to 80 per cent, of the heat in the fuel. In heating a room, the hot surface of the stove, being at a higher temperature than that of the surrounding objects in the room, radiates heat directly to those objects. In addition, heat is given to the air of the room by contact with the hot surface of the stove. In selecting a stove to heat a given room care should be taken to choose one of ample size so that only in the coldest weather would it be necessary to keep the drafts wide open in DIFFERENT METHODS OF HEATING 27 order to heat the room. At the present time the stove as a general source of heat is being rapidly discarded because of the attendance required, the space occupied, the unsightly appearance of the stove, and the fact that a separate stove is required in every room for satisfactory results. 23. Hot-air Furnaces. The hot-air furnace is the natural outgrowth of the stove. In this system one large furnace is placed in the basement of the building, and the air is taken from the outside or recirculated from the house, passed over the surfaces of the furnace, and carried up through the flues to the rooms to be heated. In the simplest type, the so-called pipeless furnace, the heated air is delivered only to the room directly over the furnace, and passes into the other rooms through the open doorways by natural circulation only. For any but the smallest houses, however, a f urnape having separate pipes to the individual rooms is "preferable. The principal fl.Hva,T)tfl,p;ps of the hot-air furnace are that it provides a cheap and rather efficient method of furnishing both heat and ventilation, requires little attendance, and does not deteriorate rapidly when properly taken care of. The greatest disadvantage of this system is fhat tho^circulation of the heated air depends entirely upon natural draf^that is, it depencTslipoiT the difference in weight between the air inside the flues and the air outside the flues. This difference is extremely small, so that the force prpxju^ing circulation in the flue is not large. When a very strong wind blows against one side of the house, air from the outside enters through the window cracks and other small opening forming a slight pressure in the rooms and preventing the > arm a i r f ro m entering, thus making it difficult to heat the rr jOms on that side of the house. If the system is carefully d 3S i g ned, however, this difficulty can be overcome in a measu re> Another serious objection to the hot-air furnace is that it j'g se ldom dust-tight, and dust, ashes, and gases from the fire are Carried into the rooms. In general, the hot-air furnace may bff. considered as a very good type of heating plant for small Residences, but because of the_smalL force available for produlr cm g circulation its use is limited to buildings where the lengtlj O f the horizontal flues does not exceed 15 feet. In ! the case of the hot-air furnace, the heat is carried from the furnace by the air which passes around the furnace and then ente/ rs theTobms through the flues. This air circulates in the roo % and heats the contents of the room and supplies the heat 28 HEATING AND VENTILATION which is lost through the walls. The economy of the hot-air system will vary, depending on the relative proportions of the air taken from the outside and from the rooms. If the air enter- ing the furnace is taken from the house and not from the outside, the economy of the hot-air furnace will be about the same as that of the steam system. If, however, cold air be taken from the outside, an additional amount of heat will be used in heating this cold air up to the temperature of the rooms. Control of the heat supply, with a hot-air furnace, is readily obtained by adjusting the dampers at the registers in each room and by manipulating the furnace drafts. 24. Direct Steam Heating. From the standpoint of ventila- tion, direct steam heating, without other means for ventilation, is not as desirable as the hot-air furnace. Mechanically, how- ever, it has many advantages. The radiator is easily adapted to almost any location in the room and its operation is not affected by the winds. The circulation of the system is positive and a distant room can be heated as easily as those close to the boiler. In the older forms of direct steam-heating systems control of the heat supply is difficult because the radiators, being large enough to heat the room on the coldest days, give off too much heat for average conditions. The construction of the older forms of this type of system is sihnivhat the radiator must give off its full output of heat if it is in use ?-t all. To maintain an even temperature in average weather, fu^uent opening and closing of the radiator valves is necessary. In r ecent years this disadvantage has been overcome in the so-cJled "vapor" systems which make use of steam at pressures but Sightly higher than atmosphere, and in some cases below atmos 1 ^here. In these systems the steam supply to each radiator can be Controlled at the inlet valve so that only the quantity actually reVl u i re d is admitted to the radiator, and much better regulation js there- fore possible providing the proper attention is given to tl ie con- trol of the heat supply by the occupants of the buildingA Automatic control of the heat supply also eliminates th is tr

content of flue eases. ner cent. . 1,110.00 309 00 0.07 10.26 1,284.00 691.00 318 40 0.07G 8.10 ia Heat Analysis of a Hot-air Furnace," by JOHN R. ALLEN, Trans. A/S. H. & V. E., 1916. 48 HEATING AND VENTILATION Test No. 7 11 21 Kind of fuel Mixed stove and ctrir Gas coke 22 Total weight of fuel fired 23 Total weight of ash and refuse anthracite 255.00 37 00 330.50 16 50 24 Proximate analysis of fuel, per cent. Moisture 78 6 00 Volatile 4 75 3 60 Fixed carbon 88 61 86 10 Ash 12 86 4 30 26 Heat value per pound as fired 12,856 00 13026 00 28 Total water evaporated from water pan, pounds 62 00 123 00 Heat balance, per cent. 43 Heat input in fuel 100 00 100 00 44 Heat absorbed by air 61 60 63 00 45 Heat given to water 2 05 3 10 46 Heat given to air, gross 47 Heat lost up the stack 48 Heat lost in unburned fuel 63.65 11.65 1 60 66.10 13.50 70 49 Heat lost from furnace by radiation 50 Unaccounted-for losses 51 Efficiency net (Item 46) per cent 11.00 12.10 63 65 8.83 10.87 66 10 52 Efficiency gross (Items 46 + 49 + ^ of 50) per cent 80 70 80 36 It will be noted that the heat given up to the air passing through the furnace is from 63 to 66 per cent, of the heat input in the fuel. In most installations, however, the heat radiated from the furnace is largely utilized, making the " gross" efficiency about 80 per cent. Problem 1. Compute the required size of the leaders, risers, and wall registers for the following rooms. Room No. 1 2 3 4 Heat loss from room 16,000 10,800 8,700 5,000 Floor First Second Third Second A CHAPTER V PROPERTIES OF STEAM 45. The Formation of Steam. The different types of heating systems discussed in Chapter III owe most of their characteristic features to the element used to convey the heat from the boiler or furnace to the rooms. Perhaps the most important is the steam heating system, in which steam serves as the conveying medium. Before taking up the design of steam heating systems, it is necessary to study the nature and properties of steam. Many substances can exist in more than one state Under the proper conditions of temperature and pressure. Water exists as ice at low temperatures and as steam at higher temperatures, the temperature depending upon the pressure. If we apply heat to a vessel partly filled with cold water, the temperature of the water will rise until a certain temperature is reached, at which small particles of water are changed into steam. The steam bubbles rise through the mass of water and escape from the surface. The water is then said to boil. The temperature at which the water boils depends upon the pressure in the vessel. If the pressure is raised as by partly closing the outlet, the temperature of the water will rise to the point corresponding to the existing pressure. Steam when still in contact with the water from which it is produced remains at the temperature corresponding to its pres- sure and under this condition the steam is said to be saturated. If it is removed from contact with the water and further heated, its temperature will rise and the steam will then be superheated. 46. Superheated Steam. Superheated steam is steam at a temperature higher than the temperature of the boiling point corresponding to the pressure. If water were to be intimately mixed with superheated steam some of the heat in the steam would be used in evaporating the water and the temperature of the steam would be lowered. If sufficient water were added the superheat would be entirely used up in evaporating the water and the steam would then be saturated. Superheated steam can 4 49 50 HEATING AND VENTILATION have any temperature higher than that of the boiling point. When raised to any temperature considerably above the boiling point it follows very closely the laws of a perfect gas and may be treated as a perfect gas. 47. Saturated Steam. When steam is at the temperature of the boiling point corresponding to its pressure it is said to be saturated. If this saturated steam contains no suspended mois- ture it is said to be dry saturated steam, or in other words, dry saturated steam is steam at the temperature of the boiling point and containing no water in suspension. If heat is added to dry saturated steam, not in the presence of water, it will become superheated. If heat is taken away from dry saturated steam it will become wet steam. The steam produced in most heating boilers is saturated steam and nearly always contains moisture, so that the substance used as a heating medium is really a mixture of steam and water. Steam at a pressure equal to or slightly above atmosphere is commonly known as vapor. It should be remembered, however, that the difference between vapor and steam is merely one of pressure, and that vapor is in no sense a separate state of the substance. Dry saturated steam is not a perfect gas and the relations of its pressure, volume, and tem- perature do not follow any simple law but have been determined by experiment. The properties of dry saturated steam were originally determined by Regnault between 60 and 70 years ago, and so carefully was his work done that no errors in his results were apparent until within very recent years, when the great difficulty of obtaining steam which is exactly dry and saturated became appreciated, and new experiments by various scientists proved that Regnault 's results were slightly high at some pres- sures and slightly low at others. 48. Properties of Steam. The heat used in the formation of one pound of superheated steam at any pressure from water at 32 may be divided into three parts: (a) the heat of the liquid, which is the heat required to raise the temperature of the water from 32 to the temperature of the boiling point; (6) the latent heat of vaporization, which is the amount required. to change one pound of water at the temperature of the boiling point to dry saturated steam at the same temperature; and (c) the "heat of superheat" or, more simply, the superheat, which is the heat added to one pound of steam to raise it from the boiling point temperature to the final temperature. PROPERTIES OF STEAM 51 49. Heat of the Liquid. The heat of the liquid may be deter- mined for any boiling point temperature by the expression h = c(t - 32) in which h = the heat of the liquid. t = the boiling point temperature. c = the specific heat of water. For approximate results c may be taken as = 1. The change in the volume of the water during the increase in temperature is extremely small, and the amount of external work done may be neglected and all of the heat of the liquid may be considered as going to increase the heat energy of the water. The heat of the liquid, together with the other properties of saturated steam, is given in Table XI for various steam pressures. This table is condensed from Marks and Davis' complete tables which are generally accepted as being accurate. 50. Latent Heat. The latent heat of steam has been defined as the heat required to convert one pound of water at the tempera- ture of the boiling point into dry saturated steam at the same temperature. Experiments show that the latent heat, usually designated by L, diminishes as the pressure increases. When water is changed into steam, the volume is greatly increased, so that a considerable portion of the latent heat is used in doing external work. The remainder may be considered as being utilized in changing the physical state of the water. Let P be the pressure at which the steam is generated, V the vol- ume of one pound of steam, and v the volume of one pound of water; then the external work done is equal to P(V - ) At 212 the external work done in producing one pound of steam is equivalent to 73 B.t.u. or about one-thirteenth of the latent heat. Experiments show that the latent heat of steam diminishes about 0.695 heat units for each degree that the temperature of the boiling point is increased. If t be the temperature of the boiling point, then, approximately, L = 1072.6 - 0.695(* - 32) When steam condenses the same amount of heat is given up as was required to produce it. In the steam heating system the 52 HEATING AND VENTILATION latent heat is added to the water in the boiler, converting it into steam. The steam is conducted to the radiators in which it condenses. In condensing, it gives up its latent heat which goes to warm the room. 51. Total Heat of Steam. The total heat of dry saturated steam is the heat required to change one pound of water at 32 into dry saturated steam. This quantity will be designated by H } and H = h +L The experimental results given in the table for the value of the total heat may be approximated very closely by means of the formula H = 1072.6 + 0.305( - 32) It is more accurate, however, to take the values of the total heat from the tables than it is to compute them from the formula. The total heat in one pound of steam under any condition of mois- ture or superheat is the amount of heat required to change it from water at 32 to its existing condition. When steam contains entrained water the percentage by weight of dry steam in the mixture is termed the quality of the steam. If we let q represent the quality of the steam, then the latent heat in one pound of wet steam equals qL 100 and the total heat in one pound of wet steam equals 52. Steam Tables. The following table shows the properties of dry saturated steam. More complete tables will be found in Marks and Davis' " Steam Tables" and in the engineering handbooks. Column 1 gives the absolute pressure of the steam in pounds per square inch. Absolute pressure is the pressure shown on the steam gage plus the atmospheric or barometric pressure. For sea-level barometer the atmospheric pressure is 14.7 pounds per square inch. Column 2 gives the corresponding temperature of the steam in degrees Fahrenheit. Column 3 gives the heat of the liquid, and column 4 gives the latent heat. Column 5 gives the total heat of the steam and is the sum of the quantities in columns 3 and 4. Column 6 is the volume of one PROPERTIES OF STEAM 53 pound of dry saturated steam at the different pressures. Column 7 is the weight of one cubic foot of steam at the different pressures. TABLE XI. PROPERTIES OF SATURATED STEAM 1 1 Absolute pressure, Ib. per sq. in. 2 Temp., deg. F. 3 Heat of the liquid 4 Latent heat of evap. 5 Total heat of the steam 6 Sp. vol., cu. ft. per Ib. 7 Density, Ib. per cu. ft. P t h L H V 1/D 10 193.22 161.1 982.0 1,143.1 38.38 0.02606 11 197.75 165.7 979.2 1,144.9 35.10 0.02849 12 201.96 169.9 976.6 1,146.5 32.36 0.03090 13 205 . 87 173.8 974.2 1,148.0 30.03 0.03330 14 209 . 55 177.5 971.9 1,149.4 28.02 0.03569 15 213.00 181.0 969.7 1,150.7 26.27 0.03806 16 216.30 184.4 967.6 1,152.0 24.79 0.04042 17 219.40 187.5 965.6 1,153.1 23.38 0.04279 18 222.40 190.5 963.7 1,154.2 22.16 0.04512 19 225 . 20 193.4 961.8 1,155.2 21.07 0.04746 20 228.00 196.1 960.0 1,156.2 20.08 0.04980 21 230.60 198.8 958.3 1,157.1 19.18 0.05213 22 233.10 201.3 956.7 1,158.0 18.37 0.05445 23 235.50 203.8 955.1 1,158.8 17.62 0.05676 24 237.80 206.1 953.5 1,159.6 16.93 0.05907 25 240.10 208.4 952.0 1,160.4 16.30 0.0614 30 250.30 218.8 945.1 1,163.9 13.74 0.0728 35 259.30 227.9 938.9 1,166.8 11.89 0.0841 40 267.30 236.1 933.3 1,169.4 10.49 0.0953 45 274 . 50 243.4 928.2 1,171.6 9.39 0.1065 50 281.00 250.1 923.5 1,173.6 8.51 0.1175 55 287.10 256.3 919.0 1,175.4 7.78 0.1285 60 292 . 70 262.1 914.9 1,177.0 7.17 0.1394 65 298.00 267.5 911.0 1,178.5 6.65 0.1503 70 302 . 90 272.6 907.2 1,179.8 6.20 0.1612 75 307 . 90 277.4 903 . 7 1,181.1 5.81 0.1721 80 312.00 282.0 900.3 1,182.3 5.47 0.1829 85 316.30 286.3 897.1 1,183.4 5.16 0.1937 90 320 . 30 290.5 893.9 1,184.4 4.89 0.2044 95 324.10 294.5 890.9 1,185.4 4.65 0.2151 100 327.80 _ 298.3 888.0 1,186.3 4.429 . 2258 105 331.40 302.0 885.2 1,187.2 4.230 0.2365 110 334 . 80 305.5 882.5 1,188.0 4.047 0.2472 115 338.10 309.0 879.8 1,188.8 3.880 0.2577 120 341.30 312.3 877.2 1,189.6 3.726 0.2683 125 344.40 315.5 874.7 1,190.3 3.583 0.2791 130 347.40 318.6 872.3 1,191.0 3.452 0.2897 135 350.30 321.7 869.9 1,191.6 3.331 0.3002 MARKS and DAVIS' "Steam Tables and Diagrams." 54 HEATING AND VENTILATION 53. Mechanical Mixtures. Problems involving the resulting temperature and final condition when various substances at different temperatures are mixed mechanically are often met with in heating work. They are best treated by first determining the heat in B.t.u. that would be available for use if the tempera- ture of all of the substances were brought to 32F., and using this heat (positive or negative) to raise (or lower) the total weight of the mixture to its final temperature and condition. Another method of solving such problems is by equating the heat absorbed to the heat rejected and solving for t, the resulting tem- perature. It is often difficult to decide upon which side of the equation a material should be placed. In such a case a trial cal- culation should be made, and the temperature determined by the trial will settle this question. In a mixture of substances which pass through a change of state during the mixing process it is almost necessary to make a trial calculation. Take for example a mixture of steam with other substances. The steam may all be condensed and the resulting water cooled also; the steam may all be condensed only; or the steam may be only partially condensed. The equations in each case would be different. If one pound of dry saturated steam at a temperature ti is con- densed and then the temperature of the condensed steam is low- ered to a temperature t 2) the amount of heat H f given off would be H' = L! + c(i - t*) where LI is the latent heat corresponding to the temperature t\ and c is the specific heat of water. If the steam were condensed only, the heat given off would be H' = L 1 and the temperature of the mixture is the temperature corre- sponding to the pressure. If the steam is only partly condensed let q f equal the per cent, of steam condensed. Then loo and the temperature of the mixture is the temperature corre- sponding to the pressure. The general laws of thermodynamics do not apply in the case of mixtures as the equations become discontinuous. The general expression for heat absorbed in passing from a solid to a gaseous state may be stated as follows: PROPERTIES OF STEAM 55 Let ci, c 2 , c 3 be the specific heats of the material in the solid, liquid, and gaseous states, respectively. Let w be the weight of the material, t the initial temperature, t\ the temperature of the melting point, U the temperature of the boiling point, 3 the final temperature, Hf the heat of liquefaction, and L the heat of vaporization. Then H' = M;[CI(*I -t) + H f + c 2 (t 2 - + L + c 3 fe - * 2 )1 Example.- -Find the final temperature and condition of the mixture after mixing 10 pounds of ice at 20, 20 pounds of water at 50 and 2 pounds of steam at atmospheric pressure. Mixture takes place at the pressure of the steam. The specific heat of ice may be taken as 0.5 and the heat of liquefaction as 144 B.t.u. FIRST METHOD Solution. Heat to raise ice to 32 = 10 X 0.5(32 - 20) =60.0 Heat to melt ice = 10 X 144 = 1440 Total heat necessary to change the ice to water at 32 = 1500 B.t.u. Heat given up by water when temperature is lowered to 32 = 20 X (50 - 32) = 360.0 Heat in steam above 32 (from tables) = 2 X 1150.3 = 2300.6 Total heat given up in lowering water and steam to 32 = 2660.6 B.t.u. Heat available for use = 2660.6 - 1500 = 1160.6 B.t.u. Degrees this heat will raise the mixture 1160 . 6 -=-32 = 36 . 3 .'. Final temperature of mixture = 36.3 + 32 = 68.3F. Ana. 32 pounds water at 68.3F. SECOND METHOD Assume that the steam is all condensed and that the final temperature of the mixture is t. Then the heat necessary to raise the ice to the melting point equals 10 X 0.5(32 - 20) The heat necessary to melt the ice equals 10 X 144; the heat necessary to raise the melted ice to the temperature of the mixture equals W(t 32); the heat necessary to raise the water to the temperature of the mixture equals 20 (t 50); the heat given up by the steam in changing to water at the temperature of the boiling point equals 2 X 970.4, and the heat given up by the condensed steam when its temperature is lowered to the temperature of the mixture equals 2(212 - t). Combining the preceding parts into one equation, we have 10X0.5(32-20) +10X144 + 10(^-32) +20(*-50) =2X970.4+2(212-0 56 HEATING AND VENTILATION 60 + 1440 + 10* - 320 + 20* - 1000 = 1940.8 + 424 - 2* 32* = 2184.8 t = 68.3 Since t is less than the temperature of the boiling point corresponding tc the pressure at which the mixture takes place, all the steam is condensed. Ans. 32 pounds water at 68.3F. Example. Find the resulting temperature and condition after mixing 10 pounds of ice at 20, 20 pounds of water at 50, 40 pounds of air at 82, and 20 pounds of steam at 100 pounds gage pressure and containing 2 per cent, moisture. Mixture takes place at the pressure of the steam. FIRST METHOD Solution. 10 X 0.5(32 - 20) 60 10 X 144 = 1440 1500 B.t.u. = heat to raise ice to water at 32. 20 X (50 - 32) = 360 40 X 0.2415(82 - 32) = 483 20(308.8 + 0.98 X 880.0) = 23,424 24,267 B.t.u. = heat given up by air, water, 1,500 and steam. 22,767 B.t.u. = heat available. 40 X 0.2415(337.9 - 32) = 2,955 B.t.u. = heat to raise air to 337.9. 19,812 B.t.u. = heat available to raise the water. 50 X 308.8 = 15,440 B.t.u. = heat to raise water to 337.9 4,372 B.t.u. = heat available to evaporate water. 4372 g 8 Q Q = 4.97 pounds steam. Ans. 40.00 pounds air \ 45.03 pounds water I at 337.9. 4.97 pounds dry saturated steam J SECOND METHOD Assume the steam to be all condensed and let the temperature of the mixture be t. Equating the heat gained by the ice, water, and air, and the heat lost by the steam, we have 10 X 0.5(32 - 20) + 10 X 144 + 10 (t - 32) + 20(* - 50) + 40 X 0.2415 (t - 32) = 20 X 0.98 X 880.0 + 20(337.9 - 60 + 1440 + lOt - 320 + 20* - 1000 + 9.7* - 792 = 17,248 + 6758 20* PROPERTIES OF STEAM 57 59.5J = 24,618 t = 413.7F. This result is of course absurd, as the temperature of the mixture cannot be higher than the temperature of the boiling point corresponding to the pressure at which the mixture 'takes place. Therefore, our assumption that all the steam is condensed must be wrong, and we know that part of it remains in the form of steam, and hence the temperature of the mixture is equal to the temperature of the boiling point corresponding to the pressure at which the substances are mixed. Then, substituting for t its value, and letting x represent the number of pounds of steam condensed, we have 10 X 0.5(32 - 20) + 10 X 144 + 10(337.9 - 32) + 20(337.9 - 50) + 40 X 0.2415(337.9 - 82) = 880.03= 60 + 1440 + 3059 + 5758 + 2472 = 880.0z 880.0z = 12,789 x = 14.53 pounds condensed. 20 X 0.98 = 19.6 pounds = original weight of dry steam. Ans. 40 pounds air 10 + 20 + (20 - 19.6) + 14.53 = 44.93 pounds water [ at 337.9. 19.6 14.53 = 5.07 pounds dry saturated steam J The difference between the results obtained in these two methods of work- ing this problem is due to the fact that in the first method we took account of the variation in the specific heat of water by using the heat of the liquid, h, from the tables, in place of (t 32) wherever possible, while in the second method we assumed this specific heat to be constant and equal to 1. Example. Find the resulting temperature and condition after mixing 10 pounds of ice at 20, 20 pounds of water at 50, and 30 pounds of steam at 100 pounds pressure and 400 temperature. Mixture takes place at 25 pounds pressure. FIRST METHOD Solution. 10 X 0.5(32 - 20) 60 10 X 144 = 1,440 1,500 B.t.u. = heat to raise ice to water at 32. 20 X (50 - 32) = 360 *30 X 0.53(400 - 337.9) = 987 30 X 1188.8 = 35,664 37,013 B.t.u. = heat given up by water and steam. 1,500 35,513 B.t.u. = heat available. 60 X 235.6 = 14,136 B.t.u. = heat to raise water to 266.8. 21,377 B.t.u. = heat available to evaporate water. *0.53 = specific heat of superheated steam. 58 HEATING AND VENTILATION . 21 377 QOQ a = 22.89 pounds steam. Ans. 37.11 pounds water } ^QQ gOF 22.89 pounds dry saturated steam / SECOND METHOD Assume the steam to be all condensed and let the temperature of the mixture be t. Then 10 X 0.5(32 - 20) + 10 X 144 + lQ(t - 32) + 20(t - 50) = 30 X 0.53 (400 - 337.9) + 30 X 880.0 + 30(337.9 - t) 60 + 1440 + 10* - 320 + 20t - 1000 = 987 +26,400 + 10,137 - 30t 60 = 37,344 t = 622.4 This result is, of course, impossible and we see at once that only part of the steam is condensed, and that the temperature of the mixture must be that of the boiling point corresponding to the pressure at which the ' mixture takes place. This problem differs from the previous ones in that the pressure of the mixture is different from the original steam pressure, and we must proceed in a slightly different manner. Assume for the moment that the steam has all been condensed and that we have 60 pounds of water at 622. 4F. Then assume that the temperature of the water is dropped to the temperature of the boiling point (266.8) corresponding to the pressure (25 pounds) at which the mixture is made. Each pound will give up, approximately (622.4 266.8) B.t.u. This heat can then be used to re-evaporate part of the water. Therefore, since the latent heat corresponding to 25 pounds is 933.6, we have 60(622.4 - 266.8) 60 X 355.6 21,330 933.6 -933:6 = 933^ = 22 ' 85 pounds Ans. 37.15 pounds water 22.85 pounds dry saturated steam Problems 1. Required the temperature after mixing 3 pounds of water at 100F., 10 pounds of alcohol at 40F., and 20 pounds of mercury at 60F. 2. Required the temperature and condition after mixing 5 pounds of ice at 10F. with 12 pounds of water at 60F. 1 3. Required the temperature and condition after mixing 10 pounds of ice at 15F. with 1 pound of water at 212F, 4. Required the temperature and condition of the mixture after mixing 5 pounds of steam at 212F. with 20 pounds of water at 60F. 5. One pound of ice 2 at 32 is mixed with 10 pounds of water at 50 and 1 Specific heat of ice equals 0.5. 2 Latent heat of fusion of ice = 144 B.t.u. PROPERTIES OF STEAM 59 20 pounds of steam at 212. What is the temperature and condition of the resulting mixture? 6. Ten pounds of steam at 212 are mixed with 50 pounds of water at 60 and 2 pounds of ice at 32. What will be the resulting temperature and condition of the mixture? 7. Ten pounds of steam at atmospheric pressure, 5 pounds of water at 50 and 10 pounds of ice at 32 are mixed together, (a) What will be the resulting temperature of the mixture? (b) What will the condition of the mixture be? (c) If the steam is not all condensed, determine what per cent, of the steam will be condensed. 8. Five pounds of steam at atmospheric pressure, 10 pounds of water at 60, and 2 pounds of ice at 20 are mixed at atmospheric pressure. What will be the resulting temperature? 9. Ten pounds of ice at 10, 20 pounds of water at 60 and 5 pounds of steam at atmospheric pressure are mixed at atmospheric pressure. Find the resulting temperature and condition of the mixture. 10. Twenty pounds of steam at atmospheric pressure, 10 pounds of water at 60 and 50 pounds of air at 100 are mixed together at the pressure of the steam, (a) What will be the resulting temperature? (b) If the steam is not all condensed, determine what per cent, of the steam will be condensed. 11. A mixture is made of 10 pounds of steam at atmospheric pressure, 5 pounds of ice at 20, 10 pounds of water at 50, 30 pounds of air at 60. (a) What will be the temperature of the resulting mixture? (b) What will be the percentages by weight of air, steam, and water in the mixture? 12. What would be the resulting temperature and condition of a mixture of 10 pounds of water at 40, 20 pounds of water at 60, and 8 pounds of steam at 5 pounds pressure? Mixture takes place at 5 pounds pressure. 13. Ten pounds of steam at 5 pounds pressure, 1 pound of ice at 32, and 20 pounds of water at 60 are mixed at 5 pounds pressure. What will be the temperature and condition of the resulting mixture? 14. Five pounds of ice at 5, 10 pounds of water at 50, 20 pounds of air at 80, and 5 pounds of steam at 20 pounds pressure are mixed at the pres- sure of the steam. Find the resulting temperature and condition of the mixture. 15. Required the temperature and condition of the mixture after mixing 10 pounds of steam at a pressure of 30 pounds absolute and a temperature of 250.3F., 2 pounds of ice at 10F., and 20 pounds of water at 40F. Mix- ture takes place at the pressure of the steam. 16. Fifty pounds of air at 100, 10 pounds of steam at atmospheric pres- sure, and 10 pounds of water at 60 are mixed at atmospheric pressure. What is the temperature of the mixture and how much steam is condensed? 17. Required the final temperature and condition after mixing at the pressure of the air 100 pounds of air at a temperature of 500 and a pressure of 100 pounds absolute, and 2 pounds of steam at 100 pounds absolute having a quality of 98 per cent. 18. Five pounds of steam at 5 pounds gage pressure are mixed at atmos- pheric pressure with 10 pounds of water at 60. What is the temperature and condition of the resulting mixture? 19. Thirty pounds of water at 60, 10 pounds of steam at 115 pounds 60 HEATING AND VENTILATION r absolute and a temperature of 400F., and 10 pounds of ice at 20 are mixed at atmospheric pressure. What will the resulting temperature be? What is the condition of the mixture? 20. Ten pounds of ice at 20F., 18 pounds of water at 80, and 10 pounds steam at 75 pounds pressure and 90 per cent, quality, are mixed at atmos- pheric pressure. What is the resulting temperature and condition of the mixture ? 21. Two pounds of steam at 150 pounds absolute and a temperature of 400, 5 pounds of ice at 22, and 10 pounds of water at 60 are mixed at atmospheric pressure. Find the final temperature and condition of mixture. 22. Required the final temperature and condition after mixing at atmos- pheric pressure 3 pounds of ice at 22 and 3 pounds of steam at 100 pounds pressure and containing 2 per cent, moisture. 23. Find the resulting temperature and condition of a mixture of 10 pounds of steam at 150 pounds absolute and a temperature of 400F., 10 pounds of water at 60F., and 50 pounds of air at 112F. Mixture takes place at atmospheric pressure. 24. Five pounds of ice at 0, 20 pounds of water at 75, and 15 pounds of steam at 50 pounds absolute and 95 per cent, quality are mixed at 20 pounds absolute. What is the resulting temperature and condition of the mixture? 26. How many pounds of water will 10 pounds of dry steam heat from 50 to 150 if the steam pressure is 100 pounds gage? 26. If 10 pounds of steam at 100 pounds gage raised 93 pounds of water from 50 to 140, what per cent, of moisture is in the steam, radiation being zero? 27. A pound of steam and water occupies 3 cubic feet at 110 pounds absolute pressure. What is the quality of the steam? CHAPTER VI RADIATORS 54. Classification. In a steam or hot-water heating system the conveying medium absorbs heat at the boiler and then flows to the radiators whose function is to deliver the heat to the air, walls, etc. of the room. There are several forms of radiation, the proper one to be used in any particular case depending upon the nature and use of the building. The selection of radiators of the proper size for each room in the building is very important. If the radiators are too small it will be impossible in the coldest weather to warm the building to the required temperature within a reasonable time, if at all. On the other hand, the installation of radiators of too large a size adds unnecessarily to the cost of the heating system, and tends to cause the rooms to be overheated during a large part of the time. In order to compute intelligently the amount of radiating surface required, it is necessary to study the various forms of radiation and the factors affecting the rate of heat transmission from each. Radiators may be divided into three classes : (a) direct radia- tors, (6) indirect radiators, and (c) semi-indirect radiators. Direct radiators; as explained in Chapter III, are located in the rooms to be heated, while indirect radiators are located elsewhere and a current of air conveys the heat from them to the rooms. Semi-indirect radiators are a combination of the other two forms, the radiators being installed in the rooms but delivering a large proportion of their heat output by means of a current of air which passes through them. 55. Direct Cast-iron Radiators. Direct radiators are made of cast iron, pressed iron, and wrought iron or steel pipe, the cast-iron radiator being by far the most common. It is com- posed of several sections cast separately and assembled, the number of sections varying according to the amount of surface required. The sections are made in several different widths and heights so that for a radiator of a given surface, a wide range of shapes and sizes is available. The wider sections are divided through most of their length by vertical slots into from two to six segments or " columns." The standard heights vary from 61 62 HEATING AND VENTILATION 15 to 45 inches but the 38-inch height is the one most often used. In Fig. 20 are shown several forms of cast-iron radiators. Radia- i ni Single Column Radiator Two Column Radiator Three Column Radiator Four Column Radiator Window Type FIG. 20. tors are finished in several designs to harmonize with room decorations. RADIATORS 63 In general appearance the form of radiator used for steam is quite similar to that used for water. The two designs are funda- mentally different, however, in that the sections of the steam radiator are joined together at the bottom only, while those in a hot-water radiator are connected at both top and bottom. Hot- water radiation may be used for steam but steam radiation could not be satisfactorily used for hot water because air would become trapped in the top of each of the sections, preventing the water from filling them. The sections are joined by means of nipples. One method is to use a smooth tapered "push nipple," fitting into tapered holes in the adjacent sections. Draw-bolts extending the full length of FIG. 21. Methods of assembling cast-iron radiators. the radiator are used to force the joints to a tight fit. Another method is to use nipples threaded with right and left threads. These nipples are cast with internal lugs and are turned up by means of a special wrench. The two methods of assembling are shown in Fig. 21. Cast-iron radiators are usually given a hydraulic pressure test at the factory of about 120 pounds per square inch. They are therefore suitable for working pressures approaching this figure but are seldom subjected to any such pressure except in the case of hot-water systems in tall buildings where the hydrostatic head is high. The weight of cast-iron radiators averages about 7 pounds per square foot of surface and the internal volume is about 64 HEATING AND VENTILATION 30 cubic inches per square foot of surface. This internal volume is largely fixed by the requirements of manufacture, the only stipulation from an engineering standpoint being that the pas- sages must not be so small as to restrict the flow of the water or steam. Cast-iron radiation is also furnished in the form of "wall radiators" as illustrated in Fig. 22. This type of radiation is so FIG. 22. Wall radiator. proportioned that it takes up very little lateral space and is intended to be hung from brackets. It is well adapted for use in factory buildings. The rated external surface of radiators of various widths and heights is given in Table XII in square feet of surface per section. TABLE XII. HEATING SURFACE PER SECTION CAST-IRON RADIATION Height, inches One- column Two- column Three- column Four- column Six-column or "window" pattern 45 5 6 10 38 3 4 5 8 32 w 3M 43^ 6^ 26 2 2% m 5 23 1% 2^ . . '22 . . . 2M 3 4 20 1H 2 5 18 . . . 2^ 3 . . . 16 . . . . . . m 15 IK . . . . . . 14 . . . . . . 13 3 RADIATORS 65 WALL RADIATORS Size of section, Heating surface, inches (approx.) square feet 14 by 16 5 14 by 22 7 14 by 29 9 It should be noted that the height of a radiator is taken as the total height above the floor for radiators having legs of standard height. The rated surface given in the table does not corre- spond exactly with the actual surface, but the difference may be neglected as the heat transmission from radiators is usually given in terms of rated surface. 56. Radiator Tappings. The end sections of cast-iron radia- tors are usually tapped for a 2-inch pipe thread and furnished with bushings having openings whose size depends on the size of the radiator. The sizes of the reduced openings for radiators intended for use with different systems of piping are as follows : TABLE XIII. RADIATOR TAPPINGS Single-pipe Work Size of radiator, Pipe size of tapping, square feet inches Up to 24 1 24 to 60 IK 60 to 100 IK Above 100 2 Two-pipe work Supply Return Up to 48 1 % 48 to 96 IK 1 Above 96 IK IK Water radiators Supply Return Up to 40 1 1 40 to 72 IK IK Above 72 1>'2 IK For vapor systems supply, % inch, return, K inch. Air valve tapping, K inch on all radiators. 57. Pressed-metal Radiators. In recent years radiators made of pressed metal have been introduced and are now some- times used. Figure 23 illustrates the appearance of one design of this form of radiator, and Fig. 24 is a cross-section. The sections are made of two sheets of metal pressed to shape and welded at the edges. In other designs the joint is a lapped seam. A 66 HEATING AND VENTILATION special alloy or soft steel selected for its non-corroding qualities is used. The radiator is assembled by welding the sections together or by joining them with lapped seams. Pressed-metal radiators are made in a variety of sizes corresponding to those of cast-iron radiation. The sections are very narrow and occupy much less space than do cast-iron radiators of equal surface. , Welded FIG. 23. Pressed metal radiator. FIG. 24. Section of pressed metal radiator. The weight per square foot of surface is also much less than that of cast-iron radiation, averaging about 2 pounds. The cost is about the same as that of ordinary cast-iron radiation. The radiating surface of pressed-metal sections of various heights and widths is given in Table XIV. Because of its light weight this form of radiation is especially suitable for hanging on wall brackets. TABLE XIV. PRESSED-METAL RADIATION, SQUARE FEET OF SURFACE PER SECTION Height of radiator, inches Width of section, inches *H x 45 6 38 3 5. 32 23^ 4/^ 26 2 3% 22 1% 3 18 \y% 2M 14 l ... RADIATORS 67 58. Pipe Radiation. In factories and other industrial build- ings radiators built of pipe are often used and are a very satis- factory form of radiation. These pipe coils usually consist of a pair of cast-iron headers connected by four or more pipes of either 1 inch or 1^4 inches diameter. Pipe coils are usually made in the mitre form as shown in Fig. 25. The vertical lengths of pipe provide sufficient flexibility to allow the longer I v_s .. us =j 1 If 1 I FIG. 25. Mitre pipe coil. horizontal members to expand freely. Some such provision is essential. The openings in one of the headers or the elbows are tapped with a left-hand thread so that the coil can be readily assembled. Pipe coils of the form shown in Fig. 26 are also sometimes used, especially in hot-water work. Radiators were formerly made of vertical pipes screwed into a cast-iron base. This form of radiation is little used at present. - IB ri ri PJj gl nn Pl^t '^^^'^'^^ FIG. 26. Continuous pipe coil. 59. Heat Transmission from Radiators. Heat flows from the water or steam in a radiator into and through the metal wall and is transmitted from the outer surface partly by radiation and partly by convection. The resistance to heat flow offered by the walls of the radiator is so slight that the temperature of the outer surface is practically the same as that of the water or steam. The amount of heat transmitted per square foot of radiating surface is affected by several factors, such as the tern- L_U. U._" 68 HEATING AND VENTILATION perature difference between the radiating surface and the sur- rounding air, the nature of the surface, the height and shape of the radiator, and the location of the radiator in the room. 60. Effect of Shape of Surface. The form or shape of the radiator has a marked effect on the heat transmission, affecting both the amount radiated and that given off by convection. A greater amount of heat per square foot of surface is given off by radiation from a pipe coil or a single-column radiator than from a radiator of a wider pattern. This can be clearly understood from a study of Fig. 27 which represents horizontal cross-sections of a single-column and a three-column radiator. The rays of heat from points on the single-column radiator can travel in nearly any direc- tion without interruption, while the rays emanating from many points such as A, on the surface of the inner columns of the three-column radiator, are FlG 27. largely intercepted by the other portions of the radiator. It has been demonstrated experimentally that the amount of radiant heat given off by a radiator is very nearly proportional to the area of the enclosing envelope of the radiator, as indicated in the figure. The transmission of heat by convection is dependent upon the difference in temperature between the surface of the radiator and the air. The upper part of a radiator will transmit less heat per square foot by convection than will the lower part because of the increase in the temperature of the air as it ascends along the surface. Hence the average heat transmission per square foot is greater for short than for tall radiators, and for the same reason a radiator or pipe coil laid on its side will give off more heat than when in a vertical position. 61. Effect of Varying Width. Figure 28 shows the relative amount of heat given off by radiators of various widths that is, having one, two, three, etc., columns. The narrower radiators are the more effective because of the reasons explained in Par. 68. 62. Effect of Varying Length. The effect on heat transmission of increasing the length of the radiator is shown in Fig. 29. An increase of length has a marked effect when the radiator is RADIATORS 69 under 6 sections in length, but above 10 sections, the effect of varying length can be neglected. The reason for this is that in ISO 200 300 240 2CO 2SO 300 320 340 B.T.D. Transmitted per Sq. Ft. per Hour FIG. 28. Heat transmission from radiators of various widths. the short radiators the effect of the ends is much more apparent than in the long radiators. The effect of the end is to increase ..4CO 1 2 3 45 G 7 8 9 10 11 12 13 14 15 1C 17 18 19 20 Length of Radiator in Sectioni FIG. 29. Heat transmission from radiators of various lengths. the radiating surface in proportion to the convecting surface so that in a short radiator we get a larger proportion of radiant heat than in the long radiator. Curves are plotted for only 70 HEATING AND VENTILATION two heights of radiator, as the relative effect of length remains practically the same in radiators of different heights. A radiator may also be lengthened by increasing the spacing. A few experiments are available which show the effect of spacing. If the spacing of the standard two-column, 38~in. radiator is changed from 2J in. to 3 in. the results show that the heat loss is increased about 7 per cent. The hospital type of radiator is usually spaced % in. more than the standard type, so the hospital type may roughly be assumed to give off from 7 to 10 per cent, more heat than the standard type. 63. Effect of Painting. The effect of painting was originally determined by experiments made with a cast iron rectangle, and in applying these to radiators of standard type, corrections must be made to allow for the difference between the area of the radiat- ing and convecting surfaces. The effect of painting is to change the radiation constant of the radiating surface and has practically no effect upon the heat lost by convection. It is, therefore, a surface effect and it makes no difference what paints are placed on the radiator as a priming coat. The results are always dependent upon the last coat of paint put upon the radiator. In radiators having a large proportion of radiating surface such as pipe coils or wall coils, the effect of painting will be more marked than in four-column radiators having a comparatively small radiating surface in proportion to convecting surface. All finely ground materials have about the same radiation constant. Therefore all paints having finely ground pigments will give about the same effect. Metals have a poor radiating effect so* that any paint involving flake metal, such as bronze, will have a low radiating constant. The following table shows the heat loss from a two-column, 38-in. radiator, 10 sections long, when painted with different kinds of paints. TABLE XV. EFFECT OF PAINTING ON TWO-COLUMN 38-iN. RADIATOR, STEAM TEMPERATURE 215. ROOM TEMPERATURE 70F. B.t.u. per square -foot Condition or surface per hour Cast iron bare 240 Painted with aluminum bronze 200 Painted with gold bronze 205 Painted with white enamel 242 Painted with maroon japan 240 Painted with white zinc paint 242 Painted with no-lustre green enamel 230 RADIATORS 71 64. Effect of Enclosing the Radiator. It is very often desirable to partly enclose or conceal a radiator by means of screens or grilles. All such enclosures in general reduce the heat trans- mission from the radiator, the effect being usually to reduce both the radiant heat and the convected heat. As in most radiators at least two-thirds of the heat is transmitted by convection, these enclosures or screens largely affect the amount of convected heat. It is therefore very desirable that the current of air passing over and through the radiator should be restricted as little as possible. There has been some experimental work done, particularly abroad, with reference to these screens. There are, however, so many different cases that may arise that it will not be possible to discuss all of them but only to take up typical ones. [cT I 2ii IT- -2\ \ ~IO i zz^zzztzz^ FIG. 31. 21] FIG. 30. Case No. 1. In this case, Fig. 30, the radiator is enclosed in a box with a screen in front at the bottom, and a screen at the top, these screens extending the full length of the radiator. This ar- rangement reduces the heat transmission of the radiator from 7 to 10 per cent, and in all cases, the spaces between the radiator and the wall and the spaces between the casing and the radiator should be at least 2% inches. The reduction of heat transmission will be more in narrow radiators than in wide radiators. Experiments show that the best results are obtained when the opening at the top has twice the width of the opening at the bottom, and for radiators of ordinary type the width of opening at the bottom should be 5 in. and the opening at the top, 10 in. Case No. 2. It is sometimes desirable to place a screen in front of the radiator, leaving the top entirely open with an opening at the bottom in front for the cold air to enter the radiator, as in Fig. 31. 72 HEATING AND VENTILATION In a case of this kind the effect of the screen is to produce a strong current of air and if this screen is high enough it may even produce a chimney effect which will increase heat transmission from the radiator due to increased circulation. The effect of such screens depends entirely upon their height. Case No. 3. Radiators often have placed over them a flat shelf, as shown in Fig. 38. In such cases, they should be provided with a deflector as shown. The effect of the shelf very largely depends upon the height of the shelf above the radiator. When the dis- tance D that is the height of the shelf above the radiator is 5 in. or over, the effect of the shelf may be neglected. When the distance D is reduced to 4 in., the heat effect may be reduced by 4 per cent. A ' FIG. 33. FIG. 34. FIG. 35. Case No. 4. Radiators are often enclosed in boxes with a grille in front or recessed in the wall with a grille placed in front of them as in Fig. 33. In such cases, the height, D, is very important. With D equal to 2 % in., the heat transmission will be reduced 20 per cent., and with D equal to 6 in., the heat transmission is re- duced 10 per cent. It is assumed in this case that the entire front of the box is provided with an open grille. Case No. 5. Sometimes a grille, as shown in Case 4, is partly replaced by a solid panel with openings above and below as in Fig. 34. With the openings the full length of the radiator and 6 in. in height and with D not less than 4 in., the heat transmission will be reduced 25 per cent. As D is reduced in height, the heat transmis- sion will also be reduced and with D = 2% in., the reduction will be 40 per cent. Case No. 6. Radiators are of ten placed under seats as in Fig. 35. In this case the distance between the top of the radiator and the RADIATORS 73 bottom of the seat becomes very important and should be not less than 3 in. and if possible it should be made 6 in. Under favorable conditions, when D is at least 3 in. and A is equal to 6 in., the heat transmission will be reduced from 15 to 20 per cent. When D is small, however, say 2 in., and A is reduced to 4 in., this reduction may be 35 or 40 per cent. In tests 1 by Prof. K. Brabbee will be found other cases than those cited above. 65. Theoretical Formula for Heat Emission. We have seen that heat is given off from a radiator partly by radiation and partly by convection. In developing an expression for heat emission from a radiator, it will be necessary to treat these two factors separately as the laws governing the two forms of heat transmission are quite different. We will start out with the assumption, which has been demon- strated experimentally, that the surface radiating heat is the area of an imaginary envelope enclosing the radiator, as in Fig. 27. This radiating surface is evidently independent of the rated sur- face of the radiator. The radiant heat emitted by a radiator, according to the law of Stefan and Boltzman, is expressed as follows: in which Q = B.t.u. radiated per square foot of radiating surface per hour. T s = Absolute temperature of the radiating body, assumed to be the temperature of the steam. T r = Absolute temperature of the surrounding objects, assumed to be the temperature of the room. D = A constant depending upon the substance of which the surface of the body is composed. The value of D for cast iron radiators may be taken as about 0.157. In order to express the heat loss in terms of rated surface, let R = the ratio of the radiating surface to the rated surface. Equation (1) then becomes, for a cast iron radiator in B.t.u. per square foot of rated surface 1 Reported by GEORGE F. STUMPF, JR. in Heating and Ventilating Magazine, May, 1914, p. 23. 74 HEATING AND VENTILATION The convection loss depends upon the difference in temperature between the air entering and leaving the radiator, also upon the density and velocity of the air passing the radiator. The equation for convection may therefore be written as follows : Q 2 = mqV(t h - t r ) (3) in which Qz = B.t.u. lost by convection per square foot of rated surface per hour. q = Density of the air passing the radiator. V = Velocity of the air passing the radiator. th = Temperature of air leaving the radiator (fahr.). t r = Temperature of air entering the radiator (fahr.). m = A constant. Actual experiments show that t h bears an almost constant ratio to t a , the temperature of the steam and qV also bears an almost constant ratio to t,. We can therefore write the expression for convection : 2 = C(t s - t r ) (4) in which Qz = B.t.u. lost by convection per square foot rated surface per hour. C = The constant for convection which must be determined by experiment. t a = Temperature of the steam in the radiator (fahr.). t r = Temperature of the air in the room (fahr.) . Adding equation (2), the heat lost by radiation, to equation (4), the heat lost by convection, we have the total heat lost by the radiator. This expression for total heat loss becomes : Q = Qi + Qi or substituting values. - C (t s - t r ) (5) For the ordinary forms of cast-iron radiation C = 1 and equa- tion (4) becomes: Q 2 = (t s - t r ) (6) and equation (5) becomes: RADIATORS 75 The value of R in equation (7) will be found in Table XVI for radiators 10 sections or more in length. For shorter radiators it should be computed from the actual dimension of the radiator. In the case of a single horizontal pipe the value of R is 1 and may be considered a limiting case. The use of the formula can best be shown by assuming an example in which we have a two-column 38 in. radiator of 10 sec- tions, steam temperature 215 deg., room temperature 70 deg. R = 0.458 then: -" -<'-()>< > = 0.072 (2075 784) + 145 = 93 + 145 = 238 B.t.u. per sq. ft. per hour. The actual figure taken from experiment is 240 which gives a difference of less than 1 per cent between the computed and the measured results. 66. Radiation and Convection from Various Types of Radia- tors. By means of equations (2) and (6) it is possible to determine what proportion of the total heat is given off by radiation and by convection. A study of the various forms of radiators is given in Table XVI, which shows the proportion of radiant heat to convected heat in the various types. Radiant heat is greatest in a single hori- zontal pipe. The percentage of convected heat will be less in a wide radiator such as the four-column type. Column 5 in Table XVI shows the ratio of the radiating surface to the total surface of the radiator. Column 6 shows the radiant heat in various forms of radiators, and column 8 shows the convected heat. Column 9 shows the ratio of the convected heat given off by the radiator to the total heat. It will be noticed that in the case of wall coil about one-half the heat is given off by radiation and one-half by convection, while in a four-column radiator, about 70 per cent is given off by convection and 30 per cent by radiation. In a single horizontal pipe about 60 per cent will be given off by radiation and 40 per cent by convection. It is apparent from this table, that all radiators do not give exactly the same effects in heating a room, and that the effect of heating a room with pipe coils might be called heating with radiant heat while heating a room with 76 HEATING AND VENTILATION four-column radiation might be called heating with convected heat. TABLE XVI. RELATION BETWEEN RADIATED AND CONVECTED HEAT IN DIFFERENT TYPES OF RADIATORS. 10 SECTIONS IN LENGTH Room at 70 deg. fahr. Steam at 215 deg. fahr. Number of columns Height of radiator 10 Section rated surface 10 Section area of enclosing envelope R Ratio of radiating to total surface Radiated heat per sq. ft. rated surface Total heat per sq. ft. rated surface Con- vected heat per sq. ft. rated surface Per cent con- vected heat to total heat One 38 30 15.9 0.53 106 256 150 58.6 One 32 25 13.5 0.54 108 266 158 59.4 One 26 20 11.1 0.555 111 273 162 59.4 One 23 16 9.9 0.595 119 279 160 57.4 One 20 15 8.75 0.584 117 283 166 58.7 Two 45 50 21.45 0.43 86 234 148 63 Two 38 40 18.35 0.458 92 240 148 62 Two 32 33 y s 15.65 0.47 94 248 154 62 Two Two 26 23 26% 23W 14.00 12.70 0.53 0.544 106 109 255 260 149 151 58 58 Two 20 20 11.20 0.56 112 265 153 58 Three 45 60 22.90 0.382 76 218 142 65 Three 38 50 19.7 0.394 79 226 147 65 Three 32 45 16.85 0.375 75 233 158 68 Three 26 37 # 14.10 0.376 75 241 166 69 Three 22 30 12.20 0.407 82 248 166 67 Three 18 22tf 10.35 0.46 92 254 162 64 Four 45 100 28.05 0.28 56 205 149 73 Four 38 80 24.16 0.30 60 210 150 71.5 Four 32 65 21.52 0.331 66 217 151 69.5 Four 26 50 17.5 0.35 70 225 155 69 Four 22 40 15.27 0.382 76 232 156 67 Four 18 30 13.05 0.435 87 238 151 63.5 Wall 5 Coil Section 5A 13Me 25 21.34 0.854 171 323 152 47 7A 21% 35 27.24 0.78 156 310 154 49.7 9A 29>l6 45 35.32 0.784 157 295 138 48 In most cases, heating by convected heat is more satisfactory than heating by radiant heat. This is especially true if the occupants must sit in close proximity to the radiators. It is sometimes necessary to place shields in front of the radiators in school rooms to cut down the radiant heat. 67. Approximate Formula. The foregoing formula checks closely with test results and is particularly useful because it can be used for any type of radiator and for any steam or room temperature. For a limited range of conditions, the following RADIATORS 77 empirical formula is often used and is sufficiently exact for ordi- nary type of radiators and ordinary temperatures. H = SK (t a - t r ). in which H = Heat transmitted per hour. S = Rated area of the surface of the radiator in square feet. K= Coefficient of heat transmission in B.t.u. per square foot per hour per degree difference between radiator and room temperature. t g = Temperature of steam or water in the radiator. t r = Room temperature. This expression does not take into account the radiant heat but assumes that all of the heat is given off by convection. It is therefore applicable only through a small range of temperature. Z.U 1.9 1.8 1.7 1.6 1.5 1.4 1.3 J x \ ^ X \ ^ ^ -^ ^^^ Column x ^ ^ ^ ^^ ^ Column - \ ^^ ^"^ ^-~ ^^ Column "* ^ \ ^ ^^Z Column ^ ^ ^~ 24 28 32 36 40 44 48 Height of Radiator - Inches FIG. 36. Coefficient of heat transmission from radiators. The values of K, the coefficient of heat transmission for ordinary cast iron radiation of various heights and widths, are given by the curves in Fig. 36 which are based on the results of experiments. For other forms of radiation the values of K given in Table XVII may be taken as average figures. 78 HEATING AND VENTILATION TABLE XVII. COEFFICIENT OF HEAT TRANSMISSION FROM RADIATORS K B.t.u. per square foot per hour per degree difference in temperature Cast Iron, Height 38 Inches One-column 1 . 75 Two-column 1 . 65 Three-column 1 . 55 Four-column 1 . 45 Wall Coil: Heating surface 5 square feet, long side vertical 1 . 92 Heating surface 5 square feet, long side horizontal 2.11 Heating surface 7 square feet, long side vertical 1 . 70 Heating surface 7 square feet, long side horizontal 1 . 92 Heating surface 9 square feet, long side vertical 1 . 77 Heating surface 9 square feet, long side horizontal 1 . 98 Pipe Coil: Single horizontal pipe 2 . 65 Single vertical pipe 2 . 55 Pipe coil 4 pipes high 2 . 48 Pipe coil 6 pipes high 2 . 30 Pipe coil 9 pipes high 2.12 This data is based on a temperature difference between the radiator and the air of about 150 which represents ordinary conditions. For other temperatures formula (7), p. 74 should be used. 68. Heat Transmission from Pressed Metal Radiation. The heat transmission from pressed-metal radiation is practically the same as that from cast iron. This is illustrated in Fig. 37 which shows the results of a test 1 to determine the relative performance of the two forms of radiation under the same condi- tions. A radiator of each kind was placed in either of two similar rooms and the condensation formed in each radiator was weighed at 10-minute intervals and the room temperatures were measured. While the rate at which the room was warmed was nearly the same in both cases it will be noted that in the case of the cast-iron radiator the initial condensation of steam is con- siderably greater. 69. The Location of Radiators. The location of the radiators in the room is extremely important. If they are placed along 1 See "Coefficient of Heat Transmission in a Pressed-metal Radiator" by JOHN R. ALLEN, Trans. A. S. H. & V. E., 1914. RADIATORS 79 an inside wall, there is a tendency for uncomfortable drafts to be formed by the cooling effect of the windows and outer walls. The cold current of air thus formed flows without interruption across the floor, as illustrated in Fig. 38. This ''window chill" often causes extreme discomfort, especially in school rooms, offices, etc., and is best prevented by placing the radiators directly beneath the windows. The air current then travels as 80 40 700 GO 600 8 80 |500 2 & 60 J 20 gS400 g 80 1 40 300 1 G 20 200 80 40 100 60 5 ^ 74 72 70 68 66 64 v 62 | 60 | 58 a 56 | 54 52 50 48 46 1 ^ ^-^ " 1 I \ ^ -^ '1^ y-<^ Roo uTe mp. ,' \ o ^ o c> 1 ft ^ tf \ i \ \ 1 / 1 \ \ i it i \ \ il \ \ ij i \ \ I I I \ \ \ ; 1 1 \ ^ c ondt nsal ion- 1 Y \ Ca 3t II on / 1 ^ "*"; I / P ressc d Ir on i / .00 10 20 30 40 50 .9.00 Time FIG. 37. Result of a comparativp test of a cast iron and a pressed iron radiator. illustrated in Fig. 39, the effect of the windows being largely neutralized by the upward current of air from the radiators. A secondary circulation is set up, as indicated, between the radiator and the window. The location of the radiators beneath the windows is, on the whole, the most desirable, 1 especially in schools, auditoriums, etc., where the occupants are stationary. 1 See report of Committee on Best Position of a Radiator, Trans. A.S . H & V. E., 1916. 80 HEATING AND VENTILATION Recent tests have indicated that the transmission of heat may be slightly greater when the radiators are located in other positions, Warm Cold * FIG. 38. Effect of locating radiator away from window. FIG. 39. Effect of locating radiator beneath window. but this slight gain in effectiveness is greatly over-balanced by the other considerations noted above. RADIATORS 81 70. Proportioning Radiation. In designing the heating system for a building the heat losses are first computed and it is then necessary to determine the amount of radiator surface which will be required to supply the heat losses. It is necessary first to know the temperature of the steam or water in the radiator. If steam is the heat-carrying medium the temperature will be that corresponding to the pressure to be carried. In many heating systems it is possible to carry a pressure of at least 5 pounds when necessary and for such systems the radiation is commonly figured on the basis of this pressure. If, however, special conditions require that a lower pressure be used, the temperature of the steam which is assumed should be that corresponding to the pressure. Some types of vapor heating systems are designed to operate at nearly atmospheric pressure, and the radiation is consequently figured for 212. If hot water is used the temperature will range between 160 and 200. The factors affecting the temperatures carried in hot-water systems will be discussed later. The type of radiation and the height must next be selected from a consideration of the nature of the building and of the space available. By the methods given in the preceding paragraphs, the heat transmission per square foot of surface for the type of radiation selected can be found and the total surface necessary to transmit the heat required can than be computed. For example, consider that the room shown in Fig. 7, page 23, is to be heated by a heating system which is to operate at a pressure of 2 pounds. The heat loss from the room was found to be 8696 B.t.u. per hour with room temperature 70. Assume that 38-inch, two-column radiation is to be used. The temperature of steam at 2 pounds pressure is 218.2 and the difference in temperature between the steam and the air is 218.2 - 70 or 148.2. From the chart in Fig. 36 we,see that the value of K for 38-inch, two-column radia- tion is 1.65. For a temperature difference of 148.2 the heat transmission would be 244 B.t.u. per square foot per hour. Dividing 8696 by this figure we find that 35.6 square feet of radiation would be required. Since 38-inch, two-column radia- tion contains 4 square feet of surface per section, a radiator of nine sections would be used. 71. Checking a Contractor's Guarantee. The case often arises in which a contractor has guaranteed that the heating system as installed is capable of heating the building to 70 in 82 HEATING AND VENTILATION zero weather and it is desired to prove that this is true without waiting for extremely cold weather. By means of the following method it is possible to determine the temperature to which the building must be heated in the warmer weather if the heating system is capable of heating it to the guaranteed temperature in the coldest weather. Let ti = temperature of outside air under contract conditions, t 2 = temperature of air in building under contract con- ditions. fo = temperature of steam in radiator at pressure specified. Test made with steam at same pressure. 4 = temperature of outside air during test. 6 = inside temperature to be maintained during test if system fulfills guarantee. h = computed heat loss from building per degree dif- ference in temperature. The heat loss from the building under conditions specified in guarantee would be h(t z - (1) The heat loss from the building under test conditions is h(t* - tj (2) The heat loss from the radiators under contract conditions would be K(t* - (3) in which K is the coefficient of heat transmission from the radiator. The heat transmission from the radiator under test conditions is K(t> - t b ) (4) Then the quantity (1) must be equal to the quantity (3) and the quantity (2) must be equal to (4), hence and h - Equating the right-hand members of equations (5) and (6), we have - U RADIATORS 83 Assuming ti = 0, t 2 = 70, and tz = 228, the temperature corresponding to 5 pounds steam pressure, and solving for 5 we have Z 5 = 0.695*4 + 70 (8) The following table has been computed from equation (8) and shows the room temperature, for different outside temperatures existing during the test, which must be maintained to fulfill a guarantee which specifies the temperatures and steam pressure given above. For other conditions equation (7) must be solved for U. TABLE XVIII. ROOM TEMPERATURE FOR VARIOUS OUTSIDE TEMPERATURES Outside temperature during test Room temperature, two-column radiation Room temperature, three-column radiation -30 52.0 53.0 -20 58.0 59.0 -10 64.0 64.0 70.0 70.0 10 77.5 75.0 20 83.0 83.0 30 90.0 89.0 40 97.0 95.0 50 103.5 105.5 60 110.0 108.0 70 117.0 115.0 80 123.5 121.5 90 130.0 128.0 100 137.0 134.5 72. Indirect Radiators. Indirect radiators are so named be- cause they are located outside of the room to be heated and the heat is conveyed from the radiator to the room by a current of air. Indirect radiators arfe of two classes: gravity indirect, in which the circulation of the air over the radiating surface is produced by the difference in weight of the heated and unheated columns of air, and fan coils, over which the air is forced by a fan. Only the former will be considered here, the various types of fan systems being discussed in Chapter XV. There are two reasons for the use of gravity indirect radiators. Their chief advantage is that they can be arranged to introduce fresh air from outside and they are therefore desirable from a standpoint of ventilation. Another advantage is that the radia- 84 HEATING AND VENTILATION tors are out of sight, which is desirable in any room or apartment where appearance is an important factor. It is seldom that indirect radiators are installed throughout an entire building because of the increased cost of installation and operation as compared with direct radiation. In a residence, indirect radiation is often installed in the living rooms where ventilation is most desired and where the appearance of the radiators would be objectionable, and direct radiation is used in the bedrooms, halls, etc. The increased operating cost where indirect radiation is used is due to the fact that the large quantities of air which are brought in from outside must be heated up to room tempera- ture or above. 73. Forms of Indirect Radiation. As indirect radiators are concealed, their appearance is not an important factor and they FIG. 40. FIG. 41. Forms of indirect radiators. are therefore designed and installed from a standpoint of effec- tiveness rather than appearance. Since the resistance to heat transmission between the outer surface of the radiator and the air is greater than that from the steam or water to the inside surface of the radiator wall, it is desirable to make the external surface of greater area than the internal. This is accomplished by adding projections in the form of pins or fins. Two forms of indirect radiation are illustrated in Figs. 40 and 41. The sections are joined together in the same manner as are the sections of direct radiators. The form shown in Fig. 41 is of the so-called short-pin type. A similar form having longer pins can also be obtained. 74. Arrangement of Indirect Radiators. Two common arrange- ments for indirect radiators taking air from outside are illus- RADIATORS 85 trated in Fig. 42 and Fig. 43. The radiator is placed in a chamber or box usually situated in the basement of the building, as close as possible to the base of the flue leading to the room to be heated. The air is admitted to the radiator chamber by a duct or flue from an opening in the outside wall or from the room above. This duct should be provided with a suitable damper, arranged if possible to close when the steam or water supply to the radiator is shut off. A bypass damper should also be provided, with a means of controlling it from the room, so that the temperature of the air can be readily adjusted. 00000 oooo Warm Air 000 J 00 O OO0 0000000000 O 000 0000 I Damper Control Cable - Cleanout FIG. 42. Indirect radiator with bypass. The casing surrounding indirect radiators is usually built of galvanized iron and it should be bolted together with stove bolts so that the sections can be easily removed. A much better method of construction, though a more expensive one, is to enclose the radiator in a brick chamber of sufficient size to permit access to the radiator. The duct leading from an indirect radiator should be carried to the room as directly as possible. Long horizontal pipes should be avoided. The indirect radiators are usually suspended in the box or chamber on iron pipes supported by rods from the joists. There should be at least 10 inches clearance between the radiator and the bottom and top of the casing, but the sides of the casing should fit the radiator as closely as possible, so that all of the air 86 HEATING AND VENTILATION must pass through the radiator. Indirect radiators should be placed at least 2 feet above the water line of the boiler if they are to be operated on a gravity steam system, and should be so FIG. 43. Indirect radiator. 1 arranged that the condensation will drain from them by gravity. The tappings of these radiators are the same as for two-pipe direct steam radiators. The following table gives the size of flues required for indirect radiators of various sizes. TABLE XIX. SIZE OF FLUES FOR INDIRECT RADIATORS Heating surface, square feet Area of cold- air supply, square inches Area of hot- air supply, square inches Size of brick flue for hot air, inches Size of register, inches 20 30 40 8X8 8X8 30 45 60 8 X 12 8 X 12 40 60 80 8 X 12 10 X 12 50 75 100 12 X 12 10 X 15 60 90 120 12 X 12 12 X 15 80 120 160 12 X 16 14 X 18 100 150 200 12 X 20 16 X 20 120 180 240 14 X 20 16 X 24 140 210 280 16 X20 20 X24 iFrom "Pipe-fitting Charts" by W. G. SNOW. RADIATORS 87 Indirect radiators are sometimes arranged to re-circulate the air from the room instead of drawing in fresh air from out- side. No ventilation is obtained by such an arrangement and the only advantage of the indirect radiator so installed is that it is concealed. 75. Heat Transmission from Indirect Radiators. Heat is transmitted from indirect radiators almost entirely by convec- tion. The amount of heat which will be transmitted from a given indirect radiator depends upon the temperature of the entering air, the temperature of the radiator, and the quantity of air passing through the radiator. The last quantity depends FIG. 44. in turn upon the relative temperatures of the heated air and the unheated air, and upon the friction in the air ducts. In Fig. 44 let h' be the average vertical distance from the radiator to the point of delivery to the room. The force effective in producing the flow of air is then p=h'(D 1 -D 2 ) in which DI = density of outside air. D 2 = density of heated air. During a state of constant flow the quantity of air passing through the radiator will always be just sufficient so that the friction loss due to the air passing through the system will equal the available head producing flow. Owing to the impossi- bility of determining in advance the resistance of the duct, because of lack of a standard type of construction, it is very 88 HEATING AND VENTILATION difficult to compute accurately the quantity of air which will pass through the system. The action is also complicated by the stack effect of the heated room above. Accordingly the methods used in designing indirect radiators are based on experi- mental data. Table XX gives the amount of heat transmitted from standard and long-pin radiators under various conditions. It will be noted that the temperature to which the air is heated by the long-pin radiator is less than that to which it is heated by the short-pin radiator with the same quantity of air passing. This is undoubtedly due to the fact that the pins are so long that the rapid removal of heat by the air causes the ends to become cooled. The long-pin type, however, is very desirable for use when large quantities of air are required, as the air passages are ample. This is the work for which it is primarily designed. The short-pin type gives better results for ordinary residences and other buildings where only small quantities of air pass through the radiator. TABLE XX. HEAT TRANSMISSION FROM PIN RADIATORS Cubic feet of air passing per square foot of radiation per hour Rise in temperature of the air Pounds of steam condensed per square foot of radiation B.t.u. transmitted per square foot of radiation per degree difference in temperature between steam and air Standard pin Long pin Standard pin Long pin Standard pin Long pin 50 147 140 0.125 0.150 0.80 0.95 75 143 137 0.170 0.210 1.17 1.27 100 140 135 0.240 0.260 1.51 1.60 125 138 132 0.295 0.310 1.85 1.90 150 135 129 0.355 0.360 2.22 2.20 175 132 126 0.410 0.405 2.57 2.47 200 130 123 0.470 0.450 2.90 2.72 225 127 120 0.530 0.490 3.25 3.00 250 123 118 0.585 0.530 3.60 3.20 275 121 115 0.645 0.570 3.90 3.40 300 119 112 0.700 0.610 4.22 3.60 76. Calculation of Indirect Radiation. In order to determine the required size of an indirect radiator it is necessary to assume the quantity of air that will pass through the radiator. In school buildings and other buildings where a large air supply is desired and where the flues will be of ample size, the amount of air passing per square foot of radiation may be assumed to be 200 RADIATORS 89 cubic feet per hour. In residences and buildings where the flues are usually small, the amount of air passing per square foot of surface per hour does not exceed 150 cubic feet. The air should be assumed to enter the radiator at the minimum outside tem- perature for which the system is to be designed. If this tempera- ture is 0, for example, and the quantity of air passing is taken as 200 cubic feet per hour per square foot of radiation, the air will be heated according to figures given in Table XX to about 130. The air which enters the room at this temperature gives up its heat to supply the heat lost by conduction through the walls, and finally finds its way out of the room through the window cracks, foul air flues, etc. Each cubic foot of air, there- fore, gives up enough heat to lower its temperature from 130 to 70, if the latter is the room temperature. This amount of heat is equal to ~ X 200 = 218 B.t.u. available for heating per square DO foot of radiator surface. This amount is available for supply- ing the heat losses through the walls and the amount of surface in the indirect radiator for the case given above would be equal to the computed heat loss through the walls divided by 218. If ventilation requirements made necessary a greater quantity of air, then part of the air would be by-passed around the radiator. 77. Combination of Direct and Indirect Radiators. A very common arrangement is to install enough indirect radiation to give the proper amount of air for ventilation and to install direct radiation to supply the heat losses from the walls and windows. The direct radiation would then be computed in the ordinary manner, as if there were no other source of heat. This system has the advantage of being more economical, as less cold air need be heated per hour. Further, when the rooms are unoc- cupied, the indirect radiators may be entirely shut off, resulting in a considerable saving of fuel. 78. Semi-indirect Radiators. When only a small quantity of air is needed for ventilation semi-indirect or "flue" radiators may be used in place of indirect radiators. A radiator of this form is shown in Fig. 45. The air enters through a grating in the wall behind the radiator and passes into a metal box which encloses the lower part of the radiator and thence up through the spaces between the sections. Dampers in the fresh air opening and in the base may be adjusted to allow part or all of the air to 90 HEATING AND VENTILATION re-circulate from the room. Radiators used for this purpose are of a special design, the sections being so shaped that the passages between them are divided into a number of vertical flues. A test recently conducted on a flue radiator showed that about 45 per cent, of the total heat transmitted is carried off by the air E'ecirculatiug Dam FIG. 45. Flue radiator. passing through the flues, the remaining 55 per cent, being given off by radiation and by convection from the outer surfaces. When flue radiators are used the amount of surface allowed should be about 25 per cent, greater than if direct radiation were used. Problems 1. To be properly heated, a certain building requires 5627 square feet of 30-inch, one-column radiation. How much would be required if wall coil, of sections containing 9 square feet of surface, long side horizontal, were used? How much would be required if pipe coils, 9 pipes high, were used? 2. A heating system is guaranteed to heat a building to 70 in zero weather at 5 pounds pressure. A test is made with the outside tempera- ture at 10. What inside temperature must be reached to fulfill the guarantee? RADIATORS 91 3. A heating system is guaranteed to heat a building to 65 with the outside temperature at 10 and a steam pressure of 1 pound. A test is made with the outside temperature at 15. What inside temperature must be maintained to fulfill the guarantee? 4. Given a radiator whose rated surface is 67 square feet. Area of enclos- ing envelope is 35 square feet. Steam temperature 220, room temperature 68. What is the total heat loss per hour from the radiator? 5. Given a radiator whose enclosing envelope is 7 inches wide, 30 inches long and 36 inches high. The radiator consists of 12 sections of 38 inch two- column radiation. Steam temperature 190, room temperature 70. What is the heat transmission per hour per square foot of rated surface? 6. Assume a radiator whose rated surface is 98 square feet. Area of enclos- ing envelope is 40 square feet. Steam temperature 220, room temperature 70. What is the percentage of the total heat which will be given off by convection? 7. Assume that the room in Fig. 7, p. 23, is to be heated by indirect radiation. Inside temperature 70, outside temperature 0. How much radiation would be required and what would be the proper size for the flues and registers? 8. Take the same room as in Prob. 7 and figure the amount of indirect radiation required if the inside temperature is 65 and the outside tempera- ture 10. CHAPTER VII STEAM BOILERS 79. Fuel. Before taking up the subject of boilers, it is desir- able to study the various kinds of fuel and the general principles of combustion. Coal, coke, wood, oil, and gas are used as boiler fuels. Coal is by far the most widely used fuel in the United States, and is found in varying amounts in no less than thirty States in the Union. It is of vegetable origin, being the remains of vegetation which existed during a former geological period and which gradu- ally reached its present state through the action of decay and of earth pressure. The chief constituents of coal are carbon, hydrogen, oxygen and nitrogen. The carbon exists partly in an uncombined or " fixed, " state and partly in combination with the hydrogen and oxygen as hydrocarbon compounds which are given off as gases when the coal is heated. Coals are classified as anthracite, bituminous, etc., according to the relative pro- portions of fixed carbon and volatile matter as given in Table XXI. TABLE XXI. CLASSIFICATION OF COALS Kind of coal Composition per pound of combustible Calorific value per pound of combustible B.t.u. Volatile matter per cent. Fixed carbon per cent. Ahthracite 3.0- 7.5 7 . 5-12 . 5 12.5-25.0 25.0-40.0 35.0-50.0 97.0-92.5 92.5-87.5 87.5-75.0 75.0-60.0 65.0-50.0 14,900-15,300 15,300-15,600 15,600-15,900 15,800-14,800 15,200-13,700 Semi-anthracite Semi-bituminous Bituminous Eastern . . Bituminous Western All coals contain more or less non-combustible matter, con- sisting principally of moisture and ash. The nitrogen in the coal is also a non-combustible but it is customary to treat it as combustible matter. The moisture content of different coals varies from 2 per cent, to as much as 20 per cent, and the ash content from 4 to 20 per cent, by weight of the coal as mined. 92 STEAM BOILERS 95 It will be noted that the percentages in Table XX are base- , 1 pound of combustible. The bituminous and semi-bituminous coals are the n- j abundant and are the kinds used for most industrial purpo, ^ Many bituminous coals are of the variety known as "caki^ coals because, when heated, the lumps fuse together into a soli crust, while the so-called " non-caking " or free-burning coals do not possess this quality. Bituminous coals burn with a char- acteristic yellow flame and emit smoke unless burned under favorable conditions. They are sold in the sizes given in Table XXII and as " run-of-mine " or ungraded. TABLE XXII. COMMERCIAL SIZES OF BITUMINOUS COAL Kind of coal Will pass through bars spaced Will not pass through bars spaced Lump . 1V inches Nut \Y inches % inch Slack % inch The slack coal does not command as high a price as the larger sizes because of its higher ash content and the difficulty of burning it. Anthracite or hard coal is principally used for domestic pur- poses and for other conditions where a smokeless coal is required. It ignites slowly but burns steadily with a short blue flame. It is of relatively great density and does not crumbleLe_asily. It is marketed in the sizes given in Table XXIH. TABLE XXIII. COMMERCIAL SIZES OF ANTHRACITE COAL Kind of coal Will pass through Will not pass through Rice ^ -in mesh 3^-in mesh Buckwheat ^ -in. mesh 34 -in. mesh Pea . . . 3^-in mesh 3^ -in mesh Chestnut li^ -in mesh 5^-in mesh Stove or range 1/^-in mesh 1/^-in mesh EEC 2J^-in. mesh 1^4 -in mesh Large egg 4-in. mesh 2% -in. mesh 80. Composition and Analysis of Coal. Coal consists of carbon, hydrogen, sulphur, oxygen, and nitrogen combined in various ways, together with moisture and ash. The moisture includes HEATING AND VENTILATION that originally contained in the coal and that acquired dur- storage and shipment. The moisture content of a given coal is ^rmined by subjecting a finely powdered sample to a tempera- 3 of about 220F. for about 1 hour and noting the loss in weight .ring that time. This method, while not giving an absolutely ccurate result, is the one universally employed. The amount of volatile matter is determined by subjecting a sample of dried coal to a high temperature out of contact with air until there is no further loss of weight, and noting the decrease in weight. The residue left after distilling off the volatile matter consists of the fixed carbon and ash. By burning the sample in an uncovered crucible the fixed carbon can be removed, leaving the ash. There are two forms of coal analysis the " Proximate Analy- sis" and the "Ultimate Analysis." The former consists of a determination of the moisture, volatile matter, fixed carbon, and ash in the manner just described. This is the more useful form of analysis and is the one generally used by engineers, as it serves to show the type of coal and its more important charac- teristics. The ultimate analysis, which consists of a determina- tion of the carbon, hydrogen, oxygen, nitrogen, and sulphur, is necessary only when a close study of the combustion of coal is being made. In the proximate analysis, the percentages may be reckoned either on a basis of dry coal or coal "as received." In the former case the moisture content is given in addition. The heat value or calorific value of a fuel is the amount of heat developed by its combustion, expressed in B.t.u. per pound of fuel. The heat value of coal is determined by igniting a sample of known weight in a closed vessel surrounded by water and noting the rise in temperature of the water. From the pre- viously determined thermal capacity of the vessel and water the heat developed can be computed. The calorific values of the various kinds of coal were given in Table XXI. 81. Cpfee. Coke is the residue left after the volatile matter is driven off from bituminous coal and consists mainly of carbon. It is jDjoduced as a byproduct in the manufacture of artificial gas and is also manufactured for various industrial purposes. Its bulk is so great that the firepot will hold only a relatively small weight of fuel which is consumed rapidly so that frequent firing is required unless a very deep bed of fire is maintained. Coke is a very useful fuel when a quick, hot fire is required or STEAM BOILERS 95 where absolute smokelessness is needed. It is coming into wider use as a household fuel, particularly in the smaller sizes. 82. Combustion. Combustion may be defined as the chemical combination of a substance with oxygen which proceeds at such a rate that a high temperature is produced. Carbon is the principle combustible in coal. When its combustion is complete, it forms carbon dioxide (CO 2) ; when it is incomplete it forms carbon monoxide (CO). The hydrogen in the coal unites with oxygen to form water vapor and the nitrogen, which is an inert substance, - is set free. For economy in fuel consumption it is necessary that combustion be complete and to this end the supply of air must be ample. In order to insure a sufficient supply to all parts of the fuel bed, it is necessary to supply from 150 to 300 per cent, of the theoretical requirements. As all of this excess air leaves the boiler at the flue-gas temperature, it is evident that in the interest of economy this necessary amount of excess air should be reduced to the minimum. The best index of the amount of excess air is the percentage of CO 2 in the flue gases. If exactly enough air is supplied the CO 2 content, by volume, of the flue gases would be approximately 21 per cent. In practice, however, the best results are obtained with a CO 2 content of from 10 to 15 per cent., the higher figure being attainable only with mechanical stokers. In th.e ordinary hand-fired furnaces of heating boilers the CO 2 content of the flue gases ranges between 13 and 5 per cent, which represents an excess of air of from 50 to 250 per cent. Incomplete combustion results when the air supply is deficient or is incompletely mixed with the volatile matter which is given off by the fuel. The presence of carbon monoxide (CO) in the flue gases is an indication of incomplete combustion. In the case of bituminous coal, incomplete combustion is usually accompanied by smoking. 83. Smoke. Smoke consists principally of unburned carbon in finely divided particles set free by the splitting up of unburned hydrocarbon gases. While the waste represented by the visible products themselves is not great, smoke is an indication of incom- plete combustion and consequently of wasted fuel. A great deal of damage is caused by smoke and in most communities the making of excessive smoke is prohibited by law. Smoke may be avoided by the use of anthracite coal, coke, or the semi-bituminous coals, which have little volatile matter, 96 HEATING AND VENTILATION or by insuring complete combustion when coals high in volatile matter are used. When coal containing much volatile matter is placed on a hot bed of fuel, the volatile matter is distilled off. In order that complete combustion of this gas may take place, sufficient air must be supplied and intimately mixed with the combustible gases. Furthermore, the combustion space must be of sufficient size so that combustion can be completed before the gases come into contact with the relatively cold surfaces of the boiler. The air supply must not be so copious or at such a low temperature as to chill the mixture below the temperature required for combustion. These requirements are met by the use of various appliances and of furnaces of special design which will be discussed later. 84. Ash and Clinker. Ash is foreign matter in the coal, part of which is inherent in the vein of coal, the remainder coming from above and below the vein as it is mined. Ash is objectionable because it reduces the heating value of the coal and because of the trouble which it causes in the furnace. An excessive amount of ash obstructs the passage of air through the fuel bed, causes clinker formation, and carries much unburned fuel with it into the refuse pile. Clinker is simply ash which has fused and run together. When the ash has a low melting point clinker formation is most frequent and troublesome. The melting point is thought to be dependent upon the presence of sulphur and of iron oxides in the ash. 85. Comparison of Different Fuels. The following is a sum- mary of the advantages and disadvantages of the more common fuels. This comparison is made only from a standpoint of their use in heating boilers and furnaces. BITUMINOUS COAL < Advantages: Low cost Disadvantages: Dirty to handle Difficult to burn without smoke and soot Forms clinkers SEMI-BITUMINOUS COAL Advantages: Low cost. Burns with little smoke Disadvantages : Dirty to handle STEAM BOILERS 97 ANTHRACITE COAL Advantages: Clean to handle Burns without smoke Maintains a steady fire with infrequent attention Disadvantages: High cost Sometimes high in ash content COKE Advantages: Fairly clean to handle Burns without smoke Moderate cost Disadvantages: Requires frequent firing Difficult to maintain a steady fire Except for its high and increasing cost, anthracite coal is undoubtedly the most suitable fuel for heating plants of moderate size. Its increasing scarcity and consequent high price makes the use of other fuels more attractive, however, and furnaces of suitable design are being constantly developed for burning the higher volatile coals. Semi-bituminous coals, such as Pocahontas and New River are capable of being burned in an ordinary furnace with little smoke, though they are rather dirty to handle. The bituminousjsoals contain the greatest heat value per unit of cost, but have some marked disadvantages. Bituminous coal is particularly dirty to handle, which is a strong argument against its use in residences. It is also difficult to burn it with- out smoke except in furnaces of special design, intelligently and carefully operated. With the increasing cost of coal and growing scarcity of anthracite, it is beco'ming more widely used, however, in all classes of work and many special furnaces are being devel- oped for it. 86. Boilers. Strictly speaking, a boiler is a vessel in which steam is generated by the application of heat. The furnace in which the heat is developed is often practically an integral part of the boiler, however, and the term " boiler" therefore often refers to the combination of boiler and furnace. The primary requirement in a boiler is that it be of sufficient strength to withstand the pressure which is to be carried in it. In boilers used for heating purposes only, this is comparatively simple 98 HEATING AND VENTILATION *^\ / as the pressure carried rarely exceeds 10 pounds. Secondly, the heating surface must be sufficient in proportion to the grat$ surface so that the heat will be largely removed from the flue gases before they leave the boiler; and the^ boiler should be so designed that the flue gases are made to impinge upon and rub along the heating surfaces to the greatest possible extent as this action increases the rate of heat transfer. The boiler must be so designed that the water may circulate freely to the heating sur- faces and the steam pass away from them withouit restriction, Also, the area of the surface of the water must be sufficient so that the bubbles of steam rising through the water can escape without excessively disturbing the water level^ If the liberating surface is restricted or if the steam space is too s'mall, there is a tendency for priming (i.e., the carrying of water into the steam pipes) to take place, particularly when the boiler is being forced. This consideration is more important in a low-pressure boiler than in a high-pressure boiler as the bubbles of steam have a greater volume at the lower pressure. In boilers used for heating pur- poses, it is desirable to have a large storage of water so that steam will be continuously generated in spite of slight variations in the condition of the fire. A very large volume of water is not desir- able, however, when the boiler is operated intermittently as the entire mass of water must be heated whenever the boiler is put into service. 87. Types of Boilers. The most common type of boiler for heating residences and small buildings is the round cast-iron boiler shown in Fig. 46. This type of boiler consists of from three to five main castings such as A. B, and C (Fig. 46). The castings are joined by the tapered nipples N, N, and are drawn and held together by vertical bolts. For a boiler of a given diameter, the amount of heating surface can be varied by the size or number of the intermediate sections such as B in the figure. Naturally the taller boilers are somewhat the more efficient since the ratio of heating surface to grate area is the greater. Round boilers may be obtained having rated capacities up to about 1600 square feet of radiation. The " sectional" boiler, as shown in Fig. 47 is obtainable in rated capacity. up to about 18,000 square feet of radiation. It consists of from five* -to ten sections joined with nipples. In the larger sizes the sections are made in halves, the idea being to make the boiler capable of being easily transported and erected. STEAM BOILERS 99 One of the advantages of sectional boilers is the possibility of erecting them in an existing building without the necessity of cutting holes in the floor or walls. C FIG. 46. Round cast-iron boiler. FIG. 47. Sectional cast-iron boiler. Steel boilers are freo l uently used for heating, particularly in large buildings. A common type is the return-tubular boiler illustrated in Fig. 48. The return-tubular boiler (so named D,amper FIG. 48. Horizontal return-tubular boiler. because the gases flow through the flues toward the front of the boiler) is desirable for heating purposes because of its large water storage, ample circulating areas, and large liberating 100 HEATING AND VENTILATION surface. Another type of horizontal fire-tube boiler is the firebox boiler shown in Fig. 49. Boilers of this type in which the furnace FIG. 49. Firebox boiler. is incorporated with the boiler are known as portable boilers as distinguished from brick-set boilers of which that in Fig. 48 is an example. Uptake FIG. 50. Marine-type boiler. Steel boilers of the return-tubular and firebox types are suitable for working pressures up to 100 pounds. The marine-type boiler shown in Fig. 50 can be used for higher pressures as the STEAM BOILERS 101 fire does not touch the outer shell. Water-tube boilers, in which the water circulates through the tubes and the flue gases over the outside of them, are used for capacities of over 150 horsepower and for high-pressure work. 88. Grates. For heating boilers the grates are usually of the shaking type, consisting of a number of toothed bars as shown in Fig. 51, having a bear- ing at either end and con- nected to a rocking link. The free area through the grate is about 50 per cent. of the gross area and the FIG. 51. Shaking grate bar. width of the openings varies from %g to J inch, depending upon the size of fuel to be used. In_ large steel boilers the grates are often stationary and the ashes are removed through the firing door. 89. The Downdraft Boiler. Owing to the difficulty of burning bituminous coal without smoke in the ordinary boiler, many boilers have been designed with special furnaces for this purpose, FIG. 52. Sectional downdraft boiler. chief among which is the downdraft boiler illustrated in Fig. 52. The furnace consists of two separate grates placed one above the other. Coal is fed to the upper grate only and the..air,. instead of passing upward through the fuel bed as in the ordinary furnace, enters at the top and passes downward through it. Combustion 102 HEATING AND VENTILATION is most actiye at the bottom of the fuel bed, and to prevent the grate from being burned out, it is made of hollow bars through which the water in the boiler circulates. The volatile matter is freed from the coal on the top of the fuel bed and passes down through the incandescent fuel where most of ru'is ignited. The lower grate contains an incandescent fuel bed consisting of small pieces of coke from which the gases have been driven and which have fallen down through the bars of the upper grate. In the hot combustion chamber between the grates the gases descend- ing from the upper fuel bed mingle with the hot air which enters through the lower grate and complete and smokeless com- bustion takes place. In addition to the important feature of burning any grade of coal without smoke and with complete combustion of the vola- tile matter,, the downdraft furnace has other advantages. No trouble is v experienced^from clinkers, if the boiler is properly fired, and the performance is uniform as there are no cleaning periods to disturb the fuel bed. In firing a downdraft furnace, it is important that the main fuel bed be not seriously disturbed. It should be frequently sliced, but just sufficiently to crack the caked mass of fuel so that air can find its way through it. No green coal should ever be fed to the lower grate; it should contain only such material as falls through from the upper grate. The main air supply of course enters through the firing door of the upper grate and the fire is controlled by the regulation of this air opening. The one great disadvantage of the downdraft furnace is the necessity for fairly careful firing, without which the smokeless feature is lost. If green coal is shovelled on the lower grate, if the lower grate is not properly covered, or if the upper fuel bed is violently dis- turbed by poking, much smoke will be formed. Any of these things are very liable to be done by a careless attendant. 90. Other Special Furnaces. Another means of promoting the thorough mixing and combustion of the air and volatile matter necessary for smokelessness is by the use of some form of brick ignition arch or wall. In the boiler shown in Fig. 53 the gases are made to pass from the fuel bed into the " mixing" chamber and thence through the vertical slot in the ignition wall to the combustion chamber. The ignition wall becomes highly heated and serves to assist in the ignition of the gases, the narrow slot causing a thorough intermingling of the gases and air. The STEAM BOILERS 103 air supply enters principally through the fuel bed and an auxiliary air suppry^is provided above the fuel bed. With a boiler of this type, some smoke is unavoidable during the firing periods when the doors are open, admitting great vol- umes of cold air and when the green coal thrown upon the fire is giving off a large amount of hydrocarbon gases. For the greater part of the time, however, smokeless combustion is obtained. Another type of smokeless boiler which is coming into wider use employs a secondary air supply which is preheated and mixed Ignition. Wall \ Mixing Chamber ~ 3>- " FIG. 53. Smokeless boiler with brick ignition wall. with the combustible gases at the proper point in their path, thus promoting complete combustion. Other devices for the prevention of smoke consist of ignition arches of various designs, and of steam jets directed into the furnace so as to cause a thorough mixing of the air and gases. An interesting type of special boiler is the magazine-feed type designed primarily for burning the small sizes of anthracite coal and coke. These fuels cannot be burned successfully in an ordi- nary boiler because of the difficulty of getting air through a fuel bed of any considerable thickness, while a thin fuel bed requires very frequent firing. With the magazine-feed such as illustrated 104 HEATING AND VENTILATION in Fig. 54 the fresh fuel is fed by gravity as required and the fuel bed is at all times sufficiently thin to allow air to pass through it. The magazine holds sufficient fuel so that the boiler needs atten- tion only at much less frequent intervals than does the ordinary boiler. FIG. 54. Magazine feed boiler. 91. Proportions of Boilers. The heating surfaces in a boiler are defined as those surfaces which have water on one side and hot gases on the other side. In order that the boiler may be efficient the ratio of heating surface to grate surface should be large. The ratio is limited in practice., however, by such factors as the cost of the boiler and the friction introduced in the path of the flue gases. In small boilers it is usual to allow 1 square foot of grate surface to every 15 to 30 square feet of heating surface. For boilers of 50 horsepower an>d over, it is usual to allow from 30 to 40 square feet of heating surface per square foot of grate sur- face, while in very large boilers the ratio is 50 or 60 to 1. Expe- rience has shown that in small heating boilers it is advisable to allow each square foot of heating surface to evaporate only about 2 pounds of water per hour as a greater rate of steaming results in a high exit temperature of the flue gases. In large boilers the STEAM BOILERS 105 evaporation rate varies from 3 to 6 pounds per square foot of surface. Small heating boilers are distinctly different in operation from large power or heating boilers. In the latter, coal is being fed to the boiler almost continuously and the flues are carrying a large quantity of gases. Small heating boilers, on the other hand, are fed with coal only at infrequent intervals and very little of the heat is transmitted to jthe water by the flue surfaces, the greater part of the heat being transmitted by the fire surfaces, i.e., those which are in the paths of the heat rays emanating from the fuel bed. During the periods when the drafts are closed most of the steaming in the boiler is produced: by the fire surface. It is good practice to have about 60 per cent, fire surface and 40 per cent, flue surface in small cast-iron boilers. 92. Boiler Rating. The standard unit_ofj3oiler capacity is the boiler horsepower which is defined as the equivalent of 34.5 pounds_Qf^ibeam evaporated "from and at" 212 (i.e.. from water at 212 into saturated steam at the same temperature). As each pound of steam so evaporated requires the transmission of 970.4 B.t.u., the boiler horsepower is equivalent to 33,479 B.t.u. per hour. It is customary to allow 10 square feet of heating surface per boiler horsepower for establishing the rated capacity of a boiler. On this basis, one square foot of surface when working a^j^ted__capacity evaporates 3.45 pounds of water per hour. Large boilers have an overload capacity of from 50 to 100 per cent. Heating boilers are not usually rated in horsepower but by the amount of radiation which they will handle or in B.t.u. per hour. The radiation ratings are published by each manufacturer for his own boiler but do not always represent the true capacity of the boiler, so that it is necessary to use them with caution unless they have been established by actual tests. The capacity of a heating boiler depends upon quite different factors from those on which a power boiler is rated. A heating boiler, unless of large size, must run for several hours on one charge of fuel. The amount of steam which it is capable of generating depends upon the amount of fuel burned $er hour and this is in turn^fixed by the fuel holding capacity of the boiler and the allowable 3 iength of the firing period. The firebox must be large enough to holol the fuel required for a given firing period plus at least 20 per cent, excess for igniting the next charge. Consequently, a given boiler may be driven at a high rate with a 106 HEATING AND VENTILATION short firing interval or at a lower rate with a longer firing interval- It is always necessary to consider the firing period when determin- ing the rating of a boiler. The efficiency of the boiler is also a factor in the output of which it is capable. The efficiency usually decreases with increas- ing loads, principally because the amount of heat lost in the flue gases increases. It is thus evidently impossible to determine the capacity of a boiler accurately except by test. The leading manufacturers use this method in rating their boilers. The capacity of a heating boiler may be expressed as follows: Q = W X G X H~X E in which Q = boiler output in B.t.u. per hour. W = weight of fuel burned per hour per sq. ft. of grate area. G = grate area, sq. ft. H = calorific value of fuel, B.t.u. per pound. E = combined efficiency of boiler and grate. In computing the boiler output necessary for a given heating system, it is customary to assume that a square foot of direct steam radiation requires 250 B.t.u. per. hour and a square foot of hot water radiation requires 150 B.t.u. per hour. To this must be added the equivalent of the mains and risers. If uncovered, such piping should be computed as an equal amount of radiation. If insulated, the heat loss should be computed according to the kind of covering. Twenty-five per cent, of the radiator surface is often used as an approximate figure to represent the loss from piping. An additional factor of safety to allow for such things as dirty flues, poor fuel, etc., should usually be added, amounting to from 15 to 25 per cent. Sometimes it is desirable to increase this factor, in case the building must be heated intermittently and quickly. Table XXIV 1 gives the square feet of direct steam radiation per square foot of grate area at various combustion rates and efficiencies, based on anthracite coal having a calorific value of 12,000 B.t.u. per pound. For example, with a combustion rate of 7 pounds per square foot per hour, a boiler operating at 65 per cent, efficiency could supply 201.6 square feet of direct steam 1 From report of Committee on Rating of Heating Boilers, Trans. A. S. H.* & V. E., 1911. STEAM BOILERS 107 TABLE XXIV. RATINGS OF CAST-IRON BOILERS IN TERMS OF SQUARE FEET OF DIRECT STEAM RADIATION PER SQUARE FOOT OF GRATE AREA, WITH DIFFERENT RATES OF COMBUSTION AND DIFFERENT BOILER EFFICIENCIES ASSUMPTIONS. (a) Coal heat value = 12,000 B.t.u. per pound; (6) boiler efficiency = ratio of heat given off beyond nozzle to heat-value of coal burned; (c) one square foot of direct steam radiating surface gives off 250 B.t.u. per hour. NOTE. All radiating surface giving off different amounts of heat than 250 B.t.u. per hour per square foot may be reduced to " equivalent direct surface" at 250 B.t.u. per hour per square foot for use in connection with this table. Boiler efficiencies o3 v ftft (Per cent.) If 50.0 52.5 55.0 57.5 60.0 62.5 65.0 67.5 70.0 75.2 75.0 Square feet of direct radiation i 24.0 25.2 26.4 27.6 28.8 30.0 31.2 32.4 33.6 34,8 36.0 2 48.0 50.4 52.8 55.2 57.6 60.0 62.4 64.8 672 69.6 72.0 3 72.0 75.6 79.2 82.8 86.4 90.0 93.6 97.2 100.8 104.4 108.0 4 96.0 100.8 105.6 110.4 115.2 120.0 124.8 129.6 134.4 139.2 144.0 5 120.0 126.0 132.0 138.0 144.0 150.0 156.0 162.0 168.0 174.0 180.0 6 144.0 151.2 158.4 165.6 172.8 180.0 187.2 194.4 201.6 208.8 216.0 7 168.0 176.4 184.8 193.2 201.6 210.0 218.4 226.8 235.2 243.6 252.0 8 192.0 210.6 211.2 220.8 230.4 240.0 249.6 259.2 268.8 278.4 288.0 9 216.0 226.8 237.6 248.4 259.2 270.0 280.8 291.6 302.4 313.2 324.0 10 240.0 252.0 264.0 276.0 288.0 300.0 312.0 324.0 336.0 348.0 360.0 radiation per square foot of grate area. If the grate is 20 inches in diameter (area 2.18 sq. ft.) the total capacity is 2.18 X 201.6 = 439.5 sq. ft. Heating boilers, using anthracite coal, usually operate at from 55 to 65 per cent, efficiency at full capacity. The rate of com- bustion to be assumed depends upon the size of the boiler and the kind of fuel used. In general, the larger the boiler, the higher the allowable rate of combustion per square foot of grate area. A combustion rate of 5 to 7 pounds per hour per square foot is good practice for ordinary conditions. The volume of the fire pot must be sufficient to contain the fuel needed for the firing period plus a reserve of approximately 20 per cent, to ignite the next charge of fuel. For ordinary conditions, with small or medium sized boilers burning anthracite coal, the firing period assumed should be at least 8 hours. For residences, a 10 hour firing period is preferable. For larger 108 HEATING AND VENTILATION boilers where frequent or continual attendance is available, the charges of fuel will naturally be more frequent and smaller and the combustion rate higher. In the foregoing example, the boiler burning 7 pounds of coal per square foot per hour should have a fire pot large enough to hold 7 (pounds) X 2.18 (square feet) X 8 (hours) X 1.20 = 146.5 pounds of coal. It is custom- ary to use as the depth of the fire pot the distance from the center of the furnace door to the grate. For anthracite coal, the weight per cubic foot is taken as 50 pounds. 93. Use of Bituminous Coal. In all of the foregoing, the boiler performance is based on anthracite coal which is assumed to have a heating value of 12 ; 000 B.t.u. per pound. If bituminous coal is used, the firing conditions are somewhat different. This fuel requires more frequent attention for slicing the fire and for charging fuel. The large quantities of soot emitted cause accumulations on the heating surfaces which reduce the efficiency and consequently the capacity of the boiler. Bituminous coal occupies 25 per cent, more space per pound than anthracite and the size of the furnace must be based on this volume. The calorific value varies considerably, ranging from 10,000 to 14,000 B.t.u. per pound. Some engineers install two boilers in buildings of considerable size, each having a capacity sufficient to take care of about two- thirds of the maximum load which could be expected. This practice enables one boiler to be operated at an active rate of combustion during the greater part of the time and provides a spare boiler sufficient to handle almost the entire load if forced. In very large buildings even more spare capacity should be provided. 94. Boiler Accessories. Every steam boiler should be equipped with a safety valve of sufficient capacity to handle all of the steam which the boiler can generate. A safety valve of the spring-loaded type is shown in Fig. 55. A safety valve of the weight arid lever type is undesirable as it can be rendered in- operative through the suspending of extra weights on the lever. The safety valve should be piped a few feet away from the boiler so that a discharge of steam from it will not injure the covering of the boiler. The valve should be set to operate at from 2 to 5 sounds above the normal pressure. ^A jva/ter column is required to indicate the level of the water in the boiler. It should be equipped with a gage glass and with try- STEAM BOILERS 109 cocks as shown in Fig. 56, the latter being desirable for use in case the gage glass becomes broken or to verify its showing. C3> A steam pressure gage similar to that in Fig. 57, is also required. FIG. 55. Safety valve. FIG. 56. Water column. To facilitate the control of the drafts,|yid to maintain an even steam pressure some form of damper regulator operated by the pressure in the boiler is very desirable. The form shown in FIG. 57. Steam pressure gage. FIG. 58. Damper regulator. Fig. 58 consists of a corrugated metal bellows which expands under pressure, closing the ashpit damper and opening the check damper in the flue by means of chains or rods connected to the 110 HEATING AND VENTILATION lever. The pressure at which the action takes place depends upon the location of the weight on the lever arm. 95. Draft and Chimney Construction.-t-In order to maintain combustion in a furnace a continuous supply of air must be moved through the fuel bed. In the ordinary heating boiler, the air is drawn through by means of a chimney, which also serves to dispose of the smoke and other products of combustion. The chimney produces a " draft" or movement of the air because of the difference in weight between the column of hot gases in the chimney and the cold outside air. .. The intensity of the force produced depends upon the average difference in temperature between the hot gases in the stack and the outside air and upon the height of the stack. This force must be sufficient to move the required amount of air and gases through the boiler and stack against the frictional resistances interposed by the various obstructions. These resistances consist of (a) the resistance of the fuel bed, (6) the resistance of the flues of the boiler, (c) the resistance of the damper and breeching, and (d) the resistance of the stack itself. The first three items are fixed by the kind of fuel used and by the design of the boiler. The last item depends upon the height, cross-section, and construction of the stack. If the cross-sectional area of the stack is too small, the friction in the stack itself will be great and the sum of the various resistance factors may be greater than the available draft produced by the stack. Increasing the area of the stack results in a reduction of its frictional resistance and therefore in an increase in the net amount of draft available at the foot of the stack for overcoming the boiler and breeching losses. Increasing the height of the stack obviously increases the available draft. The dimensions of a chimney can be computed from a consid- eration of the principles stated above, 1 but for ordinary cases they can be determined by empirical rules. Table XXV gives the dimensions of chimneys for various amounts of steam or water radiation. The available draft of such chimneys, properly designed and constructed, as measured with an ordinary draft gage, should approximate the values given in Table XXVI. In measuring the available draft the gage should be connected to the breeching on the chimney side of the damper. The fire should be regulated so that the temperature of the stack gases 1 For methods of chimney design see GEBHARDT, "Steam Power Plants." STEAM BOILERS 111 TABLE XXV. MINIMUM CHIMNEY FLUE SIZES FOR BOILERS AND FURNACES Warm air furnace capacity in leader pipe, sq. in. Boiler hot water rating, sq. ft. Capacity steam (direct) rating, sq. ft. Number of heaters attached to each flue 1 2 3 Dimensions, in. A M^J '< w Dimensions, in. +a A **-tJ "3* 4 " 1 W Dimensions in. J3 .5~ 6 5.000 4.506 15.708 14.156 19,635 15.947 0.763 9.030 12.538 8 5 5.563 5.047 17.477 15.856 24.306 20.006 0.686 7.198 14.617 8 6 6.625 6.065 20.813 19.054 34.472 28.891 0.576 4.984 18.974 8 7 7.625 7.023 23.955 22 . 063 45.664 38 . 738 0.500 3.717 23 . 544 8 8 8.625 8.071 27.096 25 . 356 58.426 51.161 0.442 2.815 24 . 696 8 8 8.625 7.981 27.096 25.073 58 . 426 50.027 0.442 2.878 28.554 8 9 9.625 8.941 30.238 28.089 72.760 62.786 0.396 2.294 33.907 8 10 10.750 10.192 33.772 32.019 90.763 81.585 0.355 1.765 31.201 8 10 10.750 10.136 33.772 31.843 90.763 80.691 0.355 1.785 34 . 240 8 10 10.750 10.020 33 . 772 31.479 90 . 763 78.855 0.355 1.826 40.483 8 11 11.750 11.000 36.914 34 . 558 108.434 95.033 0.325 1.515 45.557 8 12 12.750 12.090 40.055 37.982 127.676 114.800 0.299 1.254 43.773 8 12 12.750 12.000 40.055 37.699 127.676 113.097 0.299 1.273 49.562 8 13 14.000 13.250 43.982 41.626 153.938 137.886 0.272 1.044 54.568 8 14 15.000 14.250 47.124 44.768 176.715 159.485 0.254 0.903 58 . 573 8 15 16.000 15.250 50.265 47.909201.062 I 182.654 0.238 0.788 62.579 8 standard weight because of slight variations in the thickness of the sheets from which it is made. For extremely high pressures, "extra strong " and "double extra strong" pipe may be obtained. PIPE, FITTINGS, VALVES, AND ACCESSORIES 129 The extra thickness of the walls is added on the inside of the pipe, reducing the internal area and not affecting the outside diameter. These heavier grades are seldom used in heating work. 112. Pipe Threads. In order that they may be screwed to a tight joint, pipe threads are made with a taper of 1 in 32 with the axis of the pipe, and the threads in the fittings are tapped to the same taper. Pipe threads are commonly made to conform to the so-called Briggs standard, illustrated in Fig. 75, which calls for a thread having a 60-degree angle, with the top and bottom slightly flattened. The number of threads per inch varies for the different sizes of pipe. 8 or 4 Threads, Imperfect Top and Bottom 2 Threads Perfect at Root Imperfect at Top \^60 -w" VVWvWW FIG. 75. Briggs standard pipe thread. 113. Screwed Fittings. The common forms of screwed fittings used in heating work are shown in Fig. 76. All except the nipples and ordinary coupling are made of cast iron. In desig- nating reducing tees the size of the openings opposite each other is given first and then the size of the branch opening. For example, the reducing tee in Fig. 76 is a 1J^ by 1 by J^-inch tee. For pressures over 125 pounds, an " extra heavy" pattern is available which is suitable for working pressures up to 250 pounds. Extra heavy fittings are made with a greater wall thick- ness and are of larger dimensions throughout. 114. Unions. Where screwed fittings are used, provision should be made, at intervals in the line, for disconnecting the piping for repairs, etc. " Right and left" couplings or "unions" are used for this purpose. The former, as the name indicates, are couplings tapped at one end with a left-hand thread, so that both threads can be screwed up simultaneously. Longitudinal ridges are cast on right and left couplings so that they can be identified after installation. For pipe sizes up to 2 inches, nut unions, consisting of two 130 HEATING AND VENTILATION pieces screwed to the ends of the pipe and held together by means of a threaded nut are used. Flanged unions are used with larger sizes of pipe. In Fig. 77 are shown these various 90 Elbow- Cross 45 .Elbow Reducing Elbow Reducing Tee Reducing Coupling Plug Cap Bushing Coupling Close Nipple Shoulder Nipple FIG. 76. Screwed fittings. types of pipe connections. The ground-joint union is superior to the gasket union in that it can be disconnected repeatedly without trouble, whereas the gasket in the latter type must be frequently replaced. Brass Lap Union Iron Iron, and Brass Iron Union with Union Brass Seat Ring FIG. 77. Pipe unions. 115. Flanged Fittings. In heating work, piping of the larger sizes (over 3 or 4 inch) is usually designed with flanged connec- tions, in order that any section of pipe or any fitting can be PIPE, FITTINGS, VALVES, AND ACCESSORIES 131 readily removed. With screwed fittings it is necessary, in order to remove any member, to take down all of the line from the nearest union or flanged connection. Flanges are commonly screwed to the pipe, especially for low-pressure work. For high- pressure work they may be welded to the pipe or attached by the .Screwed Flange Welded Flange FIG. 78. Various forms of flanges. Improved Van Stone Flange "Van Stone" method in which the pipe extends through the flange and is formed to a flat face as shown in Fig. 78. Some forms of standard weight flanged fittings are shown in Fig. 79. These fittings are suitable for pressures up to 125 pounds. There is an extra heavy pattern of flanges and flanged 90 Elbow 45 Elbow Reducer Reducing Tee Tee FIG. 79. Flanged fittings. Cross fittings which differ both in general dimensions and in the number and spacing of the bolts. 116. Gaskets. In bolting together flanged fittings it is neces- sary to insert a gasket between the faces in order to insure a tight joint. Gaskets are made of sheet rubber for water and low-pressure steam lines; for high-pressure lines gaskets of 132 HEATING AND VENTILATION corrugated copper or of various compositions containing asbestos are used. Gaskets are preferably cut in a plain ring to fit inside of the flange bolts. 117. Valves. In Fig. 80 are shown the various types of valves. The gate valve is the form ordinarily used in steam piping. Iron body gate valve non-ris- ing stem. Iron body globe valve rising stem. Angle valve. All bra^s gate valve. All brass globe valve. FIG. 80. Swing check valve. Globe valves are not permissible in horizontal steam lines as they are so constructed as to dam up the water and cause it to accumu- late in the bottom of the pipe, but on vertical steam pipes and on PIPE, FITTINGS, VALVES, AND ACCESSORIES 133 water pipes they are permissible and are especially desirable when the flow of steam or water is to be throttled. The angle valve is a very good type of valve for locations where it can be used. Valves in sizes up to 3 inches are made entirely of brass and the larger sizes are usually made of cast iron, with the gates and seats faced with bronze to give a non-corroding surface. The bronze mountings can be replaced when worn. The covei or bonnet of these larger valves is bolted instead of screwed to the body. Gate valves are made either with a rising or non-rising stem. With a rising stem valve the amount to which the valve is open is always apparent, which is often of great advantage but the space occupied by the valve is somewhat greater. * Check valves are frequently used in heating work. The swing check illustrated in Fig. 80 is the most satisfactory form. 118. Radiator Valves. The ordinary radiator valve for steam is of the angle pattern and is provided with a union for connecting to the radiator, as shown in Fig. 81. The valve disc is made of hard rubber and is renewable. These valves are also made in the " corner" pattern. The stem of the ordinary radiator valve is packed to prevent leakage with a soft stranded packing. The packing is seldom permanently tight, however, and the resulting leakage is often a source of considerable annoy- ance. In the more modern valves the packing is replaced by a grooved hard- rubber washer which is held against a seat by a spring. The construction of these so-called "packless" valves is shown in Fig. 82. Valves so con- structed are much superior to the ordi- nany type, as all leakage and the necessity of renewing the packing are eliminated. The ordinary steam-radiator valve may be used in hot-water work. A special hot-water valve is made, however, which consists of a sleeve having an orifice equal to the pipe%rea. By a half turn of the hand-wheel the sleeve is turned so that the FIG. 81. Ordinary radiator valve. 134 HEATING AND VENTILATION orifice is brought opposite the opening to the radiator. When closed, the valve allows enough circulation through the radiator to prevent freezing. Fig. 83 shows a valve of this type. FIG. 82. Packless valve. FIG. 83. Hot water radiator valve. 119. Pipe Covering. The piping of a heating system which is not intended to serve as radiating surface is insulated with some material of low heat conductivity. Most insulating materials owe their useful property to air enclosed in extremely small volumes. If the material is to be an efficient insulator these air volumes must be so minute that the circulation of the air in them is reduced to a minimum and in addition, the material itself must be of low conductivity. A satisfactory pipe covering must also be able to withstand the effect of high temperature and vibration, and to retain its insulating qualities throughout a long period of years. Pipe coverings are made of magnesia, asbestos, infusorial earth, hair felt, wool felt, and other materials. These substances form the basic element and are usually combined with other materials for mechanical reasons. The material which is probably the most widely used as an insulator is magnesium carbonate. It is in the form of a white powder, and some fibrous material such as asbestos fibers must be used with it as a binder, the aggregate being molded into blocks or into segments curved to fit the various sizes of pipe. Infusorial earth, which consists of the siliceous shells of minute PIPE, FITTINGS, VALVES, AND ACCESSORIES 135 organisms, is also combined with various binding materials to form a very efficient covering. Many forms of pipe covering are made of asbestos in combina- 'tion with some cellular material. The compound is rolled into sheets and the covering built up in corrugations so as to enclose air spaces. While not the most efficient type, these coverings are often the most suitable because of their low price. Fig. 84 shows a covering of this type. Hair felt, composed of matted cattle hair, is very efficient but cannot be placed in direct contact with steam pipes owing to its tendency to char at steam temperatures. In the selection of a pipe covering the cost of the pipe covering should be balanced against the saving which is effected by the reduction of the heat loss from the piping. Tests have recently been made on commercial pipe coverings by L. B. McMillan and FIG. 84. Cellular pipe covering. the results of his extensive investigations are shown by the curves in Fig. 85 which give the heat loss through several commercial coverings of standard thickness for various temperature differ- ences between the surface of the pipe and the air. It is nearly always desirable to provide insulation on the boiler and on the basement and attic mains in a heating system. It is usually desirable to cover also the supply risers, because they would otherwise give off heat continuously whether needed or not. Return risers are seldom covered in a system equipped with thermostatic traps. It is seldom proper, in heating work, to install the most effi- cient covering, as the cost of such a covering may easily offset the decrease in heat loss obtained. In fact, the heat radiated from the covered mains and risers of a heating system is not entirely a loss as it is partially utilized. In general, where the 136 HEATING AND VENTILATION steam temperature is high, the service continuous, and the coal expensive a more efficient covering is called for than in the case of low steam pressure and intermittent service, with a low-priced coal. 0.95 0.90 0.85 0.70 No.VII Sail-Mo Expanded No.VI J-M Wool Felt No.IV J-M Eureka No.X Carey Duplex No.XIX Plastic 85%M,agnesi No. XII Sail-Mo Wool Felt "0 50 100150200 250300 350400 450 500 Temperature Difference, Degrees Fahrenheit (Pipe Temp .-Boom Temp.) FIG. 85. Results of tests by L. B. McMillan on single thickness pipe coverings. 120. Covering for Boilers and Fittings. The exposed surfaces of heating boilers are usually covered with an insulating cement, containing asbestos fibers and some sort of a filler. The cement is applied to the hot boiler with the hand to a depth of from 1 to 2 inches and bound with wire, after which a finishing 'coat of cement and a canvas jacket are applied. The pipe fittings are also covered with cement to the same thickness as that of the pipe covering. For large flanges and fittings removable cover- ings can be obtained which allow repeated access to the 'joints without damage to the covering. PIPE, FITTINGS, VALVES, AND ACCESSORIES 137 121. Air Valves. In the ordinary steam heating system the air which fills the radiators when they are cold is forced out by the entering steam through some form of air valve installed on the end of the radiator opposite the supply connection. These air valves may be simply hand-operated cocks, which must be opened whenever the radiator is turned on, but the many forms of air valves which allow the air to escape but close automatically when steam reaches them, are greatly to be preferred. Auto- matic air valves are also designed to close when flooded with water as sometimes happens when a radiator does not drain properly FIG. 86. FIG. 87. FIG. 88. Riser vent. or becomes filled with water because of a leaky inlet valve. The common design is illustrated in Fig. 86. The composition post A expands when steam reaches it, causing the valve stem B to close against its seat. If water reaches the valve the inverted cup C, to which the valve stem B is attached, is raised by the buoyancy of the enclosed air and the valve closes. The force thus developed for closing the valve is small, however, and these valves cannot therefore be depended upon to prevent entirely the escape of water. The valve shown in Fig. 87 operates on the same general principle, the expansion of a volatile fluid in the cylinder acting to close the valve when the steam reaches it and the cylinder serving as a float which closes the valve when water reaches it. While more expensive, this form of air valve is more reliable than the cheaper grades. It is always desirable 138 HEATING AND VENTILATION to use air valves of good quality, as the faulty operation of an air valve is a source of extreme annoyance. Where large quantities of air are to be handled as in the case of a large riser or main, it is better to install a valve with a larger opening than that of the ordinary radiator air valve, so that the air can be discharged in a short time. Such air valves are com- monly called "riser vents" and take the form shown in Fig. 88. The valves used on an air-line system are intended to close against steam only. If water reaches them it is allowed to run into the air lines, from which it is drained at the lowest point. The expansion member may be either a composition post or a chamber containing a volatile liquid. The latter type is coming into general use. Fig. 89 illustrates these two types. FIG. 89. Air line valves. 122. Traps. A steam trap is a device whose function is to drain the water from a steam pipe, separator, or radiator, with- out allowing steam to escape. For radiators, special traps of the float or thermostatic form described in Par. 103 are used. For draining steam lines and separators, there are two kinds of traps in use, designated as " float " and "bucket" traps. The former consists of a receiver having a discharge valve controlled by a float in such a way that a raising of the water level from an influx of water causes the float to open the valve, allowing water to be discharged by the pressure of the steam until the water level is lowered to its normal point. One design of float trap is shown in Fig. 90. A gage glass on the trap indicates the water level. There is normally several inches of water above the valve and the PIPE, FITTINGS, VALVES, AND ACCESSORIES 139 existence of the proper water level affords an indication that the trap is operating properly. If the glass is empty, the trap is allowing steam to blow through; if it is full, the trap is not adequately taking care of the water. The bucket trap consists of a chamber containing a bucket which is floated by the water in the chamber. To the bucket are attached the valve stem and valve, as shown in Fig. 65. The water flowing into the trap enters and fills the bucket, finally causing it to sink and thereby opening the discharge valve. The steam pressure forces the water out through the valve and empties the bucket, which rises and closes the valve. FIG. 90. Float trap. FIG. 91. Bucket trap. It is possible to lift the condensation by means of a trap to a height approaching that equivalent to the steam pressure, i.e., about 2.3 feet per pound pressure. It is better, however, if possible, to locate the trap so that it will discharge by gravity. There is another type of trap which is used where large quanti- ties of water must be handled. This is the tilting trap, one. form of which is shown in Fig. 92. The condensation flows by gravity into the chamber which is hinged on the trunnions A-A and balanced by the weight B. As the chamber fills, the weight B is overbalanced and the chamber falls, opening the discharge valve C. The pressure of the steam forces the water out through the discharge valve and when the chamber becomes empty, it tips back into the filling position and the discharge valve closes. The tilting trap in a slightly different form can be used for lifting the condensation from low-pressure piping to a considerable height, if high-pressure steam is available. In such a trap an 140 HEATING AND VENTILATION additional inlet Valve is provided for the high-pressure steam, and the valves are so arranged that when the chamber fills and Inlet FIG. 92. Tilting trap. drops, the main inlet valve closes and the high-pressure inlet valve opens, admitting high-pressure steam which forces out the water and is capable of raising it to any height up to that equiva- lent to the steam pressure. Tilting traps are sometimes very useful but they require considerable attendance in order to insure their reliable operation. 123. Separators. The function of a steam separator is to remove condensation from steam lines. The sepa- rator accomplishes this by abruptly changing the direc- tion of flow of the steam and SIDE SECTION END SECTION thereby causing the entrained FIG. 93. Steam separator. 1,1 , , water to be thrown out, by its momentum, against a suitably designed baffle, usually having a series of grooves which conduct the water into a receiver PIPE, FITTINGS, VALVES, AND ACCESSORIES 141 below. The water is discharged through a trap or seal. This form of separator is illustrated in Fig. 93. Separators are placed in the exhaust line from pumps and reciprocating engines, where they remove the oil as well as the water from the steam. In choosing a separator care must be taken to select a size cor- responding to the quantity of steam flowing rather than to the size of the pipe line, for a certain velocity through the separator is necessary to insure the elimination of the water. FIG. 94. Reducing valve. 124. Reducing Valves. Steam is occasionally supplied to a building at a pressure much higher than is necessary or desirable for heating purposes, making it necessary to employ a reducing valve, a simple form of which is illustrated in Fig. 94. The pressure on the reduced pressure side of the valve is transmitted through the balance pipe to the under side of the diaphragm, 142 HEATING AND VENTILATION tending to close the valve. The force thus exerted is balanced by that due to the weights W-W and the valve will assume such a position that just enough steam will pass through it to maintain the required pressure on the reduced side, which pressure is governed by the position of the weights on the lever arm. The reduced pressure may be changed as desired by shifting these weights. The valve shown in Fig. 94 is double-seated, so that its movement is independent of the steam pressure on either side of the discs and is controlled solely by the reduced pressure acting on the diaphragm. Reducing valves should be installed with a bypass so that they can be removed for repairs without interruption of the steam supply. CHAPTER X STEAM PIPING 125. General Arrangement. The elementary arrangement of the different systems of steam heating was shown diagrammat- ically in Chapter VIII. Most of the principles involved in the design of the piping apply equally to all of them. FIG. 95. Single pipe up-feed system. In Fig. 95 is shown the piping for a single-pipe upfeed system. The supply mains circle the basement, pitching away from the boiler, and are dripped at the ends into the return main. For 143 144 HEATING AND VENTILATION a two-pipe system, the return mains and risers would be arranged in a similar manner. FIG. 96. Overhead vapor or vacuum system. Fig. 96 shows an overhead vapor or vacuum system in a tall building. Return risers extend from the top-floor radiators to STEAM PIPING 145 the basement, where they tie into the main return line. In large buildings the first floor is often divided into small stores which require heat at times when none is needed in the remainder of the building and vice versa, making it desirable to install a separate main to supply the first-floor radiators and arranged so that it can be controlled independently of the main heating system. This scheme also has the advantage of making it much easier to install connections to the first-floor radiators which are often so located that it is difficult to reach them from the risers. In extremely tall buildings it is better to feed the risers from the bottom as well as from the top and a supply main is installed in the basement for that purpose. 126. Principles Involved in Piping Design. In designing and installing a system of piping, attention must be given to the following fundamental requirements: 1. Provision for expansion. 2. Proper drainage of condensation from the steam lines. 3. Proper arrangement of piping and use of pipes of the proper size, so that the pressure drop due to friction will be small. 127. Expansion. Perhaps the most important consideration is the proper provision for the linear expansion of the pipes. When steam is turned into or shut off from a system of piping, a change of temperature of the pipe amounting to from 140 to 170 takes place and provision must be made for allowing the resulting change of length to occur without putting excessive strains on the fittings. The curve in Fig. 97 shows the theoretical expansion of wrought-iron pipe due to an increase in temperature from 60 to the temperature corresponding to various steam pressures. The temperature of 60 is assumed to be that at which the piping is originally installed. For low-pressure piping a rough rule is to allow 1J^ inches of expansion per 100 feet length of pipe. The force which an expanding pipe is capable of exerting is extremely great. If constrained at the ends with sufficient rigidity the increase in length will cause the line to "bow" in the center, and the enormous strain thus imposed upon the flanges and fittings is almost certain to crack them. In designing any pipe line some point should be selected as a fixed or anchored point and a comprehensive study made of the amount and direc- tion of the expansion. Provision must be made for properly taking care of the elongation of all parts of the system. There are in general three ways in which the expansion in a 10 146 HEATING AND VENTILATION system of piping may be absorbed: (a) by the turning of some of the threaded joints, (b) by the bending of the pipes, and (c) by the use of special devices designed to absorb the movement. The absorbing of the expansive movement by the turning of threaded joints is permissible only in low pressure piping work. Continued twisting of a threaded joint will in time often result in a leak, particularly when the pressure is high. In heating work it is common practice to depend upon this method of caring for expansion. In many cases it is feasible to depend upon the bending of parts of the piping, and this is usually a very satis- 2.0 1.0 20 120 140 40 SO 80 100 Steam Pressure - Lbs. per Sq, In. Gage OcfeihaF Temperature 60 FIG. 97. Elongation of wrought iron pipe with various steam pressures. factory method. Examples of both of these methods will be described later. For extremely large or long pipes it is some- times necessary to use special expansion fittings. 128. Drainage. There is always some water in pipes carrying saturated steam. In some kinds of heating systems, in addition to the condensation formed in the pipe itself there is also con- densation from other parts of the piping and from the radiators. The proper provision for the flow and drainage of the water is important. In horizontal pipes the water should if possible travel in the same direction as the steam and to accomplish this the pipes should be given a pitch of at least 1 inch in 10 feet in the direction of the flow. In case it is necessary to drain the con- STEAM PIPING 147 densation against the flow of the steam, as in a branch to a riser, a much greater pitch should be allowed and pipes of larger diameter should be used so that the velocity of the steam will be low. Drainage should be provided for any necessary pockets or low points where water might accumulate. 129. Mains and Branches. Horizontal mains are usually anchored at the boiler and allowed to expand freely from that point. The amount of movement of any point along the length of the pipe is evidently proportional to its distance from the fixed point. In connecting risers and branches the movement of the main is best taken care of by either of the arrangements in Figs. 98 and 99. As the main moves longitudinally the FIG. 98. FIG. 99. Methods of connecting branches. threaded joints C-C turn slightly. The arrangement of Fig. 99 is somewhat the better as the 45-degree elbow offers less resistance to the flow of steam than the 90-degree elbow in Fig. 98. The expansion of the horizontal branch is taken care of by the spring of the riser, which arrangement is quite permissible as such branches are rarely over 10 feet long. The arrangement shown in Fig. 100 is sometimes used when the expansion of the main is great. It has the disadvantage of offering considerable resis- tance to the flow of steam. Branches are sometimes taken from the bottom of the main as in Fig. 101. It is then necessary to install a drip connection in the manner shown. This arrange- ment is undesirable in one respect. If for any reason the water level rises in the return system above the horizontal connection to the riser, then the riser will be entirely sealed from the main 148 HEATING AND VENTILATION The one-pipe relief system and its steam supply will be cut off. is usually piped in this manner. In very long horizontal mains in which the movement would be too great to be absorbed by the branch connections it is neces- Drip FIG. 100. FIG. 101. sary to anchor the pipe at two or more points and to provide a swivel joint of the form shown in Fig. 102. One objection to this method is the resistance to the flow of steam offered by the fittings. FIG. 102. Expansion swivel. FIG. 103. Another scheme which is sometimes used where the main makes a turn of 90 degrees is that shown in Fig. 103. With this arrangement the expansion is largely absorbed by the spring of the members. FIG. 104. FIG. 105. When the size of the main is reduced an eccentric reducer should be used as in Fig. 105 so that no water pocket will be formed. The accumulation of water in shallow pockets such as STEAM PIPING 149 that formed by the reducing tee in Fig. 104 gives rise to severe cracking and pounding when the heating system is started up. 130. Risers. In small buildings where the supply mains are in the basement, the expansion of the risers is usually downward and the movement is taken care of by the spring of the branches (see Figs. 98 and 99). In larger buildings, where there is a main in the attic, the risers are anchored near the middle and the expansion takes place in both directions. When the expansion is too great to be handled by an ordinary branch connection the arrangement in Fig. 106 may be used. This gives a perfect swivel joint and is especially serviceable when the basement main must FIG. 106. Flexible connection for riser. FIG. 107. Expansion loop for riser. be installed near the foot of the risers. Its disadvantage is the resistance to the steam flow offered by the fittings. The branch connection shown in Fig. 99 will easily take care of the expansion of risers about four stories high, and that in Fig. 106 about eight stories. For taller buildings an expansion loop of the form shown in Fig. 107 is installed in the middle of each riser. Such an expansion loop is easily capable of handling a length of riser of at least four stories in either direction and gives perfect flexibility. Space is required in the furring to conceal the loop. 131. Drip Connections and Air Venting. The ends of mains are dripped in the manner shown in Fig. 108. An air valve should be installed at such points to free the main of air when the system is started up. Drips from different mains should not be con- 150 HEATING AND VENTILATION Last Brunch Connection - Main Valvp nected together above the water line as the pressure of the steam in them may be different, in which case the flow of the condensa- tion would be interfered with and a water-hammerset up. Air vents should be located at the ends of all mains and at other places where air is liable to become pocketed. 132. Pipe Hangers. The piping in a heating system must be substan- tially supported either from the building struc- ture or from special sup- ports. Horizontal mains Orip FIG. 108. Drip at end of main. are usually hung from the joists or steel work of the floor above. For pipes of moderate size the hanger shown in Fig. 109 is widely used. The perforated metal can be obtained in strips and cut to any required length. This hanger is of low cost and can be installed very cheaply. FIG. 109. Simple form of pipe hanger. For heavier pipes the hanger shown in Fig. 110 is a common design. The turnbuckle is used to adjust the elevation of the pipe when it is being installed. Both of these hangers permit STEAM PIPING 151 the free longitudinal movement of the pipe line. Hangers should be placed at intervals of 20 feet or less on all horizontal pipes. FIG. 110. Hanger for large pipes. 1 PLAN FIG. 111. Anchor for riser. 1 Risers are supported at the anchor points in some such manner as is illustrated in Fig. 111. From " Pipe-fitting Charts" by W. G. SNOW. 152 HEATING AND VENTILATION 133. Return Piping. Return pipes of any kind of a steam system should be designed with ample provision for expansion as they may at times be heated to steam temperatures. Dry- return mains should be given a pitch of at least 1 inch in 10 feet toward the boiler. Wet return mains should also be pitched toward the boiler so that they may be entirely drained of water when necessary. Return pipes should never be buried in the ground without protection. When it is necessary to con- ceal them the best plan is to arrange them in trenches with remov- able cover plates. An alternate scheme is to cover them with cylindrical tile with cemented joints which will keep out the FIG. 112. Water level in return line of vapor system. water. When buried in soil, return pipes corrode and deteriorate very rapidly. 134. Vapor and Vacuum Systems. In a vapor system, since the return lines are under atmospheric pressure, the water will build up in the return leg (Fig. 112) to a height above that in the boiler equivalent to the pressure in the boiler. In order to pre- vent the return mains from becoming flooded the distance from the water line of the boiler to the horizontal return main, desig- nated by h in Fig. 112, should be as great as possible and should never be less than 2J^ feet. In some cases it is necessary to place the boiler in a pit below the basement floor, in order to accomplish this. The supply main of a vapor system can often STEAM PIPING 153 be dripped at the end into the return main through a thermo- static trap. This, however, necessitates starting the return main at an elevation below the end of the supply main which, with the necessary pitch toward the boiler, may bring it very close to the water line. A better arrangement is to install a separate drip line from the end of the supply main, which allows the return main to be placed much higher. This arrangement Drip from End of FIG. 113. Method of dripping supply main when basement is shallow. is shown in Fig. 113, the dotted line representing the necessary elevation of the return main if the drip line is omitted. In an overhead vapor or vacuum system each riser is dripped at the bottom through a thermostatic trap as in Fig. 114. In order to catch the dirt and scale which would clog the trap a dirt pocket should be provided, consisting of a short capped pipe. Steam mains are dripped into the return line in a similar manner. XI Kiser Trap Dirt Pocket Return Main' FIG. 114. Drip connection to riser in a vapor or vacuum system. Bypasses are sometimes provided for the most important traps to enable them to be easily cleaned or inspected and dirt strainers are also sometimes used. 135. Valves. The location of valves in a heating system should be given careful consideration. While valves are desirable in many locations, there are also some places where they should never be installed unless the plant is in the hands of a competent 154 HEATING AND VENTILATION engineer, because of the possibility of accidents resulting from ignorant handling of them. In a small system as few valves should be installed as possible. Indeed for residence systems it is seldom necessary to install any valves except at the radiators. Valves should never be installed on the steam outlet of the boiler or on the return connection unless the plant is under careful supervision or unless two boilers are used in parallel, in which case valves are necessary in order to enable one boiler to be cut out of service for repairs. In large buildings a valve should be provided on each riser, if possible, so that a riser can be shut off for repairs, etc., without necessitating the shutting down of the entire system. Valves should also be provided on each branch main and return line in such buildings. Gate or angle valves should be used in preference to globe valves. 136. Radiator Connections. The connections to a radiator must be sufficiently flexible so that the main or riser is perfectly FIG. 115. Connection to first floor radiator. FIG. 116. Connections from risers where ver- tical movement is small. free to expand without straining the fittings. They must also be designed to allow the radiator to drain properly and must be free from water pockets. Figs. 115, 116, and 117 show some proper methods of connecting radiators in a single-pipe system. That shown in Fig. 115 is used for first-floor radiators connected directly to the main. The connection in Fig. 116 is suitable for risers whose vertical movement is small enough to be absorbed by the spring of the horizontal pipe. An objection to this arrangement is the fact that the connection is under the floor and inaccessible unless the horizontal branch is exposed in the room STEAM PIPING 155 below as shown by the dotted lines. In the connection shown in Fig. 117 a radiator valve of the " corner" pattern is used and the FIG. 117. Flexible connection, plan view used when riser has considerable vertical movement. use of the elbows gives a very flexible combination which is well suited for tall buildings where the movement of the risers is considerable. FIG. 118. Radiator connections vapor system. The connections to a radiator of a vapor system are shown in Fig. 118. These connections are also very flexible and the use of 45-degree elbows reduces the frictional resistance. U FIG. 119. Wrong method. In no case should a radiator be connected as in Fig. 119. The short, stiff connection allows no free vertical movement of the riser and causes severe strains on the fittings. 156 HEATING AND VENTILATION 137. Pipe Coils. Pipe coils may be connected in the manner shown in Figs. 120a and 1206. The arrangement in Fig. 120a is used for a two-pipe system and that in Fig. 1206 for a single-pipe system. A return connection is always used on pipe coils because of the difficulty of draining the large amount of condensa- FIG. 120a. FIG. 1206. Methods of connecting pipe coils. tion formed in radiation of this type back through the inlet connection. The check valve in Fig. 1206 prevents steam from entering the coil through the return connection. In order to open the check valve against the pressure of the steam in the riser a water head must be built up above it equivalent to the drop in pressure through the coil, which may be quite appreciable. Therefore, a short length of vertical pipe should be installed above the check valve as shown, to receive the water column which would otherwise occupy the lower part of the pipe coil. Steam Main Return Ai a i n FIG. 121.' Boiler connections. 138. Boiler Connections. The usual method of arranging the connections to a steam boiler is shown in Fig. 121. In addition to the supply and return connections there is required a blow-off cock and a city water connection with a shut-off valve STEAM PIPING 157 and a check valve. It is sometimes necessary to connect two boilers in parallel. This must be carefully done so that there will be no chance of either boiler losing water to the other. Connections of ample size between both steam and return connections should be made so that the pressure and water levels in both boilers will be always the same. 139. Flow of Steam in Pipes. When any fluid flows through a pipe a certain pressure is necessary to move it against the resistance caused by the friction of the fluid against the inner surface of the pipe. The following laws governing the friction of fluids in pipes have been established by experiment: 1. The total amount of frictional resistance is independent of the absolute pressure of the fluid against the pipe wall. 2. The frictional resistance varies nearly as the square of the velocity. 3. The frictional resistance varies directly as the area of contact between the fluid and the pipe wall. 4. The frictional resistance varies directly as the density of the fluid. Consider a condition of steady flow in a pipe and let pi (Fig. 122) be the unit static pressure of the fluid, at one point and FIG. 122. let pz be the pressure at another point at a distance L from the first. The drop in pressure due to the friction of the fluid in passing through the distance L is then P = Pi- P2 Expressing the laws of friction stated above in algebraic form we have Pa = FSDv 2 (1) in which P = drop in unit pressure in pounds per square foot. a = cross-sectional area of the pipe in square feet. F = a constant depending on the nature of the fluid and the nature of the pipe surface. S = area of contact between the fluid and the pipe in square feet. D = density of the fluid in pounds per cubic foot. v = velocity of the flow in feet per second. 158 HEATING AND VENTILATION Then P = ^FSDv* (2) Let F be made arbitrarily = ^ Then equation (2) becomes 1 v 2 P = -fSD^ (3) a 2g v* This is done simply to bring into the expression the term 5- which is the usual form for expressions of this nature. For round pipes of diameter d and length L, S = irdL and a = 4' Then P = Let w = the weight of steam flowing in pounds per minute. Then w = ^XvXDXQO = 47.l2d 2 vD and v = 4fr 10 , 9 -7v (5) p Let p be the pressure drop in pounds per square inch = JT^ and let di be the diameter in inches - 12d. Substituting in (4) these values for v, P and d we have p= 0.04839 ^ 5 (6) The coefficient / was found by Unwin to be = K (l -f YTJJ) The value most commonly used for X for steam is that de termined by Babcock which = 0.0027. Substituting in (6) we have p = 0.0001306 w 2 L(l + ~> in which p = pressure drop in pounds per square inch. w = weight of steam flowing in pounds per minute. L = length of pipe in feet. di = diameter of pipe in inches. D = average density of steam in pounds per cubic foot. STEAM PIPING 159 The value of the coefficient / given above has been found to be correct for small pipes and comparatively low velocities, For large pipes and high velocities the value of / is considerably lower. 1 140. Factors Affecting the Size of Pipes. The sizes of pipes to be used in a heating system depend upon several factors. The fundamental requirement as regards the supply pipes is that they must be of sufficient capacity to transmit the required quantities of steam with the pressure differential which is avail- able. The latter depends somewhat upon the source of the steam supply. When exhaust steam from an engine or turbine is used for heating, it is best, from the standpoint of economy, to make possible the carrying of a low back-pressure by designing the heating system to operate with an initial pressure of not over 2 pounds per square inch. The same practice should usually be followed when steam is taken direct from a boiler, as it may be desired at some future time to use exhaust steam. The circulation will also be much better and the system more satisfactory if the pipe sizes are ample. When a vacuum pump is used the greater pressure differential thus set up makes possible the use of smaller pipes but it is well, nevertheless, to design the supply piping to operate as a gravity system with a moderate pressure drop so that the pump can be shut down at times if desired. The return pipes, however, can be made somewhat smaller if a vacuum pump is to be used. Another factor which makes an extreme reduction in the size of the supply pipes undesirable is the noise caused by the result- ing high velocity of the steam flowing through them. On the other hand, to make the pipes of excessive size increases unneces- sarily the cost of the system. Because of these various factors it is common practice to take as a safe standard for the rate of pressure drop in the supply piping a drop of from 0.03 to 0.10 pounds per 100 feet of pipe. There are other factors beside that of pressure drop which affect the size of the supply pipes, such as the provision for the carrying of condensation. In general all steam pipes in which the condensation drains in the opposite direction to the flow of steam should be larger than if both flow in the same direction. 1 See "The Transmission of Steam in a Central Heating System" by J. H. WALKER, Trans. A. S. H. & V. E., 1917. 160 HEATING AND VENTILATION This applies particularly to single-pipe radiator connections and branches and to the risers of single-pipe systems. The proper size of return pipes is based upon experience and good practice as there is no definite law upon which their size can be computed. They must first of all be sufficiently large to carry the condensation. Second, they srioji]iLbeJarge enough so that they will not become plugfedwith dirt ; and third, they musl, inji vapor or vacuum system, be large enough to"liandle the air from the radiators as well as the condensation, when the radiators are first turned on. 141. Selection of Sizes of Supply Pipes. In a large or impor- tant system it is very desirable to make a detailed calculation of the pressure drop through the system. Besides insuring ample pipe sizes this will enable the pipe sizes to be reduced in some cases below those which would be chosen arbitrarily. In a large building a considerable saving may be effected by judiciously choosing the pipe sizes for the risers and mains. In a system in which the supply to individual radiators is controlled by gradu- ated valves it is very desirable to have approximately the same pressure at all radiator valves. To accomplish this fully would be an impossibility, but such a condition can be approximated by careful design. In selecting the pipe sizes, the desired pressure drop through the system is chosen and the approximate average drop per unit length of pipe is found, after which the exact drop can be com- puted by means of formula (7), Par. 139. In order to facilitate the calculations, the chart in Fig. 123 may be used and the pressure drop per 10 feet of pipe read directly. The chart is based on an average density of the steam corresponding to a pressure of 2 pounds gage, which is sufficiently accurate for the range of pressure which occurs in a heating system. In figuring the capacities of the pipes no allowance need be made for con- densation in the pipes themselves as this will ordinarily be negli- gible if the pipes are covered, but if the pipes are to be left bare their radiating surface should be included with that of the radiators. The scales at the bottom of the sheet read directly in square feet of radiation having an assumed heat transmission of 245 B.t.u. per square foot per hour, which is the amount which would be transmitted from 38-inch, two-column radia- tion with a room temperature of 70 and a 'steam temperature corresponding to the pressure of 2 pounds. The scales at the STEAM PIPING 161 top of the sheet read in B.t.u. delivered per hour, and are con- venient for use when the B.t.u. to be delivered by each radiator is known. As an example of the use of the chart, consider a riser 218 feet long supplying 3000 square feet of radiation. If the drop through the riser is to be not more than 0.1 pound, find the proper pipe size. The drop of 0.1 pound in 218 feet is Use upper scale for pipe siz 2,000 3,000 4,000 20 30 40 es 5"and over Heat Delivered per Hour Thousands of B.t.u. a. 6,000 8,000 10,000 20,000 40,000 60.00080,000100,000 200,000 50 60 708090100 200 300 400 500600 800 1,000 2,000 .10 .09 .08 .07 .06 .05 .04 1 1 ,i 1 1, i, i i i l'l A, J i I, i ^J- i -L- j r^ ,j_ , , , , , / - / \\ .'I/,'.,',; i , i 1 1 i i -j- J- ^> ii'|i|l| rn.10 /f " / - / / / Tffn 44^-/^ 53 ^ / / t: .03 En /fit 7 / / - -/ -!/- M/ / A / j :: .07 J ~ j. T 1 :i / / i i? / 08 i , | ii c JL \ y\ / / / / / i ' - 4- / J i 4s & ^ ; / A Tnr /-4 4^^= / 2 = - / -. :: .05 s^ = P iyi!= / 1 7 ip; 1^ ' ii : : _ V_ 7 _ _ -4/4 / - ^ -^i- / / / - - 03 .02 .010 .009 .003 .007 .006 .005 .004 T ZI / -X ST / / / 7 ~/n?" 7 o / / A F :: / / t / j V -> ?p::=? f 2 / / -JT i -ZI / ^_ /- / /; , -/-^ //- 11 / / ;. f i / / / / ? "" / i ^ ::5= ^ 7* i - - -- / ^2 / 7* t/ / -f- / 7 "2 ~f /i / r/ 7 / y / / T- --/ / / L / / -- .010 1 [/1 1 /- / -r^ / -7 H ___ / -- .009 /i '/ 1 / T / _L yj__ / / / _ ~-t- ~iL~ if - - .008 rp / , / / .007 r 7 / 1 > / / 7 -I / /- \ V itt I / / 1 / I 7 T _._ _, ^ /I / / v .003 .002 .001 / 5 :::?iy_i / / r\ / / / z / /P r, RE S ss T (1 1 00 U =; ;ll t: R V tl 0( E u 7 D PI Fc ) 2 / ROP PES rmui -- .003 N ?,. ge ?o: 1* .001} / / / / i / / ~_ ^ / j ^~ Z / / 2 / __Z - /- / i / ~ Steam Pressure Slbs.ga Steam Temp. 218.5 de at Transmission of Radial 245 B.t.u .per sq.ft.perh / / I / / / 1 7 y 7 i / / y T He / y / / d (_ zr_._ T7 50 60708090100 200 300 400 500600 800 1,000 6,000 10,000 20,000 30,000 40,000 60,00080,000100,000 TJie l5 and is equal to The pressure on the right-hand side is evidently Adding these pressures algebraically, we obtain for the result- it pressure tending to move A -A to the left 170 HEATING AND VENTILATION Let Dp = Dl * Dz and D R = ^-|" 4 Then the unit pressure p' available for producing circulation is p' = h(D R - D F ) (1) It is evident that this pressure is the same at any point in the circuit BCEGB. It is independent of the relative lateral positions of the radiator and the boiler and depends only on the height h and the densities DR and DF. It is convenient to express this pressure as a "head," i.e., the height of a column of water of the same density as that in the system which will produce the given pressure at its base. Let D be the average density of the water and hi the head equivalent v f to the unit pressure p'', then p f = hiD and hi = js Sub- stituting in equation (1) we have (DR-DF) D hi is then the head available for producing circulation. If D, D R) and D F are expressed in pounds per cubic foot and h in feet, then hi will be in feet of water column. To express the head in inches, which is a more convenient unit, the right-hand member is multi- plied by 12, and The density D in equation (2) represents the average density of the water in the system. A close approximation would be to make D = Substituting in (2) h' is then the available circulating head in inches of water. 149. Friction. The general expression for the loss of pressure due to friction for fluids in round pipes according to equation (4), page 158, is ' HOT-WATER SYSTEMS 171 in which P = loss of pressure due to friction, pounds per square foot. / = a constant depending on the nature of the fluid and of the pipe wall. D = average density of the fluid, pounds per cubic foot. v = velocity, feet per second. d = pipe diameter, feet. g = acceleration of gravity = 32.2. L length of pipe in feet. To express the frictional resistance in equation (4) in terms of fluid head, let P = h" D in which P is in pounds per square foot and D in pounds per cubic foot, h" being the equivalent head in feet of the fluid at density D. Substituting in (4) <> Let P = 4/, then h " = p-^- (6) Now if v is expressed in inches per second, and d in inches, the head h" will be expressed in inches of water, without any change in the equation, the inch unit being the more convenient. Equation (6) gives the frictional resistance to flow through straight lengths of pipe only. The resistance due to elbows and other fittings must also be taken into account. The resistance of such obstructions has been found to be nearly proportional to the square of the velocity of flow, and may therefore be expressed in the form av 2 2g in which a is a constant to be determined. The summation of all such "single resistances" may then be expressed as and the entire frictional resistance will be In order to impart to the mass of water in the system the 172 HEATING AND VENTILATION velocity v, a certain head must be used up in overcoming this v 2 ''starting resistance" which is equal to ~ , in which g 1 ', the acceleration of gravity, is expressed in inches per second per second so that this last term will be expressed in inches of water head as are the others. The complete expression for the head required to start and to maintain flow may then be written In which h" is in inches of water head. d is in inches. L is in feet. v is in inches per second. g is in feet per second per second. g' is in inches per second per second. In considering only the force required to maintain a steady flow, the last term does not enter, however. 150. Condition of Steady Flow. When the circulation in a heating system has become constant, the head available for producing flow must be exactly equal to the frictional resistance. This condition must invariably be fulfilled. If the available head increases or decreases, the velocity will change also until it assumes such a value that the frictional resistance will equal the available head. The relation 1 may be expressed by equating the right-hand members of equations (3) and (8) -'+" 151. Types of Gravity Systems. Two-pipe Multiple -circuit System. There are several different ways of arranging the piping in a gravity system. The most common method for installations of moderate size is the two-pipe multiple-circuit system shown in Fig. 127. The water leaves the boiler through the flow main, passes through the radiators and into the return main. A single pair of mains may be installed to circle the basement, but a better method is to install two or more pairs which extend in different directions. In order to insure a suffi- cient flow of water to each radiator, it is best to provide sepa- J For further discussion see "Heating and Ventilation" by A. H. BARKER. HOT-WATER SYSTEMS 173 rate supply and return risers to each radiator from the mains. Both the supply and return mains are given a pitch toward the boiler of about J-^ inch in 10 feet, so that no air will accumulate in the piping and so that the system can be drained at the boiler. Two-pipe systems are often installed with a " re versed" return main, as shown in Fig. 128. The flow in the return main is in the same direction as in the supply main and is so arranged that the length of the circuit through each radiator is the same. This tends to equalize the resistance to flow through all the radiators and the system therefore operates more uniformly]throughout. n n ft FIG. 127. Two pipe multiple circuit system. FIG. 128. Reversed return. A modification of the two-pipe system was formerly used, in which separate supply and return pipes were provided for each radiator. Although such an arrangement gives good results, the complication and cost of the piping have rendered it prac- tically obsolete. 152. Expansion Tank. The change of volume of the water in a hot-water system under varying temperatures is quite appreciable and an expansion tank must always be provided. The tank is located well above the highest radiator in the system and is provided with a vent and an overflow to the sewer, as illustrated in Fig. 129. If located in an unheated room, a connection should be made to it from both supply and return mains to insure sufficient circulation to prevent freezing. If possible, the connection to the tank should be taken from the supply main as near the boiler as possible so that the air which is liberated from any fresh water which is fed to the boiler will rise to the expansion tank and escape rather than accumulate in the radiators. 174 HEATING AND VENTILATION The required capacity of the expansion tank is evidently a function of the quantity of water in the system and may be determined by computing the volumetric expansion, for the maxi- mum temperature range, of the esti- mated quantity of water in the system. A rough rule is to make the capacity of the exp ansion tank in gallons equal to the radiation in square feet divided by 40. Overflow and Vent FIG. 129. Arrangement of expansion tank. 1 FIG. 130. Two-pipe overhead system. 1 153. Two-pipe Overhead System. In Fig. 130 is shown the two-pipe overhead system. The supply main is located in the attic and parallel supply and return risers drop to the basement as shown. This system is best adapted to rather large buildings. 1 From " Pipe-fitting Charts" by W. G. SNOW. HOT-WATER SYSTEMS 175 154. One -pipe System. It is possible, though not common practice, to use a single pipe for both flow and return. A one- pipe overhead system is arranged - as shown in Fig. 131. The re- turn line from each radiator is connected to the riser at a point below the supply connection. The circulation through any radiator may be accelerated by lowering the point at which its return con- nection reenters the riser, as at B. One disadvantage of this system is the fact that the cool water from the radiators lowers the average temperature of the water in the riser and the radiators on the lower floors are therefore supplied with water at a relatively low temperature, so that they must have a larger surface. The ad- vantages of the one-pipe system are its simplicity and somewhat lower cost. The one-pipe circuit system is shown in Fig. 132. The main circles the basement and separate connections are usually taken off to each radiator, although some- times a first-floor and a second- floor radiator are connected to the same risers. The main should be of uniform size throughout its length. In large buildings, a separate main is sometimes installed for each floor. This system has the inherent disad- FIG. 131. One-pipe overhead system. FIG. 132. One-pipe circuit system. vantage of all one-pipe hot-water systems, that the temperature of the water in the main is lowered as that from the radiators is 176 HEATING AND VENTILATION mixed with it and the radiators at the remote end must there- fore be of larger size. Its chief advantage lies in its simplicity and in the smaller amount of piping required. 155. Water Temperatures. The water temperatures in a hot-water system will vary according to the heating require- ments. Most ordinary gravity systems are designed to operate at a water temperature, leaving the heater, of 180 to 190 and with a drop in temperature through the system of 20 to 30. 156. Study of Various Types of Systems. Fig. 133 represents a multiple-circuit system and Fig. 134 an overhead system. The head available for producing circulation through any radiator is proportional to the elevation of the radiator above the boiler, and to the temperature difference between the flow and the return as expressed in formula (3), page 170. In the ^1 m. a 6 =" u m "T L a' 6' P hi ..Lf il FIG. 133. FIG. 134. FIG. 135. two types of systems illustrated, the inlet and outlet connections of the radiators are both at the bottom and the effective height should therefore be measured from the radiator connections to the center of the boiler. The f rictional resistance to flow varies almost directly as the length I of the circuit from the boiler through the radiator and the circulating head varies directly as the height h of the radiator above the boiler. It is therefore evident that the radiators marked D in both figures are the least favor- ably situated, since the ratio K is the least for these radiators. The size of the pipes in the mains must therefore be based on the circulating head due to these radiators. This can be more clearly comprehended when it is remembered that the source of the circulating force is the radiator itself. Radiators C and D, Fig. 133, may be thought of as centrifugal pumps of different working heads operating in parallel and pumping the water HOT-WATER SYSTEMS 177 around the circuit. It is evident that in such a case if both pumps are to deliver water, the force producing circulation could not be greater than that developed by the pump having the smaller head, which corresponds to radiator D. If the pipes are well insulated, the effect of the small amount of heat lost from them will be negligible; if, however, they are left uncovered, the effect on the circulating head will be con- siderable. In the basement main system, a loss of heat in the flow mains and risers tends to decrease the circulating head, and a loss of heat from the return mains and risers tends to increase it. In the overhead system, a loss of heat from the flow mains and risers as well as from the return piping tends to aid circula- tion, while a loss from the main riser tends to retard it. This should be evident from a consideration of the direction of flow in these pipes. 157. Single-pipe System. In the single-pipe system, as illus- trated in Fig. 135, the water reaching the inlet connection of a radiator as at a, divides, part of the water passing through the radiator and part through the riser from a to b. The available head for producing flow through the radiator depends upon the distance a-b and the difference between the average temperature of the water in the radiator and the water in the pipe a-b. A lowering of the point at which the return connection from the radiator enters the riser, as at b', Fig. 135, will tend to cause a greater portion of the water to flow through the radiator. The circulation through the mains and risers depends upon the lowering of the temperature in the risers themselves. The aver- age temperature in the risers is not necessarily the mean of the temperature at the top and bottom, but depends upon the pro- portion of the heat removed at the various radiators. 158. Method of Computing Pipe Sizes. In order to make certain that the system will operate with the same temperature drop and water quantities for which it is designed, it is necessary that the available circulating head be computed from the assumed temperatures and that the pipe sizes be so chosen that the fric- tional resistance will approximately balance this circulating head. This condition is expressed by equation (10), page 172, D R -D F Lv z v* This calculation is, of course, made for the maximum condition. At other times the temperature of the water leaving the boiler, 12 178 HEATING AND VENTILATION and consequently the available circulating head, will be less than under maximum conditions. In Fig. 136 are given the values of the expression 24 rr~T~rr L>R H- UF for various flow and return temperatures. To compute the avail- able circulating head, it is then only necessary to multiply the values obtained from the curves by h, the height of the radiator 140 u 150 160 170 180 190 c .Temperature -of Flow FIG. 136. 1 200 210 220 above the boiler. The height h should be taken from a point midway between the flow and return connections of the boiler. If both of the radiator connections are at the bottom, the distance h is measured to the connections. If the inlet connection is at the top, the height h is usually measured to a point located at 1 By A. H. BARKER. HOT-WATER SYSTEMS 179 a distance above the bottom connection equal to one-fourth the height of the radiator. In order to determine the pipe friction, it is necessary to know the value of p. This has been determined experimentally by many investigators, but their results differ considerably. 0.0595 According to Weisbach, p = 0.01439 + j=- for water in iron 100 ter Column per 10 Feet of Pipe ~, g xbo M to * o,o>-5 g g SgS ^s \ 3g ~k^ ? -i ^ ~~} / ^ V^V^. / > 1 2 e c ^c^ / 1 / f ^ k ^ > r / \/ "V v^ \J / 1 \~f ( ~i {_ ' s / v^ / / ^ - On- f ^ ^ /^ / ^ IS^ / 1 / i \ >^ / 5 ^ / N, 1 / ^ ^^^ , 1 j<: > \ -V 1 / ^^ / i A^ ^, s 1 V s ^ f- \ t / 1% Sty 'j " v - y J / ^ ^ L/ / / ?: ,A ^ c ^ y / =11 V / " ~ f^ /i -} / -> :zz: S 7 ^ 'Xr ->o > ~ K^~ ~j -^ I ^ ^n g / ^ Ny / / f \ / \, ^ \ ^^ j 1 / / ^^N^ / f j / I . * f ^ 25 f V * "^^^ 7 \^ / * / ,-y / \ ^ .' / ^v ^ / ^ 3 \L ( N i / / / J *\, ^ ^ / / v /\ L ' t / " / r ^^i , / / L Loss -Inches of Wa o V o * en cc-i -^ A- : *~/~ ~2 ^ -T^ 3 / -/ / r^ 1 i (? / v ^ / / F^ / / ^ ^ / / ^ < 2i ^ < / f } v^ / f f / ?^ ^'c / ^/ / / ^ 7 |/ 1 f / / \ / / / / / v i^ / f / Lo as of Head by Friction for Water in Iron Pipes Temp. 160 Deg.E. t / / / ^: yt > / / / ' "; A \ / / || * .04 .03 .02 ,01 j ~7 y- / ^, 3 ^ --/- / X / "x f 7 yi Based on the Formula f j ,/ ^> y f ) / / / / / / / ** x / ( in which P = .01439 4- -^ t \/v / / / / / ^ > / / / / / / / ^^X / f / / / f* V / f f / ^/ / f / / / ' / i / / / / ^_ / J / / / . / < / / aa given Jby Weisbach i 1 1 i i i i i i i i 1 1 \ r 1 i ill ii i o o o o i s is 1 1 1 11 II 11 S S 3 3888 8 888 S3 1 CO * CO 00 Quantity of Water Flo wing. -Pounds per Hour " FIG. 137. pipes, v being the velocity in inches per second. The frictional resistance under various conditions of flow is given by the chart in Fig. 137 which is based on Weisbach's value for p. 1 Having 1 The results of later researches, not fully confirmed, indicate that the Weisbach coefficient is somewhat high and also somewhat in error in that it does not take into account any variation of the friction with the pipe diam- eter. However, the results obtained from its use are sure to be on the safe 180 HEATING AND VENTILATION given the weight of water flowing and the pipe size, the resistance in inches of water can readily be taken from the chart. For the computation of the resistance of the fittings or " single resistances," it is very convenient to consider that the resistance so introduced is equal to that of a certain length of pipe of the same diameter. Approximate determinations of the value of a indicate that at the average velocities occurring in heating work, the length] of pipe in feet equivalent to a 90-degree elbow is equal to twice the number of inches diameter of the pipe. For example, a 3-inch elbow is equivalent in resistance to 6 feet of 3-inch pipe. Values for the various single resistance are given in Table XXXII. TABLE XXXII. VALUES OF SINGLE RESISTANCES Equivalent length in feet equals diameter in inches multiplied by 90-degree elbow 90-degree elbow long sweep 2 1 45-degree elbow 1 Radiator 4* Boiler 4* Valve. 1 to 2 * Diameter of pipe connections. The procedure in calculating the pipe sizes according to this method is then as follows: The piping is completely laid out according to the system chosen, i.e., whether overhead or with basement mains, etc. The circuit supplying the most unfavorably situated radiator is the first to be considered. The pipes in this circuit are assigned tentative sizes and the single resistances noted and the equivalent lengths obtained from Table XXXII. The total equivalent length of each section of the cir- cuit is then computed and the friction drop taken from the curves in Fig. 137. The available circulating head must next be corn- side and it has been used in the design of many successful installations. For further discussion see: "The Determination of Pipe Sizes for Hot Water Heating Systems," by F. E. GEISECKE, Trans. A. S. H. & V. E., 1915. "The Friction of Water in Iron Pipes and Elbows," by F. E. GEISECKE, Trans. A. S. H. & V. E., 1917. "The Mechanics of Heating and Ventilat- ing," by KONRAD MEIER. "Heating and Ventilating" by A. H. BARKER. HOT-WATER SYSTEMS 181 puted. From the curves in Fig. 136, the value of 24 n -- r p.- JD R -\- Up is found for the flow and return temperatures which have been assumed. This value, multiplied by the height in feet of the radiator under consideration, above the boiler, gives the circulat- ing head in inches of water. If the friction head does not agree within about 5 per cent, with the circulating head, as it probably will not in the first calculation, the size of some of the pipes in the circuit must be changed and the total friction drop again computed. By successive refinements the two quantities can be made nearly equal. This circuit having been established, the circuits to the other radiators are worked out in a similar manner, the parts in common with the circuit first computed being left as first set down. In the case of a single-pipe system, the cir- culation to the most unfavorably situated riser is first computed, with the circulating head taken as that due to the riser. 159. Necessity of Accurately Choosing the Pipe Sizes. Let us examine the effect of an improper selection of pipe sizes. There are three possible ways in which errors can be made. I. By making all the parts of the system too small but of the proper relative size. II. By making all of the pipes too large. III. By making the resistance of some circuits much greater than that in the others. If the pipe sizes are all too small, the primary effect will be to decrease the quantity of water passed through the entire system in unit time. If the temperature of the water leaving the boiler is kept constant, the effect of the decrease in the quantity will be to increase the temperature drop in the radiators. This will increase the available circulating head which will in turn increase the velocity of flow. Unless the error is extreme, the system will therefore approach the performance set for it. If the pipes are too large throughout, the primary effect will be to increase the flow of water through the system. This will cause a decrease in the temperature drop through the radiators, a reduc- tion in the circulating head, and a consequent reduction of the flow to some value approaching the proper one. The same action takes place in the case of the individual circuits or radiators. If the pipes are too small, the reduction in flow causes an increase in the temperature drop and the net result is usually but a slight decrease in the heat delivered to the room. 182 HEATING AND VENTILATION It is thus apparent that gravity hot-water systems are to some extent self -regulating. It is due to this property that the ordinary hot-water systems, installed without exact design, operate with satisfaction. Indeed, for the usual small system it is not practi- cable to make exact calculations of the pipe sizes, experience having evolved empirical rules which give pipe sizes which are on the safe side and produce entirely acceptable results. While the heat delivered to the rooms may vary by several per cent, from the theoretical requirements, the error is well within that due to inaccuracies in computing the heat losses from the room. In large installations, the exact method has some distinct advantages. The liberality with which the pipe sizes of a small system are selected cannot be practiced on a large system without a considerable increase in the cost of the installation, while any pipes which may be chosen too small can be replaced only at great expense. Throttling valves, while they should be placed on the branch circuits as a precaution, are difficult to adjust and are easily tampered with. A calculation of the pipe sizes in the manner outlined is therefore desirable for large or important installations. 160. Approximate Rules for Pipe Sizes. Table XXXIII gives the capacity of mains of various pipe sizes for different kinds of systems. TABLE XXXIII. SIZE OF MAINS Assumed Length 100 Feet, Temperature Drop in Radiators 20 Pipe diam. Capacity, square feet of direct radiation Two-pipe upfeed One-pipe upfeed Overhead m 75 45 130 m 110 65 190 2 200 121 340 V/2 310 190 530 3 540 330 920 3^ 780 470 1,330 4 1,100 650 1,800 5 1,900 1,100 3,200 6 3,000 1,800 5,000 7 4,300 2,700 7,200 8 5,900 3,500 9,900 Table XXXIV gives the capacity of risers in square feet of radiation HOT-WATER SYSTEMS 183 TABLE XXXIV. SIZE OF RISERS Assumed Temperature Drop in Radiators, 20 C Pipe size Upfeed Downfeed risers, not exceeding four floors First floor Second floor Third floor Fourth floor 1 33 46 57 64 48 1/4 71 104 124 142 112 l/^ 100 140 175 200 160 2 187 262 325 375 300 23^ 292 410 492 580 471 3 500 755 875 1,000 810 The following schedule of tappings is used for hot-water radiators : TABLE XXXV. -RADIATOR TAPPINGS Size of radiator Supply and return tapping Up to 40 square feet 1 inch 40 to 72 square feet \y inches Over 72 square feet 1^ inches 161. Piping. Many of the principles governing the design of steam piping apply to hot-water work. Expansion must be provided for with care, although it is less in amount. Connec- tions and fittings must be installed so as to interpose as little resistance to flow as possible. The venting of the air from the system is important. In addition to a vent at the expansion tank, a small pet-cock should be provided on each radiator and at any other points at which air may accumulate. Mains should be given a pitch of at least % inch in 10 feet toward the boiler and provision should be made for draining the water from the entire system as is necessary when the plant is shut down in cold weather. 162. Closed Systems. In the open-tank systems which have been described, the water temperature is limited to 212 because the pressure at the top of the system is at atmosphere; but if the pressure of the water at the top of the system is raised above atmosphere, its boiling point and consequently the allowable temperature is raised, increasing the heat output of the system. For maintaining the increased pressure on the system, some device such as a mercury seal is inserted in the pipe leading to the expansion tank. One form of these so-called "generators" is 184 HEATING AND VENTILATION shown in Fig. 138. The water from the system, as its tempera- ture rises, exerts an increasing pressure on the surface of the mercury in the chamber B, forcing mercury up the tube A until it bubbles out of the top of the tube. A pressure equivalent to the height of the mercury column thus formed may be built up at the top of the system and the water may be heated nearly to the corresponding boiling point. As the water in the system cools and decreases in volume, the mercury falls down the tube and more water enters the system from the expansion tank. To Expansion Tank FIG. 138. Mercury seal "generator." Generators are especially useful for increasing the output of a heating system which has been inadequately designed or which has become inadequate. 163. Forced Circulation. When hot-water heating is used in large buildings or groups of buildings, the circulating power is obtained from a pump and smaller pipes are used, the water flowing at much higher velocities than in a gravity system. In systems employing forced circulation, the water usually passes through the pump, then to the heater, and to the radiators. The piping is arranged in the same general manner as in the gravity systems. The action is somewhat different from that in the gravity systems HOT-WATER SYSTEMS 185 in that the force producing circulation is from the pump and not from the cooling action of the radiators , for although the tempera- ture difference in the system has some effect, it is so far over- balanced by the force exerted by the pump as to be negligible. The flow through the various parts of the system is therefore governed to a greater extent by the frictional resistance, as the system does not possess the self-regulating qualities of the gravity system. 164. Pumpage, Friction, and Temperature Drop. The quan- tity of heat delivered per hour may be expressed by the equation H = Q (t l - < 2 ) (1) in which H = quantity of heat delivered per hour. Q = weight of water pumped per hour. ti t z = drop in temperature of water. It is evident that the quantity of water and the temperature drop may vary, the requirement being that their product remain constant. As the temperature drop is increased, however, the average temperature of the radiators is lowered and somewhat more surface must be installed. It is common practice to allow a temperature drop under maximum conditions of about 20. Before a circulating pump can be intelligently selected, it is necessary to choose the differential pressure at which the system is to be operated. If a large pressure drop is allowed, the pipes can be made relatively small, but the power required for pumping the water will be greater. Although it is true that the energy used up in friction is converted into heat and is therefore utilized, the energy thus recovered is only a portion of the energy input to the pumping unit. The cost of the power must therefore be taken into consideration. If the pump is steam-driven and the exhaust used for heating the water, the cost of power will be lower than if current is purchased for a motor-driven pump. In each case a study should be made, balancing the annual invest- ment charges of the piping system against the cost of power to determine the most economical combination. The pressure drop usually allowed is from 10 to 30 pounds. The velocity of flow in the pipes is limited to about 40 inches per second in build- ings where the noise produced by a higher velocity would be objectionable. In industrial buildings, no such limit is imposed. 165. Calculation of Pipe Sizes. The calculation of the pipe sizes in a forced circulation system is much more important 186 HEATING AND VENTILATION than in a gravity system, because the former does not possess the self -regulating property of the gravity system. If any one circuit is unfavorably designed, there will be a tendency for it to be short-circuited. Furthermore, the resistance of the entire system must be made approximately equal to the rated head of the pump. The procedure in designing a forced cir- culation system is as follows. The heat loss from the building having been computed, the temperature drop in the radiators is chosen and the amount of water to be supplied per hour is com- 3 91,200 Lbs.per Hr. 4 70,050 5 00,840 r 4i ! 42 I 13 ll ! 45 15 47 43 49 | 5U I 51 7 8 9 ; ' 12 13 14 15 16 17 -D-i -O- JT3- 18 19 20 21 22 23 24 25 26 27 28 -O-i ^a- 4^- -n- -o- -n- -n- -O- -Q- -o- H=l- ~ l== h -p- -n- -n- -i=h _n- 30 31 32 33 34 35 | th 1,607 -n- -n- -n- -o- -Tl- JT3- -n- -0- _rn- -TT 36 37 ' 38 39 40 4=1- -t=h 4=V ^=h -1=1- -n- -JZJ- -O- -TV 4=^- -D- 4=}- -n- 9 91,300 54 76,150 53 60.840 FIG. 139. puted from formula (1), Par. 164. From a consideration of the various factors mentioned in the preceding paragraph, the differ- ential head is chosen and a pump is selected which will operate most efficiently under the given conditions. The piping must then be designed so that this differential pressure is used up in friction. The general scheme followed in choosing the pipe sizes is similar to that used for a gravity system, the available circulating head, which in this case is produced by the pump, being balanced by the pipe friction. HOT-WATER SYSTEMS 187 The method can best be explained by working out a specific installation. In Fig. 139 is shown diagrammatically one part of an overhead two-pipe system. The weight of water flowing per hour is indicated for the circuit which supplies the radiator marked 30-41, the assumption being made that these water quantities have been computed in the manner previously explained. The circuit through this radiator is the longest and should therefore be computed first and the other parallel circuits designed to give the same resistance. In column 4, Table XXXVI, the actual length of each section of the circuit is given. The system will be designed on a basis of a pressure differential of 10 pounds. The length of the circuit is 481 feet. The average TABLE XXXVI. CALCULATION OF PIPE SIZES FORCED CIRCULATION SYSTEM s Q IH 43 OQ O o 03 ^ le- |-S .9 i a 7*3, c g 8 1 II a a IH a 1 13 ft's Number of "o a 111 O?s3 a Proposed di 1e g la J* Single resist p Resistance feet length I 3 a 'a |a Single resisi o 1 if Resistance feet length 1 3 o H 1 2 3 4 5 6 7 8 9 10 11 12 13 1-2 106,470 4 21 1 X 8 29 4.0 11.6 2-3 106,470 4 158 3X8 182 4.0 72.8 3-4 91,260 3 22 22 9.4 20.7 4-5 76,050 3 22 22 6.8 15.0 5-6 60,840 3 22 22 4.6 10.1 2H 22 9.0 19.8 6-30 15,210 2 10 1 X 4 14 2.4 3.4 IH 1 X 3 13 7.5 9.8 30-41 1,667 1 8 2X2 12 0.9 1.1 41-42 1,667 1 12 12 0.9 1.1 42-43 3,000 1 12 12 2.8 3.4 43-44 4,333 1 12 12 5.2 6.2 44-45 5,667 12 12 2.7 3.2 45-46 7,000 1 }>4 12 12 3.9 4.7 46-47 8,333 1 /"i 12 12 5.3 6.4 47-48 9,667 I/- 2 12 12 3.3 4.0 48-49 11,000 1W 12 12 4.1 4.9 49-50 12,333 l 1 ^ 12 12 4.9 5.9 50-51 13,667 IJ , 12 12 5.9 7.1 51-52 15,210 2' 3 1 X 4 7 2.4 1.7 52-53 60,840 3 22 22 4.6 10.1 214 22 9.0 19.8 53-54 76,150 3 22 22 6.8 15.0 54-29 91,360 3 22 . 22 9.4 20.7 29-55 106,470 4 29 3X8 53 4.0 20.2 Total 249.3 275. 1 Pounds 8.8 9.7 188 HEATING AND VENTILATION friction loss per 10 feet of pipe in inches of water column at a 1 temperature of 160 will be 40 i v~fii~n = ^ mcnes f water. With the given quantities of water flowing, and using a friction loss of approximately 5.9 inches per 10 feet, the pipe sizes can be chosen from the chart in Fig. 137, page 179. They are set down in column 3. The length equivalent to the single resis- tances is computed and the total equivalent lengths set down in column 6. From the friction chart the resistance per 10 feet for each section is found. These are multiplied by the equiva- lent lengths and the results set down in column 8. The sum of all of them is found to be 249.3 inches of water which is equal to 8 . 8 pounds as against the 10 pounds originally specified. The sections 5-6, 6-30, and 52-53 may be decreased one pipe size to increase the resistance, as given in columns 9 to 13. The total resistance will then be 275.1 inches or 9.7 pounds which is sufficiently close to the desired resistance. The circuit 2-3-5- 53-29-55 and all of the remaining circuits must then be worked out in a similar manner to give an equal resistance, the parts which have already been computed being left as they stand. It is desirable to install a "lock and shield" valve on each riser and at each radiator in order that the distribution can be adjusted after the system is completed. 166. Pumps. Either the centrifugal or the reciprocating pump may be used to produce the circulation; but the centrifugal type is by far the more suitable. It possesses the advantages of pro- ducing a uniform flow of water, does not transmit jars or vibration to the piping, requires little attendance, and is economical in operation. Centrifugal pumps may be driven by either a steam turbine or a motor, the former drive being used when high-pres- sure steam is available. CHAPTER XII TEMPERATURE CONTROL 167. Manual Control. In every heating system the radiators, boiler, and other component parts are selected on the basis of the maximum requirements, i.e., for the lowest outside temperature which is to be expected. Consequently the capacity of the sys- tem is much greater than is required in average winter weather. In many localities, for example, where heating plants are designed for a minimum outside temperature of 0, the average temperature for the heating season is from 35 to 40. In order to prevent excessive room temperatures the heat output of the system must be regulated, either manually or automatically, to correspond approximately with the heat losses from the building. Temperature control is accomplished in different ways accord- ing to the kind of heating system and the nature of the building. In many cases manual control of the radiators or of the furnace drafts is all that is necessary; in other cases, automatic tem- perature control, applied to the individual radiators, is very desirable. In hot-air furnace installations and in small steam and hot-water systems the universal method is to regulate the heat output of the boiler or furnace by adjusting the drafts. When the building is large, however, it is often impossible to regulate accurately the temperature throughout the building by this means and control of the radiators must be resorted to. In vapor systems equipped with graduated inlet valves accurate control is possible if sufficient attention is given by the occupants of the room to the adjustment of the valves. In single-pipe steam systems the supply of steam to each radiator cannot be controlled. It is therefore sometimes desir- able to provide at least two radiators in each room so that one or both can be used as required. In a vacuum steam system the heat output can be varied within certain limits by varying the steam pressure. For example, if the steam pressure can be varied from 10 inches of vacuum to 10 pounds pressure, the temperature of the radiating surfaces will 189 190 HEATING AND VENTILATION FIG. 140. Bellows thermostat. change from 193.2 to 240.1, which, if the room temperature is 70, would give a range of heat output of about 38 per cent. This is about the maximum range which could be secured by this means. 168. Automatic Control Applied to Boiler or Furnace. Tem- perature control by adjusting the drafts of the boiler or furnace can be accomplished automatically by means of any one of several designs of thermostats. The simplest of these consists of a bellows containing a volatile liquid which causes an expansion and contraction of the bellows with changes of temperature. The bellows is installed at the point from which the tem- perature is to be controlled and its move- ment is transmitted by means of a cable to the dampers on the boiler or furnace in such away that a lowering of the room temperature causes an increase in the air supply to the fuel bed and a resulting increase in the heat output. This form of thermostat is shown in Fig. 140. In another form of thermostat the dampers are operated by a motor located in the basement and started electrically from a controller placed in the room above. Fig. 141 illustrates the controller of such a thermostat. The member A consists of two strips of metals, having different coefficients of expansion, brazed together. This member is fixed at point B and the end C is deflected to the right or left by the unequal expansion of the metals with changes of tempera- ture. The controller is con- nected electrically with the motor in such a way that, as the temperature drops and the strip C makes a contact with D, a current of low voltage is transmitted through the circuit, and, by means of a relay, starts the motor, which opens the drafts on the boiler. Similarly, a slight increase of temperature above the established point causes a contact to be made between C and E and the motor FIG. 141. Controller for damper thermostat. TEMPERATURE CONTROL 191 is started, closing the drafts. The temperature for which the controller is set can be changed by moving the knob F which shifts the position of D and E. The controller can be obtained with a clock mechanism which will cause the drafts to close at night and to open in the early morning at some predetermined time. The motor may be a clock mechanism, in which the energy is obtained from a spring which is wound periodically by hand. The electric motor is more desirable, however, as it requires no winding. The method of connecting the motor to the dampers is shown in Fig. 142. Wire FIG. 142. Method of connecting thermostat. In installing this form of thermostat the location of the con- troller is of prime importance. As the heat supply for the entire building is to be controlled from one point, it is essential that the controller be installed in some central location where the tem- perature is approximately an average of that in the entire building. It is the difficulty of controlling the temperature satisfactorily from a single point that limits the use of such thermostats to residences and small buildings. These devices do not maintain an absolutely constant tempera- ture. There is usually a noticeable rise and fall in the tempera- ture because of the sluggishness with which the furnace or boiler 192 HEATING AND VENTILATION responds to the opening and closing of the dampers. In the average case a variation in the tem- perature at the thermostat of from four to six degrees must be expected. 169. Automatic Control Applied to Individual Radiators. In large build- ings, in order to regulate the tem- perature automatically, the radiators in the various rooms must be operated as separate units, by means of a con- troller located in each room. The power for operating the radiator valves is obtained from compressed air, supplied from a central source, and the air supply to the individual F IG . 143. Radiator valve radiator valves is regulated by a small for compressed air system of valve operated by the expansion ele- ment in the controller. The system temperature regulation. may be designed so that the radiator valves are either fully open or fully closed, or the amount of opening may be graduated FIG. 144. FIG. 145a. Compressed air thermostat. FIG. 145&. according to the room temperature. The former arrangement is necessary on single-pipe radiators and is known as the " positive" TEMPERATURE CONTROL 193 type, while the latter or " graduated" type is applicable to steam radiators having a separate return connection, and to hot-water radiators. The type of radiator valve used is shown in Fig. 143. The valve is closed when air under sufficient pressure is admitted to the space surrounding the corrugated metal bellows. When the air pressure is released the spring forces the valve open. If a pressure less than that required to close the valve exists around the bellows the valve will take an intermediate position depending on the amount of that pressure. In the graduated system the intermediate positions of the radiator valve are obtained by creating this partial pressure. A common design of compressed-air thermostat 1 of the positive type is shown in Fig. 144. 1 The operation of the thermostat is as follows: Compressed air is supplied to the thermostat at 15 pounds per square inch through the tube B. Another tube A leads to the diaphragm valve on the radiator. Passage way C around the valve stem is an exhaust passage to the free air. Compressed air from B is admitted to and exhausted from A by the threeway valve M, the action of which will be explained later. A very small portion of the compressed air from the supply pipe B passes through D and a small orifice E to chamber G and exhaust port F allows the air to escape from chamber G faster than it can enter through E when the thermostat is in the position shown in Fig. 145o. Fig. 145a shows the position of the various parts of the thermostat when the room has reached the proper temperature and the thermostat has closed off the steam valve on the radiator. The thermostatic bi-metal bar H, which is composed of two metals having different coefficients of expansion welded together in the form of a bar, will be in the position which allows the air entering cham- ber G to escape through F faster than it enters at E, with the result that the diaphragm (7) will be in a collapsed position. Connected to this dia- phragm (7) is a lever J fulcrumed at its lower end and provided at the upper end with a chamber containing a spring K. Spring K is a coil spring which. wraps itself around a ball L attached to the stem of valve M. In the position shown in Fig. 145a the spring K acting on the ball L tends to hold the valve M tight against the exhaust port C thereby allowing the com- pressed air to pass from the pipe B to the pipe A and thence to the diaphragm operated valve on the radiator causing same to close. The thermostatic bi-metal bar H is so constructed that as the temperature in the room falls this bar will move to the left causing the passage F to close as shown in Fig. 1456. Now as the air can no longer escape from F it will pass into chamber G through the passage E and accumulate behind the diaphragm (7) causing (7) to bulge outward, forcing lever J to the right. Lever J causes the spring K to ride over the top of the ball L. The moment K passes the widest diameter of the ball L it will contract on the ball, forcing the ball L suddenly 13 194 HEATING AND VENTILATION 170. Compressors. The air supply is obtained from a small compressor, usually motor-driven, located in the basement. A storage tank is required and a constant pressure is maintained in the tank by means of a governor which automatically starts and stops the compressor, as required. The pressure carried on the tank is usually about 25 pounds per square inch. The mixing dampers and the heating coils of a fan system can be readily controlled by thermostats, through the use of a dia- phragm motor as shown in Fig. 146. The control of humidity is also possible by the use of similar devices. These applications will be considered more fully under "Fan Systems." FIG. 146. Diaphragm motor. 171. Advantages of Automatic Control. The advisability of installing a system of thermostatic control depends largely upon the type of building under consideration. The compressed air type of thermostat is a rather delicate apparatus and should not be installed in any building where it will not be given the proper attention. The accuracy of control which is obtained varies in different cases. Usually a large room with several thermostats and radiators will be kept at a more constant temperature than a very small room. The principal advan- tages of thermostatic control are the convenience and the increased comfort which it affords the occupants. Without any to the left thereby opening the exhaust port C and closing off the supply of compressed air from B. The compressed air in the pipe A leading to the diaphragm operated radiator valve will then be exhausted through the passage C causing the radiator valve to open and admit more heat to the room. The spring K is a continuous coil spring in the form of a ring embracing the ball L. The action of the spring on the ball is such that the valve can never be centered between the inlet and exhaust ports, but will always be on one or the other port and when the valve changes it does so instantaneously giving thereby a quick action to the diaphragm operated radiator valve. As the thermostatic bar H has no work to perform beyond that of closing the very small passage F it is extremely sensitive to rapid changes in temperature. The operation of a graduated thermostat is somewhat similar except that the mechanism takes up intermediate posi- tions depending upon the amount of deflection of the member H, and the pressure in the pipe A is varied accordingly. TEMPERATURE CONTROL 195 manipulation of the radiator valves, the temperature of the rooms is maintained at the most comfortable point, regardless of the outside temperature. In many cases a considerable saving in fuel can be effected by the use of automatic control, due to the fact that with manual control there is always a tendency for the rooms to become overheated through lack of attention to the radiator valves. This may be true even when graduated valves or other means of facilitating hand control are provided. The actual amount of the saving in fuel is problematical, being given by many as from 10 to 30 per cent. In the average case it is probable that the lower figure is the more nearly correct. The objections to the compressed-air systems of thermostat ic control are the rather high initial cost of the apparatus and the cost of maintaining and of keeping in adjustment the various parts of the system. Thermostatic control is especially desirable for hotels, schools, office buildings, and other buildings of a public character. For fan systems, automatic control of the dampers and coils is very much to be desired, and in most cases is abso- lutely necessary if satisfactory results are to be obtained. CHAPTER XIII AIR AND ITS PROPERTIES 172. Composition of Air. The atmosphere of the earth is a mixture of several gases and vapors, the proportions of which vary somewhat in different localities and under different weather conditions. In general the proportions of nitrogen and oxygen, the two most important constituents of dry air, are approximately as follows : By weight By volume Nitrogen 76.9 79.1 Oxygen 23.1 20.9 Carbon dioxide and water vapor are also contained in air in varying amounts and there are in addition small quantities of other gases, such as argon, ozone, and neon, which are of less importance. Air is not a chemical combination but is a mechan- ical mixture of these gases. 173. Oxygen. Oxygen, (0), which constitutes about one-fifth of the air by volume, is the element upon which animal life is dependent for its existence. In the process of respiration the lungs draw in and expel periodically a small quantity of air and a portion of the oxygen unites chemically, while in the lungs, with impurities of the blood, and thereby cleanses it. Some of the resulting products of this chemical reaction are exhaled in the form of gases and vapors. Our health and bodily comfort are dependent upon the proper performance of this process. 174. Nitrogen. Nitrogen, (N), which constitutes nearly all of the remaining four-fifths of the air by volume, is a relatively inert gas. It performs the important function of diluting the oxygen. As the human body is organized this dilution is essen- tial; an atmosphere of pure oxygen would soon burn up and destroy the body tissues. 175. Carbon Dioxide. Carbon dioxide, (C0 2 ), exists in small amounts in the open air, the purest air containing from 3 to 4 parts of CO2 by volume in 10,000. Carbon dioxide is also known as car- bonic acid gas, as it forms a weak acid when dissolved in water. Being one of the products of respiration it is found in larger quantities in the air of occupied rooms. Carbon dioxide was 196 AIR AND ITS PROPERTIES 197 for a long time believed to have a poisonous effect when taken into the lungs, but is now known to be quite harmless, of itself, even in appreciable amounts. It has the effect, however, of diluting the oxygen content of the air. This necessitates an increase in the rate of breathing and under extreme conditions causes great discomfort. Haldane and Priestly found that with 2 per cent, of C02 the lung action was increased 50 per cent.; with 3 per cent, of C02 about 100 per cent.; with 4 per cent, of C0 2 about 200 per cent.; and with 6 per cent, of C0 2 about 500 per cent. With 6 per cent, breathing becomes very difficult, while with more than 10 per cent, there occurs a loss of con- sciousness, but no immediate danger to life. Exposure to an atmosphere containing even 25 per cent, of CCh does not result in immediate death. Being a product of respiration the amount of C02 present in the atmosphere of a room is an indication of the amount of air being supplied to the room. The measurement of the C02 content of air is therefore of importance in ventilating work. There are several methods of measurement in use, the most accurate of which is that devised by Petterson and Palmquist. The apparatus is provided with a graduated chamber into which a sample of air is drawn and measured. It is then made to flow into a burette containing a saturated solution of caustic potash which absorbs the C02- The air is then forced back to the measuring chamber and the decrease in volume noted. The apparatus is calibrated to read directly in parts per 10,000. Another method sometimes used is that of Wolpert. A solu- tion of sodium carbonate of known concentration is made up and a small quantity of phenolphthalein indicator is mixed with it. A suitable piston arrangement is used to force a known volume of the air to be analyzed into contact with the solution and the apparatus is shaken to promote the reaction between the acid C02 and the alkaline solution. The process is repeated several times until the original pink color of the solution dis- appears. The number of charges of air necessary to cause the color change gives an indication of its CC>2 content. 176. Water Vapor. Water vapor is an important constituent of the atmosphere. It is the most variable in quantity of any of the atmospheric elements, its amount depending largely on the weather conditions. In the northern part of the United States the range of the moisture content of the atmosphere is 198 HEATING AND VENTILATION very great. In New York, for example, it varies at different times from 0.5 grain to 7 grains per cubic foot. Water vapor, strictly speaking, is nothing other than steam at very low pressures, and its properties are similar to those of steam. This fact should always be borne in mind when dealing with the subject of atmos- pheric moisture. Another conception that should be thoroughly understood is that of Dalton's law of partial pressures. Accord- ing to this law, in any mechanical mixture of gases, each gas has a partial pressure of its own which is entirely independent of the partial pressures of the other gases. For example, consider a cubic foot of hydrogen gas at an absolute pressure of 5 pounds per square inch. If a cubic foot of nitrogen at an initial pressure of 10 pounds per square inch be injected into the same space, the resulting total pressure will be 15 pounds per square inch and the volume 1 cubic foot. In air, therefore, the oxygen, nitrogen, water vapor, and other gases each have their own partial pressure, the sum of all of them being equal to the total or barometric pressure. For every temperature there is a corresponding partial pres- sure of water vapor at which the vapor is in a saturated state, its condition then being exactly similar to that of saturated steam, i.e., with the maximum number of molecules occupying a unit space. When the water vapor is in a saturated condition the air is also spoken of as being saturated since it then contains the maximum weight of vapor which it can hold at that temperature. If the temperature of the air is higher than that corresponding to the partial pressure of the water vapor, the vapor is superheated ; if the temperature drops below the saturation point some of the vapor is condensed and the vapor pressure is lowered to that corresponding to the new temperature. The saturation tem- perature is termed the dew point. The partial pressure of saturated vapor increases as the temperature increases. Conse- quently air at higher temperatures is capable of holding a greater weight of water per cubic foot. It should be remembered that the water vapor exists independently of the air except for the tem- perature effect of the latter; and the vapor may be thought of as occupying the given volume at its own partial pressure. The state of intimate mixture of the air and vapor causes their tem- peratures to be always the same. 177. Relative and Absolute Humidity. Atmospheric mois- ture is termed humidity. Absolute humidity is the actual AIR AND ITS PROPERTIES 199 vapor content expressed in grains per cubic foot or per pound of air. The ratio of the vapor content to the vapor content of saturated air at the same temperature, expressed in per cent., is called the relative humidity. For example, given a sam- ple of air at 70 having an absolute humidity of 4 grains per cubic foot. Since saturated air at 70 contains 8 grains per cubic foot, the relative humidity is 50 per cent. 178. Total Heat of Air. The total heat above of air con- taining aqueous vapor is the sum of the heat of the air and the heat of the vapor. The latter has three components: the heat of the liquid, the heat of vaporization, and the superheat. The vapor is always in a superheated condition unless the air is at the saturation point. In dealing with air containing vapor it is often convenient to use the units of weight instead of volume as a basis for calcula- tions. The total heat above in 1 pound of dry air at tempera- ture t a is equal to H - C pa (t a - 0) in which t a is the air temperature and C pa = 0.2415., the specific heat of air at constant pressure. Let W w = the weight of water vapor contained in 1 pound of a mixture of air and water vapor. Then for saturated atmosphere H = (1 -- W w ) X C pa (t a - 0) + W w (h' + r) in which h' = heat of the liquid above for the water vapor r = latent heat of the water vapor. For atmosphere below saturation (and therefore containing superheated vapor) at temperature t a H = (1 - W w ) X C pa (t a - 0) + W w (h r + r + C' ps (t a - t d )) in which td is the temperature at the dew point and C' ps is the specific heat of water vapor at constant pressure. 179. Adiabatic Saturation. When air below saturation is brought into intimate contact with water there is always a tendency for some of the water to vaporize, adding to the mois- ture content of the air. If no heat is added from an outside source and none removed, the heat of vaporization for the mois- ture which is added will be supplied entirely at the expense of the heat of the air and of the superheat of the original quantity of water vapor., The process will continue until the saturation point is reached. A process of this nature taking place without 200 HEATING AND VENTILATION a transfer of heat to or from an outside source is called adiabatic and the final temperature which is reached is therefore termed the temperature of adiabatic saturation or wet-bulb temperature. Its depression below the original temperature of the air will depend upon the amount of moisture which was added to bring the air to saturation. If the air is saturated, no moisture can be added, and the wet-bulb and dry-bulb temperatures coincide. The heat used in the vaporization of the moisture which was added is exactly equal to the heat given up by the air and by the water vapor which it contained originally, assuming that the water which was added was at the temperature of adiabatic saturation. The action may be expressed algebraically as follows: 1 Let t = temperature of the air. t' = temperature of adiabatic saturation. W = weight of water vapor mixed with 1 pound of dry air at saturation at temperature t'. W = weight of water vapor mixed with 1 pound dry air at temperature t. W - W = weight of water added per pound of dry air. r = latent heat of vaporization at temperature t. C P8 = specific h^at of water vapor at constant pressure. C pa = specific heat of dry air at constant pressure. (W - W)r = C ps W(t - O + C pa (t - t') (1) W = rW ' ~ C * (t ~ V (2 } r + C p8 (t - t') 180. Measurement of Humidity. The principle stated in the preceding paragraph affords a convenient means for measuring humidity, through the use of the wet- and dry-bulb ther- mometer. The instrument consists of two mercury thermome- eters, the bulb of one of which is covered with cotton wicking. The end of the wicking extends into a bottle of water and the entire length is kept wet by absorption. As the water is evapo- rated from the wicking its temperature is lowered to the tem- perature of adiabatic saturation or "wet-bulb" temperature. By reading both thermometers when they have reached a con- stant point the wet-bulb depression is obtained and the moisture content of the air (W) can be found from equation (2), Par. 179. 1 From "Rational Psychrometric Formulae," W. H. CARRIER, Trans. A. S. M. E., 1911. AIR AND ITS PROPERTIES 201 Distinction should be drawn between the wet-bulb temperature and the dew point, which was denned in Par. 176. The former temperature is produced by adding moisture to the air and causing its temperature to drop by reason of the giving up of heat to vaporize the water. The dew point, on the other hand, is reached by removing heat from the air without changing its moisture content. In order to obtain accurate results with a wet- bulb thermometer it is necessary that the air surrounding the wet bulb be in motion so that the maximum evapo- ration may be secured. For this reason the best form of wet- and dry-bulb thermometer is the " sling psychro- meter" illustrated in Fig. 147. In this instrument the wet- and dry-bulb thermometers are mounted on a metal strip pivotted to a handle. In using the instrument the wick surrounding the wet bulb is moistened and the in- strument is whirled rapidly and read at intervals until there is no further drop in the wet-bulb temperature. Somewhat more accurate results are obtained with the " aspiration" psychrometer in which a continuous current of air is drawn over the wet-bulb thermometer by means of a small fan driven by clockwork. It is necessary that the water used to moisten the wet bulb of the sling psy- chrometer be at approximately the wet- bulb temperature; otherwise the time required to bring the water to the wet-bulb temperature might be so great that parts of the wicking would become dry. The ideal psychrometric chart in Fig. 148 is constructed for use with the sling psychrometer. 1 This chart gives the moisture content of air in grains per cubic foot, the volume basis being the more convenient for ordinary ventilating work. In Figs. I and II, in the Appendix, are given the psychrometric charts which give the properties of air on the basis of 1 pound of air. 1 From "Fan Engineering," Buffalo Forge Company. FIG. 147. Sling psychrom- eter. 202 HEATING AND VENTILATION 181. Example of Use of Psychrometric Chart. Given a dry-bulb temperature of 80 and a wet-bulb temperature of 70, find the relative and absolute humidity and the dew point. From the 80 point on the horizontal scale follow the vertical line to its intersection with the diagonal line representing the wet-bulb temperature of 70. Passing horizontally to the left from this point to the left-hand scale we find that the absolute humidity is 6.65 grains per cubic foot. To find the relative humidity we note that this same point lies between the 60 and 100* 90# 80* 70# 25 30 35 40 45 50 55 60 65 70 75 80 85 Dry Bulb Temperature FIG. 148. Psychrometric chart. 90 95 100 J05 70 per cent, relative humidity lines (the curved lines extending upward to the right) and that the relative humidity is 62 per cent. To find the dew point, follow left horizontally from this same point to the curved line of wet-bulb temperatures, called the saturation line. The dew point is 64.5. The relation between the wet- and dry-bulb temperatures and the dew point should be thoroughly understood. 182. Application to Air Conditioning. If water is sprayed continuously into the path of a current of air and the same water is recirculated repeatedly the temperature of the water will approach the wet-bulb temperature of the air. The latter will not change as the air passes through the water spray but the dry- AIR AND ITS PROPERTIES 203 bulb temperature of the air will be lowered until it approaches the wet-bulb temperature, and at saturation the two will coincide. The wet-bulb temperature depends upon the total heat of the air and vapor and will be constant so long as the total heat of the mixture of air and vapor is constant. In the process mentioned the heat of the air above the wet-bulb temperature and the superheat of its TABLE XXXVII. PROPERTIES OF DRY Am 1 Barometric Pressure 29.921 Inches Tem- per- ature, d R' Weight per cu. ft., pounds Ratio to volume at 70 F. B.t.u. absorbed by 1 cu. ft. dry air per (teg. F. Cu. ft. dry air warmed 1 per B.t.u. Tem- pera- ature, deg. F. Weight per cu. ft., pounds Ratio to volume at 70 F. B.t.u. absorbed by 1 cu. ft. dry air per deg. F. Cu. ft. dry air warmed lper B.t.u. 0.08636 . 8680 0.02080 48.08 130 0.06732 1.1133 0.01631 61.32 5 0.08544 0.8772 0.02060 48.55 135 0.06675 1 . 1230 0.01618 61.81 10 0.08453 0.8867 0.02039 49.05 140 0.06620 1.1320 0.01605 62.31 15 0.08363 0.8962 0.02018 49.56 145 0.06565 1.1417 0.01592 62.82 20 0.08276 0.9057 0.01998 50.05 150 0.06510 1.1512 0.01578 63.37 25 0.08190 0.9152 0.01977 50.58 160 0.06406 1.1700 0.01554 64.35 30 0.08107 0.9246 0.01957 51.10 170 0.06304 1 . 1890 0.01530 65.36 35 0.08025 0.9340 0.01938 51.60 180 0.06205 1.2080 0.01506 66.40 40 0.07945 0.9434 0.01919 52.11 190 0.06110 1.2270 0.01484 67.40 45 0.07866 0.9530 0.01900 52.64 200 0.06018 1.2455 0.01462 68.41 50 0.07788 0.9624 0.01881 53.17 220 0.05840 1.2833 0.01419 70.48 55 0.07713 0.9718 0.01863 53.68 240 0.05673 1.3212 0.01380 72.46 60 0.07640 0.9811 0.01846 54.18 260 0.05516 1.3590 0.01343 74.46 65 0.07567 0.9905 0.01829 54.68 280 0.05367 1.3967 0.01308 76.46 70 0.07495 1.0000 0.01812 55.19 300 0.05225 1.4345 0.01274 78.50 75 0.07424 1.0095 0.01795 55.72 350 0.04903 1 . 5288 0.01197 83.55 80 0.07356 .0190 0.01779 56.21 ' 400 0.04618 1 . 6230 0.01130 88.50 85 0.07289 .0283 0.01763 56.72 450 0.04364 1.7177 0.01070 93.46 90 0.07222 .0880 0.01747 57.25 500 0.04138 1.8113 0.01018 98.24 95 0.07157 .0472 0.01732 57.74 550 0.03932 1.9060 0.00967 103.42 100 0.07093 .0570 0.01716 58.28 600 0.03746 2.0010 0.00923 108.35 105 0.07030 .0660 0.01702 58.76 700 0.03423 2.1900 0.00847 118.07 110 0.06968 .0756 0.01687 59.28 800 0.03151 2.3785 0.00782 127.88 115 0.06908 .0850 0.01673 59.78 900 0.02920 2.5670 0.00728 137.37 120 0.06848 .0945 0.01659 60.28 1000 0.02720 2.7560 0.00680 147.07 125 0.06790 .1040 0.01645 60.79 1200 0.02392 3.1335 0.00603 165.83 original water vapor content go to supply the heat of vaporiza. tion for the added moisture, as expressed by equation (1), Par- 179. This means is often employed to cool the air for ventilation. If a spray of artificially cooled water be used the air can be cooled to within a few degrees of the water temperature. If this 1 From "Fan Engineering," Buffalo Forge Company. 204 HEATING AND VENTILATION temperature is below the dew point of the air some of the moisture content will be condensed and the resulting condition will be one of saturation at the final temperature. These principles are applied practically in the cooling and dehumidifying of air which will be discussed in Chapter XVII. 183. Properties of Dry and Saturated Air. The properties of dry air are given in Table XXXVII and the properties of satu- rated air in Table XXXVIII at the standard barometric pressure of 29.92 inches of mercury. TABLE XXXVIII. PROPERTIES OF SATURATED Am 1 Weights of Air, Vapor of Water, and Saturated Mixture of Air and Vapor at Different Temperatures, Under Standard Atmospheric Pressure of 29.921 Inches of Mercury Temper- ature, deg. F. Vapor pres- sure, inches of mercury Weight in a cu. ft. of mixture B.t.u. ab- sorbed by 1 cu. ft. sat. air per deg. F. Cubic feet sat. air warmed 1 per B.t.u. Weight of the dry air, pounds Weight of the vapor, pounds Total weight of the mixture, pounds 0.0383 0.08625 0.000069 0.08632 0.02082 48.04 10 0.0631 0.08433 0.000111 0.08444 0.02039 49.05 20 0.1030 0.08247 0.000177 0.08265 0.01998 50.05 30 0.1640 0.08063 0.000276 0.08091 0.01955 51.15 40 0.2477 0.07880 0.000409 0.07921 0.01921 52.06 50 0.3625 0.07694 0.000587 0.07753 0.01883 53.11 60 0.5220 0.07506 0.000829 0.07589 0.01852 54.00 70 0.7390 0.07310 0.001152 0.07425 0.01811 55.22 80 1.0290 0.07095 0.001576 0.07253 0.01788 55.93 90 1.4170 0.06881 0.002132 0.07094 0.01763 56.72 LOO 1.9260 0.06637 0.002848 0.06922 0.01737 57.57 110 2.5890 0.06367 0.003763 0.06743 0.01716 58.27 120 3.4380 0.06062 0.004914 0.06553 0.01696 58.96 130 4.5200 0.05716 0.006357 0.06352 0.01681 59.50 140 5.8800 0.05319 0.008140 0.06133 0.01669 59.92 150 7.5700 0.04864 010310 0.05894 0.01663 60.14 160 9.6500 0.04341 0.012956 0.05637 0.01664 60.10 170 12.2000 0.03735 0.016140 0.05349 0.01671 59.85 180 15.2900 0.03035 0.019940 0.05029 0.01682 59.45 190 19.0200 0.02227 0.024465 0.04674 0.01706 58.80 200 23.4700 0.01297 . 029780 0.04275 0.01750 57.15 From "Fan Engineering," Buffalo Forge Company. AIR AND ITS PROPERTIES 205 184. Specific Heat of Air. The specific heat of a gas may be expressed in either of two ways: i.e., the specific heat of constant pressure, and the specific heat of constant volume. The reason for this has already been stated (Par. 6). In ventilating work the former quantity is the one involved. Its value as determined by Carrier is 0.2415 B.t.u. Problems 1. Given wet-bulb temperature 66, dry-bulb temperature 80. Find dew point, per cent, saturation, and moisture content. 2. Given air at a temperature of 60 and containing 5 grains of water vapor per cubic foot. What is its relative humidity? 3. The air outside of a building is at a temperature of 31 and has a rela- tive humidity of 84 per cent. On being drawn into the building it is heated to 70. What is its relative humidity at the higher temperature? 4. Air at 80 is 87 per cent, saturated. When cooled to 55 what is its new moisture content? 5. Air at 25 has a humidity of 90 per cent. How much moisture must be added to give it a humidity of 50 per cent, when heated to 70? CHAPTER XIV VENTILATION 185. Ventilation Requirements. Ventilation may be defined as the science of maintaining atmospheric conditions which are comfortable and healthful to the human body. The effect of civilization in causing mankind to remain indoors for long periods has made proper ventilation of great and increasing importance. The science of ventilation has only recently approached a satisfactory stage. The difficulty has been not one of providing the proper mechanical equipment but of learning what condi- tions are necessary for good ventilation and of establishing the proper standards to be attained. It is only very recently that the physiological effects of certain atmospheric conditions have been understood, and the quantitative measurement of others and the knowledge of permissible limits are still lacking. The atmosphere affects the human body in two ways. Por- tions of the surrounding air are being continually drawn into the lungs and expelled and certain qualities of the atmosphere such as odors, dust, bacteria, and other injurious substances affect the respiratory organs. The degree of humidity of the air also has an effect on the respiratory passages. Secondly, the condition of the atmosphere has an important effect on the surface of the body, for the temperature, degree of humidity, and amount of air motion govern the rate at which heat is dissi- pated from the skin a most important factor in bodily comfort. To sum up, the following factors must be taken into account in providing proper ventilation: 1. Amount and distribution of air supply 2. Temperature 3. Humidity 4. Motion 5. Odors 6. Dust 7. Bacteria 8. Other injurious substances 200 VENTILATION 207 Ventilation, as the term is commonly used, refers primarily to the effect of atmospheric conditions on the human body. The condition of the atmosphere is regulated in many manu- facturing processes from a purely manufacturing standpoint and without particular references to the factors mentioned above as they affect the human body. This is usually termed "air conditioning." 186. Sources of Air Pollution. The percentage of oxygen in the atmosphere necessary for the support of human life has been shown to be quite low, and a considerable reduction may take place without even causing great discomfort. In general, it may be stated that the quantity of air to be supplied for proper ventilation is governed by other factors which necessitate a greater quantity than that required to maintain a sufficient oxygen content. The air of occupied rooms becomes the recipient of many polluting elements, the most important of which are the prod- ucts of respiration. The average person breathes at the rate of about 17 respirations per minute while at rest. At each respira- tion, about 30)^2 cubic inches of air are inhaled or about 18 cubic feet per hour, which amounts to about 34 pounds of air in 24 hours or a little over 7 pounds of oxgyen. The inhaled air loses about 5 per cent, of its oxygen content while in the lungs and gains from 3J^ to 4 per cent, of carbon dioxide. The percentage composition of free air and of expired air, by volume, is about as follows: Free atmosphere, per cent, (approximately) Expired air, per cent, (approximately) Oxygen . . 20 9 15 4 Nitrogen . . 79 1 7Q 2 Carbon dioxide 03 to 04 4 03 to 4 04 Ordinarily there is not enough carbon dioxide in the air of even poorly ventilated rooms to be harmful. Its amount is merely an indication of the quantity of air being supplied. Water vapor is also an important product of respiration. The moisture thus added to the air will increase the humidity above the comfort point unless the atmosphere is renewed with sufficient frequency. 208 HEATING AND VENTILATION There are also emanations from the mouth, lungs, and skin which give rise to disagreeable odors and which are believed by some to have a poisonous effect when taken into the lungs. Although this belief is not widely accepted, and although the exact effect of this organic matter is not known, common clean- TABLE XXXIX. AIR SUPPLIED TO VARIOUS CLASSES OF BUILDINGS Cubic feet per hour per occupant No. of renewals of air per hour Churches, auditoriums and assembly rooms . . Theatres. . . ... 1,200-1,800 600-900 Grade schools 1 000-1 500 High schools College class rooms 1,800-2,000 1,500-2,000 Hospitals for ordinary di oa*os Hospitals for children Hospitals for contagious diseases Hospitals for wounded Barracks 2,500-3,500 2,000-2,500 5,000-5,500 3,500-5,000 1,000-1,800 Living rooms in residences 1,200 1-2 Stairways and halls Bedrooms Work shops 600 1,000 600-2,000 H-l IH Public waiting rooms 4 Public toilet rooms . . . 20 Small convention halls 4 General offices 3 Private offices Public dining rooms 4 4 Banquet halls 5 Basement restaurants .... ... ... 8-12 Hotel kitchens 10-20 Public libraries 3 Textile mills 4 Engine rooms 10-20 Boiler rooms. . . . 10-20 Railroad roundhouses 12 liness alone demands that sufficient fresh air be supplied to dilute such impurities considerably. The dilution of the bacteria in the expired air is also of some value in reducing contagion. There are other sources of air pollution, such as the products given off by the combustion in gas and oil lamps and from manufacturing processes. Gas lights give off carbon dioxide, VENTILATION 209 water vapor, and traces of sulphuric acid. If the burners are not properly adjusted, carbon monoxide, which has a poisonous and sometimes a fatal effect, may also be generated. Manufacturing and chemical processes give off various gase- ous impurities, but such conditions require individual study and no set rules can be given. 187. Amount of Air Required. The proper amount of air supply has been determined from experience for different classes of buildings. For buildings such as theatres and schools, it is customary to provide a certain volume of air per minute for each occupant. For rooms where the number of occupants is vari- able or where there is pollution from sources other than respira- tion, sufficient fresh air is provided to renew that in the room a certain number of times per hour. For ordinary conditions of temperature and humidity, Table XXXIX gives the usual practice as to the amount supplied. 188. Methods of Measuring Air Supply. When the air enters a room through but one or two ducts, the quantity can be directly measured by a pitot tube or anemometer, the use of which will be discussed in Chapter XV. Another method which in many cases is more convenient is based on the measurement of the carbon dioxide content of the air combined with a knowledge of the rate at which the carbon dioxide is added by the exhalation from the occupants. If it be assumed that each person produces 0.6 cubic feet of CO 2 per hour, then ' 6000 1 C.F.H. CO,- X 1 Let V = volume of air admitted to the room in cubic feet per hour. a = volume of CO 2 contained in a unit volume of the air admitted. TI = amount of CO 2 per unit volume of air in the room at the begin- ning of the test. r 2 = amount of CO 2 per unit volume of air in the room at the end of the test. r = amount of CO2 per unit volume of air in the room at any time during the test. R = volume of room in cubic feet. c = amount of CO 2 produced in the room, in cubic feet per hour. t = time of experiment in hours. During any small period of time dt, the amount of air entering the room is Vdt and the amount of CO 2 contained in the entering air is aVdt. The amount of CO 2 produced during the time dt is cdt. During the same interval, 14 210 HEATING AND VENTILATION in which C.F.H. = cubic feet of air per hour supplied to the room per occupant. CO 2. = carbon dioxide content of room air in parts per 10,000. X = carbon dioxide content of outside air in parts per 10,000 (usually assumed as 4). This formula is recommended by Dr. E. V. Hill and is used by the Health Department of the City of Chicago. The chart in Fig. 149 shows the air supply per person when any given CO 2 content exists in the room. The above method of determining an equal volume Vdt leaves the room through the exhaust flues and its CC>2 content is rVdt. The net increase in the volume of CO 2 in the room is then (aV + c)dt - rVdt = (aV - rV + c)dt Let the increase in the CO 2 content of the air in the room per cubic foot during the interval dt be represented by dr. Then the total net increase is Rdr. Equating the two Rdr = (aV -rV + c}dt (1) and r- - - * aV + c - Vr -c-Vr) _ R Vn -aV -c ~ v ge Vr 2 -aV - c V = 2.303 y log yp-jj -^ ~_ C c (3) If 7*1 7*2, which means that there is no increase in the CC>2 content of the air in the room, then the amount entering the room, plus the amount pro- duced must equal the amount leaving the room, or aV + c = Vr 2 from which V = r r-ir^ and 7*2 = 7*1 = a + ^ (4) If c =0, then from (3) V = 2.303 - logio Tl ~ a (5) t 7*2 O, Equation (4) is applied practically by assuming a certain production of CO 2 per hour per person, which figure is usually taken as 0.6 cubic foot. Equation (4) then becomes 6000 VENTILA TION 211 the air supply does not apply when there is any source of carbon dioxide other than the lungs of the occupants. 189. Air Distribution. Merely to supply enough air to a room is not sufficient for good ventilation; it must be distributed in a fairly uniform manner so that each occupant receives approxi- mately the specified amount. The methods of distribution will be dealt with later. To determine the uniformity of distribu- tion, the common method is to take measurements of the C02 content in different parts of the room and thus determine the variation of the quantity supplied per occupant at the different points from the average quantity. ibic Ft. of Air Supplied per Hr. per Person Formula CO 2 Transposed ' X may be ta of outside 6000 CFH per oc jecomes CFH = icen as 4 if ai air is not ma cupant "*"* 6000 \ co 2 -x i analysis de \ V ^^^ ~- . - == =^^MM 50 55 GO O 5 10 15 20 25 30 35 40 45 CO 2 Content in 10,000 Parts of Air FIG. 149. Chart showing air supply per person for various amounts of 65 190. Temperature, Humidity and Air Motion. The removal of heat from the human body at the proper rate is one of the essential requirements for satisfactory ventilation. According to Prof. Foster the amount of heat given off by the body is 335 to 460 B.t.u. per hour, depending upon the age, sex, diet, exertion, etc. About 15 B.t.u. of this amount are carried off by the expired air itself and 35 B.t.u. by the moisture absorbed from the lungs by the air. Approximately 70 B.t.u. are removed by the evapora- tion of moisture from the skin, leaving about 250 B.t.u. to be taken care of by radiation and convection from the skin. The two latter quantities vary considerably. For example the sur- rounding air may be at a higher temperature than the body, so that no heat is removed by radiation or convection from the skin and all of the heat must be removed by evaporation. The temperature regulating mechanism of the body would in such a 212 HEATING AND VENTILATION case cause more perspiration to be produced to increase the evaporative cooling. The amount of heat carried off by radiation and convection depends upon the temperature of the air and the amount of its motion, while the evaporative cooling effect depends upon the amount of air motion and upon the capacity of the air for absorb- ing moisture. The moisture absorbing property of the air, strictly speaking, depends upon the difference in the pressures of the water vapor in the air and at the surface of the body. When the vapor pressure in the air is low the higher vapor pres- sure on the skin causes more moisture to be evaporated. The relative humidity of the air serves as an approximate index of its moisture absorbing power. When the air is stagnant, a layer of warm moist air is formed about the body which reduces the rate of heat removal. A mod- erate amount of air movement augments cooling, both by con- vection and evaporation, through replacing this envelope with cooler and dryer air. The temperature, humidity, and motion of the air are thus very important factors in ventilation. They may vary within certain limits as long as their combined effect satisfies the re- quirements for the rate of heat removal from the body. The sensations of drowsiness, oppression, and headache often felt in crowded rooms are due to the effect of heat stagnation on the skin rather than to any effect of the atmosphere on the lungs. This has been demonstrated by various experimenters by means of tests on human subjects confined in air tight observation chambers. After the subject has remained in such a chamber for a time the wet-bulb temperature rises considerably and great discomfort is felt which is not relieved by breathing air from outside through a tube, but which is greatly mitigated by stirring up the air in the chamber by electric fans and thus increasing the cooling power of the atmosphere. Other subjects outside of the chamber feel no discomfort on breathing air from the chamber through tubes. 191. The Comfort Zone. The relation between the tempera- ture and humidity necessary for comfortable conditions is shown by the chart in Fig. 150 which was constructed by Dr. E. V. Hill from a series of tests made by Prof. J. W. Shepherd. These tests were made in still air and with the subjects at rest. The dashed line drawn through the center of the comfort zone cord- VENTILATION 213 responds very closely to a wet-bulb temperature of 56. It appears, therefore, that for still air and when no physical exertion is being undertaken, a wet-bulb temperature of 56 produces comfortable conditions. Later tests have established the wet- bulb temperature which must exist with various rates of air motion to produce conditions of comfort. (See Fig. 151, p. 216.) The wet-bulb thermometer is without a doubt a more accurate instrument for an index of room conditions than is the dry-bulb thermometer which is commonly used for the purpose. The humidity of the inside air varies as does that of the outside air, and with a constant dry-bulb temperature the cooling power of the air will vary over a wide range. If, on the other hand, the proper wet-bulb temperature is maintained, the cooling power of the air will be constant. 55 30 32 34 36 38 68 70 72 74 76 78 42 44 46 48 50 52 54 56 58 60 62 64 Relative Humidity Per Cent FIG. 150. "Comfort Zone" showing the temperature and humidity required to produce comfortable conditions in still air. 192. Air Motion. A moderate amount of air movement is desirable, especially in crowded rooms, as it reduces heat stagna- tion by changing the aerial envelope which surrounds the body. The velocity of movement should be limited to not more than 2 feet per second, for a higher velocity is uncomfortable. In general, a movement toward the face is preferable to a movement from the rear. In a room supplied with fresh air, either from open windows or from a mechanical ventilating system, there will be a certain amount of movement of the air caused by the introduction of fresh air and the removal of foul air. The chill- ing effect of the outside walls and windows and the convection currents set up by radiators also create a considerable amount of air motion. 214 HEATING AND VENTILATION Cubic space is an important factor in ventilation. When a room is over-crowded it may be impossible to move a sufficient amount of air through it without causing uncomfortable drafts. Also a certain amount of space is desirable as a reservoir of fresh air dilutes the products of respiration. Dr. Billings recom- mends the following as the minimum amount of space to be allowed per occupant. Cubic feet per person Lodging or tenement house 300 School room 250 Hospital ward 1,000-1,400 Auditorium 200 In computing the cubic space for this purpose all space over 12 feet from the floor should be neglected. 193. Humidity. The humidity of the atmosphere has an important effect on the respiratory tractin addition to its bearing on the cooling power of the air. When the cold outside air enters a building by infiltration or otherwise and is heated to room temperature, its absolute moisture content remains the same, but its relative humidity is decreased and consequently its capacity for absorbing moisture is increased. From the chart in Fig. 1 of the Appendix (p. 300) we see that air at 20, containing 12 grains of moisture for each pound of dry air, has a relative humidity of about 80 per cent. If its temperature is raised to 70 the relative humidity is lowered to approximately 13 per cent. The low vapor pressure corresponding to this condition results in an increased evaporation of moisture from surrounding objects. The dryness of the air which prevails in most buildings during the heating season has an extremely bad effect on the respiratory tract. The mucous membranes lining the nasal cavity and throat become dry and irritated and especially liable to infection. The change from the dry indoor air to the mcist outdoor air is also believed by some physiologists to be deleterious. It is desirable to maintain a humidity of from 40 to 50 per cent, under average conditions. 194. Odors. Another function of ventilation is the removal or reduction of odors, the most common of which arise from human bodies. The sources of these odors are emanations from the mouth, throat, and lungs, the perspiration from the skin, and soiled clothing. In factories there are odors created by various manufacturing processes. VENTILATION 215 The so-called crowd smell is not harmful of itself, for it has been shown that healthful existence is quite possible in such an atmos- phere. Repulsive odors are indirectly harmful, however, in that they cause the occupants of the room to breathe less deeply; but regardless of their actual physiological effect, modern standards of cleanliness require that sufficient air be supplied to occupied rooms to maintain a wholesome atmosphere. As yet, no accurate standard has been found for the measure- ment of odors. One method is to compare the odor in the room with a number of odoriferous solutions of varying intensities. Sometimes an odor may be nearly imperceptible as such, but may still impart an impression of stuffiness to the atmosphere. 195. Dust and Bacteria. The air, especially that of cities, contains a large amount of dust in very finely divided particles. These particles consist of many different substances, most of which are mineral. In large cities, tons of cinders and smoke particles are cast out into the air annually, which adds to the production of dust from other sources. Ordinary dust in itself is not particularly injurious to health but it serves as a carrying medium for all sorts of bacteria. There are some industrial dusts that are injurious to health such as that from pearl buttons, hair, mineral wool, stone, etc. Several methods of determining the dust content of air have been devised. The most successful scheme is to draw a sample of air into a suitable cylinder containing a glass disc coated with an adhesive varnish and so placed that the indrawn air impinges upon it. The number of dust particles determined by micro- scopic count affords an indication of the amount of dust in the air. Dust can be quite thoroughly removed from air by means of the air washer, to be described later. 196. Ventilation Tests. We have seen that good ventilation demands the fulfillment of several distinct requirements. Any adequate method of testing the ventilation of a room must (a) determine the degree to which each requirement is fulfilled and (b) combine the individual results to show how nearly the ventila- tion of the room approaches what is known as perfect ventila- tion. The synthetic air chart devised by Dr. E. V. Hill and adopted as a standard by the American Society of Heating and Ventilating Engineers offers a means of determining the percent- age of perfect ventilation by considering all of the factors involved. The chart is shown in Fig. 151. The chart contains seven 216 HEATING AND VENTILATION SYNTHETIC AIR CHART FOR DETERMINING THE PERCENTAGE OF PERFECT VENTILATION WET BULB DIFFERENCE DDST PAETICLES PER CU.FOOT BACTERIA COLONIES TWO MIN.PLATE ODORS PERCENT FREE FROM C0 2 PARTS PER 10,000 OTHER INJURIOUS SUBSTANCE ) DISTRIB- UTION PERCENT PERCENT OF >ERFECT TO" ~15T 15 C.F.M. -% 54 15 I3L _ -SO" T? 85 85 50 20 44 12 CO 12 100,000 100 10 10 5 40 90 70 70 GO -24 -80- 80 50,000 DO 50 95 95 "70~ 80 -14- 90 100. 100 100 1 I TEMPERATURE HUMIDITY AIR MOTION BAROMETRIC PRESSURE 29.92" 100 150 200 AIR MOTION FEET PER MINUTE FIG. 151. The synthetic air chart. VENTILATION 217 vertical columns, one for each of the various factors to be con- sidered and a column in which all of the results are summarized. The base of each column represents the ideal condition or 100 per cent, perfect. Bordering on either side of each main column are two narrow columns marked " %" and " + %." The former denotes the penalization to be made in the Per cent, of Perfect column for that particular factor, and the " + %" denotes the condition considering only the one factor. The various factors are divided into three groups which are separated by the double lines. First, Wet-Bulb Difference, which means the difference between the actual wet-bulb tempera- ture and the ideal, and which includes the factors of Tempera- ture, Humidity, and Air Motion; second, Dust, Bacteria, and Odors; third, Carbon Dioxide, which serves as an indicator of the amount of air supplied. There is also a column for Other Injurious Substances, for use in special cases, and one for Distri- bution . The upper limit of any of these columns represents condi- tion where life would be impossible. Hence at this point the " ~ %" column would indicate 100 per cent, penalization. (Since the upper ends of the columns represent conditions not obtained in practice they are not included in the chart.) To illustrate the method of graduating the columns, consider the first which is headed Wet-Bulb Difference. When at rest with no air motion, the ideal wet-bulb temperature is 56. The upper end of the column (not shown) represents the unlivable condition which is approximately 106 with 100 per cent, humidity or a wet-bulb difference of 50. Any variation from 56 would therefore represent a definite percentage of variation from the ideal. The graduations in the other columns were constructed in like manner. After the values of all the factors have been determined by test, the results are shown on the chart by a heavy vertical line (% in. wide) and the height of the line will indicate the results obtained in the test. Penalizations for all the factors may then be read directly opposite the top of each line. All the " %'s" are then totaled and the sum subtracted from 100 per cent, to determine the per cent, of perfect ventilation for the room as a whole. This result is plotted in the last column headed Per cent, of Perfect. For example, if the sum of all " %'s" found in the different columns is 15% per cent., then the difference between 100 and 15%, or 84% per cent., is plotted in the last 218 HEATING AND VENTILATION column as the final per cent, of perfect and represents the quality of the ventilation in the room. 197. Method of Making Test. Temperatures and humidities are determined with a sling psychrometer. The velocity and direction of air movement may be determined by timing the passage of a puff of smoke or vapor. An ammonium chloride cloud formed by the simultaneous production and mixing of hydrochloric acid and ammonium vapors is generally used. Dust determinations are made by the use of a direct counting instrument as described in Par. 195. Bacterial determinations should be made in accordance with the standard adopted by the American Public Health Associa- tion. Petrii dishes 4 inches in diameter containing standard agar are exposed in the room for two minutes. They are then carefully covered and incubated for 48 hours, after which the colonies of bacteria are counted. Odors are determined in accordance with the following rating : 100 per cent, freedom from odors Perfect 95 per cent, freedom from odors Very faint 90 per cent, freedom from odors Faint 85 per cent, freedom from odors Noticeable 80 per cent, freedom from odors Distinct 75 per cent, freedom from odors Decided 70 per cent, freedom from odors Strong The determination should be made immediately upon going into the room from the outer air. For carbon dioxide determinations samples are taken at various stations in the room. The best method is to use 120 c.c. bottles and to fill them by means of a large rubber bulb which is inflated by a pumping bulb until it holds considerably more air than the volume of the bottle. The air is then allowed to rush into the bottle and displace the air originally in it. The operation is repeated, care being taken not to hold the apparatus where the air expired by the operator will be drawn in, and the bottle is then carefully sealed. Analyses are made with a Peterson-Palmquist instrument. The air supply may be deter- mined from the CC>2 readings by means of the chart in Fig. 149. The distribution of the air in a room may be determined from the CC>2 readings taken in the various parts of the room. The following example illustrates the method of calculating the VENTILATION 219 result. Assume four samples taken, resulting in the following analysis : Station Parts of CO 2 per 10,000 1 6.4 2 7.4 3 9.2 4 5.0 Average 7.0 The variation at the various stations above or below the average is as follows: Station 1 7.0 - 6.4 = 0.6 2 7.4 - 7.0 = 0.4 3 9.2 - 7.0 = 2.2 4 7.0 - 5.0 = 2.0 Then the average variation from the average C02 is determined as follows: 0.6 + 0.4 + 2.2 + 2.0 _ 1 f ~^r The percentage of variation is therefore equal to 1.3 -?- 7.0 = 18.6 per cent. Therefore the percentage distribution = 100 18.6 = 81.4 per cent. The column headed "Other Injurious Substances" is used only in special cases where, owing to the nature of the processes carried on, some particularly injurious substance is being given off to the air. The column is then graduated, consistent with the nature of the substance. 198. Comfort Chart. The inter-relation of temperature, hu- midity, and air motion is shown in the lower portion of the chart. The intersection of the Air Motion line and the Physical State line determines the proper wet-bulb temperature. This point should be indicated on the chart by a small angle (thus ~i) the apex of the angle coinciding with the point of intersection of the lines. The observed dry bulb'and wet bulb is also indi- cated by an angle (thus i_). The difference between the desir- able wet bulb and the observed wet bulb is plotted in the first column of the air chart marked Wet-Bulb Difference. 220 HEATING AND VENTILATION 199. Recording the Results. To illustrate the method of deter- mining the percentage of perfect ventilation, consider the results of a test as given below : Dry-bulb temperature 72 Wet-bulb temperature 58 Air Motion 20 ft. per minute Physical state Light work Dust 10,000 particles per cubic foot Bacteria 10 colonies on a 2-minute plate Odors 90 per cent, free from CO 2 7 parts per 10,000 Other injurious substances None Distribution 81.4 These values are now represented on the chart by a %-in. vertical line drawn in the center of each of the respective columns. The proper wet-bulb temperature is determined by noting the point of intersection of the "light work line" and the 20-ft. air motion line; this is 55 wet bulb. Since the actual wet-bulb temperature as determined by the test is 58 then the wet-bulb difference is 3. This value is plotted in the first column and the penalization as read in the " %" portion is 5% per cent. For the 10,000 particles of dust, the penalization is a 1 per cent.; for the bacteria, 1 per cent.; for the odors 1^2 per cent.; for the COz % per cent.; for other injurious substances, per cent., and for distribution 5% per cent. The sum of all these penalizations is 15% per cent. Therefore the per cent, of perfect ventilation in the room is 100 15% = 84% per cent. This value is then plotted in the last column marked Per cent, of Perfect. 200. Ozone. Ozone is used to some extent as a means for counteracting odors and bacteria. Ozone is simply a form of oxygen in which the molecule consists of three instead of two atoms. The additional atom is readily liberated and the sub- stance is consequently an active oxidizing agent. Ozone is present in very minute amounts in the atmosphere. When injected into the atmosphere of a room with a con- centration of not more than 1 part per million, ozone is capable of obliterating even very marked odors. The exact action which takes place is at present a matter of debate. By some it is believed that ozone actually destroys the odors through its oxidizing action. It is known, however, that it is quite possible VENTILATION 221 to compensate one odor with another so that its effect upon the olfactory membrane is neutralized, and it may be that the real action of the ozone is a masking of the odors by what is called olfactory compensation rather than a destroying of them. It is very essential that the concentration of the ozone be kept very low, for in an atmosphere of more than about 1 part per million of ozone, serious irritation of the throat and lungs is liable to result. The common method of producing ozone is by means of an electrical discharge at high voltage. Several commercial ma- chines are available for the purpose. 201. Humidification. Artificial humidification of the air is generally believed to be desirable in nearly every class of build- ing. There is no doubt but that the dry atmosphere produced by the heating up of the cold outer air is detrimental to health by rendering the respiratory passages more liable to infection. Where a modern ventilating system with an air washer is installed, humidification is very simply and satisfactorily accom- plished but in buildings not so equipped, artificial humidifi- cation is more difficult. Humidifiers for hot air furnaces have been described (Par. 35, p. 39). In rooms heated by direct radiation there are several forms of humidifiers which may be used, most of which consist of water pans of some sort to be attached to the radiator. Very few of such devices are really successful, however, because they do not evaporate a sufficient quantity of water. Another type consists of a small bleeder valve which admits steam from the heating system directly into the room. Others inject a finely divided spray of water into the air, but these devices are used principally in connection with manufactur- ing processes. 202. Methods of Introducing Air. In providing ventilation for a room, it is necessary to adopt a definite scheme for the introduction of fresh air and the removal of the vitiated air. When the air quantities are small the leakage around the windows may be relied upon as a means for permitting the escape of the air^ but in general, it is necessary to install a system of vent flues. There are two general methods of circulating the air through a room. In the upward system, the air is introduced through the floor or through the side walls near the floor and is removed 222 HEATING AND VENTILATION near the ceiling. In the downward system, the air is introduced through registers, in the ceiling or in the side walls 7 to 10 feet above the floor, and is removed near the floor. The former method is especially adapted to theatres and auditoriums where a large number of small openings can be provided in the floor, thus securing a very even distribution. The upward system is also suitable for restaurants and rooms where there is smoking or where other impurities or odors are created which have a natural tendency to rise. The downward system is used in schools, hospitals, etc. where it is not practicable to have openings in the floor. FIG. 152. Effect of various locations of inlet and outlet: The relative location of the inlet and outlet openings affects the thoroughness of the air renewal throughout the room. It has been demonstrated that the most effective scheme is to place the outlet near the floor and on the same side of the room as the inlet. The effect of various locations of the inlet and outlet are shown in Fig. 152, in which the arrangement d is in general the besjb. In some types of ventilating systems the air is introduced at approximately the room temperature and at a sufficient velocity to distribute itself laterally across the room. Some- what better distribution can usually be obtained, however, if the air is introduced at somewhat above room temperature. It will then spread out in a layer over the room and move gradually VENTILATION 223 downward as it is cooled and displaced by fresh warmer air from above. Problems 1. A test made in a room in which there are several people shows a CO 2 content of 12 parts per 10,000. What quantity of air is being supplied per hour per occupant? 2. A test of the air of an occupied room shows a CO 2 content of 13 parts per 10,000. Outside air contains 3^ parts per 10,000. How much air is being supplied per hour per occupant? 3. A ventilation test shows the following results: Dry-bulb temperature 70 Wet-bulb temperature 53 Air motion 50 feet per minute Physical state At rest Dust 20,000 particles per cubic foot Bacteria 17 colonies Odors Very faint CO 2 6 parts per 10,000 Other injurious substances None Distribution 91.0 per cent. What per cent, of perfect is the ventilation? 4. The outside air has a dry-bulb temperature of 22 and a wet-bulb temperature of 20. The air inside of a building has a dry-bulb temperature of 68. How many gallons of water must be used per hour to raise the wet- bulb temperature of the inside air to 56? The net cubic space in the building is 30,000 cubic feet. Assume one air renewal per hour. CHAPTER XV FAN SYSTEMS FOR VARIOUS TYPES OF BUILDINGS 203. Types of Fan Systems. Fan systems are installed primarily to provide fresh air for ventilation, although in some classes of buildings they are preferable from a heating standpoint also. There are various types of fan systems and combinations with direct radiation, as brought out in Chapter III. Perhaps the most common type of system is the so-called split system, in which the heat losses from the building are supplied by direct radiation and the fan system supplies air for ventilation at nearly room temperature. This system is very well adapted to buildings which require ventilation for only part of the time, such as office buildings. The proper temperature can be main- tained in the building by means of direct radiation and the fan system need be operated only when ventilation is required. In such a system the amount of air supplied is determined entirely by the ventilating requirements. This type of system is widely used in office buildings, schools, manufacturing establishments, etc. One objection to it is its rather high initial cost. In the second type of fan system some of the heating is done by the fan system and direct radiation is installed to take care of the balance of the heating requirements. The fan system therefore delivers air at somewhat above room temperature. This system is principally used in schools and is believed by many to provide better air distribution because the warm air spreads out over the room and descends uniformly as it is gradually displaced by fresh warmer air above. It is not feasible in most climates to dispense with radiators in schools and similar buildings and to supply all of the heating requirements with the fan system, for the radiators are needed to counteract the curtain of cold air descending in front of the windows. In the third type of system the heating and ventilating are both accomplished by the fan system and no radiation is installed. This is often called the hot blast system. In such a system the amount of air required may be governed by either the heating or the ventilating requirements. This system is used in theatres, 224 FAN SYSTEMS FOR BUILDINGS 225 226 HEATING AND VENTILATION auditoriums, and churches. It is most suitable for a building which must be continually ventilated during the time of day when it is heated. In some cases means can be provided of recirculat- ing the air during the warming up period so as to reduce the fuel consumption. The fourth type of fan system has little or no provision for drawing in fresh air but is used mainly for heating. Its use is confined to factories where the volume per occupant is large. It has some advantages over direct radiation in point of first cost. 204. Office Buildings. Office buildings are nearly always heated entirely by direct radiation and when a ventilating system is installed the split system is used. Fig. 153 shows a basement plan of an office building equipped with a system of this type. The air is drawn from outside and passes through the heaters and air washer to the fan which discharges it into a trunk duct. Branches and risers convey the air to the various rooms in the building. 205. Fan Systems for Schools. Perhaps the most commonly used system in well built school buildings is the second type which FIG. 154. Arrangement of single duct system. has been described in which the ventilating requirements and part of the heating requirements are taken care of by the fan system. The general arrangement of such a system is shown in Fig. 154. The air upon entering is passed through a tempering heater which raises its temperature somewhat above the freezing point. It then flows through the air washer and then in some cases through a reheater and then is drawn into the fan. The fan discharges it through an enlarging duct to the heating coils. Part of the air passes through the coils and is heated to about 120 or 130, and a portion passes below the heater and enters the tempered air chamber at a temperature of about 68. Each duct leading to a room is provided with a double damper so FAN SYSTEMS FOR BUILDINGS 227 arranged that air can be taken partly from the hot air chamber and partly from the tempered air chamber. Thermostats, located in the rooms above, regulate the positions of these dampers so that air of the proper temperature to satisfy the heating requirements is delivered to the respective rooms. The volume of air remains nearly constant. A mixing damper is shown in Fig. 155. The hot air and tempered air chambers are often jointly termed the plenum chamber. They are usually separated by a double decking or by an insulated partition to prevent the transfer of heat. This type of system is often called FIG. 155. Mixing damper. a single duct or individual duct system. A basement plan of a school building having such a system is shown in Fig. 156. School buildings are sometimes ventilated by the trunk duct or split system similar to that shown in Fig. 153. One method of distribution in a split system is shown in Fig. 157. The air for ventilating is carried in a trunk duct or plenum chamber exca- vated below the corridor. Risers take air to the various rooms and the ducts are carried across above the suspended ceiling and discharge the air downward at several points, thus insur- ing even distribution throughout the room. Such a system is only practicable where the building construction permits the installation of the horizontal ducts. The type and arrange- 228 HEATING AND VENTILATION ment of the ventilating system is very often considerably affected by requirements or limitations imposed by the building construction. The trunk duct system is usually somewhat less costly than the single duct system. FAN SYSTEMS FOR BUILDINGS 229 ff HI IL I: 7 r Fresh Air ' Exhaust Ducts Di \ cts "E tr~ ~TT IT II i : *-Wr* 1; )= ~ PLAN / \ // Diffuser G.I. Sweep 2nd Fl. Exhaust / / I ] / / u Suspended Ceiling-^ 1st Fl.v Exhaust- ELEVATION Attic Space Main Exhaust Dust Suspended Ceiling Corridor Dumpers Plenum Chamber FIG. 157. Ceiling distribution in a schoolroom. 230 HEATING AND VENTILATION 206. Exhaust Ducts. Provision must be made for removing the air from the rooms at the same rate at which it is supplied : -V IT ^- and a system of vent flues is provided^for that purpose. The flues from the separate rooms join together in a trunk duct and FAN SYSTEMS FOR BUILDINGS 231 Fan and Heater Located in Pent House Branch Duct lead to a common discharge at the roof. The attic is sometimes used as a discharge chamber, the flues leading directly to it. Exhaust flues are figured at a velocity of 600 to 750 feet per minute and are assumed to carry off the same amount of air as is delivered to the room. In some cases an exhaust fan is installed to facilitate the removal of the foul air. The velocity in the exhaust flues can then be from 1200 to 1500 feet per minute. In public buildings over three or four stories in height, where the friction in the exhaust flues is appreciable, an exhaust fan is desirable. 207. Factory Heating. The hot-blast system is often the best system for industrial buildings as it affords a means of supplying fresh air to replace that containing the fumes or moisture from manufacturing processes. It is also desirable in factory buildings where the space required by direct radiation cannot be spared. Owing to the fact that such buildings are seldom divided into many rooms the air can be supplied at a constant temperature through a trunk system of ducts. A draw-through arrangement is almost uni- versally used, the heating coils being placed on the suction side of the fan, which dis- charges directly into the main duct. For ordinary shop buildings of steel construc- tion, the ducts are of galvanized iron and are suspended from the columns or roof trusses. An example of this arrangement is shown in Fig. 158. In modern rein- forced-concrete buildings the columns are frequently made hollow and used as the air ducts, the heating apparatus and the trunk duct being located on the roof and arranged to discharge the air into the top Fm. 159. Hollow column . T-X- i method of distribution. of each column. Discharge openings are made in the columns at each floor. The trunk duct and branch ducts which are on the roof must be well insulated. Details of this method of construction are shown in Fig. 159. The air is sometimes carried underground in brick or concrete ducts, but the heat loss from such ducts is considerable. 208. Fan Systems for Churches, Theatres, and Auditoriums. Buildings of this class are usually both heated and ventilated 232 HEATING AND VENTILATION by the fan system, except that where there are windows in the auditorium, as in churches, it is advisable to install direct radia- tors under them to counteract the cold down draft which they create. The offices, entrance lobby, stage, etc. of such buildings require direct radiation. The ventilating requirements in such BASEMENT PLAN TS"- LONGITUDINAL SECTION FIG. 160. Ventilation of auditorium by plenum chamber method. 1 buildings are paramount and in fact the problem is often one of cooling rather than heating, after the audience has gathered. The air for ventilation may be admitted through registers near the stage and along the sides of the auditorium. It is 1 Courtesy of SMITH, HINCHMAN & GRYLLS, Architects & Engineers. FAN SYSTEMS FOR BUILDINGS 233 always preferable to cause the air to move toward the faces of the audience rather than to blow on them from the rear. More uniform distribution can usually be secured by introducing the air through a large number of small openings in the floor beneath the seats. To accomplish this the space below the floor is used as a plenum chamber. Fig. 160 shows a fan system FIG. 161. Unit ventilator. in a church building arranged in this manner. This building has an exhaust system also, which draws the foul air from the upper part of the auditorium. A recirculating duct (not shown) conducts the exhausted air back to the fresh air shaft when desired, so that the warming up of the building can be accom- 234 HEATING AND VENTILATION plished economically. No recirculating is done when the audi- torium is occupied. The chief objection to the plenum method of distribution is the cost of the plenum chamber. 209. Unit Ventilation System. A comparatively recent devel- opment in ventilating systems is the unit ventilator system. In this system one or more small fans and heaters are located in each room and discharge air directly into the room. In factory buildings they usually simply recirculate the air but some types are arranged to draw air from outside. One of the latter, sometimes used in schools, is shown in Fig. 161. The principal advantage in unit ventilators is the saving in air duct work, which in some instances is considerable. The disadvantages are the space occupied, their appearance and the fact that no air washer can be installed. 210. Methods of Estimating Heating Requirements. It is frequently necessary to estimate the cost of heating a building, prior to its construction. It is very difficult to do this accurately, first, because of the inaccuracies that are inevitable in the com- putation of the heat losses, and second, because of the pro- nounced effect of the manner in which the firing is done and in which the heating and ventilating system is handled. The most satisfactory method is to compute the theoretical heat loss and to apply a factor to allow for the manner in which it is believed the plant will be handled. To compute the total heat loss from the building, it is necessary to assume the tempera- ture at which the building is to be carried and the average out- door temperature. The heat required for ventilation will depend upon the amount of air used and the number of hours of use. Example. Given a school building heated with direct radiation and equipped with a ventilating system. With the following data furnished, what would be the annual fuel cost? Heat loss from the building per hour per degree difference in temperature between the inside and outside, 12,500 B.t.u., not including ventilation. Average outside temperature for heating season, 38. Hours use of building, 8: 00 a.m. to 4: 00 p.m., 5 days per week. Amount of air supplied for ventilating, 40,000 cubic feet per minute. Cubic feet of space, 300,000. The actual time during which the building is used is 8 hours per day. Let us assume that a temperature of 68 is maintained for 10 houfte of each of the 5 school days or 50 hours per week. Allowing for vacations, we may assume that the school is occupied for 32 weeks of the heating season, or FAN SYSTEMS FOR BUILDINGS 235 1,600 hours per year. For the remainder of the 8 months or 5,760 hours in the heating season, the temperature may be assumed to average 50. The heat loss, not including ventilation, would then be as follows: 12,500 X (68 - 38) X 1,600 = 600,000,000 B.t.u. 12,500 X (50 - 38) X 4,160 = 623,000,000 B.t.u. 1,223,000,000 B.t.u. The ventilating fan, if properly handled, would be operated only during the actual hours of occupancy or 40 hours per week, 1,280 hours per year. The air handled by the fan is heated from the average outside temperature of 38 to the room temperature, 68. The heat loss from this source would be 60 X 40,000 X 1,280 X 0.019(68 - 38) = 1,750,000,000 B.t.u. During the remainder of the time, the air may be assumed to change 1^ times per hour due to infiltration. 300,000 X 1.5 X 4,480 X 0.019(50 - 38) = 460,000,000 B.t.u. The total heat loss is then, 3,433,000,000 B.t.u. Assume that the coal used contains 13,000 B.t.u. and costs $6 per ton. For a plant of this nature, operated by efficient help, we may safely assume that 60 per cent, of the heat in the fuel is delivered to the building. The total annual cost would then be 3 - 433 ' 000 - 000 X *-- $1,309 13,000 X 0.60 2,000 This is the estimated cost on a strict basis. It would be well to add about 10 per cent, for safety, making the final estimate $1,440. If unskilled help were to have been used or if there were other known factors tending to ex- travagance in the use of heat, it might be necessary to increase the strict figure by as much as 30 per cent, in extreme cases. 211. Heating Requirements of Various Types of Buildings. The variation in the amount of heat used in different types of buildings is shown in Table XL, which gives data for a number of steam-heated buildings in Detroit, Michigan. These build- ings are all heated from a central station. The heat loss per hour per degree difference in temperature is given for each building. It will be noticed that the steam consumption per B.t.u. of computed heat loss varies greatly for the individual buildings and that the average figures for the different classes of buildings are also quite different. 236 HEATING AND VENTILATION TABLE XL. STEAM CONSUMPTION OF BUILDINGS AT DETROIT, MICHIGAN Heating Season of 1914-15 Average Temperature for Heating Season (Oct. 1 to May 31) 38.9 | I o '^ fl 1 "" 1 ft* fU 1 I 1 !i H ffl: !]i+ !5+ is w.2 3 P. 11 S-fl s US- s^J S^IP^ it ^1 S o |l* iiu jui OFFICE BUILDINGS Building No. 1 6,524 549,000 26,600 3,091,264 474 5,630 116.2 2 2,755 326,000 16,000 2,393,000 868 7,330 149.5 3 3,820 273,000 13,100 1,860,676 487 6,810 142.0 4 5,280 367,000 16,700 3,563,200 668 9,700 213.5 5 15,300 1,350,000 65,000 12,632,048 825 9,350 194.2 6 7,940 584,000 29,100 4,942,767 622 8,460 169.8 7 50,0003 3,220,000 120,000 34,209,387 684 10,630 285.0 8 79,500 4,900,000 205,000 41,850,000 527 8,540 204.2 Totals and weighted aver- R a ETAHY STORE 171,119 11,569,000 491,500 104,542,342 610 9,020 212.5 BUILDINGS Building No. 1 1,673 160,960 8,715 627,200 375 3,900 71.9 2 1,256 111,500 6,400 364,700 290 3,270 57.0 3 16,100 2,725,100 104,000 7,254,078 451 2,660 69.8 4 11,3153 1,063,100 42,400 6,012,348 531 5,660 141.9 5 3,864 403,000 18,700 2,110,900 550 5,250 112.9 6 2,684 459,400 18,400 987,000 368 2,150 53.6 7 4,413 325,500 17,700 1,677,800 380 5,140 94.6 8 1,701 199,000 8,690 1,437,600 843 7,210 165.0 9 3,632 613,000 21,600 3,133,650 862 5,110 145.0 10 2,620 393,000 16,500 1,539,560 587 3,910 93.2 11 2,513 350,000 11,890 2,214,200 880 6,320 186.1 12 2,162 197,800 8,200 1,072,900 496 5,420 130.8 Totals and weighted aver- R a ESIDENCES: ' 53,933 7,001,360 283,195 28,431,936 527 4,060 100.5 Totals and av- erages for 1 14 buildings 65,421 3,156,800 304,499 37,484,000 573 11,870 123.0 GARAGES: Totals and av- erages for 12 buildings 11,414 1,219,700 74.243 9,949,800 870 8,160 134.0 1 B.t.u. per hour per degree difference between inside and outside temperatures. 2 Including steam for heating water. 3 Including equivalent of fan coil. CHAPTER XVI DESIGN OF FAN SYSTEMS 212. Calculation of Air Quantities. The first step in the de- sign of a fan system is the calculation of the quantity of air to be handled and the amount of heat which must be imparted to it. When ventilation only is considered the quantity of air to be handled by the fan is governed by the number of people in the building and the amount of air to be supplied per person. In Chapter XIV the considerations affecting ventilation require- ments were discussed, and in Table XXXIX, page 208, are given the quantities required per person or the number of air changes per hour for various classes of buildings. In the case of a fan system supplying air for ventilation only, as in the split system previously described, the heat which must be added to the air is that which is required to raise its tempera- ture from the outside temperature (taken as the minimum to be expected) to the temperature of delivery to the room. If Q is the total quantity of air to be introduced per hour and H l is the heat which must be added to the air in B.t.u. per hour, then: H v = QD 2 C P (1 2 - h) (1) in which C p = specific heat of air at constant pressure (= 0.2415). ti = temperature of outside air. ti = temperature of delivery to rooms. D 2 = density of air at temperature 2 in pounds per cubic foot. In this expression the heat absorbed by the water vapor is neglected but the formula is sufficiently accurate for ordinary purposes. If the minimum outside temperature, for which the system is to be designed, is and the inside temperature is 70, then D 2 = 0.07495 and formula (1) becomes H v = Q X 0.07495 X 0.2415(70 - 0) Hi = 1.27Q (2) In the case of a fan system supplying the heat which is lost through the wall and glass surface a further amount of heat must 237 238 HEATING AND VENTILATION be added to the air delivered. The air after entering the rooms is cooled to room temperature and discharged to the outside at that temperature. The total heat added to the air may there- fore be thought of as being divided into two parts: (a) that which would be added were ventilation only being considered, which is the quantity required to raise the air from the outside temperature to room temperature, and (6) the additional amount added to supply the heat lost through the walls. The latter quantity may be expressed in the following form, using the same notation as above. H h = QD,C P (t, - t 2 ) (3) in which t 3 = temperature at which the air is delivered. Z>2 = density at room temperature, pounds per cubic foot. The air volume Q is ordinarily taken at room temperature, assumed to be 70. Then II = H v + H h = QD,C p (t, - h) + QD,C p (t, - t,) (4) The quantity of air Q may be governed either by the venti- lating requirements or by the heating requirements. If the heat loss from the building is large, a large quantity of air at the maximum temperature to which it is practicable to heat it, must be introduced, and this quantity may be greatly in excess of that required for ventilation. On the other hand, if the room is to contain a large number of people and if the heat loss is compara- tively small, then the quantity of air will be fixed by the venti- lation requirements and the temperature of delivery, 3 , will be fixed by the heating requirements. Example. Consider an auditorium which seats 400 people and which is to be ventilated with an allowance of 1500 cubic feet per hour per person. Assume that the fan system is to supply the heat losses as well as the ventila- tion requirements, and that a temperature of 68 is to be maintained. Let Hh, the heat loss through the exposed wall and glass surface be 860,000 B.t.u. per hour, and assume that the air is to be delivered, under maximum conditions, at a temperature of 140. From formula (3) Hh = QDzC p (ta it) and Hh 860,000 W ~ D 2 C p (t z - t 2 ) ~ 0.07524 X 0.2415(140-68) = 657,000 cubic feet per hour. DESIGN OF FAN SYSTEMS 239 Since the amount of air required for ventilation was set at 600,000 cubic feet per hour, it is evident that the amount introduced for heating require- ments will be ample for ventilation. Now, assume that instead of 400 people, there are 500 to be provided for, requiring 750,000 cubic feet per hour. The 657,000 cubic feet demanded by the heating requirements will then be insufficient and the quantity delivered must be that required for ventilation, its temperature, t Zj being below 140. The temperature, t 3 , may be computed from equation (3). 860,000 = 750,000 X 0.07524 X 0.2415( 3 - 68) tt = 131 In some cases the*fan system is designed to take care of a portion of the heat losses only, the balance being supplied by direct radiation. The quantity H h is then taken as an arbitrary part- usually one-third of the computed heat loss. 213. Flow of Air in Ducts. When air, like other fluids, is moved through a pipe or duct, a certain pressure or head is necessary to start and maintain the flow. This head has two components. The static head is that which is required to over- come the frictional resistance of the air against the surface of the duct. The velocity head is the pressure required to produce the velocity of flow. The sum of these two components is termed the total or dynamic head. The static and velocity heads are mutually convertible. The velocity head depends entirely upon the velocity of flow and if the velocity in the duct is decreased at any point because of an increase in the cross-sectional area, a portion of the velocity head will be converted into static head. Conversely, when the area is reduced, the static head is partially converted into velocity head. The interchange, however, is always accompanied by a certain amount of net loss of head, depending upon the abrupt- ness of the change in area and shape of the section in which the change of area takes place. The velocity head may be considered as the height of a column of air which will have at its base a pressure sufficient to produce the given velocity, the relation being represented by the common expression, v 2 = 2gh. To express the velocity head in inches of water, the usual standard, let D = density of air under the given conditions, pounds per cubic foot. D f = density of water = 62.3 pounds per cubic foot at 70. Ji v = velocity head in inches of water. h = velocity head in feet of air. 240 HEATING AND VENTILATION Then ^-s* or * = it V 2 = 3600 X 20 in which V is the velocity in feet per minute. V = 1096.5 - v (1) The static head or pressure in an air duct may be thought of as the pressure tending to burst the duct and it may therefore be readily measured by means of a water gage communicating with the duct in the manner shown at A in Fig. 162. The deflection of the water levels will then indicate the static pressure directly in inches of water. The total or dynamic head is measured by a tube whose open end points against the flow as at B. Since the velocity varies at different points in the cross-section of the duct, any single reading of the total pressure applies only to the particu- lar location of the tube in the duct. The velocity head, which is equal to the difference between the total and static heads, can be computed from them or can be measured directly by con- necting the U-tube as at C in Fig. 162. The relation between the velocity and the velocity head affords a convenient method for measuring the flow of air through pipes. For this purpose the pitot tube illustrated in Fig. 162a is used in practice. The tube is inserted into the pipe in such a manner that the head AB is parallel to the flow of air, with the end A toward the flow. The part AB consists of an inner tube which transmits the total pressure to the tube D and an outer jacket through which the static pressure is transmitted to the tube C. This outer jacket contains several small holes through which the static pressure is transmitted. The two pressures are transmitted to the ends of the differential slant gage E, which is a U-tube arranged with one leg at an angle so that the linear deflection per inch of height is increased. Gages of this type are usually filled with oil but are calibrated to read in inches of water column. The reading on the gage is evidently the velocity head, being the difference between the static and total heads. DESIGN OF FAN SYSTEMS 241 As has been stated, the velocity of flow is not constant at all points in the cross-section of the duct. Near the walls it is retarded by friction and it reaches a maximum at the center of the pipe. It is therefore necessary to measure the velocity at several points in the pipe in order to obtain an average figure. In a square or rectangular duct the cross-section is divided into FIG. 162. Inclined Manometer FIG. 162a. Pitot tube. several equal rectangles and readings are taken with the pitot tube at the center of each of these divisions. The velocity cor- responding to the pressure at the point where each reading is taken is then computed from formula (1), p. 240, in feet per minute. The average of these computed velocities is taken as the -average velocity in the pipe. The quantity of air flowing can be readily computed from the velocity and the cross-sec- tional area of the pipe. 16 242 HEATING AND VENTILATION For a round pipe the cross-sectional area should be divided into a number of annular zones of equal area and a traverse of the pipe should be made in both a vertical and a horizontal direction, as shown in Fig. 163. For each foot of pipe diameter the cross- section should be divided into at least three of these zones. Table XLI gives the distance from the center of the pipe at which each reading should be taken in per cent, of the pipe diameter. 1700 1800 1900 2000 Velocity FIG. 163. Division of round pipe into annular zones. It is important that the velocities be computed separately and averaged, for the velocity varies as the square root of the pressure and accurate results can not be obtained by averaging the pressure readings. The method outlined above is the standard method adopted by the American Society of Heating and Ventilating Engineers. 1 TABLE XLI. PIPE TRAVERSE FOR PITOT TUBE READINGS Distance from Center of Pipe to Point of Reading in Per Cent, of Pipe Diameter No. of equal areas in traverse No. of readings Istfli 2d R 2 3d R 3 4th R* 5th Rt, 6th R& 7th #7 8th fig 3 12 20.4 35.3 45.5 4 16 17.7 30.5 39.4 46.6 5 20 15.5 27.2 35.3 41.7 47.4 6 24 14.5 25.0 32.3 38.2 43.3 47.9 7 28 13.4 23.1 29.9 35.3 40.1 44.3 48.2 8 32 12.5 21.6 28.0 33.2 37.6 41.5 45.1 48.4 1 Report of Committee on Standardization of Use of Pitot Tube. Trans. A. S. H. & V. E., 1914. DESIGN OF FAN SYSTEMS 243 214. The Anemometer. For very approximate results, the anemometer, Fig. 164, is a convenient instrument for measuring the flow of air at the duct outlets. For very low velocities it is not suitable, as the power required to revolve the propeller is then the source of a considerable error. In using the anemometer the face of the register is divided into a number of equal areas and the readings taken at the several areas are averaged. The dial FIG. 164 .Anemometer. is calibrated to read directly in feet and the velocity is obtained by taking the registration of the instrument during a definite period of time. 215. Friction Loss. The general expression for the friction of fluids in pipes (equation (3), page 158) is applicable to air: or for round ducts of perimeter R and length L fRL Dv 2 fRL v 2 Jr - or h a = - a 2g a 2g 244 HEATING AND VENTILATION in which P = pressure required to overcome friction, pounds per square foot. a = cross-sectional area of duct, square feet. D = density of air, pounds per cubic foot. v velocity, feet per second. / = coefficient of friction. h a = height in feet of a column of air equivalent to P. 8 1 8 8 o 8 & S J9 v: 8 S 8 SS S3 N . w . ^." S . . c ~. oc . i3 \ Faction in Inches Water Gage per 100 Feet FIG. 165. Fractional resistance in round air ducts. It is more convenient to express the friction head in terms of inches of water. If the density of air at 70 be taken as 0.075 DESIGN OF FAN SYSTEMS 245 and the density of water as 62.3 pounds per cubic foot then the head in inches of water is k -^g* - 0.00022 62.3 a 2g a .2 The value of / was found by Reitschel and others to be about TABLE XLII. DIAMETER OF ROUND DUCTS EQUIVALENT TO RECTANGULAR DUCTS OF VARIOUS DIMENSIONS Side rectangular duct 4 6 8 10 12 14 15 16 18 20 22 24 Equivalent diameters 3 4 4.4 5 4.9 6 5.4 6.6 7 5.8 7.0 8 6.1 7.6 8.8 9 6.5 8.0 9.3 10 6.8 8.4 9.8 11.0 11 7.1 8.8 10.2 11.5 12 7.4 9.2 10.7 12.0 13.2 13 7.6 9.6 11.1 12.5 13.7 14 7.6 9.9 11.5 12.9 14.3 15.4 15 8.2 10.2 11.9 13.4 14.7 16.0 16.5 16 8.4 10.5 12.3 13.8 15.2 16.5 17.1 17.6 17 8.6 10.8 12.6 14.2 15.7 17.0 17.6 18.2 18 8.9 11.1 13.0 14.6 1ft, 1 17.4 18.1 18.7 19.8 19 9.1 11.4 13.3 15.0 16;5 17.9 18.6 19.2 20.4 20 9.3 11.6 13.6 15.4 17.0 18.4 19.0 19.7 20.9 22.0 22 9.7 12.1 14.2 16.1 17.8 19.2 19.9 20.6 21.9 23.1 24.2 24 10.0 12.6 14.8 16.8 18.5 20.0 20.8 21.5 22.8 24.0 25.2 26.4 26 10.4 13.1 15.4 17.3 19.2 20.8 21.6 22.3 23.8 25.1 26.3 27.5 28 10.8 13.5 15.9 18.0 19.8 21.5 22.4 23.1 24.6 26.0 27.3 28.5 30 11.0 13.9 16.4 18.5 20.5 22.2 23.1 23.9 25.4 26.8 28.2 29.5 32 11.3 14.3 16.9 19.1 21.1 22.9 23.8 24.6 26.2 27.7 29.1 30.5 34 11.6 14.7 17.3 19.6 21.6 23.5 24.4 26.3 26.9 28.5 30.0 31.3 36 11.9 15.1 17.7 20.1 22.2 24.2 25.1 26.0 27.7 29.3 30.8 32.2 38 12.2 15.4 18.2 20.6 22.8 24.8 25.8 26.7 28.4 30.0 31.5 33.1 40 12.5 15.7 18.6 21.1 23.3 25.4 26.4 27.3 29.1 30.8 32.4 33.9 42 12.7 16.1 19.0 21.6 23.8 25.9 26.9 27.9 29.8 31.4 33.0 34.5 44 13.0 16.4 19.4 22.0 24.3 26.5 27.5 28.5 30.3 32.1 33.7 35.3 46 13.3 16.7 19.8 22.4 24.8 27.0 28.1 29.1 31.0 32.8 34.6 36.2 48 13.5 17.0 20.1 22.8 25.2 27.5 28.6 29.6 31.6 33.4 35.2 37.0 50 13.7 17.3 20.4 23.2 25.7 28.0 29.2 30.3 32.2 34.1 35.9 37.6 52 13.9 17.6 20.8 23.6 26.2 28.5 29.6 30.7 32.9 34.7 36.5 38.3 54 14.1 17.9 21.1 24.0 26.6 29.0 30.1 31.2 33.4 35.3 37.2 38.9 56 14.3 18.2 21.5 24.4 27.0 29.5 30.6 31.7 33.9 35.9 37.8 39.6 58 14.6 18.4 21.8 24.7 27.4 30.0 31.1 32.2 34.4 36.4 38.4 40.3 60 14.7 18.7 22.1 25.1 27.8 30.5 31.6 32.7 34.9 37.1 39.1 40.9 62 15.0 19.0 22.4 25.5 28.2 30.9 32.1 33.2 35.4 37.7 39.6 41.6 64 15.1 19.2 22.7 25.9 28.6 31.3 32.6 33.7 35.9 38.2 40.2 42.2 66 15.3 19.5 23.0 26.2 29.0 31.7 33.0 34.2 36.4 38.7 40.8 42.8 68 15.5 19.7 23.3 26.5 29.4 32.1 33.4 34.7 36.9 39.2 41.4 43.4 246 HEATING AND VENTILATION 0.0037 for smooth iron ducts. Prof. J. E. Emswiler 1 reports values for / ranging between 0.004 and 0.006 for velocities of 800 feet per minute and over, the coefficient decreasing slightly as the velocity increases. For practical purposes a somewhat higher coefficient is used, giving larger duct sizes. Allowance is thereby made for roughness of the duct surfaces and for accidental obstructions. The chart in Fig. 165, which is published by the American Blower Co., gives the friction in inches of water per 100 feet length of duct for various quantities of air. The chart is for round ducts; to figure the friction in a square or rectangular duct, it is necessary first to obtain the diameter of the equivalent round duct, which can be done by means of Table XLII. Example. Find the friction loss in a 20- by 10-inch duct 67 feet long, carrying 2,000 cubic feet of air per minute. From Table XLIT we find that the diameter of the equivalent round duct is 15.4 inches. From the chart in Fig. 165 the friction drop per 100 feet of duct for the given flow and for a diameter of 15.4 inches is readily found to be 0.31 inches of water. For a length of 67 feet the drop would be 0.3 X 0.67 = 0.201 inches of water. The loss of pressure caused by various obstructions, such as elbows, branches, etc., is usually expressed as a multiple of the velocity head. The actual loss, however, is of course a loss of static head, since the velocity head at all points in a pipe, for a given quantity of air flowing, depends entirely upon the cross- sectional area at each point. The center line radius of elbows should be equal to at least 1^2 times the width of the duct, as demonstrated by Frank L. Busey, 2 who obtained the following results for elbows of square cross-section : Center line radius in per Per cent, of velocity cent, of pipe width head lost 50 95 75 34 100 17 150 8 200 7 Another method is to add to the actual length of straight pipe a certain length which will have the same friction loss as that due 1 See " Coefficient of Friction of Air Flowing in Round Galvanized Iron Ducts," by J. E. EMSWILER, Trans. A. S. H. & V. E., 1916. 2 See " Loss of Pressure Due to Elbows in the Transmission of Air through Pipes or Ducts," by FRANK L. BUSEY, Trans. A. S. H. & V. E., 1913. DESIGN OF FAN SYSTEMS 247 to the resistance in question. The following table gives the loss of pressure due to various obstructions. TABLE XLIII. PRESSURE Loss DUE TO VARIOUS OBSTRUCTIONS Per cent, of velocity pressure Equivalent length of straight pipe Round elbow (c 1 radius 1/^j X width). . ... 8-10 10 X width SVifl/rD elbow 100.0 Sciuare tee 100.0 Branch from main duct Angle, 15 degrees (per cent, of v. p. in branch)... 30 degrees 10 20 45 degrees 25 Abrupt entrance to pipe 50-90 Coned entrance to pipe 25 Registers (free area = duct area = % total area of register). 1.25 Air washers: Velocity through washer, feet per minute 400 500 600 700 Pressure loss, inches of water 0.15 0.25 0.35 0.45 Example. Given an air duct of square cross-section carrying air at a velocity of 900 feet per minute, and at a temperature of 70. Find the loss of head due to an elbow of diameter 1^ X width. From formula (2), 1 QQ6 5 J X 0.07495 = 0.0505 inches. The pressure loss is 0.08 X 0.0505 = 0.004 inches. 216. Proportioning Duct Systems. It is highly desirable that the size of the ducts be intelligently selected and that the pres- sure loss in the system be computed as accurately as possible. The principal reason for doing this is to insure the selection of a fan of the proper characteristics; for in order that the required quantity of air be delivered it is necessary that a fan be selected with working head sufficient to overcome the resistance of the system. Furthermore, the proper proportioning of the various branches will result in the delivery of the proper air quantities to the various rooms without too great a dependence upon the use of the dampers. In designing a duct system it is necessary first to select the static resistance against which the fan is to operate. Since the 248 HEATING AND VENTILATION power consumption depends upon the resistance, the cost of power is a consideration in air-duct design. A reduction in the power required can be obtained by increasing the duct sizes; but the increased cost of the larger ducts and the greater space required are opposing factors. There are two general systems of air distribution and the method of choosing the duct sizes depends upon the type of system. In public buildings, particularly in schools, the single- duct system is often used, in which the air is delivered to a plenum chamber by the fan and separate ducts radiate to the various rooms. In such a system the duct having the greatest resistance is first designed, which fixes the pressure to be carried in the plenum chamber. The other ducts are then so designed as to deliver the required quantities with the given pressure differential. The longest duct is designed on a basis of certain assumed velocities; Table XLIV gives those recommended by W. H. Carrier: TABLE XLIV. VELOCITIES IN SINGLE-DUCT SYSTEMS Velocity, feet per minute Vertical flues 400-750 Horizontal runs 700-1200 Wall registers 1 200-400 Floor registers 1 125-175 In industrial buildings the trunk duct system is used, consist- ing of one or more main ducts with branches taken off at inter- vals. Such ducts are so proportioned as to give an equal friction loss per foot of length. The outlets are designed for certain velocities depending upon the size of the room and upon the distance through which it is desired to blow the air, the possi- bility of objectionable drafts being considered. It is customary to assume an outlet velocity of from 700 to 1,500 feet per minute, an average figure being 1,000 feet per minute. Where the rooms are small or where the outlets are not located well above the heads of the occupants, lower velocities are necessary, i.e., 300 to 400 feet per minute. The branches from the main duct should be so proportioned as to deliver the required air quanti- ties and it is usually best to provide dampers on the outlets so that any inequalities in distribution can be adjusted after the system is installed. It is desirable to design all air ducts on a 1 Over gross area. DESIGN OF FAN SYSTEMS 249 basis of an air density corresponding to the maximum air tem- perature to be expected. 217. Correction for Temperature. The quantities for which the duct sizes are computed are the volumes at the actual temperature of the air flowing. On the other hand, the volumes fixed by the heating and ventilating requirements are on a basis of room temperature, i.e., about 70. The volumes upon which the air ducts are designed must therefore be determined by mul- tiplying the volumes at 70 by the ratio: Density of air at 70' Density of air at duct temperature PT ^ ; TH 1 f 4 *- n u 1 I-H \\ I EH \\ 1 \( ct 1 3t N-S\ ^N. 250' 1GOO C.E.M. FIG. 166. These ratios are given in Table XXXVII, page 203, in the column headed " Ratio to Volume at 70F." 218. Example of Single Duct System. Assume that a single duct system is to be designed and that the longest duct is arranged as in Fig. 166. The air quantity when corrected for the actual temperature is 1,600 c.f.m., the temperature being 120. We will figure the horizontal run on a basis of 1,000 feet per minute and a duct of rectangular section will be used. The area of the horizontal duct will be 1,600 -r- 1,000 = 1.6 square feet and a 12- by 19-inch duct will be used. For the riser a velocity of 600 feet per minute will be used and the required area is 1,600 -r- 600 = 2.75 square feet, requiring a 16- by 24-inch duct. From Table XLII we find that the diameter of a round pipe equivalent to a 12- by 19-inch rectangular duct is 16.5 inches and for a 16- by 24-inch duct 21.5 inches. From the chart in Fig. 165 we find that a pipe of 16.5 inches diameter will transmit 1,600 c.f.m. 250 HEATING AND VENTILATION with a friction loss of 0.14 inch per 100 feet, and the loss for a 21.5-inch pipe is 0.034 inch per 100 feet. To the actual length of straight pipe we must add the equivalent of the elbows, which may be taken (see Table XLIII) as ten times the actual width of the duct measured on the radius of the elbow. The total friction drop due to the straight pipe is then as follows: (250 + 10) X ~ + (40 + 13.3) X = 0.382 inch The resistance of the register may be taken as 1.25 times the velocity head corresponding to a register velocity of 300 feet per minute, upon which basis the size of the register will be selected. The velocity head we may compute by means of formula (2), page 240. ^X 0.06848 = 0.0051 inch. The loss through the register is 0.0051 X 1.25 = 0.006 inch. The loss at the entrance to the duct from the plenum chamber we will take as 80 per cent, of the velocity head corresponding to the velocity of 1,000 feet per minute. 0.80 X h v = 0.80 X (An^Vx 0.06848 = 0.045 inch (QQO N l pgg 5 ) The total resistance of the duct is then 0.382 + 0.006 + 0.045 = 0.433 inch and the total pressure in the plenum chamber must be equal to this plus the velocity head corresponding to 1,000 feet per minute or 0.433 + 0.062 = 0.495 inch. The remaining ducts must then be of such a size as to use up this available total pressure of 0.501 inch. Assume the following data for one of the ducts : Quantity of air delivered, 1,150 c.f.m. Register velocity, 300 feet per minute. Velocity, throughout entire length, 800 feet per minute. Total equivalent length, including resistance of elbows, 110 feet The following quantities can be computed : Resistance of register = *~n5S * 0.06848 = 0.0051 inch. Loss at entrance to duct = 0.80 X (i 095 5 V X 0.06848 = 0.029 inch. DESIGN OF FAN SYSTEMS 251 Velocity head at entrance _ / 800 \ ~ Vl,096.5/ X 0.06848 = 0.036 inch. Static head to be used up by friction = 0.495 - (0.0051 + 0.029 + 0.036) = 0.425 inch. The friction loss per 100 feet of duct must then be 0.425 -f- 1.10 = 0.386 inch. From the chart in Fig. 165 the diameter of the round pipe which will give this friction loss for 1,150 c.f.m. is 12.0 inches. This is equivalent (see Table XLII) to a rectan- gular pipe 10 by 12 inches or 8 by 15 inches, either of which could be used. The equivalent length allowed for the. elbows, which must necessarily have been estimated, should be revised if the computed width of the duct is greatly different from the assumed width upon which the equivalent lengths were estimated, and the calculation repeated. 1.800 1,500 FIG. 167. 219. Trunk-line System. In a trunk-line system, the pro- cedure would be as follows: Assume a system laid out as in Fig. 167, in which the quanti- ties as given are on a basis of 70. The system will be designed for a temperature of 135 and the actual quantities flowing in the various sections are as follows: A-B 11,100 X 1.1230 = 12,465 c.f.m. B-C 5,800 X 1.1230 = 6,513 c.f.m. C-D 1,800X1.1230= 2,021 c.f.m. B-E 3,300 X 1.1230 = 3,706 c.f.m. E-F 1,500 X 1.1230 = 1,684 c.f.m. The total head at point A must be equal to the friction loss in the trunk duct plus the velocity head at D, the end of the 252 HEATING AND VENTILATION trunk duct. The method of proportioning by a uniform friction loss leads to a reduction in the velocity toward the end of the trunk and a consequent conversion of some of the velocity head to static head. The absolute values of the velocity and static heads at A are not important, the requirement being that their sum be equal to the friction loss plus the velocity head at D. On a basis of velocity of 1,000 feet per minute the velocity head at D will be equal to( t nnA ,) *X 0.06675 = 0.055 inch on * ijUyo.o/ a basis of 135. The friction drop may be fixed arbitrarily and we will choose it in this case as 0.20 inch per 100 feet, giving a total pressure at point A of 0.20 X 2.25 -f 0.055 = 0.505 inch. For a friction drop of 0.20 inch per 100 feet the diameters of sections A-B, B-C, and C-D, would be respectively 34.0, 26.0, and 17 inches. The diameter of the outlet at D would be increased to 19 inches to give the required outlet velocity of 1,000 feet per minute. The branch pipe could be designed for the same pressure loss per unit length but it is more economical to take advantage of the full available head and reduce the size of the pipe. The static head at B can be found by subtracting from the static head at A the loss in section A-B. Allowing for the loss due to entrance in the branch at B and for the final velocity head at F the allowable friction loss in sections B-E and E-F can be determined and the size of pipe chosen accordingly. All outlets should be provided with dampers so that the proper delivery can be obtained by adjusting them after the system is installed. 220. Power Required for Moving Air. The power required for moving air through a system of ducts may be expressed as follows : Let p = unit total pressure, inches of water. a = cross-sectional area of duct, square feet. v = velocity of air, feet per minute. Then the horsepower required is 12 X 2.3* xoOO = - 00158 * If q is the volume of air delivered per minute in cubic feet, then q = av and Hp. = 0.000158 pq DESIGN OF FAN SYSTEMS 253 221. Theory of the Centrifugal Fan. The centrifugal fan consists fundamentally of a wheel having several radial vanes revolving in a casing. Air enters near the axis of the wheel, flows to the circumference under the influence of the centrifugal force produced by the rotation, and is discharged through the outlet which is located tangentially with respect to the fan wheel. The pressure created in a fan has two separate and independent sources, (a) that due to the centrifugal force imparted to the masses of air enclosed between the vanes, and (6) the pressure due to the linear velocity of the air as it leaves the tip of the blades. The efficient conversion of the velocity head into static head depends upon the proper design of the fan housing, as will be shown later. Fig. 168 represents an elementary cen- trifugal fan. Consider a thin layer of air of thickness dx between two of the vanes at a distance x from the axis and having an area of S. The volume of this layer of air is then Sdx, and if its density is D, then the weight will be SdxD. Assume that the fan outlet is completely closed and that the wheel revolves at the rate of o> radians per second. Then the centrifugal force 1 FIG. 168. df 'xSdx D df The unit pressure dp corresponding to df is evidently = -~ and the equivalent head __ dp __ df Then dh = 2 xdx ~lj 18H 1.79 457 2,620 0.37 501 2,870 0.48 4 20 H 2.33 400 3,430 0.48 439 3,750 0.63 u 23 H 2.95 356 4,340 0.60 390 4,750 0.80 5 26 H 3.64 320 5,350 0.74 351 5,870 0.98 5X 28H 4.41 291 6,470 0.90 319 7,100 1.19 6 31 H 5.25 267 7,710 1.07 292 8,450 1.41 7 36 H 7.14 229 10,490 1.46 251 11,500 1.92 8 42 9.33 200 13,700 1.91 219 15,020 2.51 9 47 11.81 178 17,340 2.41 195 19,000 3.18 10 52 14.58 160 21,400 2.98 175 23,460 3.93 11 58 17.64 146 25,900 3.60 160 28,390 4.75 12 63 21.00 133 30,820 4.29 146 33,780 5.65 13 68 24.65 123 36,180 5.03 135 39,650 6.63 14 73 28.68 114 41,950 5.84 125 45,990 7.69 15 78 32.80 107 48,160 6.70 117 52,790 8.83 Static pressure is 77>^ per cent, of total press. 1 From "Fan Engineering," Buffalo Forge Co. DESIGN OF FAN SYSTEMS 261 TABLE XLVL No. 10 NIAGARA CONOIDAL FAN (TYPE N) Capacities and Static Pressures at 70F. and 29.92 Inches Barom. 1 Outlet velocity, ft.-min. Capac- ity, cu. ft., air per mm. Add for total press. }-in. s.p. %-in. s.p. 1-in. s.p. l^i-in. s.p. 2-in. s.p. R.p.m. Hp. R.p.m. Hp. R.p.m. Hp. R.p.m. Hp. R.p.m. Hp. 1,400 20,410 0.122 164 2.92 206 4.61 243 6.59 308 11.1 1,500 21,870 0.141 163 3.13 204' 4.78 240 6.83 305 11.5 1,600 23,330 0.160 164 3.42 202 5.02 238 7.05 302 11.8 357 17.0 1,700 24,790 0.180 165 3.74 201 5.30 235 7.28 299 12.1 353 17.5 1,800 26,240 0.202 166 4.13 200 5.61 233 7.59 295 12.4 350 17.9 1,900 27,700 0.225 168 4.55 200 6.01 232 7.91 293 12.7 347 18.3 2,000 29,160 0.250 171 5.04 200 6.48 231 8.32 291 13.0 343 18.7 2,100 30,620 0.275 174 5.56 201 7.00 231 8.77 288 13.5 340 19.2 2,200 32,080 0.302 177 6.12 203 7.54 230 9.31 286 13.9 338 19.6 2,300 33,540 0.330 180 6.76 205 8.16 231 9.92 285 14.4 336 20.1 2,400 34,990 0.360 183 7.43 207 8.86 232 10.60 284 15.0 332 20.6 2,600 37,910 0.422 190 8.95 213 10.40 235 12.10 282 16.3 329 21.8 2,800 40,830 0.489 198 10.70 219 12.20 240 13.90 283 18.1 327 23.3 3,000 43,740 0.560 206 12.70 226 14.30 246 16.00 285 20.1 326 25.0 3,200 46,660 0.638 215 14.80 234 16.70 251 18.30 288 22.4 327 27.4 NOTE. Bold-face figures indicate point of highest static efficiency. The fan tables are based on actual tests made by operating the fan at constant speed against different artificial resistances con- sisting of plates, having openings of various sizes, placed at the end of a straight pipe about 30 diameters in length. In Fig. 173 are shown the performance curves for a multi-blade fan, based on the percentage of rated capacity, the latter being taken as the point at which the fan operates with the highest total efficiency. It should be borne in mind that these perform- ance curves are based on a constant speed. It is frequently necessary to find the performance of a fan at some pressure different from any given in the tables. The method of doing this can best be shown by a typical example. Assume that 38,000 cubic feet of air per minute is to be delivered by a No. 10 Conoidal fan against a static resistance of 1J inches. Find the required speed and horsepower. The data for 1-inch static is given in Table XLVL The corresponding capac- ity of the fan at 1-inch static may be found by multiplying by the square root of the ratio of 1-inch to IJ^-inch, since we know that the pressure varies as the square of the speed and conse- quently as the square of the volume delivered. The capacity on The Centrifugal Fan, by FRANK L. BUSEY, Trans. A. S. H. & V. E., 1915. 262 HEATING AND VENTILATION a 1-inch basis is thus found to be 34,100 c.f.m. From Table XL VI we find that the speed and horsepower for 33,540 c.f.m. at 1-inch static are respectively 231 r.p.m. and 9.92 horsepower. The speed and horsepower at 1^4 inches static we can compute from our knowledge that the speed varies directly as the capacity and the power as the cube of the capacity. The fan will deliver 38,000 c.f.m. against \Y inches static with a speed of 258 r.p.m. and a power consumption of 13.9 horsepower. 20 40 140 60 80 100 Per Cent of Bated Capacity FIG. 173. Performance curves of Niagara conoidal fans. 160 In selecting a fan for a given installation it is usually possible to fulfill the required conditions with two or even three different sizes of fans. In such a case the first cost, operating cost, and out- let velocities should be considered in making the selection. The smaller the fan the greater will be the outlet velocity for the same volume. In the case of schools or other buildings where quiet operation is essential the outlet velocity should not be over about 2^200 feet per minute. In industrial buildings, how- ever, outlet velocities of about 3,000 feet per minute are quite permissible. 229. Correction for Temperature. The fan tables are based on an air density corresponding to a temperature of 70. In a system in which the fan is so located with respect to the heating coils that it handles air at a different temperature, a correction DESIGN OF FAN SYSTEMS 263 must be made. This can be done by making use of the relations stated in Par. 224. For example: Assume that it is required to handle 11,700 c.f.m. against a static head of 1% inches at 140. As brought out in Par. 224, at constant capacity and speed, the horsepower and pressure vary inversely as the absolute temperature of the air. Therefore, if we select a fan which will handle 11,700 c.f.m. against a pressure of 1.75 X ^7: = 1.98 inches at 70 deliver the same quantity against a pressure of 1.75 inches at 140 at the same speed. From the fan tables we find that a No. 90 steel plate fan will do this at a speed of 403 r.p.m. and a power consumption of 7.32 horsepower. The power consumption at 530 140 would be 7.32 X = 6.46 horsepower. It should be remembered that the volume of air fixed by the heating or ventilating requirements is usually based on the room temperature and the equivalent volume of the same weight of air at the temperature at which it enters the fan must be found by means of the volume ratios given in Table XXXVII, page 203. 230. Disc Fans. The disc fan as illustrated in Fig. 174 is well adapted for handling considerable quantities of air against very low pressures. It is therefore widely used where the air is moved into or from a room without passing through a system of ducts. While not highly efficient, this type of fan is easily installed, is of mod- erate cost, and requires little space. Such a fan is usually inserted di- rectly into a wall or partition and is driven by a direct-connected motor. 231. Heaters. In a fan system the heat is transmitted from the heating units entirely by convection, the air being drawn over them at a fairly high velocity. There are two types of heater used for such work the cast-iron heater and the wrought-iron pipe coil. The former is made up of sections, as shown in Fig. 175, connected together at the top and bottom by right- and left-hand nipples cast with a hexagonal nut at the middle. A row of sections thus connected constitutes a stack. 264 HEATING AND VENTILATION The sections are obtainable in nominal lengths of 30, 40, 50, 60, and 72 inches. All sizes are connected at both top and bottom and are therefore suitable for hot water as well as steam. The sections are furnished in two widths, the " regular" and the "nar- row," and by the use of nipples of different lengths the distance between sections can be made either 4^, 5, or 5% inches center to center, the 5-inch spacing being standard. The surfaces are broken up by a large number of projections which extend into the air passages and serve to augment the heating surface in an effective manner. The principal dimensions of the sections of various sizes are given in Table XL VII. The method of installing the stacks in a sheet-metal casing is shown in Fig. 176. The stacks are staggered so as to break up the stream lines and increase the intimacy of the contact between the air and the heating surface. The spaces left at the ends of the stacks due to the staggered arrangement are partially closed by strips of angle iron. TABLE XLVII. DIMENSIONS OF VENTO SECTIONS, INCHES FIG. 175. Cast iron heater. Nominal size Square feet of surface Actual height Width 30 8.00 30 9H 40 10.75 41^4 9M Regular width 50 13.50 50% 2 9M 60 16.00 60 1 ^ 6 9>6 72 19.00 72% 2 9M 40 7.50 41^4 6^ Narrow 50 9.50 502% 2 SH 60 11.00 60% Wi Approximate weight 8.2 pounds per square foot of surface. 232. Pipe-coil Heaters. Heaters made of 1-inch pipes are also widely used. The pipe is made into loops with ordinary elbows, and the loops are screwed into a cast-iron base. The DESIGN OF FAN SYSTEMS 265 base is so partitioned that the steam flows in at one end of each of the loops. The sections are arranged as shown in Fig. 177, FIG. 176. Vento heater installed in casing. P~~ O O O^O O O P r ID lL - L -Q- -@_ QJOL -_ fl L@_ O. j .O-O-O.Q.Q-fl & FIG. 177. Pipe coil heater. the pipes being staggered with reference to the flow of air through the heater. The sections are built in different sizes and a wide 266 HEATING AND VENTILATION range in heating surface is available. The complete heater is composed of several units in series, as in the case of the cast- iron heaters. 233. Transmission of Heat from Fan-coil Surfaces. The heating units are arranged in series, the outside air entering the first section and being heated up to the required delivery temperature during its passage through the successive sections. Since the rate of heat transmission varies nearly as the tem- perature difference between the steam and the air, the heat transmitted from the last stacks is much less than from those with which the cold air first comes into contact. The final temperature to which the air is heated depends upon the number of stacks through which the air passes in series and upon the velocity of the air. The cross-sectional area of the heater depends upon the quantity of air delivered, the stacks being chosen of sufficient size so that the free area between the sections will allow that quantity to pass through at the velocity chosen. The free area per section for Vento heaters is given in Table XL VIII. Similar data is published by the manufacturers of pipe-coil heaters. TABLE XLVIII. FREE AREAS OP VENTO SECTIONS Size ^of section, inches Free area, square inches per section 5fj-in. centers 6-inch centers 4^-inch centers 30 0.542 0.460 0.390 40 0.729 0.620 0.525 50 0.905 0.768 0.650 60 1.085 0.921 0.781 72 1.303 1.104 0.937 The velocity to be assumed depends upon the nature of the installation. In public buildings and in other places where the noise which accompanies high velocities is objectionable, the velocity through the heater should be limited to between 1,000 to 1,300 feet per minute while in factories and similar buildings a velocity between 1,200 and 1,600 feet per minute is permissible. For this purpose velocities are based on an air density correspond- ing to 70, this being merely an arbitrary standard adopted for convenience in making computations. In very cold climate's a DESIGN OF FAN SYSTEMS 267 TABLE XLIX. FINAL TEMPERATURES AND CONDENSATION Regular Section Standard Spacing, 5-inch Centers of Sections Steam, 227, 5 Pounds Gage a vw Velocity through heater in feet per minute measured at 70 | .a 600 800 1,000 1,200 1,400 1,600 1,800 2,000 i fc Final Cond. fe-o &!* tC f I au : Ib. per . . s Si3 leav- sq. ft. fr d S o fr U p-i O fe ^ 3 fc H ing heater per hour -20 -10 34 1.69 1 43 1.65 38 1.95 35 2.24 32 2.46 20 58 1.46 54 1.75 51 1.99 49 2.23 47 2.42 45 2.56 43 2.65 42 2.82 30 66 1.39 62 1.64 60 1.92 58 2.17 56 2.33 54 2.46 52 2.54 51 2.69 -20 63 1.60 55 1.92 49 2.22 44 2.46 40 2.69 37 2.92 34 3.12 31 3.27 -10 69 1.52 62 1.85 56 2.12 51 2.35 47 2.56 44 2.77 41 2.94 38 3.08 2 75 1.44 681.74 62 1.99 582.23 54 2.42 51 2.62 48 2.77 462.95 20 87 1.29 81 .57 76 1.80 72 2.00 69 2.20 66 2.36 64 2.54 622.69 30 93 1.21 87 .46 83 1.70 79 1.89 76 2.06 73 2.21 71 2.37 69 2.50 -20 91 1.42 82 .74 75 2.03 69 2.28 64 2.51 59 2.70 55 2.88 52 3.08 -10 96 1.36 87 .66 80 1.92 75 2.18 70 2.39 66 2.60 62 2.77 58 2.90 3 101 1.30 93 .59 86 1.84 81 2.08 76 2.27 72 2.46 68 2.62 65 2.78 20 110 1.15 103 .42 97 1.65 92 1.85 88 2.06 85 2.22 82 2.38 79 2.52 ' 30 115 1.09 108 .33 103 1.56 98 1.75 94 1.91 91 2.08 88 2.23 85 2.35 -20 114 1.29 103 .58 96 1.86 90 2.12 84 2.34 78 2.51 74 2.71 70 2.88 -10 117 1.22 108 .51 101 1.78 95 2.02 89 2.22 84 2.41 80 2.60 76 2.76 4 121 1.16 113 .45 106 1.70 100 1.92 95 2.13 90 2.31 86 2.48 82 2.63 20 130 1.06 122 .31 115 1.52 110 1.73 105 1.91 101 2.08 97 2.22 94 2.37 30 134 1.00 126 .23 120 1.44 115 1.63 110 1.80 106 1.95 102 2.08 99 2.21 -20 132 1.17 122 1.46 114 1.72 107 1.95 100 2.15 94 2.34 90 2.54 86 2.72 -10 135 1.13 126 1.40 118 1.64 111 1.86 105 2.06 99 2.24 95 2.42 91 2.59 5 138 1.06 129 1.32 122 1.56 115 1.77 109 1.96 104 2.14 100 2.31 96 2.46 20 144 .95 136 1.19 130 1.41 124 1.60 119 1.78 114 1.93 110 2.08 107 2.23 30 148 .91 140 1.13 134 1.33 128 1.51 123 1.67 118 1.80 115 1.96 112 2.10 -20 146 1.06 137 1.34 129 1.59 121 1.81 115 2.02 110 2.22 105 2.40 100 2.56 -10 149 1.02 140 1.28 132 1.52 125 1.73 119 1.93 114 2.12 109 2.29 104 2.44 6 152 .97 143 1.22 135 1.44 129 1.65 123 1.84 118 2.02 113 2.17 109 2.33 20 156 .87 148 1.10 142 1.30 129 1.49 130 1.65 126 1.81 122 1.96 118 2.09 30 159 .83 151 1.04 145 1.23 139 1.40 134 1.56 130 1.71 126 1.85 122 1.97 -20 159 .98 150 1.25 141 1.47 134 1.69 128 1.90 122 2.08 117 2.26 113 2.44 -10 161 .94 152 1.19 144 1.41 137 1.62 131 1.81 126 1.99 121 2.16 117 2.33 7 163 .90 154 1.13 147 1.35 140 1.54 135 1.73 130 1.90 125 2.06 121 2.22 20 167 .81 159 1.02 152 1.21 146 1.39 141 1.55 136 1.70 132 1.85 128 1.98 30 169 .76 161 .96 155 1.15 149 1.31 144 1.46 139 1.60 135 1.73 132 1.87 -20 168 .90 159 1.15 151 1.37 144 1.58 138 1.77 133 .96 128 2.14 123 2.29 -10 170 .87 161 1.10 153 1.31 147 1.51 141 1.69 136 .87 131 2.04 126 2.18 8 172 .83 164 1.05 156 1.25 150 1.44 144 1.62 139 .78 134 1.93 129 2.07 20 175 .75 167 .94 161 1.13 155 1.30 150 1.46 145 .60 141 1.74 137 1.87 30 177 .71 169 .89 163 1.07 158 1.23 153 1.38 148 .51 144 1.64 140 1.76 268 HEATING AND VENTILATION velocity of 800 feet per minute or less is advisable because of the tendency for the condensation to freeze in the coils. The velocity thus chosen is used both as a basis for computing the height and width of the heater and also for determining its depth, i.e., the number of stacks to be used. In Table XLIX are given the final temperatures obtainable from heaters of vari- ous depths for air at different initial temperatures and velocities. Difference between Final Temperature and Initial Temperature of Air 3,000 2,500 2,000 1,500 1,000 900 2 800 700 600 I 500 I 400 2 300 200 227Steam g | S|S|$SSSS.8S S S 38 Frictional Resistance in Inches of Water FIG. 178. Friction curves for pipe coil heaters. 2.0 The final temperature for which the heater is designed depends upon the amount of heat to be supplied and upon whether the fan system is to be used for ventilating alone or to supply the heating requirements also. The temperature of the entering air used in the computations should be the minimum for which the system is to be designed. DESIGN OF FAN SYSTEMS 269 Example. Assume that a factory is to be heated and that 1,400,000 cubic feet of air per hour are required at a temperature of 140. Minimum out- side temperature 0. What size Vento heater should be used? Free area (square feet) = volume (cubic feet per minute at 70) velocity (feet per minute) Free area = 1,400,000 1200 X 60 X 1.1320 , r or r = 17.17 square feet Difference between Final Temperature and Initial Temperature of Air, 9.0 8.0 7.0 6.0 5.5 5.0 4.5 4.0 3.5 3.0 1 1 a 1.0 if 2 5.5 g .5 4.5 3.5 ..3 2.5 ,2 y f^j-fo] for 22 7 Steam ~" C 13130. V Ml -m :1 72 -u /: .M ^3 S 5 w i C3 2 c- s a OJ CO /. X rsr- x rt CM CO " *> ; - d ^ X ^ X A/1A \ ; ^ ^ ^ ^ o S ^ % s* X" ^ x " 9 000 1.94 *ff - ^ I/ -^ ^ x- X 1 xf I x ^^ X / 1063 / nin. =* ^ 1 ^ K ^ ^ x^ ^ 1 1,000 X^ X' 1}'^^ ^X^^x ' X ^xH ^^ x^ - 9002 800 2 ( X X ' ^x> ^ ^ * x ^> ^x- ^ ^x^ 'x^ - 700 S ^x^ _^ X x' ^^' ^ * ;xjx^ | .s^ ^x^ ^ ^ ;S x^ ^^^ , ^^ - 600g ^ ^^ ^^- ^ ^ x;^ t ^s^ ^^ x^ x *s ^^ -*^* f * *y*** w ^^ ^. ^^ ^ ^ s\_ ^_s- 400 a -, ~' .x ^~, ^ X. X x ^ a ^ X " ^x ^x; ^ x^ ^ s 300 > x^ -" x^> ^ X | ^d ^ ^ - 200^ f . S8S !3 8 a 8 , Frictional Resistance in Inches of Water FIG. 179. Friction curves for vento heaters. Referring to Table XLVIII it is seen that by using eighteen 60-inch sections, spaced 5 inches center to center, the free area will be 18 X 0.921 = 16.58 square feet, which is sufficient, giving a velocity of 1,244 feet per minute. From Table XLIX it is seen that a heater seven stacks deep would raise the air from a temperature of to 140 at a velocity of 1,200 feet per minute. The heater should therefore be seven stacks deep. Ordi- narily it would be divided into a tempering coil of three stacks and a heating coil of four stacks. 270 HEATING AND VENTILATION Pipe-coil heaters are chosen in a similar manner from the data furnished by their manufacturers. Recent tests 1 have shown that the heating effect of both cast- iron and pipe-coil heaters is closely related to the friction loss undergone by the air in passing through them; and that for the two different types of heaters, the friction loss will be practically identical for the same increase in temperature of the air. This might logically be expected as the heat transmission depends upon the thoroughness of the rubbing action of the air over the heating surfaces. From the curves in Figs. 178 and 179 the friction drop can be determined for either Vento or pipe coil if the other facts are known, and vice versa. These curves are based on the following formula which was developed from the results of tests mentioned above on pipe coils and upon tests made on Vento heaters by L. C. Soule. C = ^ " KN in which C = condensation in heater pounds per square foot per hour. V = velocity of air feet per minute. ti tz = temperature rise of air. N = number of stacks in heater. K = a constant = 15,307 for pipe coil and 13,130 for Vento. As an example of the use of the charts we will take an assumed case. With five stacks and an entering temperature of 10, the final temperature for 1,200 feet velocity is found from pipe- coil data to be 129, making the increase in temperature 119. In Fig. 178 the horizontal dotted line representing 1,200 feet velocity intersects the vertical line representing 119 at the point A. From point A we draw the 45 line until it intersects the vertical line for five stacks. From this point we extend a horizon- tal line to the right-hand side of the chart and we see that the condensation per square foot per hour is 1.89 pounds. The frictional resistance is obtained by extending the horizontal line for 1,200 feet velocity to the right until it intersects the diagonal line for five stacks; a vertical line from this intersection shows the 1 See "Comparison of Pipe Coils and Cast-iron Sections for Warming Air," by JOHN R. ALLEN, Proc. A. S. H. & V. E., 1917. DESIGN OF FAN SYSTEMS 271 resistance to be 0.25 inch of water. In Fig. 179 the same case is worked out for Vento heaters as indicated by the dotted lines. The condensation is found to be about 1.94 pounds and the velocity 1,068 feet for the same resistance and temperature rise. It will be noted that while the heating effect and resistance of the two heaters are the same, the velocities are quite different. 234. Installation and Piping Connections. The heating units are usually mounted on a brick or concrete pier and enclosed by a metal duct. The proper arrangement of the steam piping Trap By-pass Plate Center air vent section used when desired. Recommended for stacks of 17 to 30 sections. 3i"lron Plate on / Top of Piers hermostatically Operated Inlet Valves These air removal connections required., only with stacks of 17 to 24 sections) each. Thermostat! Air Val Floor Line FIG. 180. Piping connections for vento heaters. connections for Vento heaters is shown in Fig. 180 for a double- tier installation. The center section of a long stack is tapped for an air vent as shown. Separate valves should be provided for each stack or pair of stacks. Special care is necessary in arranging the return connections from fan heaters, as any accumulation of condensation will soon be frozen by the cold air. There is always a considerable drop in pressure through the heaters and the inlet connections, so that the pressure at the return connections should not be de- pended upon to lift the condensation; the discharge should be by gravity or a vacuum pump should be used. 272 HEATING AND VENTILATION 236. Thermostatic Control for Fan Systems. Thermostatic control is absolutely necessary on most types of fan systems. Hot blast systems in factories and other industrial buildings are among the exceptions. The thermostats, located in the system at suitable points, operate valves on the supply to the heating and tempering coils. There are many different arrangements of the thermostats and valves which may be used, depending upon the results desired. In Fig. 181 is shown a method of applying thermostatic control to a ventilating system. From Thermostat . . 1 '"TIT Room above ' *~ ' FIG. 181. Thermostatic control applied to a fan system. Problems 1. In the example in Par. 212, assuming that 657,000 cubic feet of air per hour are delivered, if the heat loss as given was computed for 0, what should be the delivery temperature when the outside temperature is 20? 2. A factory building is to be heated by a hot-blast system with complete recirculation. With the following data given compute the amount of air which must be handled per hour by the system. Heat loss from building 27,800 B.t.u. per hour per degree difference in temperature. Inside temperature Outside temperature Temperature at which air is delivered. 65 -10 120 3. In the single duct system of Fig. 166 assume that the longest duct is to carry 1100 c.f.m. What is the total pressure required in the plenum chamber? 4. Compute the pipe sizes for a trunk duct system similar to that in Fig. 167 except that the air quantities in the different sections on a 70 basis are as follows: Section Air quantity A B 19,000 c.f.m. B C 7,500 C D 2,000 B E 6,000 EF 4,000 Maximum air temperature 130. DESIGN OF FAN SYSTEMS 273 5. Find the speed, horsepower, and outlet velocity for three different sizes of steel plate fan 1 delivering 18,000 c.f .m. against a static resistance of 13^ inches at 70. 6. Find the speed, horsepower, and outlet velocity for three different sizes of multi-blade fan 1 delivering 12,000 c.f.m. against a static resistance of 2 inches at 70. 7. A multi-blade fan is to handle 9000 c.f.m. against a static head of 1^ inches at 140. What is the required speed and horsepower? 8. What would be the size of vento heater required to heat 800,000 cubic feet of air per hour from an outside temperature of 10 to a delivery tempera- ture of 140? Assume a velocity through the heater of 1500 feet per minute. 9. What would be the size of vento heater required to heat 1,100,000 cubic feet of air per hour from an outside temperature of to a delivery tempera- ture of 70? Assume a velocity through the heater of 1100 feet per minute. 10. Find by means of the friction chart in Fig. 179 the frictional resistance of a vento heater, 5 stacks deep, for a velocity of 1500 feet per minute. Find the resistance of a vento heater, 3 stacks deep, for a velocity of 900 feet per minute. 1 See tables in Appendix, pages 302 to 325. 1 CHAPTER XVII AIR WASHERS AND AIR CONDITIONING 236. The Air Washer. Various methods of filtering or wash- ing air have been in use for many years. In the older forms of apparatus the dust was usually filtered from the air by means of muslin screens; but this method is not very effective and has the disadvantage that the screens soon become clogged with dirt, greatly increasing the resistance to the flow of air through them. Screen filters have been superseded by the modern air washer, in which the dirt is removed from the air by water sprays and by the contact of the air against wet surfaces. A typical air washer is shown in Fig. 182. It consists of three elements the spray nozzles, the scrubber plates, and the eliminator plates. The nozzles are placed in a bank across the path of the air and the water is forced through them by a pump and is discharged in a fine conical spray or mist in the direction of the air flow. In some cases two banks of nozzles are used. The air, drawn through the washer by the fan, is thus brought into intimate contact with the water and some of the dirt and soluble gases are removed. The really effective cleansing is done by the scrubber plates which are designed to change the direction of flow so that the dirt will be thrown out from the air by its inertia and by the rubbing of the air over the wet surfaces. The plates are kept flooded either by the spray nozzles or by a separate row of nozzles placed above them. Following the scrubber plates are a series of eliminator plates whose function is to remove the entrained water from the air. The lower part of the washer constitutes a tank into which the water falls and from which it is taken by the circulating pump. A float valve admits fresh water as required to replace that evaporated. Proper provision must be made in an air washer to prevent trouble from the large quantities of dirt which are washed from the air and deposited in the tank. A screen of ample area is necessary on the suction line to the pump to prevent the dirt from being carried into the circulating system, and in some types of washers special devices are necessary to enable the spray 274 AIR WASHERS AND AIR CONDITIONS 275 Fresh-Wat,- 8upplj\ Suction Strainer. Drain-"" END VIEW FIG. 182. Air washer. 276 HEATING AND VENTILATION nozzles to be cleaned periodically by flushing. The accumulated dirt must be removed from the tank at frequent intervals. The air washer is placed between the tempering coils and the heating coils of a fan system, this arrangement being necessary in order to insure that the air entering the washer will be at a temperature sufficient to keep the spray water from freezing. 237. Air Conditioning. The air washer in addition to cleans- ing the air has other functions. When properly equipped and operated it can be used for humidifying, cooling, and dehumidi- fying. In an ordinary ventilating system it is commonly used for humidifying, in order to satisfy the ventilation requirements explained in Chapter XIV, and in some instances it is used for cooling. Cooling and dehumidification, however, are principally sought in industrial applications of the air washer. There are many industrial processes which can be carried on to much better advantage in a dry atmosphere, a cool atmosphere, or in some cases a moist atmosphere. The manufacture and packing of certain kinds of confectionery, for example is greatly facilitated by a dry atmosphere. In many textile processes, and in the manufacture of powder, photographic films, etc., the proper con- ditioning of the air is of great importance. 238. Humidification. Humidification is accomplished by heating the spray water so that the air will absorb the proper amount of moisture while passing through the spray chamber. Sufficient heat is added to the spray water, first to evaporate the moisture necessary to bring the air to saturation at its entering temperature and, second, to add further amounts of heat and moisture until the air leaves the washer at saturation and at such a temperature that it contains the requisite quantity of water vapor. It then passes to the heating coils which raise its tem- perature without affecting its moisture content. For example, suppose that it is required to deliver air to a room at a temperature of 70 and a relative humidity of 60 per cent., which requires a moisture content of 4.85 grains per cubic foot. We will assume that the outside air has a dry-bulb tem- perature of 25 with a relative humidity of 20 per cent. Refer- ring to Fig. 183, the entering air is heated by the tempering coils to a temperature of 40, as represented by the line AB. In the washer moisture is absorbed from the spray water until the air becomes saturated at 40, as represented by BC. Both heat and moisture continue to be absorbed from the spray water until the AIR WASHERS AND AIR CONDITIONS 277 air reaches the condition represented by point D, in which it contains 4.85 grains per cubic foot and has a temperature of 55. It is then heated by the heating coils to the delivery temperature of 70, at which it will have the required relative humidity of 60 per cent. During this last process the moisture content per pound of air remains the same, the weight of the vapor per cubic foot decreasing slightly because of its expansion due to the tem- perature increase. For approximate calculations this difference may be neglected and the line DE representing this last step on 10056 90 % 80* 20 25 30 35 40 45 50 55 60 65 70 75 Dry Bulb Temperature FIG. 183. 90 95 100 105 the chart in Fig. 183 may be taken as a horizontal line. For very accurate work the charts in Figs. I and II in the Appendix, which are constructed on the basis of 1 pound of air, may be used. Every final condition of the air has a corresponding tempera- ture at saturation, to which the air is brought before it passes to the heating coils. If, in the case given above, the temperature of the outside air were above 56 it would be lowered because of the heat given up by it to evaporate the moisture which it absorbs provided, however, that its original moisture content be con- siderably below saturation. The action would then be repre- sented by the line FD. If the dry-bulb temperature of the entering air were between 40 and 55 no heat would be added 278 HEATING AND VENTILATION by the tempering coil and moisture would be added at a con- stant dry bulb temperature until the air reached saturation, after which it would follow the line CD to 55 as before. 239. Spray-water Heater. In order to supply heat to the spray water, a heater is installed in the water circulating line, between the pump and the spray nozzles. If high-pressure steam is available it is injected directly into the water through a suitable valve. If low-pressure steam or hot water are used a closed heater, in which the spray water circulates through tubes surrounded by the heating medium, is necessary. 240. Humidity Control. The steam supply valve of the heater is controlled usually by automatic means so that the proper Water Inlet Water Outlet ' FIG. 184. Spray- water heater. amount of heat is added to the water. In a compressed-air system of control, a diaphragm valve is placed on the supply to the water heater and may be operated by means of a "hygrostat" or "humidostat," which corresponds to the thermostat of a tem- perature control system. In place of the thermostatic element there is used some material such as wood or hair which under- goes a change in length when the moisture content of the surrounding air changes The " humidostat" is placed either in the main duct or in the principal room of the building and con- trols the supply valve on the heater. An injector type of heater with a diaphragm control valve is shown in Fig. 184. 241. Dewpoint Method. Another and a more rational method of humidity control, called the dewpoint method, is based on the fact that the air always leaves the washer in a saturated condition and therefore its moisture content will depend upon its tempera- ture. From a thermostat placed in the path of the air leaving the washer the heat added to the spray water is controlled so that the exit temperature of the saturated air is at the point fixed by the humidity required. In the example given in Paragraph 238 the thermostat at the washer outlet would be set for 55 and the temperature of the air leaving the washer AIR WASHERS AND AIR CONDITIONS 279 would be maintained at that point. A special duct-type thermo- stat of the form shown in Fig. 185 is used for the purpose, having a bulb extending into the path of the air and controlling the air supply to the diaphragm valve of the spray-water heater. Humidification may also be accomplished by steam jets when no washer is used, in which case the jets are located in the same position as the washer and may be automatically controlled. Another type of humidifier is located directly in the room and discharges a finely atomized "spray which vaporizes after leaving the apparatus. If the steam supply is perfectly free from oil and does not possess a disagreeable odor, humidifiers of the type which discharge stearn directly into the room may be employed. JTo Diaphragm Valve on Spray Water Heater Stem in Path of Air Air Supply FIG. 185. Duct thermostat for dewpoint method of humidity control. They are not always suitable for use in moderate weather, how- ever, as a considerable amount of heat is given up by the steam which might raise the room temperature to an uncomfortable point. The objection to these latter forms of humidifier is the absence of automatic means of regulating the humidity. 242. Cooling by Humidification. If no heat is added to the spray water of an air washer some evaporation will still take place but the latent heat of the vaporization in this case is taken from the air itself and the temperature of the air is consequently lowered. The extent of t the cooling effect depends upon the capacity of the entering air for absorbing moisture or, in other words, upon the wet-bulb depression of the entering air. As the air absorbs moisture in the spray chamber its dry-bulb tem- perature drops but the wet-bulb temperature, which is a measure 280 HEATING AND VENTILATION of the total heat of the mixture, remains unchanged. If the water is re-circulated its temperature soon drops to the wet-bulb temperature. In a perfect washer the dry-bulb temperature of the air would be reduced to the same point i.e., the air would become saturated, but in a commercial washer this limit is never reached. The cooling effect actually obtained averages about 60 per cent, of the wet-bulb depression; this percentage being termed the humidifying efficiency of the washer. Referring to the psychrometric chart in Fig. 186, the point A represents the original condition of the air at 90 dry-bulb temperature 100# 90? SOU 70j< 60* 25 30 35 40 45 50 55 60 65 70 75 80 Dry Bulb Temperature FIG. 186. 90 95 100 105 and 75 wet-bulb temperature. The cooling and humidify- ing action is represented by the constant wet-bulb temperature line AS, the point B representing the final condition of 81 dry-bulb temperature. The line AC represents the action if the air were cooled to saturation. The humidifying efficiency QQ gj of the washer is then = _ -? = 60 per cent., and the amount of moisture actually added is 1.2 grains per cubic foot, or approximately 60 per cent, of the 2.0 grains which it would be necessary to add to bring the air to saturation. For practical purposes, this method of cooling, by evaporation AIR WASHERS AND AIR CONDITIONS 281 only, has certain limitations. On hot, humid days when cooling in a ventilating system is most desired, little cooling effect can be obtained because of the small wet-bulb depression of the outside air. Furthermore, since the humidity of the air is increased and the wet-bulb temperature unchanged, the cooling power of the air on the human body is increased but little. 243. Cooling and Dehumidification by Refrigeration. A greater cooling effect can be obtained if the spray water be arti- ficially cooled, in which case heat will be transferred from the air to the water by direct contact and no evaporation will take place. Both the dry-bulb and the wet-bulb temperatures will fall until they coincide at the dew point. If the spray-water temperature is sufficiently low they will be reduced still further and some of the moisture will be given up by the air. This action is repre- sented by the line ADE in Fig. 186. In a properly designed washer the air can be cooled to within a few degrees of the average water temperature. This method of dehumidification is sometimes employed in industrial work. The air may be reheated if necessary from the condition indicated by the point E to whatever dry-bulb temperature is required. A washer employed for cooling in this manner is usually equipped with two banks of spray nozzles through which the air passes successively. The first bank is supplied with well water or unrefrigerated water, and the second with refrigerated water. The air is thus given a preliminary cooling before reaching the refrigerated water and the size of the refrigeration plant and the cost of operation are reduced. The refrigeration is accomplished by coils containing either brine or ammonia and placed either in the tank of the washer or arranged so that the water trickles over them. These are called Baudelot coils. In an air-conditioning system employing refrigeration the air is nearly always recirculated because of the high cost of operating the refrigerating plant. The problem of cooling the air in a building involves principles quite similar to those of heating. The amount of heat which must be removed consists of three parts ; (a) the heat which must be removed from the air initially, and from any outside air which enters, to bring it to room temperature, (6) the heat which enters through the walls, roof, etc., by conduction, and (c) the heat which is generated in the room as by industrial operations. The air must be introduced at a temperature sufficiently below 282 HEATING AND VENTILATION room temperature to absorb the heat represented by the two latter quantities. The system might be thought of as the reverse of a hot blast heating system. Problems 1. A ventilating system has an air washer for humidifying and it is desired to maintain a wet-bulb temperature in the building of 56 and a dry-bulb temperature of 70. What must be the temperature of the air as it leaves the washer? 2. An air washer has a humidifying efficiency of 60 per cent. How many degrees will the incoming air be cooled if its initial temperature is 87 and its dewpoint is 65? What will be the final temperature of the air after passing through a washer having an efficiency of 58 per cent., if the initial dry-bulb temperature is 90 and the wet-bulb temperature is 82? 3. The outside air has a dewpoint of 66 and a temperature of 85. After passing through a washer having a humidifying efficiency of 60 per cent., what will be its dew point and its wet-bulb temperature? 4. In a dehumidifying system the incoming air has a dry-bulb temperature of 85 and a wet-bulb temperature of 72. What must be the dry-bulb temperature of the air leaving the washer if it is to have a relative humidity of 48 per cent, when reheated to 70? CHAPTER XVIII CENTRAL HEATING 244. Classes of Systems. There are in general two classes of central heating systems (a) systems from which groups of buildings are heated, such as the buildings comprising an institu- tion, and (b) systems which distribute heat commercially to sections of cities. The latter are often termed district heating systems. The general engineering principles involved are the same in both cases but there are many commercial factors which enter into district heating which do not enter into institutional plants. Systems for institutions are more commonly met with and, unless otherwise noted, the following text applies to that class of systems. Inasmuch as the conditions under which such systems are installed differ widely, the suggestions which follow can be but general. 245. Location of Plant. Before starting the design of the distribution system it is necessary to have a careful survey made of the property, showing the location of the buildings to be heated and the elevation of their basements and first floors, together with a general profile of the ground through which the pipes are to run. The next step is to determine the proper location for the power plant. In general the power plant would be located as near as possible to the buildings to be heated, but the facilities for receiving coal must be taken into consideration. If it is possible to locate the plant on a railroad siding from which coal can be handled direct from the cars without- trucking, this may prove to be the most economical arrangement even if it neces- sitates locating the plant at some distance from the buildings to be heated. The cost of loading, trucking, and unloading will usually overbalance the investment charges on the additional length of the pipes required if the plant is located at the more distant point. 246. Boilers. The selection of boilers of the proper type and size is of extreme importance in the economical operation of the plant. The maximum demand for steam for heating should 283 284 HEATING AND VENTILATION be computed on a basis of the radiation installed plus a liberal allowance for transmission losses. The demand for steam due to the lighting and power requirements should be computed from a knowledge of the maximum current demand and the steam consumption of the electric generating units, allowing also for the energy used by the power-plant auxiliaries. The boiler capacity must be such as to fill whichever of the two requirements proves to be the greater. The exhaust steam should always be utilized insofar as possible for heating. When the available exhaust is not sufficient, some live steam must be used, while if there is more exhaust steam than can be utilized some of it must be discharged to atmosphere unless the size and type of the plant are such as to warrant condensing equipment. After having determined the maximum amount of steam which the plant might be called upon to furnish, the size of the boilers can be chosen. The steam output per rated boiler horsepower varies considerably according to the type of boiler, type of fur- nace, etc.,. but a rough rule for small plants is to assume that 1 square foot of heating surface in a boiler will evaporate 3 pounds of water per hour. The total boiler capacity can then be com- puted upon this basis and it should be divided into units of such sizes that the expected range of loads can be handled by operating the boilers within their range of highest economy. This can best be done by providing a certain boiler or boilers to handle the lightest loads which are expected and other boilers to handle the average operating load and the maximum load. It is desirable that there be a sufficient number of boilers in the plant so that the largest one can be cut out of service at any time for cleaning or repairs. If the boiler pressure to be carried is less than 100 pounds, either fire-tube or water-tube boilers may be used. In general, for this service fire-tube boilers are very satisfactory, as they have large water storage, repairs are easily made, and the boiler may be operated at an output considerably beyond its rated capacity. The principal objection to fire-tube boilers, except those of the Scotch marine type, is the large space which they occupy. If the boilers are to be operated at pressures much over 100 pounds, as will usually be the case if electric generating units are installed, then only water-tube or Scotch marine boilers should be used. CENTRAL HEATING 285 247. Systems of Distribution. The conveying medium for distributing heat may be either steam or water. Each has its advantages. A hot-water system is very often used in hospitals and similar institutions. Perhaps its greatest advantage is the ease in which the heat supply can be controlled, by varying the water temperature at the plant. The maintenance and operating attention are also somewhat less when the system has once been adjusted. Steam has the advantage of being more adaptable to various purposes other than heating, such as sterilizing, cook- ing, and water heating. It is also somewhat better suited for use in indirect systems. Furthermore, in case the plant contains electric generating units, it is always essential to utilize the exhaust for heating. With a hot water system it is necessary to install some form of heater to transfer the heat from the exhaust steam to the water, and a pump to circulate the water. With steam as the distributing medium this apparatus is unnecessary. 248. Steam Distribution. Gravity System. In an institu- tional plant it is quite important to return the condensation to the boilers, first, because of the heat in the water which would otherwise be wasted and, second, because the condensation is free from scale-forming materials and is consequently better for boiler feed than raw water. If the elevation of the power plant with respect to the other buildings will permit, the condensation may be returned by gravity to the boiler and no pumping is necessary. With this system any difference in steam pressure between the boiler and the extreme point in the piping system will result in a corresponding elevation of the water level in the return system at the extreme point. In gravity systems it is usual to allow for a drop in pressure of not over 2 pounds between the boiler and the extreme end of the system. In some cases the gravity-return system has been used over quite an extended area, one building so heated being as far as 2,500 feet from the boiler, and the system has given very good satisfaction. In a central heating plant using the gravity-return system, unless the steam mains are from 6 to 8 feet above the return pipes, it is necessary that the steam condensed in the mains be dripped into a separate return line and pumped back to the boilers, by a pump or a return trap. By returning the condensa- tion of the mains separately, hammering is avoided and the sys- tem can be started much more rapidly. 286 HEATING AND VENTILATION Gravity-return systems are rarely used where the boiler pres- sure exceeds 10 pounds. 249. Low-pressure Pump Return System. In a very large system where it is difficult to get enough difference in elevation between the steam and return mains, or where the drop in pres- sure exceeds 2 pounds, it is usual to install a pump return system. This will usually be necessary in case any of the buildings are piped with a two-pipe vapor or vacuum system. One of the common arrangements is to discharge the condensation from each building through a trap into the return main which carries the water back to a tank in the power house. From this tank the water is returned to the boilers by means of a pump. The drip from the steam main is trapped directly to the return main. 250. High-pressure System. Steam is sometimes distributed at high pressure and the pressure reduced before entering the building piping systems by means of a reducing valve. This method has some advantages. Because of the higher pressure, the allowable pressure drop in the distributing pipes is greatly increased. This, together with the fact that the specific volume of the steam is less at the higher pressure, allows the use of much smaller pipes in the distribution system and thereby reduces its cost. In determining the size of the steam mains, a considerable drop may be allowed under maximum conditions, providing the pressure at the most distant building is always sufficient to heat the building. A high-pressure system is only practicable when there is no low-pressure exhaust which should be utilized for heating. 251. Combination of Power and Heating System. In the majority of cases the heating system is combined with an electric lighting and power system. The piping connections may be made in a manner quite similar to the arrangement in Fig. 125, page 166, provision being made to feed live steam to the heating mains to supplement the exhaust steam when the latter is less than the heating requirements. A back-pressure valve should be provided to insure against the building up of an excessive pressure in the heating mains. When the heating load is very large in comparison with the electrical load, part of the boilers can be used as high-pressure boilers and the others can be low- pressure boilers connected directly to the heating lines. The desirability of such an arrangement, however, is determined entirely by local conditions. CENTRAL HEATING 287 252. Hot-water Heating. A hot-water system, using forced circulation, is very satisfactory if properly designed. The water is heated in a tube heater by the exhaust steam and is circulated through the system by means of a centrifugal pump. A vacuum can be carried on the engine exhaust to a degree depending upon the outgoing temperature of the water. To supplement the exhaust steam heater a live steam heater is installed, but in most cases it need be operated only in the coldest weather. The temperature of the outgoing water is adjusted by the operating engineer for the prevailing weather conditions in accordance with a prearranged schedule. The distribution lines in a hot-water system may be arranged according to either of two schemes. In the one-pipe circuit system a single main makes a complete circuit of the territory covered and the supply connection to each building is taken from the top of the pipe and the return connection is made to the bottom of the pipe a few feet further along and a resistance is inserted in the pipe between the connections to divert the water into the building system. In the multiple or two-pipe system both a flow main and a return main are installed, the water passing from the flow main through the building systems and back to the plant via the return main. The multiple system is the more commonly used although it is somewhat the more expensive to install. The systems in the buildings are arranged in the ordinary manner for either system of distribution. 253. Methods of Carrying Pipes. The pipe lines serving the buildings should always be carried underground if possible. Pipes installed above ground are extremely unsightly and are difficult to support and to insulate. Underground pipes may be installed either in a small conduit or in a tunnel of walking height. The former is a much cheaper method and is quite satisfactory when only one or two pipes are to be installed, but when a greater number of pipe lines must be provided for or when electric cables are also to be installed, a walking tunnel is desirable. There are a large number of designs of conduits ranging from a rough wooden box to a heavily insulated and waterproofed covering. The essential requirements in a conduit for heating pipes are good insulating qualities, protection of the pipe from water, provision for free expansion of the pipe, and durability. 288 HEATING AND VENTILATION A very common form of covering is the wood casing shown in Fig. 187. The casing has a wall 4 inches thick and is built of segmental staves bound tightly together with steel or bronze wire, and the assembled casing is rolled in tar and sawdust to give it a waterproof coating and is lined with bright tin to reduce the radiation loss from the pipe. Wood is a very good insulator and FIG. 187. Wood casing. if installed under favorable conditions, this form of conduit is very satisfactory. The wood deteriorates, however, if sub- jected to continued dampness. The concrete conduit shown in Fig. 188 has the advantage of being very durable and is very easily constructed from common materials. The concrete prevents any considerable amount of water from reaching the pipe and if desired can be made nearly waterproof by the addition of a waterproofing compound. ^-Standard ^Thickness Pipe Covering Crushed Stone. -4 Crock FIG. 188. Concrete conduit. The supports for the pipe in any form of conduit must be such as to allow it to move freely when it undergoes a change in length. Some form of roller is commonly used and they are placed at intervals of 10 or 15 feet. Another form of conduit is built of vitrified tile split longitudi- nally and having insulating material either molded to the walls CENTRAL HEATING 289 of the tile or packed around the pipe. The joints are cemented to render them water-tight. Such a conduit is shown in Fig. 189. There are many other types of construction in use but those which have been described are representative. Some form of drain tile, surrounded by a bed of crushed stone, must always be installed below the conduit to carry away the ground water to a sewer or elsewhere. The heat loss from underground lines depends upon the steam temperature, efficiency of the insulation, and the soil conditions. Tests made on the district heating mains of The Detroit Edison Company, in 1913-14, which are Diatomaceous Insulation FIG. 189. Split tile conduit. laid in conduit of the forms shown in Figs. 187 and 188, gave a result of 0.0511 pounds of condensation per square foot of external pipe surface per hour for steam at 5 pounds pressure. 254. Expansion Fittings. Owing to the length of the pipe lines provision is necessary to take care of the expansion. It is seldom feasible to do so by means of bends, and special fittings are required. The slip joint illustrated in Fig. 190 is a simple means of absorbing large amounts of expansion. It consists of a sleeve which is free to move in the body of the fitting, a packing gland being provided to prevent leakage. Slip joints are located at intervals of from 200 to 300 feet depending upon the steam temperature. They must be installed in manholes 19 290 HEATING AND VENTILATION or in some other place where they are accessible for packing. The type of expansion fitting shown in Fig. 191 depends upon the flexibility of a copper diaphragm for absorbing the movement of the pipe. The advantage of such a fitting is that it requires FIG. 190. Slip joint. no manhole and does not need to be packed. The amount of travel which can be allowed for each fitting is small, the fittings being usually placed at intervals of 80 to 100 feet and the pipe anchored midway between them. The body of the fitting is Seryice Outlet Position of Diapbrame nd Backin. Rings when Pipe is Expanded.. _J Backing Ring Outer Ring FIG. 191. Diaphragm expansion joint. also anchored and the expansion of the pipe on either side is taken up by the diaphragms. The cost of a pipe line fitted with diaphragm joints is considerably greater than when slip joints are used. CENTRAL HEATING 291 255. Tunnels. Tunnels of brick or concrete are used when several pipes are to be carried. The size and shape of tunnel used will depend upon the number of pipes to be carried, the character of the soil, and the depth of the tunnel in the ground. Fig. 192 shows a small tunnel suitable for pipes of about 8 inches diameter or less. It is of brick 4 inches thick and has a layer of Portland cement on the outside which is painted with a thick coat of tar or asphalt over the arch to keep out water. Ribs 4 inches thick and 8 inches wide are placed where the sup- ports are imbedded in the walls. The supports are of ordinary pipe. A drain tile may be placed on either side to carry away FIG. 192. the ground water but no such provision is necessary if the tunnel is built in a sand or gravel soil. Owing to the small size of this tunnel and its low head room it is not very suitable for large pipes or when much walking through it is necessary. In Fig. 193 is shown a larger tunnel of the same general shape. It is 6 feet high and 5 feet wide giving ample space for several pipes. In Fig. 194 is shown another form of tunnel of still larger dimensions. The space under the walkway is used for cable ducts. Pipes can be installed on both sides of the tunnel if desired. This shape of tunnel is not suitable for use at con- siderable depths below the surface because of its flat sides, 292 HEATING AND VENTILATION Tllle FIG. 193. FIG. 194. CENTRAL HEATING 293 which offer little resistance against earth pressure. The horse- shoe shapes previously described should be used in such cases. 256. Size of Pipes. The size of steam pipes to be used depends upon the amount of steam flowing, the steam pressure, and the available pressure drop. If exhaust steam is used the pressure drop is limited by the allowable back pressure. In general it is necessary to maintain at least 1^ or 2 pounds pressure at each building and in the coldest weather it may be necessary to carry a still higher pressure, especially if the piping in the buildings is not liberally designed. In underground piping the noise in the pipes is not a factor and advantage can therefore be taken of all of the available pressure drop to decrease the size of the pipes. It is best, how- ever, to allow a reasonable margin in selecting the pipe sizes. The chart in Fig. 123 is suitable or pressures of approximately 2 pounds. For higher pressures the capacity of various size pipes for a given pressure drop can be found from the basic formula of Par. 139. For hot-water systems the pipes sizes can be computed by the methods given in Chapter XI. 257. Commercial District Heating. The commercial distri- bution and sale of heat with steam or water as the conveying medium is carried on more or less extensively in many cities. The use of hot water for this purpose is not commercially satisfactory, however, because of the lack of a suitable meter for measuring the quantity of heat used by each consumer. The more successful systems are steam systems. The central business districts of cities, and residence districts of the very highest class are the most desirable territory. In many cases the exhaust steam from electric generating units is used and is distributed at a pressure of from 2 to 10 pounds gage. This combination produces both electricity and heat at a high thermal efficiency and from that standpoint is very desirable, but there are complications resulting which in some cases render the distribution of live steam, direct from the boilers, more feasible commercially. Distribution systems for exhaust steam are usually designed with a large trunk main extending from the plant through the middle of the heating district, with branches at right angles, taken off at intervals. The pipes are laid under streets and alleys and smaller pipes are taken off to supply the various 294 HEATING AND VENTILATION buildings heated. In a live-steam system of distribution the same general method is often followed, though the pipes sizes may be considerably smaller because of the greater density of the steam and the greater pressure drop allowable. The general methods of installing pipes are the same as those which have been described. The condensation is not usually returned to the plant in a district-heating system unless raw water is very costly or contains undesirable elements. The heat loss from the underground mains is an important factor and good insulation is required. The loss in distribution in a well designed system is from 15 to 25 per cent. In some cities, instead of large areas being heated from pipes in the streets or alleys, the buildings in individual blocks are interconnected and served with steam from a plant in one of the buildings. 258. Metering. The accurate meter-ing of the amount of heat supplied to each consumer is very important to the success of a district-heating system. The simplest way is to meter the condensation which is drained from the radiators and which is a sufficiently accurate index of the amount of heat supplied. There are several commercial meters available for this purpose. Large consumers are sometimes metered by a steam meter employing the pitot tube or venturi principle. 259. Advantages of District Heating. There are many advan- tages to the consumer of heat purchased from a central plant and to the community in which such a plant is located. The consumer benefits by the absence of dirt from the handling of coal and ashes in his building, by the saving in the space occupied by a boiler plant, by the freedom from labor troubles and from uncertainties of fuel supply, and by the constant availability of an ample and continuous supply of heat. The great benefits to the community are the absence of smoke due to the elimination of the small isolated boiler plant which rarely burns coal smokelessly, and the freedom from the handling of coal and ashes on the sidewalks and streets. APPENDIX TABLE I. COEFFICIENTS OF HEAT TRANSMISSION THROUGH BUILDING MATERIALS Walls BRICK WALLS Coefficient of heat transmission, (k) B.t.u. per square foot per hour per degree difference of temperature. Thickness, inches Plain Plastered on one side j Furred and plastered k k k 4 0.52 0.50 0.28 8;Hj 0.37 0.36 0.23 13 0.29 0.28 0.20 17^ 0.25 0.24 0.18 22 0.22 0.21 0.16 26^ 0.19 0.18 CONCRETE WALLS Thickness, inches Plain Furred and plastered Thickness, inches Plain Furred and plastered k k k k 2 4 0.69 0.55 0.31 16 20 0.37 0.33 0.24 0.23 6 0.49 0.30 24 0.30 0.215 8 0.47 0.28 28 0.27 0.20 10 0.45 0.265 32 0.25 0.18 12 0.43 0.25 36 0.23 0.17 BRICK WALLS, SANDSTONE FACES Thickness of brick, inches Thickness of sandstone, inches k Thickness of brick, inches Thickness of sandstone, inches k 4 4 0.31 12 8 0.16 8 4 0.22 4 12 0.26 12 4 0.17 8 12 0.19 4 8 0.29 12 12 0.15 8 8 0.20 29.3 296 HEATING AND VENTILATION TABLE I. COEFFICIENTS OF HEAT TRANSMISSION THROUGH BUILDING MATERIALS (Continued] Walls LIMESTONE WALLS Thickness, inches Furred and plastered Thickness, inches Furred and plastered k k 12 0.49 28 0.31 16 0.43 32 0.28 20 0.38 36 0.26 24 0.35 40 0.24 TILE WALLS Thickness, inches Plain tile Tile and stucco Tile, stucco, and plaster k k k 4 0.79 0.75 0.34 8 0.56 0.54 0.27 12 0.44 0.41 0.26 16 0.40 0.37 0.23 20 0.33 0.31 0.20 WOODEN WALLS Clapboard J^ g inch, studding, lath and plaster k 44 Clapboard Y\ . a ^ K *9r8 q 1 S 1 3 f n s S |2 I ft S A a * d ,J3 a s ft ^3 ft CD ft A 2-| A .&! ft ,3 g- H 8 1 P4 PQ H a PS pq S & rt ffl LJ O. tr 1 co PQ _, Q. H CQ P5 pq 3200 1000 2366 251 .287 2690 286 .415 2940 312 .519 3175 337 .630 3400 361 .743 3610 383 .868 3520 1100 2490 264 .365 2780 295 .478 3040 323 .593 3267 347 .712 3480 370 .832 3670 390 .960 3840 1200 2600 276 .435 2925 311 .554 3125 332 .673 3360 356 .800 3575 379 .932 3763 400 1.06 4160 1300 2736 290 .512 3000 319 .635 3237 344 .762 3475 369 .900 3675 390 1.04 3865 410 1.18 4480 1400 2846 302 .595 3107 330 .730 3310 351 .858 3573 379 1.00 3750 398 1.15 3965 421 1.30 4800 1500 2987 317 .697 3226 343 .833 3460 367 .977 3650 388 1.12 3860 410 1.27 4060 431 1.43 5120 1600 3130 332 .800 3350 356 .948 3565 379 .09 3765 400 1.25 3960 420 1.41 4160 441 1.57 5440 1700 3270 347 .917 3475 369 1.07 3680 391 .23 3885 413 1.39 4055 431 1.56 4250 451 1.73 5760 1800 3410 362 1.07 3607 382 1.21 3810 405 .38 4010 425 1.55 4180 443 1.76 4350 462 1.92 6080 1900 3546 377 1.19 3730 396 1.37 3935 418 .54 4120 437 1.72 4320 458 1.90 4455 473 2.08 6400 2000 3700 393 1.35 3860 410 1.53 4050 430 .71 4255 452 1.91 4423 470 2.09 4580 487 2.29 6720 2100 3850 408 1.52 4000 425 1.72 4210 447 .89 4350 462 2.11 4535 481 2.31 4680 498 2.49 7040 2200 4000 425 1.70 4168 443 1.93 4320 458 2.12 4500 478 2.32 4670 497 2.53 4800 510 2.73 7360 2300 4323 459 2.13 4450 473 2.33 4628 491 2.55 4770 507 2.77 4930 523 2.99 7680 2400 4460 473 2.31 4620 490 2.59 4740 504 2.80 4920 522 3.03 5045 537 3.25 8000 2500 4600 488 2.60 4720 502 2.83 4880 518 3.07 5036 534 3.30 5170 549 3.53 8320 2600 4910 521 3.13 5000 531 3.36 5180 550 3.61 5325 565 3.84 8960 2800 5180 550 3.71 5280 560 3.99 5435 578 4.23 5510 585 4.53 9600 3000 5485 582 4.40 5610 596 4.71 5650 600 4.96 5840 620 5.25 S. P. 1" S. P. IK" S. P. IK" S. P. IK" S. P. 2" S. P. 2K" TT_1 Js vol- ume 73 . ol d a ft "S a ft TJ a a 73 a ft T3 a ft "S a ft Q > a ft ,] a d. ,3 a a ,J3 ft o. ,4 ft$ ft ^3 a a ,J3 w & t-< to s! ej _ H & PS fl ft r* oo tf ft t" 1 CO 3840 1200 3955 420 1.21 4152 452 1.48 4470 475 1.79 4950 525 2.10 5230 555 2.44 5750 610 3.16 4160 1300 4050 430 1.32 4380 465 1.61 4550 483 1.92 5024 533 2.26 5295 561 2.61 5820 617 3.33 4480 1400 4143 439 1.45 4465 474 1.76 4700 499 2.08 5105 542 2.43 5350 568 2.80 5900 626 3.54 4800 1500 4250 451 1.59 4570 485 1.91 4850 515 2.25 5180 550 2.61 5450 578 2.97 5950 631 3.76 5120 1600 4325 459 1.74 4652 495 2.09 4950 526 2.43 5245 557 2.78 5550 589 3.18 6025 640 3.98 5440 1700 4437 471 1.91 4750 504 2.29 5040 534 2.63 5330 566 3.01 5625 598 3.39 6100 648 4.22 5760 1800 4527 481 2.08 4846 514 2.46 5110 542 2.83 5410 574 3.24 5700 605 3.63 6195 658 4.48 6080 1900 4613 490 2.27 4945 525 2.66 5230 555 3.05 5520 586 3.47 5780 613 3.89 6265 665 4.74 6400 2000 4743 504 2.48 5075 538 2.89 5325 565 3.29 5620 597 3.73 5860 621 4.16 6365 676 5.03 6720 2100 4850 515 2.69 5145 545 3.12 5440 578 3.55 5724 607 4.00 5955 632 4.43 6475 687 5.35 7040 2200 4970 528 2.94 5256 558 3.37 5550 589 3.81 5790 615 4.28 6050 642 4.72 6550 695 5.68 7360 2300 5090 540 3.33 5370 570 3.65 5630 598 4.09 5900 626 4.58 6150 653 5.05 6610 701 6.03 7680 2400 5210 553 3.48 5480 583 3.93 5750 610 4.39 6025 640 4.90 6270 666 5.38 6700 711 6.40 8000 2500 5340 567 3.78 5610 595 4.23 5850 621 4.72 6100 649 5.22 6343 674 5.74 6800 722 6.77 8320 2600 5485 582 4.09 5740 609 4.58 5980 635 5.07 6200 658 5.57 6460 686 6.13 6880 730 7.17 8960 2800 5710 606 4.82 5960 632 5.28 6230 661 5.83 6460 686 6.37 6650 706 6.91 7090 752 8.04 9600 3000 5970 633 5.54 6200 658 6.08 6460 686 6.67 6675 698 7.23 6900 732 7.82 7295 773 8.98 10240 3200 6230 662 6.37 6475 687 6.98 6730 715 7.58 6920 735 8.17 7135 757 8.80 7530 799 9.98 10880 3400 6580 698 7.36 6740 715 8.00 6960 739 8.62 7150 760 9.26 7355 781 9.87 7750 823 11.14 11520 3600 6815 723 8.40 7000 745 9.09 7200 764 9.75 7440 790 10.39 7600 807 11.08 8020 851 12.37 12160 3800 7105 755 9.58 7350 780 10.32 7475 793 10.98 7660 814 11.67 7840 832 12.33 8220 873 13.78 304 HEATING AND VENTILATION CAPACITY TABLE TABLE V. No. 70 SINGLE INLET STEEL PLATE FAN TYPE S Vnl CD S. P. K" S. P. H f S. P. y*" s. P. H" S. P. *i" S. P. W V Ol- ume 73 . 5*3 T3 a a "S a a "S a a 1 8 a -a S a "S 8 a O > a a & aS a 43 &1 a A &1 a Jg ax a ,JS 3$ a H& tf n a tr 1 oo tt pq a t-l CO rt 'Ct a t" 1 CO rt H OB PQ C a t" 1 CO 4160 1000 2366 215 .402 2690 245 .538 2940 267 .674 3175 288 .818 3400 309 .965 3610 328 1.13 4576 1100 2490 228 .474 2780 253 .622 3040 276 .771 3267 297 .925 3480 316 1.08 3670 334 1.25 4992 1200 2600 236 .565 2925 266 .719 3125 284 .873 3360 305 1.04 3575 325 1.21 3763 342 1.38 5408 1300 2736 249 .665 3000 273 .825 3237 294 .992 3475 316 1.17 3675 334 1.35 3865 351 1.53 5824 1400 2846 258 .773 3107 283 .944 3310 301 .11 3573 325 1.30 3750 341 1.49 3965 361 1.68 6240 1500 2987 271 .905 3226 293 .08 3460 315 .27 3650 332 1.46 3860 351 1.65 4060 370 1.86 6656 1600 3130 285 1.04 3350 305 .23 3565 324 .42 3765 341 1.62 3960 359 1.83 4160 379 2.04 7072 1700 3270 297 1.19 3475 316 .39 3680 335 .60 3885 353 1.81 4055 369 2.03 4250 386 2.25 7488 1800 3410 310 1.39 3607 328 .58 3810 346 .79 4010 365 2.01 4180 380 2.28 4350 396 2.49 7904 1900 3546 323 1.55 3730 339 .78 3935 357 .99 4120 375 2.23 4320 393 2.47 4455 405 2.70 8320 2000 3700 336 1.75 3860 351 .99 4050 368 2.22 4255 387 2.48 4423 402 2.72 4580 417 2.97 8736 2100 3850 350 1.97 4000 364 2.23 4210 383 2.46 4350 396 2.73 4535 413 2.99 4680 426 3.24 9152 2200 4000 364 2.21 1168 379 2.50 4320 393 2.75 4500 410 3.02 4670 425 3.29 4800 436 3.55 9568 2300 1323 393 2.77 4450 405 3.02 4628 421 3.30 4770 433 3.60 4930 448 3.88 9984 2400 4460 406 2.99 4620 420 3.36 4740 430 3.63 4920 447 3.93 5045 459 4.22 10400 2500 1600 418 3.37 4720 430 3.68 4880 443 3.99 5036 458 4.28 5170 470 4.59 10816 2600 4910 446 4.07 5000 455 4.37 5180 471 4.69 5325 483 4.98 11648 2800 5180 471 4.82 5280 480 5.19 5435 491 5.50 5510 501 5.88 12480 3000 5485 499 5.71 5610 511 6.12 5650 514 6.43 5840 530 6.82 S. P. 1" S. P. IK" S. P. 1H" S. P. W S. P. 2" S. P. 2K" Vnl O V Ol- ume "3 "3 O > 1 a a a al a a a "0 a a a al a a a | a a a T3 a a 0, H& pq H! pq nit pq s! pq EH ft EH co . 4992 1200 3955 359 1.57 4152 378 1.92 4470 407 2.33 4950 450 2.72 5230 475 3.17 5750 523 4.11 5408 1300 4050 368 1.71 4380 398 2.09 4550 415 2.50 5024 457 2.93 5295 481 3.39 5820 529 4.32 5824 1400 4143 376 1.88 4465 406 2.28 4700 427 2.71 5105 465 3.15 5350 487 3.63 5900 536 4.59 6240 1500 4250 386 2.07 4570 416 2.48 4850 441 2.91 5180 471 3.38 5450 495 3.86 5950 541 4.88 6656 1600 4325 393 2.26 4652 424 2.71 4950 450 3.15 5245 476 3.61 5550 505 4.13 6025 548 5.17 7072 1700 4437 404 2.47 4750 432 2.97 5040 459 3.42 5330 484 3.90 5620 511 4.41 6100 555 5.47 7488 1800 4527 412 2.70 4846 440 3.19 5110 465 3.67 5410 494 4.21 5700 519 4.72 6195 563 5.82 7904 1900 4613 420 2.95 4945 449 3.45 5230 475 3.96 5520 502 4.52 5780 525 5.05 6265 570 6.15 8320 2000 4743 430 3.22 5075 461 3.75 5325 484 4.28 5620 511 4.84 5860 533 5.40 6365 579 6.52 8736 2100 4850 441 3.50 5145 468 4.05 5440 494 4.61 5724 521 5.20 5955 541 5.76 6475 588 6.95 9152 2200 4970 452 3.81 5256 477 4.37 5550 505 4.96 5790 527 5.55 6050 550 6.13 6550 595 7.38 9568 2300 5090 463 4.33 5370 488 4.74 5630 512 5.32 5900 536 5.95 6150 560 6.55 6610 601 7.82 9984 2400 5210 474 4.52 5480 498 5.11 5750 523 5.70 6025 547 6.36 6270 570 6.98 6700 610 8.32 10400 2500 5340 485 4.91 5610 510 5.49 5850 532 6.13 6100 555 6.78 6343 575 7.46 6800 618 8.80 10816 2600 5485 498 5.32 5740 522 5.95 5980 544 6.58 6200 564 7.23 6460 587 7.96 6880 625 9.32 11648 2800 5710 520 6.26 5960 542 6.85 6230 567 7.57 6460 587 8.28 6650 605 8.98 7090 644 10.44 12480 3000 5970 542 7.19 6200 564 7.90 6460 598 8.66 6675 607 9.38 6900 627 10.13 7295 663 11.65 13312 3200 6230 567 8.27 6475 588 9.07 6730 612 9.86 6920 629 10.60 7135 648 11.40 7530 685 12.97 14144 3400 6580 598 9.58 6740 613 10.38 6960 632 11.19 7150 650 12.00 7355 670 12.81 7750 705 14.46 14976 3600 6815 620 10.88 7020 638 11.77 7200 655 12.66 7440 676 13.48 7600 691 14.38 8020 729 16.04 15808 3800 7105 646 12.43 7350 668 13.40 7475 680 14.25 7660 697 15.14 7840 713 16.00 8220 747 17.88 APPENDIX 305 CAPACITY TABLE TABLE VI. No. 80 SINGLE INLET STEEL PLATE FAN TYPE S Vol- S. P. K" S. P. W S. P. W S. P. H" s. P. ys S. P. %" ume 3* a 8 a a a a a 8 a a 8 a a 8 a "& 6 a 0> &1 p, jg a a ,ig a 1 a ,5 2-1 a A 8-1 a M &i a J3 ^ a tf ^g* tf pq H a tf ^& pq ^ a P5 H& tf pq 5050 1000 2366 189 .488 2690 214 .654 2940 234 .818 3175 253 .994 3400 271 1.17 3610 288 1.37 5555 1100 2490 198 .575 2780 222 .755 3040 242 .935 3267 260 1.12 3480 277 1.31 3670 292 1.52 6060 1200 2600 207 .685 2925 233 .873 3125 249 1.06 3360 268 1.26 3575 285 1.47 3763 300 1.68 6565 1300 2736 218 .808 3000 239 1.002 3237 257 1.21 3475 276 1.42 3675 292 1.63 3865 308 1.86 7070 1400 2846 227 .940 3107 248 1.144 3310 264 1.35 3573 285 1.58 3750 299 1.81 3965 316 2.05 7575 1500 2987 238 1.097 3226 257 1.314 3460 276 1.54 3650 291 1.77 3860 307 2.01 4060 324 2.26 8080 1600 3130 250 1.263 3350 267 1.497 3565 284 1.73 3765 298 1.97 3960 315 2.22 4160 332 2.48 8585 1700 3270 261 1.445 3475 277 1.695 3680 293 1.94 3885 310 2.19 4055 323 2.47 4250 339 2.74 9090 1800 3410 272 1.686 3607 287 1.920 3810 303 2.18 4010 319 2.44 4180 333 2.77 4350 347 3.02 9595 1900 3546 283 1.878 3730 297 2.165 3935 313 2.42 4120 328 2.71 4320 344 3.00 4455 350 3.28 10100 2000 3700 295 2.150 3860 305 2.425 4050 322 2.71 4255 339 3.01 4423 353 3.31 4580 365 3.61 10605 2100 3850 307 2.400 4000 319 2.71 4210 335 2.99 4350 347 3.33 4535 361 3.64 4680 373 3.94 11110 2200 4000 319 2.688 4168 332 3.04 4320 344 3.34 4500 358 3.67 4670 372 4.00 4800 383 4.32 11615 2300 4323 345 3.36 4450 354 3.67 4628 369 4.02 4770 380 4.37 4930 393 4.71 12120 2400 4460 356 3.63 4620 368 4.08 4740 378 4.42 4920 393 4.78 5045 402 5.12 12625 2500 4600 367 4.10 4720 376 4.47 4880 389 4.85 5036 401 5.20 5170 412 5.57 13130 2600 4910 392 4.94 5000 398 5.30 5180 413 5.69 5325 423 6.06 14140 2800 5180 413 5.85 5280 421 6.30 5435 433 6.67 5510 439 7.14 15150 3000 1 | 5485 437 6.93 56K 447 7.42 5650 450 7.81 5840 465 8.28 Vnl S. P. 1" STJ -11 /// . r. l^i s. P. iy 2 " S. P. 1M" S. P. 2" S. P. 2M" V Ol- ume ll al a a a jt -d a a a al a a ^ T3 a a a A 1 3 a a ,3 al a a a ,3 ^ TO P4 pq & fl 00 p4 pq - "^ m pq ft " TO tf pq a * TO pq sl pq 6060 1200 3955 315 1.91 4152 331 2.33 4470 356 2.83 4950 394 3.31 5230 417 3.86 5750 458 5.00 6565 1300 4050 322 2.08 4380 349 2.54 4550 363 3.03 5024 400 3.56 5295 421 4.12 5820 464 5.25 7070 1400 4143 329 2.28 4465 356 2.77 4700 375 3.29 5105 407 3.83 5350 426 4.42 5900 470 5.58 7575 1500 4250 338 2.51 4570 364 3.02 4850 386 3.54 5180 413 4.10 5450 434 4.68 5950 475 5.93 8080 1600 4325 345 2.75 4652 371 3.29 4950 395 3.83 5245 418 4.39 5550 442 5.02 6025 480 6.27 8585 1700 4437 353 3.01 4750 378 3.61 5040 402 4.15 5330 424 4.74 5625 448 5.35 6100 486 6.63 9090 1800 4527 361 3.29 4846 386 3.89 5110 407 4.46 5410 431 5.10 5700 455 5.73 6195 493 7.05 9595 1900 4613 368 3.59 4945 394 4.19 5230 417 4.81 5520 440 5.48 5780 460 6.13 6265 499 7.47 10100 2000 4743 377 3.91 5075 404 4.55 5325 424 5.19 5620 448 5.88 5860 467 6.57 6365 507 7.92 10605 2100 4850 386 4.25 5145 410 4.92 5440 433 5.60 5724 456 6.32 5955 475 7.00 6475 516 8.45 11110 2200 4970 396 4.64 5256 419 5.31 5550 443 6.02 5790 461 6.74 6050 482 7.45 6550 522 8.96 11615 2300 5090 405 5.36 5370 427 5.75 5630 448 6.45 5900 470 7.22 6150 490 7.95 6610 527 9.52 12120 2400 5210 416 5.48 5480 437 6.20 5750 458 6.92 6025 480 7.72 6270 500 8.48 6700 534 10.10 12625 2500 5340 425 5.96 5610 447 6,66 5850 466 7.45 6100 486 8.23 6343 505 9.06 6800 542 10.68 13130 2600 5485 437 6.44 5740 457 7.22 5980 477 7.98 6200 494 8.78 6460 515 9.67 6880 548 11.30 14140 2800 5710 455 7.60 5960 475 8.33 6230 497 9.19 6460 515 10.05 6650 530 10.90 7090 564 12.68 15150 3000 5970 476 8.73 6200 494 9.60 6460 515 10.53 6675 532 11.38 6900 550 12.33 7295 581 14.16 16160 3200 6230 497 10.05 6475 517 11.00 6730 537 11.97 6920 551 12.88 7135 568 13.86 7530 600 15.73 17179 3400 6580 524 11.62 6740 537 12.62 6960 555 13.60 7150 570 14.60 7355 587 15.55 7750 618 17.58 18180 3600 6815 543 13.23 7000 559 14.30 7200 574 15.40 7440 593 16.38 7600 605 17.48 8020 639 19.50 19190 3800 7105 565 15.10 7350 586 16.27 7475 596 17.30 7660 611 18.38 7840 624 19.44 8220 655 21.73 20 306 HEATING AND VENTILATION CAPACITY TABLE TABLE VII. No. 90 SINGLE INLET STEEL PLATE FAN TYPE S S. P. tf " S. P. W S. P. Y 2 " S. P. H" S. P. H" S. P. %" Vol- <_> ume 3 '3 "8 a a "8 3 a 2 a a 73 a a "8 a a S 8 a O> a a ,q P, a 43 a$ a A a a 43 a a jt a a 43 ^ & pq H & P? pq C ft r* 1 to pj pq H& P3 pq J a tr 1 ume 3 . 3*3 "8 a ft H a . p, TJ 8 ft "S a ft a ft Sj 8 ft 0> &1 a 43 &1 4 43 &! a 43 &i ft 43 a ft 43 as a 43 Sg e & rt pq H a p4 pq ^& rt pq ' H * a T 1 CO Ptj pq 7740 1200 3955 279 2.44 4152 294 2.98 4470 316 3.61 4950 350 4.23 5230 370 4.93 5750 406 6.38 8385 1300 4050 286 2.65 4380 309 3.25 4550 322 3.88 5024 353 4.56 5295 374 5.26 5820 411 6.71 9030 1400 4143 293 2.92 4465 316 3.55 4700 332 4.21 5105 361 4.88 5350 378 5.65 5900 417 7.13 9675 1500 4250 300 3.21 4570 323 3.86 4850 343 4.53 5180 366 5.24 5450 385 5.98 5950 420 7.57 10320 1600 4325 306 3.51 4652 329 4.21 4950 350 4.89 5245 370 5.61 5550 392 6.41 6025 427 8.02 10965 1700 4437 313 3.84 4750 336 4.61 5040 356 5.31 5330 377 6.06 5625 398 6.83 6100 431 8.48 11610 1800 4527 320 4.20 4846 342 4.96 5110 362 5.70 5410 383 6.52 5700 403 7.32 6195 438 9.02 12255 1900 4613 327 4.58 4945 350 5.35 5230 370 6.15 5520 393 7.00 5780 408 7.82 6265 443 9.55 12900 2000 4743 335 5.00 5075 359 5.81 5325 377 6.63 5620 398 7.52 5860 415 8.38 6365 450 10.12 13545 2100 4850 343 5.43 5145 364 6.29 5440 384 7.15 5724 405 8.07 5955 421 8.94 6476 458 10.78 14190 2200 4970 352 5.82 5256 372 6.78 5550 393 7.70 5790 409 8.62 6050 428 9.52 6550 463 11.45 14835 2300 5090 360 6.61 5370 380 7.35 5630 398 8.25 5900 417 9.23 6150 435 10.15 6610 467 12.13 15480 2400 5210 369 7.01 5480 387 7.92 5750 406 8.85 6025 427 9.87 6270 442 10.84 6700 474 12.88 16125 2500 5340 377 7.62 5610 396 8.52 5850 413 9.52 6100 432 10.50 6343 449 11.96 6800 480 13.63 16770 2600 5485 388 8.25 5740 405 9.22 5980 424 10.20 6200 438 11.22 6460 456 2.35 6880 487 14.44 18060 2800 5710 404 9.72 5960 422 10.65 6230 441 11.74 6460 457 12.83 6650 470 13.73 7090 501 16.20 19350 3000 5970 422 11.15 6200 438 12.25 6460 457 13.45 6675 472 14.55 6900 488 15.73 7295 515 18.05 20640 3200 6230 441 12.83 6475 451 14.05 6730 476 15.30 6920 489 16.44 7135 503 17.70 7530 533 20.10 21930 3400 6580 465 14.85 6740 477 16.10 6960 492 17.35 7150 505 18.65 7355 519 19.86 7750 548 22.45 23220 3600 6815 482 16.90 7020 497 18.25 7200 510 19.65 7440 525 20.92 7600 538 22.30 8020 567 24.87 24510 3800 7105 503 19.30 7350 520 20.75 7475 528 22.13 7660 542 23.53 7840 554 24.85 8220 581 27.75 APPENDIX 307 CAPACITY TABLE TABLE VIII. No. 100 SINGLE INLET STEEL PLATE FAN TYPE S Vol- S. P. Ji" S. P. %" S. P. W S. P. %" S. P. X" S. P. K" ume "3 75 "8 a ft "8 a ^3 TJ a ft "8 a ft "8 a ft 1 a ft 0> ftcp P. .8-8 p. ft ft o> & 8-1 d 8-1 ft e-I ft H pi PQ tj ^ t" 1 CO PQ H & PS ft C* co p4 PQ ft f CO tf PQ pi PQ 8260 1000 2366 150 .800 2890 171 1.07 2940 187 1.34 3175 202 1.62 3400 216 1.92 3610 230 2.24 9086 1100 2490 158 .942 2780 177 1.23 3040 193 1.53 3267 208 1.84 3480 221 2.15 3670 234 2.47 9912 1200 2600 165 1.12 2925 186 1.43 3125 199 1.73 3360 214 2.06 3575 227 2.40 3763 240 2.74 10738 1300 2736 174 1.32 3000 191 1.64 3237 206 1.97 3475 221 2.37 3675 233 2.67 3865 246 3.03 11564 1400 2846 181 1.53 3107 198 1.87 3310 211 2.21 3573 227 2.59 3750 239 2.96 3965 252 3.35 12390 1500 2987 190 1.79 3226 205 2.14 3460 220 2.52 3650 233 2.90 3860 246 3.28 4060 258 3.69 13216 1600 3130 199 2.06 3350 213 2.44 3565 227 2.82 3765 240 3.23 3960 252 3.63 4160 265 4.07 14042 1700 3270 208 2.37 3475 222 2.77 3680 234 3.17 3885 247 3.59 4055 258 4.03 4250 270 4.47 14868 1800 3410 217 2.75 3607 230 3.14 3810 242 3.57 4010 255 3.99 4180 266 4.53 4350 277 4.95 15694 1900 3546 226 3.07 3730 237 3.54 3935 252 3.97 4120 262 4.43 4320 275 4.90 4455 284 5.37 16520 2000 3700 235 3.47 3860 245 3.97 4050 9,'jS 4.43 4255 269 4.93 4423 282 5.41 4580 292 5.90 17346 2100 3850 245 3.92 4000 254 4.43 4210 208 4.88 4350 277 5.44 4535 289 5.95 4680 298 6.44 18172 2200 4000 254 4.39 4168 265 4.97 4320 27,5 5.47 4500 286 6.00 4670 297 6.54 4800 306 7.06 18998 2300 4323 275 5.50 4450 283 6.01 4628 294 6.57 4770 303 7.15 4930 314 7.70 19824 2400 4460 284 5.95 4620 294 6.67 4740 302 7.23 4920 313 7.82 5045 321 8.38 20650 2500 4600 293 6.70 4720 301 7.32 4880 310 7.92 5036 320 8.52 5170 329 9.13 21478 2600 4910 312 9.08 5000 318 8.52 5180 329 9.33 5325 339 9.92 23128 2800 5180 330 9.57 5280 338 10.30 5435 346 10.92 5510 351 11.67 24780 3000 5485 349 11.34 5610 357 12.14 5650 359 12.77 5840 371 13.53 TT^I S. P. 1" S. P. IK" S. P. IK" S. P. IK" S. P 2" S. P. 2M" Vol- ume 5*3 -| a ft ft^ a ft pi a cL ft d a ft | a ft "S a ft o > & Pi ,] PQ -p. -< So PJ pCj tt H^ p? PQ a t" 1 CD P5 PQ -| PQ | PS pC] PQ 9912 1200 3955 251 3.12 4152 264 3.82 4470 285 4.62 4950 315 5.42 5230 333 6.36 5750 366 8.17 10738 1300 4050 258 3.40 4380 278 4.16 4550 290 4.96 5024 320 5.83 5295 337 6.72 5820 370 8.60 11564 1400 4143 263 3.74 4465 285 4.54 4700 299 5.38 5105 325 6.25 5350 340 7.22 5900 375 9.13 12390 1500 4250 270 4.11 4570 291 4.93 4850 308 5.80 5180 329 6.72 5450 347 7.67 5950 379 9.72 13216 1600 4325 275 4.50 4652 297 5.38 4950 315 6.27 5245 334 7.18 5550 353 8.20 6025 383 10.26 14042 1700 4437 282 4.92 4750 302 5.90 5040 321 6.79 5330 339 7.75 5625 358 8.76 6100 388 10.85 14868 1800 4527 288 5.38 4846 308 6.36 5110 325 7.29 5410 344 8.36 5700 363 9.37 6195 394 11.55 15694 1900 4613 294 5.86 4945 314 6.85 5230 333 7.87 5520 351 8.97 5780 368 10.02 6265 398 12.22 16520 2000 4743 301 6.41 5075 323 7.44 5325 339 8.50 5620 357 9.63 5860 373 10.73 6365 405 12.97 17346 2100 4850 308 6.95 5145 328 8.05 5440 346 9.17 5724 364 10.32 5955 379 11.44 6475 412 13.80 18172 2200 4970 316 7.58 5256 334 8.68 5550 354 9.85 5790 368 11.03 6050 385 12.18 6550 417 14.65 18998 2300 5090 324 8.60 5370 342 9.42 5630 358 10.55 5900 375 11.82 6150 391 13.00 6610 421 15.54 19824 2400 5210 332 8.97 5480 349 10.15 5750 366 11.32 6025 383 12.64 6270 399 13.86 6700 426 16.51 20650 2500 5340 340 9.75 5610 357 10.90 5850 372 12.18 6100 388 13.46 6343 403 14.80 6800 432 17.48 21476 2600 5485 349 10.55 5740 366 11.80 5980 381 13.06 6200 394 14.37 6460 411 15.80 6880 438 18.50 23128 2800 5710 364 12.43 5960 379 13.62 6230 396 15.03 6460 411 16.42 6650 423 17.85 7090 451 20.73 24780 3000 5970 380 14.28 6200 395 15.68 6460 411 17.20 6675 425 18.63 6900 439 20.15 7295 464 28.15 26432 3200 6230 396 16.43 6475 412 18.00 6730 428 19.60 6920 441 21.07 7135 448 22.67 7530 478 25.73 28084 3400 6580 418 19.00 6740 429 20.60 6960 443 22.25 7150 455 23.88 7355 469 25.40 7750 493 28.70 29736 3600 6815 433 21.65 7020 447 23.35 7200 458 25.13 7440 473 26.75 7600 484 28.60 8020 511 31.90 31388 3800 7105 452 24.70 7350 468 26.60 7475 476 28.30 7660 488 30.10 7840 499 31.80 8220 523 35.55 308 HEATING AND VENTILATION CAPACITY TABLE TABLE IX. No. 110 SINGLE INLET STEEL PLATE FAN TYPE S S. P. K" S. P. H" S. P. H" S. P. W' S. P. K" S. P. H" Vr>1 3-s V Ol- ume +_> & > "8 a ft "8 a ft 1 a ft "8 a ft 8 a ft 1 a ft a a M a ft ,j a ft A a A JS, as P. M aS A JS a f OS PJ H m PS ffl ft M tn PS PQ H ft rt H ft p4 M C a T^ CO PQ 9760 1000 2366 137 .945 2690 156 1.26 2940 170 1.58 3175 184 1.92 3400 197 2.26 3610 209 2.6 10736 1100 2490 144 1.11 2780 161 1.46 3040 176 1.81 3267 190 2.17 3480 202 2.53 3670 212 2.9 11712 1200 2600 151 1.32 2925 169 1.69 3125 181 2.05 3360 195 2.44 3575 207 2.84 3763 218 3.2 12688 1300 2736 157 1.56 3000 174 1.93 3237 187 2.32 3475 201 2.74 3675 213 3.16 3865 224 3.5 13664 1400 2846 165 1.81 3107 180 2.21 3310 192 2.61 3573 207 3.06 3750 217 3.50 3965 230 3.9 14640 1500 2987 173 2.12 3226 187 2.54 3460 200 2.97 3650 211 3.43 3860 224 3.88 4060 235 4.3 15616 1600 3130 183 2.44 3350 194 2.89 3565 207 3.34 3765 218 3.81 3960 229 4.29 4160 241 4.8 16592 1700 3270 189 2.79 3475 201 3.27 3680 213 3.74 3885 225 4.24 4055 235 4.76 4250 246 5.2 17568 1800 3410 197 3.25 3607 209 3.71 3810 221 4.22 4010 232 4.72 4180 242 5.36 4350 252 5.8 18544 1900 3546 206 3.63 3730 216 4.18 3935 228 4.68 4120 239 5.23 4320 250 5.79 4455 258 6.3 19520 2000 3700 214 4.11 3860 224 4.68 4050 235 5.22 4255 245 5.82 4423 257 6.39 4580 265 6.9 20496 2100 3850 223 4.63 4000 232 5.24 4210 244 5.77 4350 252 6.42 4535 262 7.02 4680 271 7.6 21472 2200 4000 232 5.18 4168 242 5.87 4320 251 6.46 4500 261 7.08 4670 271 7.72 4800 278 8.3 22448 2300 4323 251 6.50 4450 258 7.10 4628 268 7.76 4770 277 8.45 4930 286 9.1 23424 2400 4460 258 7.02 4620 268 7.88 4740 275 8.55 4920 285 9.24 5045 292 9.9 24400 2500 4600 266 7.93 4720 273 8.63 4880 283 9.37 5036 292 10.05 5170 300 10.7 25376 2600 4910 284 9.55 5000 290 10.25 5180 300 11.00 5325 308 11.7 27328 2800 5180 300 11.3 5280 306 12.17 5435 315 12.88 5510 319 13.8 29280 3000 5485 317 13.4 5610 325 14.34 5650 327 15.08 5840 338 16.0 S. P. 1" S. P. IJtf" S. P. W S. P. l%" S. P. 2" S. P. 2H" Vnl fl) V Ol~ ume 3 . " 13 a ft T3 a ft iM ft "8 a ft "S a ft "8 a ft O > 0.1 a ^ aS P. ^ ftS ft ,4 ft ft ^3 o, ft A a a M H! tf ffl H a p4 ?l ' PQ H& P? PQ H a tf PQ ft tr 1 on p4 PQ 11712 1200 3955 229 3.69 4152 241 4.52 4470 259 5.47 4950 287 6.40 5230 303 7.45 5750 333 9.6 12688 1300 4050 235 4.02 4380 254 4.92 4550 264 5.87 5024 291 6.88 5295 306 7.95 5820 337 10.1 13664 1400 4143 240 4.42 4465 259 5.37 4700 272 6.36 5105 296 7.38 5350 310 8.53 5900 342 10.7 14640 1500 4250 246 4.85 4570 265 5.83 4850 281 6.85 5180 300 7.93 5450 316 9.06 5950 345 11.4 15616 1600 4325 250 5.32 4652 270 6.37 4950 287 7.40 5245 303 8.50 5550 322 9.69 6025 349 12.1 16592 1700 4437 257 5.81 4750 275 6.97 5040 292 8.02 5330 309 9.17 5625 326 10.34 6100 353 12.8 17568 1800 4527 262 6.35 4846 280 7.50 5110 296 8.62 5410 313 9.86 5700 330 11.07 6195 358 13.6 18544 1900 4613 267 6.92 4945 286 8.10 5230 303 9.30 5520 320 10.58 5780 335 11.84 6265 363 14.4 19520 2000 4743 274 7.57 5075 294 8.80 5325 309 10.03 5620 325 11.37 5860 340 12.68 6365 369 15.3 20496 2100 4850 281 8.22 5145 298 9.52 5440 315 10.83 5724 332 12.20 5955 345 13.52 6475 375 16.3 21472 2200 4970 288 8.96 5256 305 10.24 5550 322 11.63 5790 335 13.02 6050 350 14.40 6550 379 17.3 22448 2300 5090 295 10.15 5370 311 11.11 5630 326 12.48 5900 342 13.96 6150 356 15.37 6610 383 18.3 23424 2400 5210 302 10.62 5480 312 11.99 5750 333 13.39 6025 349 14.93 6270 363 16.39 6700 388 19.5 24400 2500 5340 309 11.52 5610 325 12.88 5850 339 14.38 6100 353 15.90 6343 367 17.50 6800 394 20.6 25376 2600 5485 318 12.47 5740 332 13.96 5980 346 15.43 6200 359 16.97 6460 375 18.70 6880 399 21.8 27328 2800 5710 331 14.68 5960 345 16.10 6230 361 17.75 6460 375 19.43 6650 385 21.08 7090 405 24.5 29280 3000 5970 346 16.87 6200 359 18.55 6460 374 20.39 6675 387 22.00 6900 400 23.80 7295 423 27.3 31232 3200 6230 361 19.43 6475 375 21.30 6730 390 23.10 6920 401 24.90 7135 413 26.75 7530 437 30.4 33184 3400 6580 381 22.45 6740 390 24.35 6960 403 26.55 7150 414 28.20 7355 427 30.10 7750 449 33.9 35136 3600 6815 395 25.55 7020 407 27.60 7200 417 29.70 7440 431 31.60 7600 440 33.75 8020 465 37.7 37088 3800 7105 412 29.15 7350 426 31.47 7475 433 33.35 7660 444 35.55 7840 454 37.55 8220 476 42.0 APPENDIX 309 CAPACITY TABLE TABLE X. No. 120 SINGLE INLET STEEL PLATE FAN TYPE S Vnl gj s. P. K" S. P. W S. P. M" S. P. " s. P. H" S. P. %" V Ol* ume 4 JN "S a ft T3 S ft "2 a ft "S a ft "8 a ft "8 a ft o > a a A ft a A ft a A a8 P. A & o. A a o. A H& tf pq H * p4 H ^ ft M M H & PS ffl Ct a r 1 m PJ pq 3 ft p4 pq 11950 1000 2366 125 1.156 2690 143 1.54 2940 156 1.44 3175 168 2.35 3400 180 2.77 3610 191 3.24 13145 1100 2490 132 1.36 2780 147 1.79 3040 161 2.21 3267 173 2.66 3480 185 3.11 3670 195 3.59 14340 1200 2600 138 1.60 2925 155 2.07 3125 166 2.51 3360 178 2.99 3575 189 3.48 3763 200 3.97 15535 1300 2736 145 1.91 3000 159 2.36 3237 172 2.85 3475 184 3.36 3675 195 3.87 3865 205 4.39 16730 1400 2846 151 2.23 3107 165 2.71 3310 176 3.20 3573 189 3.75 3750 199 4.29 3965 210 4.85 17925 1500 2987 158 2.60 3226 171 3.11 3460 184 3.64 3650 194 4.20 3860 205 4.76 4060 215 5.35 19120 1600 3130 166 2.99 3350 178 3.54 3565 189 4.08 3765 200 4.67 3960 210 5.26 4160 220 5.87 20315 1700 3270 173 3.42 3475 184 4.02 3680 195 4.61 3885 206 5.19 4055 215 5.88 4250 226 6.48 21510 1800 3410 181 3.99 3607 191 4.54 3810 202 5.17 4010 213 5.79 4180 222 6.56 4350 231 7.16 22705 1900 3546 188 4.45 3730 198 5.12 3935 209 5.74 4120 219 6.42 4320 229 7.10 4455 236 7.77 23900 2000 3700 196 5.04 3860 205 5.74 1050 215 6.40 4255 226 7.14 4423 235 7.83 4580 243 8.54 25095 2100 3850 204 5.68 4000 212 6.42 1210 223 7.08 4350 231 7.87 4535 241 8.61 4680 248 9.33 26290 2200 4000 212 6.36 1168 221 7.19 4320 229 7.92 4500 239 8.68 4670 248 9.47 4800 254 10.22 27485 2300 4323 230 8.08 4450 236 8.70 4628 245 9.51 4770 253 10.35 4930 262 11.15 28680 2400 1460 237 8.62 4620 245 9.65 4740 251 10.45 4920 261 11.33 5045 268 12.14 39375 2500 1600 244 9.70 4720 251 10.58 1880 259 11.48 5036 267 12.32 5170 275 13.20 31070 2600 4910 261 11.70 5000 265 12.55 5180 275 13.48 5325 282 14.35 33460 2800 5180 275 13.87 5280 280 14.92 5435 288 15.80 5510 292 16.88 35850 3000 5485 291 16.40 5610 298 17.88 5650 300 18.48 5840 310 19.60 Vnl -> S. P. 1" S. P. IK" S. P. IK" s. P. \H" S. P. 2" S. P. 2H" v 01- ume *1 'S a ft 13 a ft -0 a ft & a ft T3 a ft "8 a a > a ft A a & A a a A o, ft A ft a A a a A a "* OB PJ pq r~ ft C" 1 03 PS PQ Ct ft t" 1 02 p4 ft t- 1 oo tf pq ft tr 1 on tf pq H ft rt B 14340 1200 3955 209 4.52 4152 220 5.52 4470 237 6.69 4950 262 7.83 5230 279 9.12 5750 305 11.73 15535 1300 4050 215 4.92 4380 232 6.02 1550 242 7.18 5024 267 8.43 5295 281 9.75 5820 309 12.4 16730 1400 4143 220 5.40 4465 237 6.57 4700 249 7.80 5105 271 9.04 5350 284 10.44 5900 313 13.2 17925 1500 4250 226 5.95 4570 243 7.15 4850 257 8.40 5180 275 9.73 5450 289 11.10 5950 316 14.0 19120 1600 3325 229 6.50 4652 247 7.80 4950 263 9.08 5245 278 10.40 5550 294 11.87 6025 320 14.8 20315 1700 4437 235 7.12 4750 252 8.55 5040 268 9.84 5330 283 11.22 5625 298 12.1 6100 324 15.7 21510 1800 4527 240 7.78 4846 257 9.20 5110 271 10.56 5410 287 12.10 5700 302 13.6 6195 328 16.7 22705 1900 4613 245 8.48 4945 262 9.92 5230 277 11.33 5520 293 12.9 5780 307 14.5 6266 333 17.7 23900 2000 4743 251 9.27 5075 269 10.77 5325 283 12.3 5620 298 13.9 5860 311 15.5 6365 338 18.7 25095 2100 4850 257 10.07 5145 273 11.67 5440 289 13.2 5724 304 14.9 5955 316 16.5 6475 344 20.0 26290 2200 4970 264 10.97 5256 279 12.56 5550 294 14.2 5790 307 15.9 6050 321 17.6 6550 348 21.2 27485 2300 5090 27012.45 5370 285 13.60 5630 299 15.3 5900 313 17.1 6150 326 18.8 6610 351 22.5 28680 2400 5210 27612.98 5480 292 14.70 5750 305 16.4 6025 320 18.3 6270 333 20.1 6700 356 23.9 29875 2500 5340 28314.12 5610 298 15.78 5850 310 17.6 6100 324 19.5 6343 336 21.5 6800 361 25.3 31070 2600 5485 29115.27 5740 304 17.10 5980 317 18.9 6200 329 20.8 6460 343 22.9 6880 365 26.7 33460 2800 5710 30318.00 5960 316 19.73 6230 331 21.7 6460 343 23.8 6650 353 25.8 7090 376 30.0 35850 3000 5970 31720.68 6200 329 22.70 6460 343 24.9 6675 354 26.9 6900 366 29.2 7295 387 33.5 38240 3200 6230 330,23.80 6475 344 26.10 6730 357 28.3 6920 367 30.5 7135 378 32.8 7530 399 37.2 40630 3400 6580 34927.50 6740 357 29.85 6960 320 32.1 7150 379 34.6 7355 391 36.8 7750 411 41.7 43020 3600 6815 36231.30 7000 372 33.80 7200 382 36.4 7440 394 38.7 7600 404 41.4 8020 426 46.2 45410 3800 7105 37735.80 7350 390 38.50 7475 397 41.0 7660 407 43.6 7840 417 46.0 8220 436 51.4 310 HEATING AND VENTILATION CAPACITY TABLE TABLE XI. No. 130 SINGLE INLET STEEL PLATE FAN TYPE S Vol- g S. P. K" S. P. %" S. P. M" S. P. H" S. P. H" S. P. H" ume f -0 a ft TJ a ft i a ft 1 a ft I a ft 4 S ft 3 CX o o. ft 0) & & ft ft$ P. 9-1 ft M ft fcH oo 05 PQ * oo P5 PQ H! 05 PQ H 00 05 pq 2 ft IT 1 to 05 PQ & 05 PQ 14050 1000 2366 116 1.360 2690 132 1.820 2940 144 2.280 3175 156 2.765 3400 166 3.262 3610 177 3.810 15455 1100 2490 122 1.602 2780 136 2.101 3040 149 2.607 3267 160 3.128 3480 171 3.658 3670 180 4.218 16860 1200 2600 127 1.909 2925 143 2.433 3125 153 2.952 3360 165 3.516 3575 175 4.091 3763 184 4.668 18265 1300 2736 134 2.250 3060 147 2.790 3237 157 3.351 3475 170 3.950 3675 180 4.555 3865 189 5.162 19670 1400 2846 139 2.620 3107 152 3.190 3310 162 3.771 3573 175 4.414 3750 184 5.050 3965 194 5.710 21075 1500 2987 146 3.060 3226 158 3.660 3460 170 4.290 3650 179 4.937 3860 189 5.595 4060 199 6.290 22480 1600 3130 154 3.515 3350 164 4.168 3565 175 4.807 3765 185 5.500 3960 193 6.190 1160 204 6.918 23885 1700 3270 160 4.027 3475 170 4.717 3680 180 5.408 3885 190 6.102 4055 197 6.868 1250 208 7.620 25290 1800 3410 167 4.690 3607 177 5.345 3810 187 6.078 4010 196 6.800 1180 205 7.715 4350 213 8.423 26695 1900 3546 174 5.230 3730 183 6.020 3935 193 6.752 4120 202 7.550 1320 212 8.350 1455 218 9.147 28100 2000 3700 181 5.935 3860 189 6.250 4050 198 7.540 4255 209 8.400 1423 217 9.210 1580 225 10.04 29505 2100 3850 189 6.678 4000 196 7.550 4210 206 8.320 4350 213 9.253 1535 222 10.120 1680 229 10.97 30910 2200 4000 196 7.475 4168 204 8.452 1320 212 9.300 1500 221 10.20 4670 229 11.120 1800 235 12.02 32315 2300 4323 212 9.230 1450 218 10.23 1628 227 11.18 4770 234 12.170 1930 242 13.12 33720 2400 1460 219 10.130 1620 226 11.34 1740 232 12.30 4920 241 13.30 5045 247 14.26 35125 2500 4600 226 11.40 4720 231 12.43 4880 239 13.48 5036 247 14.48 5170 253 15.49 36530 2600 1910 241 13.75 5000 245 14.76 5180 254 15.85 5325 261 16.87 39340 2800 5180 254 16.29 5280 259 17.53 5435 266 18.60 5410 270 19.87 42150 3000 5485 269 19.30 5610 275 20.66 5650 277 21.74 5840 286 23.06 S. P. 1" S. P. IK" S. P. 1H" S. P. IX" S. P. 2" S. P. 2M" Vnl v oi- uine 73 31 i a ft ft M *1 a P. ft M s! a ft ft ft A a 4 ft ,5 9 1 a ft ft l S. P. K" S. P. H" S. P. K" S. P. W S. P. %" S. P. W V Ol ume 9 3'oi ,-C 6 a "2 a ft T3 a ft T3 a ft 1 a ft 1 S i ft O > a$ a ,4 a p. JA a ft ,C| ft Q. 43 ftS P 43 ftS ft ja H P5 pq H a tf pq u, ft tr" oo rt H& p4 H a pq ^ a PS CQ 16000 1000 2366 108 1.550 2690 123 2.072 2940 134 2.596 3175 145 3.150 3400 155 3.715 3610 164 4.337 17600 1100 2490 113 1.825 2780 127 2.392 3040 138 2.967 3267 149 3.560 3480 158 4.160 3670 167 4.800 19200 1200 2600 118 2.172 2925 133 2.770 3125 142 3.360 3360 153 4.000 3575 163 4.655 3763 171 5.318 20800 1300 2736 124 2.560 3000 137 3.175 3237 147 3.817 3475 158 4.500 3675 167 5.187 3865 176 58.80 22400 1400 2846 129 2.980 3107 141 3.630 3310 151 4.299 3573 163 5.025 3750 171 5.750 3965 180 65.10 24000 1500 2987 136 3.482 3226 147 4.168 3460 157 4.885 3650 166 5.620 3860 176 6.370 4060 185 7.160 25600 1600 3130 142 4.000 3350 153 4.747 3565 162 5.475 3765 171 6.255 3960 180 7.045 4160 189 7.870 27200 1700 3270 149 4.585 3475 158 5.368 3680 168 6.155 3885 177 6.950 4055 184 7.820 4250 193 86.70 28800 1800 3410 155 5.340 3607 164 6.087 3810 173 6.920 4010 183 7.750 4180 190 8.787 4350 198 9.590 30400 1900 3546 161 5.950 3730 170 6.850 3935 179 7.699 4120 187 8.600 4320 197 9.510 4455 203 10.4 32000 2000 3700 168 6.750 3860 176 7.690 4050 184 8.580 4255 194 9.560 4423 201 10.5 4580 209 11.4 33600 2100 3850 175 7.600 4000 182 8.600 4210 191 9.475 4350 198 10.5 4535 206 11.5 4680 213 12.5 35200 2200 4000 182 8.520 4168 189 9.625 4320 197 10.6 4500 205 11.6 4670 213 12.7 4800 219 13.7 36800 2300 4323 197 10.6 4450 20311.6 4628 210 12.7 4770 217 13.9 4930 224 15.0 38400 2400 4460 203 11.5 4620 21012.9 4740 216 14.0 4920 224 15.2 5045 229 16.24 40000 2500 4600 209 13.0 4720 21514.2 4880 222 15.3 5036 229 16.49 5170 235 17.62 41600 2600 4910 22315.6 5000 237 16.80 5180 236 18.05 5325 242 19.20 44800 2800 5180 23618.55 5280 240 19.98 5435 247 21.18 5510 251 22.62 48000 3000 5485 24921.96 5610 255 23.53 5650 257 24.76 5840 226 26.25 Vnl 4J S. P. 1" S. P. IK" S. P. IK" S. P. IK" S. P. 2" S. P. 2K" V Ol~ ume It ftl a a a 43 1 a & ft 43 -i a a ft ftl a a ft 43 1 a a 4 l a a a ^ pq H& P5 pq i a on tf pq -* x p4 pq H ^* PS pq ^_. Q tr 1 co pq 19200 1200 3955 180 6.045 4152 189 7.400 4470 203 8.965 4950 225 10.5 5230 236 12.2 5750 262 15.8 20300 1300 4050 184 6.595 4380 199 8.070 4550 207 9.637 5024 228 11.3 5295 241 13.0 5820 265 16.64 22400 1400 4143 188 7.247 4465 203 8.808 4700 212 10.4 5105 232 12.1 5350 243 14.0 5900 263 17.68 24000 1500 4250 193 7.957 4570 208 9.560 4850 221 11.2 5180 236 13.0 5450 248 14.9 5950 271 18.80 25600 1600 4325 197 8.710 4652 212 10.4 4950 225 12.1 5245 239 13.9 5550 252 15.9 6025 274 19.90 27200 1700 4437 201 9.545 4750 216 11.4 5040 229 13.2 5330 243 15.0 5625 256 16.98 6100 277 21.00 28800 1800 4527 206 10.4 4846 221 12.3 5110 232 14.2 5410 246 16.20 5700 259 18.16 6195 282 22.35 30400 1900 4613 210 11.4 4945 225 13.3 5230 238 15.3 5520 251 17.37 5780 263 19.43 6265 285 23.68 32000 2000 4743 21512.4 5075 231 14.4 5325 242 16.45 5620 255 18.65 5860 267 20.80 6365 289 25.10 33600 2100 4850 221 13.5 5145 234 15.6 5440 247 17.73 5724 260 20.00 5955 271 22.18 6475 294 26.80 35200 2200 4970 226 14.7 5256 239 16.82 5550 252 19.10 5790 264 21.38 6050 275 23.61 6550 298 28.40 36800 2300 5090 23l|l6.67 5370 244 18.21 5630 256 20.47 5900 268 22.90 6150 280 25.20 6610 301 30.20 38400 2400 5210 23717.39 5480 249 19.67 5750 261 22.00 6025 274 24.46 6270 285 26.90 6700 305 32.00 40000 2500 5340 24318.89 5610 255 21.12 5850 266 23.60 6100 277 26.10 6343 289 28.72 6800 309 33.80 41600 2600 5485 249,20.46 5743 261 22.90 5980 272 25.35 6200 282 27.85 6460 293 30.65 6880 313 35.80 44800 2800 5710 26024.08 5960 271 26.41 6230 283 29.15 6460 293 31.85 6650 303 34.60 7090 322 40.10 48000 3000 5970 27227.70 6200 282 30.40 6460 294 33.36 6675 304 36.10 6900 314 39.08 7295 332 44.90 51200 3200 6230 283!31.90 6475 294 34.90 6730 306 37.95 6920 315 40.80 7135 324 43.90 7530 343 50.00 54400 3400 6580 299:36.80 6740 307 39.92 6960 316 43.07 7150 325 46.25 7355 335 49.30 7750 353 55.70 57600 3600 6815 31041.92 7020 319 45.30 7200 327 48.07 7440 339 51.99 7600 346 55.38 8020 365 61.80 60800 3800 7105 323 47.90 7350 334 51.60 7475 340 54.92 7660 349 58.37 7840 357 61.60 8220 374 69.00 312 HEATING AND VENTILATION CAPACITY TABLE TABLE XIII. No. 160 SINGLE INLET STEEL PLATE FAN TYPE S S. P. K" s. P. H" S. P. K" S. P. H" S. P. %" S. P. %" Vol- J ume 3-3 fi a ft fi a d -0 3 d B a ft - a ft a ft O> a2> d jg 8*1 ft M .S 1 ^ ft A at> d A Di o d A D* o) ft A H& PQ H& PS pq ? & PS H a p4 H& m r*S PS pq 20250 1000 2366 94 1.957 2690 107 2.615 2940 117 3.28 3175 127 3.98 3400 135 4.69 3610 144 5.48 22275 1100 2490 99 2.31 2780 111 3.025 3040 121 3.75 3267 130 4.5 3480 139 5.25 3670 146 6.08 24300 1200 2600 104 2.75 2925 116 3.505 3125 125 4.25 3360 134 5.06 3575 142 5.89 3763 150 6.72 26325 1300 2736 109 3.23 3060 119 4.01 3237 129 4.82 3475 138 5.68 3675 146 6.55 3865 154 7.44 28350 1400 2846 113 3.77 3107 124 4.59 3310 132 5.43 3573 142 6.35 3750 149 7.26 3965 158 8.2 30375 1500 2987 119 4.40 3226 128 5.27 3460 137 6.17 3650 145 7.1 3860 154 8.05 4060 162 9.05 32400 1600 3130 125 5.06 3350 133 5.99 3565 142 6.92 3765 150 7.91 3960 158 8.9 4160 166 9.94 34425 1700 3270 130 5.78 3475 138 6.79 3680 147 7.77 3885 155 8.78 4055 162 9.88 4250 169 10.93 36450 1800 3410 136 6.75 3607 144 7.68 3810 152 8.725 4010 160 9.8 4180 167 10.1 4350 173 12.1 38475 1900 3546 141 7.52 3730 148 8.67 3935 157 9.71 4120 164 10.90 4320 172 12.0 4455 178 13.1 40500 2000 3700 147 8.54 3860 154 9.71 4050 161 10.83 4255 170 12.1 4423 176 13.2 4580 183 14.4 42525 2100 3850 153 9.60 4000 159 10.85 4210 167 11.97 4350 173 13.3 4535 181 14.6 4680 187 15.8 44550 2200 4000 159 10.74 4168 166 12.17 4320 172 13.40 4500 179 14.7 4670 186 16.0 4800 191 17.3 46575 2300 4323 172 13.44 4450 177 14.70 4623 184 16.1 4770 190 17.5 4930 196 18.9 48600 2400 4460 178 14.55 4620 184 16.30 4740 189 17.7 4920 196 19.2 5045 201 20.5 50625 2500 4600 183 16.40 4720 188 17.90 4880 194 19.4 5036 200 20.8 5170 206 21.3 52650 2600 4910 196 19.80 5000 199 21.3 5180 206 22.8 5325 212 24.3 56700 2800 5180 206 23.4 5280 210 25.2 5435 216 56.5 5410 220 28.6 60750 3000 5485 218 27.8 5610 223 29.7 5650 225 31.3 5840 232 33.1 S. P. 1" S. P. IK" S. P. IK" S. P. 1H" S. P. 2" S. P. 2M" Vol- +j ume ll i a p. ft A 1 a d ft A ! a ft ft M 1 a ft ft A -d &i a d ft ja J a d ft A H& PS m ft t*l DO PS ft IT 1 m p4 m H & P? PQ H& rt PQ r\ a t-i on p4 pq 24300 1200 3955 158 7.64 4152 166 9.35 4470 178 11.3 4950 197 13.3 5230 208 15.4 5750 229 20.0 26325 1300 4050 161 8.33 4380 175 10.2 4550 182 12.2 5024 200 14.3 5295 211 16.5 5820 232 21.1 28350 1400 4143 165 9.16 4465 178 11.1 4700 187 13.2 5105 203 15.3 5350 213 17.7 5900 235 22.4 30375 1500 4250 169 10.04 4570 182 12.1 4850 193 14.2 5180 206 16.4 5450 217 18.8 5950 237 23.7 32400 1600 4325 172 11.0 4652 186 13.2 4950 197 15.3 5245 209 17.6 5550 222 20.1 6025 240 25.2 34425 1700 4437 177 12.0 4750 189 14.4 5040 200 16.6 5330 212 19.0 5625 224 21.5 6100 243 26.6 36450 1800 4527 180 13.1 4846 193 15.6 5110 203 17.9 5410 216 20.4 5700 227 22.9 6195 247 28.3 38475 1900 4613 184 14.4 4945 197 16.8 5230 208 19.3 5520 220 21.9 5780 230 24.5 6265 249 29.9 40500 2000 4743 189 15.7 5075 202 18.2 5325 212 20.8 5620 224 23.5 5860 233 26.3 6365 253 31.8 42525 2100 4850 193 17.0 5145 205 19.7 5440 216 22.5 5724 228 25.3 5955 237 28.1 6425 257 33.8 44550 2200 4970 198 18.6 5256 209 21.3 5550 221 24.1 5790 230 27.0 6050 241 29.8 6550 261 35.9 46575 2300 5090 203 21.10 5370 214 23.1 5630 224 25.9 5900 235 28.9 6150 245 31.9 6610 263 38.1 48600 2400 5210 208 22.0 5480 218 24.9 5750 229 27.8 6025 240 30.9 6270 250 34.0 6700 267 40.4 50625 2500 5310 213 23.9 5610 224 26.7 5850 233 29.8 6100 243 33.0 6343 252 36.3 6800 271 42.8 52656 2600 5485 218 24.8 5740 229 28.9 5980 238 32.0 6200 247 35.2 6460 257 38.7 6880 274 45.3 56700 2800 5710 228 30.4 5960 238 33.4 6230 248 36.8 8460 257 40.3 6650 265 43.7 7090 282 50.8 60750 3000 5970 238 35.0 6200 247 38.4 6460 257 42.2 6675 265 45.7 6900 274 49.3 7295 290 56.7 64800 3200 6230 252 40.3 6475 258 44.2 6730 268 47.9 6920 276 51.6 7135 284 55.4 7530 300 63.0 68850 3400 6580 262 46.5 6740 268 50.5 6960 277 54.4 7150 285 58.5 7355 293 62.4 7750 308 70.3 72900 3600 6815 272 53.0 7000 279 57.3 7200 287 61.6 7440 296 65.5 7600 303 70.0 8020 320 78.0 76950 3800 7105 283 60.5 7350 292 65.2 7475 297 69.4 7660 305 73.7 7840 312 77.8 8220 328 87.0 APPENDIX 313 STATIC PRESSURE TABLES FOR NIAGARA CONOIDAL FANS 1 TABLE XIV. No. 3 NIAGARA CONOIDAL FAN (T?PE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. K" s. P. %"S.P. W s. P. H" S. P. H"S.P. K"S.P. a a a B a ft rt ft a a ft tf ft B ft tf ft B a d ft W a o. ft B 1000 1310 .063 387 .09 483 .15 1100 1440 .076 384 .11 477 .16 1200 1570 .090 387 .12 477 .17 557 .23 1300 1710 .106 393 .14 470 .18 550 .25 623 .32 1400 1840 .122 400 .16 473 .20 547 .26 617 .33 687 .42 1500 1970 .141 410 .18 477 .23 543 .28 613 .35 680 .43 743 .52 1600 2100 .160 420 .21 480 .25 547 .31 610 .37 673 .45 733 .54 1700 2230 .180 430 .24 490 .28 550 .34 607 .40 670 .48 727 .56 1800 2360 .202 443 .28 500 .32 553 .37 610 .43 667 .51 723 .59 1900 2490 .225 457 .31 510 .35 560 .41 613 .47 667 .54 720 .62 2000 2630 .250 470 .35 520 .40 570 .45 617 .52 667 .58 720 .66 2100 2760 .275 483 .39 530 .45 580 .50 623 .56 670 .63 720 .71 2200 2890 .302 497 .44 543 .50 590 .55 633 .61 677 .68 723 .76 2300 3020 .330 513 .49 557 .55 600 .61 643 .67 683 .73 727 .81 2400 3150 .360 527 .55 570 .61 610 .67 650 .73 690 .80 733 .87 2500 3280 .390 543 .60 583 .67 623 .74 660 .80 700 .86 740 .94 2600 3410 .422 560 .67 597 .74 633 .81 673 .88 710 .94 747 1.02 2800 3670 .489 590 .81 623 .89 660 .96 693 1.04 730 1.10 767 1.17 3000 3940 .560 623 .99 657 1.04 687 1.14 720 1.22 753 1.29 780 1.36 3200 4190 .638 717 1.33 747 1.42 780 1.50 810 1.58 3400 4460 .721 807 1.75 833 1.84 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1" S. P. 1>"S.P. 1M"S.P. 1^"S.P. 2" S. P. 2H" S. P. a d ft B a d f4 ft B a d P3 ft B a d ft B a a ft B a ft tf ft B 1300 1710 .106 820 .58 1400 1840 .122 810 .59 920 .80 1027 1.00 1500 1970 .141 800 .62 913 .81 1017 1.04 1110 1.25 1600 2100 .160 793 .64 903 .84 1007 1.06 1100 1.29 1190 1.53 1700 2230 .180 783 .66 893 .86 997 1.09 1087 1.32 1177 1.58 1343 2.13 1800 2360 .202 777 .68 883 .89 983 1.12 1077 1.35 1167 1.61 1330 2.16 1900 2490 .225 773 .71 877 .92 977 1.14 1067 .39 1157 .65 1317 2.20 2000 2630 .250 770 .75 873 .95 970 1.17 1057 .42 1143 .68 1303 2.24 2100 2760 .275 770 .79 867 .99 960 1.22 1050 .46 1133 .73 1297 2.29 2200 2890 .302 767 .84 863 1.03 953 1.25 1040 .50 1127 .76 1287 2.33 2300 3020 .330 770 .89 860 1.08 950 1.30 1033 1.54 1120 .81 1270 2.38 2400 3150 .360 773 .95 860 1.13 947 1.35 1027 .59 1107 1.85 1263 2.43 2500 3280 .390 777 1.03 860 1.20 943 1.41 1023 1.64 1103 1.91 1253 2.49 2600 3410 .422 783 1.09 863 1.26 940 1.47 1020 1.70 1097 1.96 12472.54 2800 3670 .489 800 1.25 870 1.43 943 1 . 63 1013 1.84 1090 2.10 12332.67 I 3000 3940 .560 820 1.44 883 1.61 950 1.81 1020 2.02 1087 2.25 1227 2.82 3200 4190 .638 8G7 1.65 900 1.83 9602.02 1023 2.23 1090 2.47 1217 3.00 3400 4460 .721 863 1.90 920 2.06 980 2,26 1033 2.47 1093 2.69 1213 3.21 3600 4730 .810 883 2.18 943 2.34 997 2.53 1050 2.76 1107 2.96 1220 3.48 3800 4990 .900 1017 2.84 1067 3.04 1117 3.28 1227 3.76 4000 5250 1.000 1087 3.39 1133 3.60 1233 4.10 1 From "Fan Engineering," Buffalo Forge Co. 314 HEATING AND VENTILATION TABLE XV. No. 3^ NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. K" s. P. ^"S.P. H" S. P. H" s. P. W S. P. K" S. P. a ft M d. w a a tt ft w a ft ft n a a fd S a P. M w d a S S 1000 1790 .063 332 .13 414 .20 1100 1970 .076 329 .14 409 .21 1200 2140 .090 332 .16 409 .23 477 .32 1300 2320 .106 337 .18 403 .25 472 .33 534 .43 1400 2500 .122 343 .21 406 .28 469 .36 529 .45 589 .57 1500 2680 .141 352 .24 409 .31 466 .38 526 .48 583 .59 637 .71 1600 2860 .160 360 .28 412 .34 469 .42 523 .51 577 .62 629 .73 1700 3040 .180 369 .32 422 .49 472 .46 520 .55 574 .65 623 .77 1800 3210 .202 380 .37 429 .33 474 .51 523 .59 572 .69 620 .80 1900 3390 .225 392 .42 437 .48 480 .56 526 .64 572 .74 617 .85 2000 3570 .250 403 .48 446 .54 489 .62 529 .70 572 .79 617 .90 2100 3750 .275 414 .53 454 .61 497 .68 534 .76 574 .86 617 .96 2200 3930 .302 426 .59 466 .68 506 .75 543 .83 580 .92 620 1.03 2300 4110 .330 440 .67 477 .75 514 .83 552 .91 586 1.00 623 1.10 2400 4290 .360 452 .74 489 .83 523 .91 557 .99 592 1.09 629 1.18 2500 4470 .390 466 .82 500 .91 534 1.01 566 1.08 600 1.17 634 1.27 2600 4640 .422 480 .91 512 1.01 543 1.10 577 1.19 609 1.27 640 1.39 2800 5000 .489 506 1.10 534 1.21 566 1.31 594 1.41 626 1.50 657 1.59 3000 5360 .560 534 1.35 563 1.42 589 1.56 617 1.65 646 1.75 669 1.85 3200 5720 .638 614 1.81 640 1.94 669 2.05 694 2.16 3400 6070 .721 692 2.38 714 2.50 Outlet velocity, ft. per min. Capacity, cu. ft. air. per min. Add for total press. 1" S. P. 1K"S.P. IK" S. P. WS.P. 2" S. P. 2^" S. P. a d M S a D, d W a P. ej S a a ft w a D. P! ft B a S ft B 1300 2320 .106 703 .78 1400 2500 .122 694 .81 789 1.08 880 1.36 1500 2680 .141 686 .84 783 1.10 872 1.41 952 1.70 1600 2860 .160 680 .86 774 1.15 863 1.45 943 1.75 1020 2.08 1700 3040 .180 672 .89 766 1.17 854 1.48 932 1.79 1009 2.14 1151 2.89 1800 3210 .202 666 .93 757 1.21 843 1.52 923 1.84 1000 2.19 1140 2.94 1900 3390 .225 663 .97 752 1.25 837 1.56 914 1.89 992 2.24 1129 2.99 2000 3570 .250 660 1.02 749 1.30 831 1.59 906 1.94 980 2.29 1117 3.05 2100 3750 .275 660 1.08 743 1.35 823 1.65 900 1.99 972 2.35 1111 3.11 2200 3930 .302 657 1.14 740 1.40 817 1.70 892 2.03 966 2.40 1103 3.17 2300 4110 .330 660 1.22 737 1.47 814 1.77 886 2.10 960 2.46 1089 3.23 2400 4290 .360 663 1.30 737 1.53 812 1.84 880 2.17 949 2.52 1083 3.31 2500 4470 .390 666 1.40 737 1.63 809 1.91 877 2.23 946 2.60 1074 3.38 2600 4640 .422 672 1.48 740 1.72 806 2.00 874 2.32 940 2.67 1069 3.46 2800 5000 .489 686 1.70 746 1.95 809 2.22 869 2.50 934 2.86 1057 3.63 3000 5360 .560 703 1.96 757 2.19 814 2.46 874 2.74 932 3.06 1052 3.84 3200 5720 .638 717 2.24 772 2.49 823 2.75 877 3.04 934 3.36 1043 4.08 3400 6070 .721 740 2.59 789 2.81 840 3.08 886 3.36 937 3.66 1040 4.36 3600 6430 .810 757 2.97 809 3.19 854 3.44 900 3.75 949 4.03 1046 4.73 3800 6790 .900 872 3.86 914 4.14 957 4.46 1052 5.12 4000 7140 1.000 932 4.61 972 4.90 1057 5.59 APPENDIX 315 TABLE XVI. No. 4 NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. K"S.P. K" S. P. X-S.P. H" S. P. K! 1 S. P. w s. P. a A ft w a ft w a S a it a ft a ft w 1000 2330 .063 290 .17 363 .26 1100 2570 .076 288 .19 358 .28 1200 2800 .090 290 .21 358 .30 418 .41 1300 3030 .106 295 .24 353 .33 413 .44 468 .56 1400 3270 .122 300 .28 355 .36 410 .47 463 .59 515 .74 1500 3500 .141 308 .32 358 .40 408 .50 460 .62 510 .77 558 .92 1600 3730 .160 315 .37 360 .45 410 .55 458 .66 505 .80 550 .96 1700 3970 .180 323 .42 368 .50 413 .60 455 .71 503 .85 545 1.00 1800 4220 .202 333 .49 375 .56 415 .66 458 .77 500 .90 543 1.05 1900 4430 .225 343 .55 383 .63 420 .73 460 .84 500 .96 540 1.11 2000 4670 .250 353 .62 390 .71 428 .81 463 .92 500 1.04 540 1.17 2100 4900 .275 363 .70 398 .80 435 .89 468 1.00 503 1.12 540 1.26 2200 5130 .302 373 .78 408 .88 443 .98 475 1.08 508 1.21 543 1.35 2300 5370 .330 385 .87 418 .98 450 1.08 483 1.19 513 1.31 545 1 . 44 2400 5600 .360 395 .97 428 1.09 458 1.19 488 1.30 518 1.42 550 1.55 2500 5830 .390 408 1.07 438 1.19 468 1.32 495 1.41 525 1.53 555 1.67 2600 6070 .422 420 1.19 448 1.32 475 1.43 505 1.56 533 1.67 560 1.81 2800 6530 .489 443 1.44 468 1.58 495 1.71 520 1.84 548 1.95 575 2.08 3000 7000 .560 468 1.76 493 1.86 515 2.03 540 2.16 565 2.29 585 2.42 3200 7460 .638 538 2.37 560 2.53 585 2.67 608 2.82 3400 7930 .721 605 3.11 625 3.27 Outlet velocity, ft. per min. Capacity, cu. ft. air. per min. Add for total press. 1" S. P. 1K"S.P. 1H"S. P. WS.P. 2" S. P. 2H"S.P. a o. ft B a ft ft w a ft ft w a ft ft w a d rt ft K a P. ft 1300 3030 .106 615 1.03 1400 3270 .122 608 1.06 690 1.41 770 1.78 1500 3500 .141 600 1.09 685 1.44 763 1.84 833 2.23 1600 3730 .160 595 1.13 678 1.50 755 1.89 825 2.29 893 2.72 1700 3970 .180 588 1.17 670 1.53 748 1.94 815 2.34 883 2.80 1008 3.78 1800 4220 .202 583 1.22 663 1.58 738 1.94 808 2.40 875 2.87 998 3.84 1900 4430 .225 580 1.27 658 1.63 733 2.03 800 2.47 868 2.93 988 3.91 2000 4670 .250 578 1.33 655 1.70 728 2.08 793 2.53 858 2.99 978 3.99 2100 4900 .275 578 1.40 650 1.76 720 2.16 7882.59 850 3.07 973 4.07 2200 2300 5130 5370 .302 .330 575 578 1.49 1.59 648 645 1.83 1.92 7152.23 7132.31 7802.66 7752.74 845 840 3.14 3.22 965 953 4.15 4.23 2400 5600 .360 580 1.70 645 2.00 710 2.40 770 2.83 830 3.30 948 4.32 2500 5830 .390 583 1.83 645 2.13 708 2.50 768 2.91 828 3.39 940 4.42 2600 6070 .422 588 1.94 6482.24 7052.61 76513.03 823 3.49 935 4.51 2800 6530 .489 600 2.23 653 2.55 708 2.90 760 3.27 818 3.73 925 4.74 3000 7000 .560 615 2.56 663 2.87 713 3.22 765 3.59 815 4.00 920 5.01 3200 7460 .638 628 2.93 675 3.25 7203.59 768 3.97 818 4.39 913 5.33 3400 7930 .721 648 3.38 690 3.67 735 4.02 775 4.39 820 4.79 910 5.70 3600 8400 .810 663 3.87 708 4.16 748 4.50 788 4.90 830 5.27 915 6.18 3800 8860 .900 7635.04 8005.41 838 5.83 920 6.69 4000 9330 1.000 815 6.02 850 6.40 925 7.30 316 HEATING AND VENTILATION TABLE XVII. No. 4^ NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per mm. Capacity, cu. ft. air per min. Add for total press. "S.P. "S.P. W s. P. H" S. P. H" S. P. K" s. P. a a ft M ft ffi ft tf ft a | & a S a W a d tf ft w 1000 2950 .063 258 .21 322 .33 1100 3250 .076 256 .23 318 .35 1200 3540 .090 258 .27 318 .38 371 .52 1300 3840 .106 262 .30 313 .41 367 .55 416 0.71 1400 4130 .122 267 .35 316 .46 365 .59 411 0.75 458 0.93 1500 4430 .141 273 .40 318 .51 362 .63 409 0.79 453 0.97 496 1.17 1600 4720 .160 280 .46 320 .57 365 .69 407 0.84 449 .02 489 1.21 1700 5020 .180 287 .53 327 .64 367 .76 4050.90 447 .07 485 1.27 1800 5310 .202 296 .61 333 .71 369 .84 407|0.97 445 .14 482 1.33 1900 5610 .225 305 .69 340 .80 373 .92 409 1.06 445 .22 480 1.40 2000 5900 .250 313 .79 347 .89 380 1.02 411 1.16 445 .31 480 1.48 2100 6200 .275 322 .88 353 1.01 387 1.13 416 1.26 447 .42 480 1.59 2200 6500 .302 331 .98 362 1.12 393 1.24 422 1.37 451 .53 482 1.71 2300 6790 .330 342 1.10 371 1.24 400 1.37 429 1.50 456 .65 485 1.82 2400 7090 .360 351 1.23 380 1.38 407 1.51 433 1.64 460 .80 489 1.96 2500 7380 .390 362 1.35 389 1.50 416 1.67 440 1.79 467 1.94 493 2.11 2600 7680 .422 373 1.51 398 1.67 422 1.81 449' 1.97 473 2.11 498 2.29 2800 8270 .489 393 1.82 416 2.00 440 2.17 462 2.33 487 2.47 511 2.63 3000 8860 .560 416 2.23 438 2.35 458 2.57 480 2.73 502 2.90 520 3.06 3200 9450 .638 478 3.00 498 3.20 520 3.38 540 3.57 3400 10040 .721 538 3.93 556 4.13 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1" S. P. 1>"S.P. 1H" S. P. \W S. P. 2" S. P. 2>$"S.P. a a H ft W a a P S a a tf a W a a tf a a a M a W a a H a W 1300 3840 .106 547 1.30 1400 4130 .122 540 1.34 613 1.79 685 2.25 1500 4430 .141 533 1.38 609 1.82 678 2.33 740 2.82 1600 4720 .160 529 1.43 602 1.89 671 2.39 733 2.90 793 3.44 1700 5020 .180 522 1.48 596 1.93 665 2.45 725 2.96 785 3.54 896 4.78 1800 5310 .202 518 1.54 589 2.00 656 2.51 718 3.04 778 3.63 887 4.86 1900 5610 .225 516 1.60 585 2.07 651 2.57 711 3.12 771 3.71 878 4.94 2000 5900 .250 513 1.69 582 2.15 647 2.63 704 3.20 762 3.79 869 5.04 2100 6200 .275 513 1.78 578 2.23 640 2.74 700 3.28 756 3.89 865 5.14 2200 6500 .302 511 1.89 576 2.31 636 2.82 696 3.36 751 3.97 858 5.25 2300 6790 .330 513 2.01 573 2.43 633 2.92 68913.46 747 4.07 847 5.35 2400 7090 .360 5143 2.15 573 2.53 631 3.04 685 3.59 738 4.17 842 5.47 2500 7380 .390 518 2.31 573 2.69 629 3.16 682 3.69 736 4.29 836 5.59 2600 7680 .422 522 2.45 576 2.84 627 3.30 680 3.83 731 4.42 831 5.71 2800 8270 .489 533 2.82 580 3.22 629 3.67 676 4.13 727 4.72 822 5.99 3000 8860 .560 547 3.24 589 3.63 633 4.07 680 4.54 725 5.06 818 6.34 3200 9450 .638 558 3.71 600 4.11 640 4.54 682 5.02 727 5.55 811 6.74 3400 10040 .721 576 4.27 613 4.64 653 5.08 689 5.55 729 6.06 809 7.21 3600 10630 .810 589 4.90 629 5.27 665 5.69 700 6.20 738 6.66 813 7.82 3800 11220 .900 678 6.38 711 6.85 745 7.37 818 8.46 4000 11810 1.000 725 7.61 756 8.10 822 9.23 APPENDIX 317 TABLE XVIII. No. 5 NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. K" s. P. K" s. P. W S. P. H" S. P. W S. P. H"S.P. a a ft w a a M ft X a A ft w a P. ft W a d d ft W a p. f4 S 1000 3640 .063 232 .26 290 .41 1100 4010 .076 230 .29 286 .44 1200 4370 .090 232 .33 286 .47 334 .65 1300 4740 .106 236 .38 282 .51 330 .68 374 .88 1400 5100 .122 240 .43 284 .56 328 .73 370 .92 412 1.15 1500 5470 .141 246 .50 286 .63 326 .78 368 .98 408 1.20 446 1.44 1600 5830 .160 252 .57 288 .70 328 .86 366 1.04 404 1.26 440 1.49 1700 6190 .180 258 .66 294 .79 330 .94 364 1.11 402 1.33 436 1.57 1800 6560 .202 266 .76 300 .88 332 1.03 366 1.20 400 1.40 434 1.64 1900 6930 .225 274 .86 306 .99 336 1.14 368 1.31 400 1.50 432 1.73 2000 7290 .250 282 .97 312 1.11 342 1.26 370 1.43 400 1.62 432 1.83 2100 7660 .275 2901.09 318 1.24 348 1.39 374 1.56 402 1.75 432 1.96 2200 8010 .302 298 1.21 326 1.38 354 1.53 380 1.69 406 1.89 434 2.11 2300 8380 .330 308 1.36 334 1.55 360 1.69 386 1.85 410 2.04 436 2.25 2400 8750 .360 316 1.51 342 1.70 366 1.86 390 2.03 414 2.22 440 2.41 2500 9100 .390 326 1.67 350 1.86 374 2.06 396 2.21 420 2.40 444 2.60 2600 9480 .422 336 1.86 3582.06 380 2.24 404 2.43 426 2.60 448 2.83 2800 10200 .489 354 2.25 374 2.46 396 2.68 416 2.88 438 3.05 460 3.25 3000 10940 .560 374 2.75 394 2.90 412 3.18 432 3.38 452 3.58 468 3.78 3200 11660 .638 430 3.70 448 3.95 468 4.18 486 4.40 3400 12390 .721 484 4.85 500 5.10 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1" S. P. IK" S. P. WS. P. W 8. P. 2" S. P. 2^" S. P. a ft ft W a A rt ft W a p. ft a o, ri ft W a Q. ft W a o. PS ft W 1300 4740 .106 492 1.60 1400 5100 .122 486 1.65 552 2.21 616 2.78 1500 5470 .141 480 1.71 548 2.25 610 2.88 666 3.48 1600 5830 .160 476 1.76 542 2.34 604 2.95 660 3.58 714 4.25 1700 6190 .180 470 1.82 536 2.39 5983.03 652 3.65 706 4.38 806 5.90 1800 6560 .202 466 1.90 530 2.47 590 3.10 646 3.75 700 4.48 798 6.00 1900 6930 .225 464 1.98 526 2.55 586 3.18 640 3.85 694 4.58 790 6.10 2000 7290 .250 462 2.08 524 2 . 65 582 3.25 634 3.95 686 4.68 782 6.23 2100 7660 .275 462 2.19 520 2.75 576 3.38 630 4.05 680 4.80 778 6.35 2200 8010 .302 460 2.33 518 2.85 572 3.48 624 4.15 676 4.90 772 6.48 2300 8380 .330 4622.48 516 3.00 5703.60 620 4.28 672 5.03 762 6.60 2400 8750 .360 464 2.65 516 3.13 5683.75 616 4.44 664 5.15 758 6.75 2500 9100 .390 466 2.85 516 3.33 56613.90 614 4.55 662 5.30 752 6.90 2600 9480 .422 470 3.03 518 3.50 564 4.08 612 4.73 658 5.45 748 7.05 2800 10200 .489 480 3.48 522 3.98 566 4.53 608 5.10 654 5.83 740 7.40 3000 10940 .560 492 4.00 530 4.48 570 5.03 612 5.60 652 6.25 736 7.83 3200 11660 .638 502 4.57 540 5.08 576 5.60 614 6.20 654 6.85 730 8.32 3400 12390 .721 518 5.27 552 5.73 588 6.28 620 6.85 656 7.48 728 8.90 3600 13120 .810 530 6.05 566 6.50 598 7.03 630 7.65 664 8.22 732 9.65 3800 13850 .900 610 7.88 640 8.46 670 9.10 736 10.5 4000 14580 1.000 652 9.40 680 10.0 740 11.4 318 HEATING AND VENTILATION TABLE XIX. No. 5H NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. K" s. P. K"S.P. K" s. P. K"S.P. K" S. P. %"S.P. a & PJ d a fk 0j d W a d M d W a d rf d W a d tf d W a d ri d B 1000 4410 .063 211 .32 264 .49 1100 4850 .076 209 .35 260 .53 1200 5290 .090 211 .40 260 .57 304 .78 1300 5730 .106 215 .45 257 .62 300 .83 340 1.06 1400 6170 .122 218 .52 258 .68 298 .88 336 1.12 375 1.40 1500 6620 .141 224 .60 260 .76 296 .95 335 1.18 371 1.45 406 1.75 1600 7060 .160 229 .69 262 .85 298 1.04 333 1.26 367 .52 400 1.81 1700 7500 .180 235 .80 267 .95 300 1.13 331 .35 366 .60 397 1.89 1800 7940 .202 242 .92 273 1.06 302 1.25 333 .46 364 .70 395 1.98 1900 8380 .225 249 1.04 278 1.19 306 1.38 335 .59 364 .82 393 2.09 2000 8820 .250 256 1.17 284 1.34 311 1.53 336 .73 364 .96 393 2.21 2100 9260 .275 264 1.32 289 1.50 316 1.68 340 .88 366 2.12 393 2.37 2200 9700 .302 271 1.47 296 1.67 322 1.85 346 2.05 369 2.28 395 2.55 2300 10140 .330 280 1.65 304 1.86 327 2.05 351 2.24 373 2.47 397 2.72 2400 10590 .360 287 1.83 311 2.05 333 2.25 355 2.45 377 2.68 400 2.92 2500 11030 .390 297 2.02 318 2.25 340 2.49 360 2.67 382 2.90 404 3.15 2600 11470 .422 306 2.25 326 2.49 346 2.71 367 2.94 387 3.15 407 3.42 2800 12350 .489 322 2.72 340 2.98 360 3.24 378 3.48 398 3.69 418 3.93 3000 13230 .560 340 3.33 358 3.51 375 3.84 393 4.08 411 4.33 426 4.57 3200 14110 .638 391 4.48 407 4.78 426 5.05 442 5.33 3400 15000 .721 440 5.87 455 6.17 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. I", S. P. IK" S. P. 1M"S.P. IK" S. P. 2" S. P . M2" S. P. i M d B a d H d B a d M d B a d tf d B a d ti d B i d d d B 1 1300 5730 .106 44711.94 1400 6170 .122 442 1.99 502 2.67 560 3.36 1500 6620 .141 437 2.07 498 2.72 555 3.48 606 4.21 1600 7060 .160 433 2.13 493 2.83 549 3.57 600 4.33 649 5.14 1700 7500 .180 4272.20 4872.89 544 3.66 59314.42 642 5.29 733 7.14 1800 7940 .202 424 2.30 482 2.99 537 3.75 587 4.54 636 5.42 726 7.26 1900 8380 .225 422 2.39 478 3.09 533 3.84 582 4.66 631 5.54 718 7.38 2000 8820 .230 420 2.52 476 3.21 529 3.93 576 4.78 624 5.66 711 7.53 2100 9260 .275 420 2.65 473 3.33 524 4.08 573 4.90 618 5.81 707 7.68 2200 9700 .302 418 2.82 471 3.45 520 4.21 567 5.02 615 5.93 702 7.84 2300 10140 .330 4203.00 469 3.63 518 4.36 564 5.17 611 6.08 693 7.99 2400 10590 .360 422 3.21 469 3.78 517 4.54 560 5.35 604 6.23 689 8.17 2500 11030 .390 424 3.45 469 4.02 515 4.72 558 5.51 602 6.41 684 8.35 2600 11470 .422 427 3.66 471 4.24 513 4.93 557 5.72 598 6.59 6808.53 2800 12350 .489 437 4.21 475 4.81 515 5.48 553 6.17 595 7.05 673 8.95 3000 13230 .560 447 4.84 482 5.42 518 6.08 557 6.78 593 7.56 669 9.47 3200 14110 .638 456 5.54 491 6.14 524 6.78 558 7.50 595 8.29 664 10.1 3400 15000 .721 471 6.38 502 6.93 535 7.59 564 8.29 596 9.04 662 10.8 3600 15880 .810 482 7.32 515 7.87 544 8.50 573 9.26 604 9.95 666 11.7 3800 16760 .900 555 9.53 582 10.2 609 11.0 669 12.7 4000 17640 1.000 593 11.4 618 12.1 673 13.8 APPENDIX 319 TABLE XX. No. 6 NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. X" S. P. H" S. P. K" s. P. W a d pi S. P. H" S. P. H" s. P. a P. d H 6 i4 PJ S B 0, rt S d a d d W a 1 4 1 d tf 1 W 1000 5250 .063 193 .37 242 .59 1100 5770 .076 192 .42 238 .63 1200 6300 .090 193 .48 238 .67 278 .93 1300 6820 .106 197 .54 235 .73 275 .98 312 1.27 1400 7350 .122 200 .62 237 .81 274 1.05 308 1.33 344 1.66 1500 7870 .141 205 .72 238 .91 272 1.13 307 1.41 340 1.72 372 2.08 1600 8400 .160 210 .82 240 1.01 274 1.23 305 1.49 337 1.81 367 2.15 1700 8920 .180 215 .95 245 .13 275 1.35 304 1.60 335 1.91 363 2.25 1800 9450 .202 222 1.09 250 .26 277 1.49 305 1.73 334 2.02 362 2.36 1900 9970 .225 228 .24 255 .42 280 1.64 307 1.88 334 2.16 360 2.49 2000 10500 .250 235 .40 260 .59 285 1.82 309 2.06 334 2.33 3602.63 2100 11030 .275 242 .57 265 .79 290 2.00 312 2.24 335 2.52 360 2.82 2200 11550 .302 248 .75 272 1.98 295 2.20 317 2.43 339 2.72 362 3.04 2300 12070 .330 257 .96 279 2.21 300 2.43 322 2.66 342 2.94 363 3.23 2400 12600 .360 263 2.18 285 2.45 305 2.68 325 2.92 345 3.19 367 3.48 2500 13120 .390 272 2.41 291 2.67 312 2.96 330 3.18 350 3.45 370 3.74 2600 13650 .422 280 2.68 299 2.96 317 3.22 337 3.50 355 3.74 374 4.07 2800 14700 .489 295 3.24 312 3.55 330 3.85 347 4.14 365 4.39 384 4.68 3000 15750 .560 312 3.96 329 4.18 344 4.57 360 4.86 377 5.15 390 5.44 3200 16790 .638 359 5.33 373 5.69 390 6.01 405 6.34 3400 17850 .721 403 6.98 417 7.35 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1"S. P. 1K"S.P. 1K"S.P. 1H" S. P. 2" S.P. 2W S. P. a d tf d W a d tf d W a d tf d W a d tf d W a d d W B d ri d a 1300 6820 .106 410 2.31 1400 7350 .122 405.2.37 460 3.18 513 4.00 1500 7870 .141 400 2.46 457 3.24 509 4.14 555 5.00 1600 8400 .160 397 2.54 452 3.36 504 4.25 550 5.15 595 6.12 1700 8920 .180 3922.62 447 3.44 499 4.36 544 5.26 589 6.30 6728.50 1800 9450 .202 389 2.73 442 3.56 492 4.47 539 5.40 584 6.45 6658.64 1900 9970 .225 387 2.85 439 3.67 489 4.57 534 5.55 579 6.59 659 8.78 2000 10500 .250 3853.00 437 3.82 485 4.68 529 5.69 572 6.73 652 8.96 2100 11030 .275 385 3.16 434 3.96 480 4.86 525 5.83 567 6.91 649 9.14 2200 11550 .302 384 3.35 432 4.11 477 5.00 520 5.98 564 7.06 644 9.32 2300 12070 .330 3853.57 430 4.32 475 5.18 517 6.16 5607.24 63519.50 2400 12600 .360 387 3.82 430 4.50 474 5.40 514 6.37 554 7.42 632 9.72 2500 13120 .390 389 4.10 430 4.79 472 5.62 512 6.55 552 7.63 627 9.94 2600 13650 .422 392 4.36 432 5.04 470 5.87 510 6.81 549 7.85 624|10.2 2800 14700 .489 400 5.00 435 5.73 .472 6.52 507 7.34 545 8.39 617 10.7 3000 15750 .560 410 5.76 442 6.45 475 7.24 510 8.06 544 9.00 614 11.3 3200 16790 .638 419 6.59 450 7.31 480 8.06 5128.93 5459.86 609 12.0 3400 17850 .721 432 7.60 460 8.24 490 9.04 517 9.86 547 10.8 607 12.8 3600 18900 .810 442 8.71 472 9.36 499 10.1 525 11.0 554 11.9 610 13.9 3800 19950 .900 509 11.3 534 12.2 559 13.1 614'15.1 4000 21000 1.000 544 13.5 567 14.4 617 16.4 320 HEATING AND VENTILATION TABLE XXI. No. 7 NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. K" s. P. H" S. P. H" S. P. H" S. P. H" S. P. K" S. P. a a ft w a a ft W a s ft W d S a o. P4 S a ci ft W 1000 7140 .063 166 .51 207 .80 1100 7860 .076 164 .57 204 .85 1200 8570 .090 166 .65 204 .92 239 1.26 1300 9290 .106 169 .74 202 1.00 236 1.34 267 1.73 1400 10000 .122 172 .35 203 1.10 234 1.43 264 1.81 294 2.26 1500 10720 .141 176 .98 204 1.24 233 1.53 263 1.91 292 2.34 319 2.83 1600 11430 .160 180 1.12 206 1.37 234 1.68 262 2.03 289 2.46 314 2.93 1700 12150 .180 184 1.29 210 1.54 236 1.83 260 2.18 287 2.60 312 3.07 1800 12860 .202 190 1.49 214 1.72 237 2.02 262 2.36 286 2.75 310 3.21 1900 13570 .225 196 1.68 219 1.93 240 2.23 263 2.56 286 2.95 309 3.39 2000 14290 .250 202 1.90 223 2.17 244 2.47 264 2.80 286 3.18 309 3.58 2100 15000 .275 207 2.13 227 2.44 249 2.73 267 3.05 287 3.43 309 3.84 2200 15720 .302 213 2.38 233 2.70 253 3.00 272 3.31 290 3.70 310 4.13 2300 16430 .330 220 2.67 239 3.01 257 3.31 276 3.63 293 4.00 312 4.40 2400 17150 .360 226 2.97 244j3.33 262 3.64 279 3.97 296 4.34 314 4.73 2500 17860 .390 233 3.27 250 3.64 267 4.03 283 4.33 300 4.70 317 5.10 2600 18580 .422 240 3.64 256 4.03 272 4.39 289 4.77 304 5.10 320 5.54 2800 20000 .489 253 4.41 267 4.83 283 5.24 297 5.64 313 5.98 329 6.37 3000 21430 .560 267 5.39 282 5.68 294 6.22 309 6.62 323 7.01 334 7.40 3200 22860 .638 307 7.25 320 7.74 334 8.18 347 8.62 3400 24290 .721 346 9.51 357 10.0 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1" S. P. WS.P. IK" S. P. l?i" S. P. 2" S. P. 2K"S.P. a d, ft W a o< * ft W a p< P4 ft W a d ti ft W a d ft W a P. S 1300 9290 .106 352 3.14 1400 10000 .122 347 3.23 394 4.33 440 5.44 1500 10720 .141 343 3.35 392 4.41 436 5.64 476 6.81 1600 11430 .160 340 3.46 387 4.58 432 5.78 472 7.01 510 8.33 1700 12150 .180 336 3.57 383 4.68 427 5.93 466 7.15 504 8.58 576 11.6 1800 12860 .202 333 3.72 379 4.85 422 6.08 462 7.35 500 8.77 570 11.8 1900 13570 .225 332 3.88 376 5.00 419 6.22 457 7.55 496 8.97 564 12.0 2000 14290 .250 330 4.08 374 5.19 416 6.37 453 7.74 490 9.16 559 12.2 2100 15000 .275 330 4.30 372 5.39 412 6.62 450 7.94 486 9.41 556 12.5 2200 15720 .302 329 4.56 370 5.59 409 6.81 446 8.13 483 9.60 552 12.7 2300 16430 .330 330 4.86 369 5.88 407 7.06 443 8.38 480 9.85 544 12.9 2400 17150 .360 332 5.19 369 6.13 406 7.35 440 8.67 474 10.1 542 13.2 2500 17860 .390 333 5.59 369 6.52 404 7.64 439 8.92 473 10.4 537 13.5 2600 18580 .422 336 5.93 370 6.86 40317.99 437 9.26 470 10.7 534 13.8 2800 20000 .489 343 6.81 373 7.79 404 8.87 434 10.0 467 11.4 529 14.5 3000 21430 .560 352 7.84 379 8.77 407 9.85 437 11.0 466 12.3 526 15.3 3200 22860 .638 359 8.97 386 9.95 412 11.0 439 12.2 467 13.4 522 16.3 3400 24290 .721 370 10.3 394 11.2 420 12.3 443 13.4 469 14.7 520 17.4 3600 25720 .810 379 11.9 404 12.7 427 13.8 450 15.0 474 16.1 523 18.9 3800 27150 .900 436 15.4 457 16.6 479 17.8 526 20.5 4000 28580 1.000 466 18.4 486 19.6 529 22.4 APPENDIX 321 TABLE XXII. No. 8 NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. K" S. P. H" S. P. M" s. P. X" S. P. W S. P. %"S.P. a a ft w a P. ' a W a d e4 S i a w i a w a a a B 1000 9330 .063 145 .67 181 1.04 1100 10270 .076 144 .74 179 1.11 1200 11200 .090 145 .85 179 1.20 209 1.65 1300 12130 .106 148 .96 176 1.31 206 1.75 234 2.25 1400 13060 .122 150 1.11 178 1.44 205 1.87 231 2.36 258 2.95 1500 14000 .141 154 1.27 179 1.61 204 2.00 230 2.50 255 3.06 279 3.69 1600 14930 .160 158 1.47 180 1.79 205 2.19 229 2.66 253 3.21 275 3.82 1700 15860 .180 161 1.69 184 2.01 206 2.39 228 2.85 251 3.39 273 4.01 1800 16800 .202 166 1.94 1882.25 208 2.64 229 3.08 250 3.59 271 4.19 1900 17730 .225 1712.20 19l'2.52 210 2.91 230 3.34 250 3.85 270 4.42 2000 18660 .250 176 2.48 1952.83 214 3.23 231 3.66 250 4.15 270 4.68 2100 19600 .275 181 2.79 199,3.18 218 3.56 234 3.98 251 4.48 270 5.02 2200 20530 .302 186 3.11 204 3.53 221 3.92 238 4.33 254 4.83 271 5.40 2300 21460 .330 193 3.48 209 3.93 225 4.33 241 4.74 256 5.22 273 5.75 2400 22400 .360 198 3.87 214 4.35 229 4.76 244 5.19 259 5.67 275 6.18 2500 23330 .390 204 4.28 219 4.75 234 5.26 248 5.65 263 6.13 278 6.66 2600 24260 .422 210 4.76 224 5.26 238 5.73 253 6.23 266 6.66 280 7.23 2800 26130 .489 221 5.76 234 6.31 248 6.85 260 7.36 274 7.81 288 8.32 3000 28000 .560 234 7.04 246 7.42 258 8.13 270 8.64 283 9.15 293 9.66 3200 29860 .638 269 9.47 280 10.1 293 10.7 304 11.3 3400 31720 .721 303 12.4 313 13.1 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1" S. P. WS.P. 1M" S.P. IX" S. P. 2" S. P. 2M"S.P. a ft tf ft a a a a P3 ft B a d P3 a B a 4 oj a B a a tf a B 1300 12130 .106 308 4.10 1400 13060 .122 3044.22 345 5.65 385 7.10 1500 14000 .141 300 4.37 343 5.76 381 7.36 416 8.90 1600 14930 .160 298 4.51 339 5.98 378 7.55 413 9.15 446 10.9 1700 15860 .180 294 4.66 335 6.11 374)7.74 408 9 . 34 441 11.2 504 15.1 1800 16800 .202 291 4.86 331 6.33 369 7.94 404 9.60 438 11.5 499 15.4 1900 17730 .225 290 5.06 329 6.53 366 8.13 400 9.86 434 11.7 494 15.6 2000 18660 .250 289 ! 5.33 328; 6. 78 3648.32 396 10.1 429 12.0 489 15.9 2100 19600 .275 289 5.61 325 7.04 360 8.64 394 10.4 425 12.3 486 16.3 2200 20530 .302 288 5.96 324 7.30 358 8.90 390 10.6 423 12.6 483 16.6 2300 21460 .330 289' 6. 35 323 7.68 356! 9. 22 388 11.0 420 12.9 476 16.9 2400 22400 .360 290 6.78 323 8.00 355 9.60 38511.3 415 13.2 474 17.3 2500 23330 .390 291 7.30 323 8.51 354 9.98 384 11.7 414 13.6 470 17.7 2600 24260 .422 294 7.74 324 8.96 353 10.4 383 12.1 411 14.0 468 18.1 2800 26130 .489 300 8.90 326 10.2 354 11.6 380 13.1 409 14.9 463 19.0 3000 28000 .560 308 10.2 331 11.5 356 12.9 383 14.3 408 16.0 460 20.0 3200 29860 .638 314 11.7 338 13.0 360 14.3 384 15.9 409 17.5 456 21.3 3400 31720 .721 324 13.5 345 14.7 368 16.1 388 17.5 410 19.1 455 22.8 3600 33590 .810 331 15.5 354 16.6 374 18.0 394 19.6 415 21.1 458 24.7 3800 35460 .900 381 20.2 400 21.6 419 23.3 460 26.8 4000 37330 1.000 408 24.1 425 25.6 463 29.2 322 HEATING AND VENTILATION TABLE XXIII. No. 9 NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. W S. P. H" S. P. Yz" S. P. W S. P. H" S. P. K"S.P. a a ft W a d rt S a 1 ft w a & ft K a ft PS W a d tf ft W 1000 11810 .063 129 .84 161 1.32 1100 12990 .076 128 .94 159 1.41 1200 14170 .090 129 1.07 159 1.52 186 2.09 1300 15360 .106 131 1.22 157 1.65 183 2.21 208 2.85 1400 16530 .122 133 1.40 158 1.82 182 2.37 206 2.99 229 3.74 1500 17720 .141 137 1.61 159 2.04 181 2.54 205 3.16 227 3.87 248 4.67 1600 18900 .160 140 1.86 160 2.27 182 2.77 203 3.36 225 4.07 244 4.84 1700 20080 .180 143 2.14 163 2.54 183 3.03 202 3.60 223 4.29 242 5.07 1800 21250 .202 148 2.45 167 2.84 185 3.35 203 3.90 222 4.55 241 5.30 1900 22440 .225 152 2.78 170 3.19 187 3.69 205 4.23 222 4.87 240 5.60 2000 23620 .250 1573.14 173 3.58 190 4.08 206 4.64 222 5.25 240 5.92 2100 24800 .275 161 3.52 177 4.03 193 4.51 208 5.04 223 5.67 240 6.35 2200 25980 .302 166 3.93 181 4.47 197 4.96 211 5.47 226 6.10 241 6.83 2300 27160 .330 171 4.41 186 4.97 200 5.48 215 6.00 228 6.61 242 7.27 2400 28340 .360 176 4.90 190 5.50 203 6.02 217 6.56 230 7.18 244 7.82 2500 29520 .390 181 5.41 195 6.01 208 6.66 220 7.15 233 7.76 247 8.43 2600 30710 .422 187 6.02 199 6.66 211 7.25 224 7.88 237 8.42 249 9.15 2800 33070 .489 197 7.28 208 7.98 220 8.67 231 9.30 243 9.88 256 10.5 3000 35430 .560 208 8.91 219 9.40 229 10.3 240 10.9 251 11.6 260 12.2 3200 37790 .638 239 12.0 249 12.8 260 13.5 270 14.3 3400 40150 .721 269 15.7 278 16.5 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1" S. P. W S. P. 1M"S.P. WS.P. 2" S. P. 2H" S. P. a a ft W a P. ft W a a ri ft W a a PS ft W a d PJ ft W a a ft W 1300 15360 .106 273 5.18 1400 16530 .122 270 5.34 307 7.15 342 8.99 1500 17720 .141 267 5.53 304 7.29 339 9.31 370 11.3 1600 18900 .160 264 5.71 301 7.57 336 9.56 367 11.6 397 13.8 1700 20080 .180 261 5.90 298 7.73 332 9.80 362 11.8 392 14.2 448 19.1 1800 21250 .202 259 6.15 294 8.01 328 10.0 359 12.2 389 14.5 443 19.4 1900 22440 .225 258 6.41 292 8.26 326 10.3 356 12.5 386 14.8 439 19.8 2000 23620 .250 257 6.74 291 8.59 323 10.5 352 12.8 381 15.2 435 20.2 2100 24800 .275 257 7.10 289 8.91. 320 10.9 350 13.1 378 15.6 432 20.6 2200 25980 .302 256 7.54 288 9.23 318 11.3 347 13.4 376 15.9 429 21.0 2300 27160 .330 257 8.04 2879.72 317S11.7 344 13.7 373 16.3 423 21.4 2400 28340 .360 258 8.59 287 10.1 316 12.2 342 14.3 369 16.7 421 21.9 2500 29520 .390 259 9.23 287 10.8 314 12.6 341 14.8 368 17.2 418 22.4 2600 30710 .422 261 9.80 288:11.3 313 13.2 340 15.3 366 17 .7 416 22.8 2800 33070 .489 267 11.3 290 12.9 314 14.7 338 16.5 363 18.9 411 24.0 3000 35430 .560 273 13.0 294 14.5 317 16.3 340 18.2 362 20.3 409 25.4 3200 37790 .638 279 14.8 300 16.4 320 18.1 341 20.1 363 22.2 406 27.0 3400 40150 .721 288 17.1 307 18.6 327 20.3 344 22.2 364 24.2 405 28.8 3600 42510 .810 294 19.6 314 21.1 332 22.8 350 24.8 369 26.7 407 31.3 3800 44880 .900 339 25.5 356 27.4 372! 29. 5 409 33.9 4000 47240 1.000 362 30.5 378 32.4 411 36.9 APPENDIX 323 TABLE XXIV. No. 10 NIAGARA CONOIDAL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. W S. P. H" S. P. H" S. P. "S.P. W s. P. w s. P. a 4 a d tf d H a d PJ d W a d tf d W a d PJ d W S d PS d a 1000 14580 .063 116 .04 145 1.63 1100 16040 .076 115 .16 143 1.74 1200 17500 .090 116 .32 143 1.87 167 2.58 1300 18960 .106 118 .50 141 2.04 165 2.73 187 3.52 1400 20410 .122 120 .73 142 2.25 164 2.92 185 3.69 206 4.61 1500 21870 .141 123 1.99 143 2.52 163 3.13 184 3.90 204 4.78 223 5.77 1600 23330 .160 126 2.29 144 2.80 164 3.42 183 4.15 202 5.02 220 5.97 1700 24790 .180 129 2.64 147 3.14 165 3.74 182 4.45 201 5.30 218 6.26 1800 26240 .202 133 3.03 150 3.51 166 4.13 183 4.81 200 5.61 217 6.55 1900 27700 .225 137 3.43 153 3.94 168 4.55 184 5.22 200 6.01 216 6.91 2000 29160 .250 141 3.88 156 4.42 171 5.04 185 5.72 200 6.48 216 7.31 2100 30620 .275 145 4.35 159 4.97 174 5.56 187 6.22 201 7.00 216 7.84 2200 32080 .302 149 4.85 163 5.51 177 6.12 190 6.76 203 7.54 217 8.43 2300 33540 .330 154 5.44 1676.14 1806.76 193 7.40 205 8.16 218 8.98 2400 34990 .360 158 6.05 171 6.79 183 7.43 195 8.10 207 8.86 220 9.65 2500 36450 .390 163 6.68 175 7.42 187 8.22 198 8.83 210 9.58 222 10.4 2600 37910 .422 168 7.43 179 8.22 190 8.95 202 9.73 213 10.4 224 11.3 2800 40830 .489 177 8.99 187 9.85 198 10.7 208 11.5 219 12.2 230 13.0 3000 43740 .560 187 11.0 197 11.6 206 12.7 216 13.5 226 14.3 234 15.1 3200 46660 .638 215 14.8 224 15.8 234 16.7 243 17.6 3400 49570 .721 242 19.4 250 20.4 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1" S. P. WS.P. iy 2 " s. P. WS.P. 2" S. P. 2M" S. P. a d ri d W a d tf d M a d P5 d W a d PJ d W a 3 d W a d pj d B 1300 18960 .106 246 6.40 1400 20410 .122 243 6.59 276 8.83 30811.1 1500 21870 .141 240 6.83 274 9.00 305 11.5 333 13.9 1600 23330 .160 238 7.05 271 9.34 302 11.8 330 14.3 357 17.0 1700 24790 .180 235 7.28 268)9.54 299 12.1 326 14.6 353 17.5 403 23.6 1800 26240 .202 233 7.59 265 9.89 295 12.4 323 15.0 350 17.9 399 24.0 1900 27700 .225 232 7.91 263 10.2 293 12.7 320 15.4 347 18.3 395 24.4 2000 29160 .250 231 8.32 262 10.6 291 13.0 317 15.8 343 18.7 39l|24.9 2100 30620 .275 231 8.77 260 11.0 288 13.5 315 16.2 340 19.2 389 25.4 2200 32080 .302 230 9.31 259 11.4 286 13.9 312 16.6 338 19.6 386 25.9 2300 33540 .330 231 9.92 258 12.0 28514.4 310 17.1 336 20.1 38126.4 2400 34990 .360 232 10.6 258 12.5 284 15.0 308 17.7 332 20.6 379 27.0 2500 36450 .390 233 11.4 258 13.3 283 15.6 307 18.2 331 21.2 376 27.6 2600 37910 .422 235 12.1 259 14.0 282 16.3 306 18.9 329 21.8 374 28.2 2800 40830 .489 240 13.9 261 15.9 283 18.1 304 20.4 327 23.3 370 29.6 3000 43740 .560 246 16.0 265 17.9 285 20.1 306 22.4 326 25.0 368 31.3 3200 46660 .638 251 18.3 270 20.3 288! 22. 4 307 24.8 327 27.4 365 33.3 3400 49570 .721 259 21.1 276 22.9 294 25.1 310 27.4 328 29.9 364 35.6 3600 52490 .810 265 24.2 283 26.0 299 28.1 315 30.6 332 32.9 366 38.6 3800 55400 .900 305 31.5 320 33.8 335 36.4 368 41.8 4000 58320 1.000 326 37.6 340 40.0 370 45.6 324 HEATING AND VENTILATION TABLE XXV. No. 11 NIAGARA CONOID AL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. K"S.P. W S. P. W S. P. M"S.P. w s. P. %"S.P. a a H s a ft 8 ft n a ft M ft H a A a W 8 ft A S a 0. H S 1000 17640 .063 106 1.26 132 1.97 1100 19410 .076 105 1.40 130 2.11 1200 21170 .090 106 1.60 130 2.26 152 3.12 1300 22930 .106 107 1.82 128 2.47 150 3.30 170 4.26 1400 24700 .122 109 2.09 129 2.72 149 3.53 168 4.47 187(5.58 1500 26460 .141 112 2.41 130 3.05 148 3.79 167 4.72 186 5.78 203 6.98 1600 28230 .160 115 2.77 131 3.39 149 4.14 166 5.02 184 6.08 200 7.22 1700 29990 .180 1173.20 134 3.80 150 4.53 166 5.39 1836.41 1987.68 1800 31750 .202 121 3.67 136 4.25 151 5.00 166 5.82 182 6.79 197 7.93 1900 33520 .225 125 4.15 139 4.77 153 5.51 167 6.32 182 7.27 196 8.36 2000 35280 .250 128 4.70 142 5.35 156 6.10 168 6.92 182 7.84 1968.85 2100 37050 .275 132 5.26 145 6.01 158 6.73 170 7.53 183 8.87 196 9.49 2200 38810 .302 136 5.87 148 6.67 161 7.41 173 8.18 185 9.12 197 10.2 2300 40580 .330 140 6.58 152 7.43 164 8.18 176 8.95 186 9.87 198 10.9 2400 42340 .360 144 7.32 156 8.22 166 8.99 177 9.80 188 10.7 200 11.7 2500 44100 .390 148 8.08 159 8.98 170 9.95 180 10.7 191 11.6 202 12.6 2600 45870 .422 153 8.99 163 9.95 173 10.8 184 11.8 194 12.6 204 13.7 2800 49400 .489 161 10.9 170 11.9 180 13.0 189 13.9 199 14.8 209 15.7 3000 52910 .560 170 13.3 179 14.0 187 15.4 196 16.3 206 17.3 213 18.3 3200 56450 .638 196 17.9 204 19.1 213 20.2 221 21.3 3400 59980 .721 220 23.5 227 24.7 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1" S. P. 1K"S.P. W S. P. W S. P. 2" S. P. 2K" S. P. a A rt ft W a A rt ft W a d ft W a A H ft W a o< S a ft ft 1300 22930 .106 224 7.74 1400 24700 .122 221 7.97 251 10.7 280 13.4 1500 26460 .141 218 8.26 249 10.9 277 13.9 303 16.8 1600 28230 .160 216 8.53 246 11.3 275 14.3 300 17.3 325 20.6 1700 29990 .180 214 8.81 244 11.6 272 14.7 296 17.7 321 21.2 366 28.6 1800 31750 .202 212 9.18 241 12.0 268 15.0 294 18.2 318 21.7 363 29.0 1900 33520 .225 211 9.57 239 12.4 266 15.4 291 18.6 316 22.2 359 29.5 2000 35280 .250 210 10.1 238 12.8 265 15.7 288 19.1 312 22.6 356 30.1 2100 37050 .275 210 10.6 236 13.3 262 16.3 286 19.6 309 23.2 354 30.7 2200 38810 .302 209 11.3 236 13.8 260 16.8 284 20.1 307 23.7 351 31.3 2300 40580 .330 210 12.0 235 14.5 259 17.4 282 20.7 306 24.3 346 32.0 2400 42340 .360 211 12.8 235 15.1 258 18.2 280 21.4 302 24.9 345 32.7 2500 44100 .390 212 13.8 235 16.1 257 18.9 279 22.0 301 25.7 342 33.4 2600 45870 .422 214 14.6 236 17.0 256 19.7 278 22.9 299 26.4 340 34.1 2800 49400 .489 218 16.8 237 19.2 257 21.9 276 24.7 297 28.2 336 35.8 3000 52910 .560 224 19.4 241 21.7 259 24.3 278 27.1 296 30.3 335 37.9 3200 56450 .638 228 22.1 246 24.6 262 27.1 279 30.0 297 33.2 332 40.3 3400 59980 .721 236 25.5 251 27.7 267 30.4 282 33.2 248 36.2 331 43.1 3600 63510 .810 241 29.3 257 31.5 272 34.0 286 37.0 302 39.8 333 46.7 3800 67030 .900 277 38.1 291 40.9 305 44.1 335 50.6 4000 70560 1.000 296 45.5 309 48.4 336 55.2 APPENDIX 325 TABLE XXVI. No. 12 NIAGARA CONOID AL FAN (TYPE N) CAPACITIES AND STATIC PRESSURES AT 70F. AND 29.92 INCHES BAROMETER Outlet velocity, ft. per min. Capacity, cu. ft. air per rain. Add for total press. K" S. P. w s. P. H" S. P. W S. P. H"S.P. K" S. P. a d pi d a a d pi d H a d ft w a d rt ft a a d tf ft w a d rf ft a 1000 21000 .063 97 1.50 121 2.35 1100 23090 .076 96 1.67 119 2.51 1200 25190 .090 97 1.90 119 2.69 139 3.72 1300 27290 .106 98 2.16 118 2.94 138 3.93 156 5.07 1400 29390 .122 100 2.49 118 3.24 137 4.21 154 5.31 172 6.64 1500 31490 .141 103 2.87 119 3.63 136 4.51 153 5.62 170 6.88 186 8.31 1600 33600 .160 105 3.30 120 4.03 137 4.93 153 5.98 168 7.23 183 8.60 1700 35690 .180 1083.80 123J4.52 1385.39 152 6.41 168 7.63 1829.02 1800 37790 .202 111 4.36 12515.06 1385.95 153 6.93 167 8.08 18119.43 | 1900 39890 .225 114 4.94 1285.67 1406.55 153 7.52 167 8.66 1809.95 2000 41990 .250 1185.59 130 6.37 14317.26 154 8.24 167 9.33 180 10.5 2100 44090 .275 121 6.27 133 7.16 145 8.01 156 8.96 168 10.1 180 11.3 2200 46190 .302 124 6.99 136 7.94 148 8.81 158 9.74 169 10.9 181 12.2 2300 48290 .330 1287.83 1398.84 150!9.74 161 10.7 171 11.8 182 12.9 2400 50390 .360 132 8.71 143 9.78 153 10.7 163 11.7 173 12.8 183 13.9 2500 52490 .390 136 9.62 146 10.7 156 11.8 165 12.7 175 13.8 185 15.0 2600 54590 422 140 10.7 149 11.8 158:12.9 168 14.0 178 15.0 187 16.3 2800 58790 .'489 148 13.0 156 14.2 165 15.4 173 16.6 183 17.6 192 18.7 3000. 62980 .560 156 15.9 164 16.7 172 18.3 180 19.5 188 20.6 195 21.8 3200 67180 .638 179 21.3 187 22.8 195 24.1 203 25.4 3400 71380 .721 202 27.9 208 29.4 Outlet velocity, ft. per min. Capacity, cu. ft. air per min. Add for total press. 1"S. P. W'S. P. 1H"S. P. 1H"S. P. 2" S. P. 2K" S. P. a d P3 ft a a d tf ft a a d pi ft a a ft pi ft a a d ft a a d d a 1300 27290 .106 205 9.22 1400 29390 .122 2039.49 230 12.7 257jl6.0 1500 31490 .141 200 9.84 228 13.0 254 16.6 278 20.0 1600 33600 .160 198 10.2 226 13.5 252 17.0 275 20.6 298 24.5 1700 35690 .180 196 10.5 223 13.7 249 17.4 272 21.0 294 25.2 33634.0 1800 37790 .202 194 10.9 221 14.3 246 17.9 269 21.6 292 25.8 333 34.6 1900 39890 .225 193 11.4 219 14.7 244 18.3 267 22.2 289 26.4 329 35.1 2000 41990 .250 193 12.0 218 15.3 243 18.7 264 22.8 286 26.9 326J35.9 2100 44090 .275 193 12.6 217 15.8 240 19.5 263 23.3 283 27.7 324 36.6 2200 46190 .302 192 13.4 216 16.4 238 20.0 260 23.9 282 28.2 322 37.3 2300 48290 .330 193 14.3 215 17.3 238'20.7 258 24.6 280 29.0 31838.0 2400 50390 .360 193 15.3 215 18.0 237 21.6 257 25.5 277 29.7 316 38.9 2500 52490 .390 194 16.4 215 19.2 236 22.5 256 26.2 276 30.5 313 39.8 2600 54590 .422 196 17.4 216 20.2 235 23.5 255 27.2 274 31.4 312 40.6 2800 58790 .489 200 20.0 21822.9 236 26.1 253 29.4 273 33.6 308 42.6 3000 62980 .560 205 23.0 221 25.8 238 29.0 255 32.3 272 36.0 307 45.1 3200 67180 .638 209 26.4 225 29.2 240|32.3 256 35.7 273 39.5 304 48.0 3400 71380 .721 216 30.4 230 33.0 245 36.2 258 39.5 273 43.1 303 51.3 3600 75580 .810 221 34.9 236 37.5 249 40.5 263 44.1 277 47.4 305 55.6 3800 79780 .900 254 45.4 267 48.7 279 52.4 307 60.2 4000 83980 1.000 272 54.2 283 57.6 308 65.7 I INDEX Absolute temperature, 4 zero, 4 Adiabatic saturation, 199, 200 Air and its properties, 196-205 Air, composition of, 196 conditioning, 202, 203, 274-282 cooling, 279-282 distribution, 211, 218, 219 -ducts, 239-252 flow of, in ducts, 239-252 friction of, in ducts, 239-252 infiltration of, 19, 20 -line system, 118 ; 119 motion, 211, 212, 213 pollution, 207, 208 properties of, 196-205 psychrometric chart for, 201, 202, 299-301 specific heat of, 205 supply, 208 measurement of, 209, 210 tables, 203, 204 total heat of, 199 -valves, 137, 138 venting, 149, 150 -washers, 274-282 Air-line system, 118, 119 valves, 138 Anemometer, 243 Anthracite coal, 92, 93, 97 Argon, 196 Ash, 96 Atmospheric system, 119, 122, 123 B Back pressure valve, 166 Bacteria, 215, 218 Bituminous coal, 92, 93, 96 Body, heat loss from the, 23 Boilers, 92-112 cast-iron, 98, 99 connections to, 156, 157 downdraft, 101, 102 firebox, 100 magazine feed, 103, 104 marine type, 100 proportions of, 104, 105 rating of, 105-108 return tubular, 99 round, 98, 99 sectional, 98, 99 smokeless, 101-103 steel, 99-101 types of, 98-101 water tube, 101 Boot, 41, 42 British thermal unit, 5 Calorific value of coal, 92, 94 Carbon dioxide, 95, 196, 197, 207, 208, 218, 219 monoxide, 95 Carbonic acid gas. See Carbon dioxide. Centigrade scale, 2 Central heating, 283-294 Centrifugal fan. See Fans. Check valve, 132 Chimneys, 110, 111 Church heating, 231-233 Clinker, 96 COa. See Carbon dioxide. Coal, 92-94 analysis of, 93, 94 composition of, 93, 94 consumption, 234, 235 sizes of, 93 327 328 INDEX Coefficients of heat transmission through walls, 13-18, 295- 298 from radiators, 77, 78 Coke, 94, 95 Cold-air pipe, 39, 40 Combustion, 95 Comfort chart, 216, 219 Comfort zone, 212, 213 Conduction, 9, 10 Conductivity, 10 specific, 10 Conduit, for pipes, 287-289 Contractor's guarantee, 81-83 Convection, 9, 10, 74-76 factor, 13, 14 Cooling, 279-282 Cost of heating, 234, 235 I) Dalton's law of gases, 198 Damper, 227 regulator, 109 De-humidification, 281, 282 Dewpoint, 198, 201 Diaphragm expansion joint, 290 Dirt pocket, 153 Disc fan, 263 District heating, 293, 294 Downdraft furnace, 101, 102 Draft, 110-112 Drainage, of pipes, 146 Drip connections, 149, 150 Dry return system, 116 Dust, 215, 218 Dynamic head, 239 E Economy of heating systems, 32, 33 Equivalent evaporation, 105 Estimating of heating requirements, 234, 235 Expansion fittings, 289, 290 of pipes, 145, 146, 148 tank, 173, 174 Exposure, factors for, 22 Factory heating, 230, 231 Fahrenheit scale, 2 Fan heaters, 263-271 systems, 32, 224-273 arrangement of, 226 design of, 237-273 types of, 32 Fans, centrifugal, blades and hous- ings, 254, 255 disc, 263 efficiency of, 256 laws of, '256 power required by, 255, 256 straight blade, 256, 257 tables, 259-261, 302-325 theory of, 253, 254 Fittings, flanged, 130, 131 screwed, 129, 130 Flanges, 131 Flow of air. See Air. Flues, foul-air, 46 Forced circulation hot-water heat- ing, 184-188 Friction, of air in pipes, 239-252 of fluids in pipes, 157, 158 Fuels, 92-95, 96 comparison of, 96, 97 Furnace, boiler, 97, 101-103 heating, 26, 34-48 hot-air, 27, 35-38 pipeless, 34 G Gage, 109 Gaskets, 131, 132 Gate valve, 132 Generator, 183, 184 Glass, heat transmission of, 18 Globe valve, 132 Grate surface, 106, 107 Grates, 25, 101 Guarantee, checking of, 81-83 Heat, 1-8 definition of, 1 INDEX 329 Heat, flow of, 1 given off by persons, 23 loss of, from a body, 9 from buildings, 9-24 calculation of,. 21, 22 coefficients of, 13-18, 295- 298 from underground pipes, 289 measurement of, 1, 4, 5 of superheat, 50 of the liquid, 50, 51 of vaporization, 50, 51 specific, 5, 6 total, 52 transmission from radiators, 67- 78, 87, 88 unit of, 4, 5 Heaters for fan systems, 263-271 friction in, 268-270 installation of, 271 pipe coil, 264, 265 vento, 263, 264, 265, 266-269 hot-water, 112 Heating, cost of, 234, 235 different methods of, 25-33 direct, 25, 28 fan systems of, 30, 31 furnace, 26 hot water, 28 indirect, 25, 30 of auditoriums, 231-233 of factories, 230 of office buildings, 225, 226 of schools, 226, 228, 229 of theatres, 231-233 steam required for, 234, 235, 236 systems, classification of, 32 economy of, 32, 33 hot-water, 28, 29, 168-188 losses in, 32, 33 steam, 28, 113-126 Horsepower, boiler, 105 Hot-air furnace heating, 27, 34-48 pipes, 39-^6 Hot-blaFt system, 224, 225 Hot-water heaters, 112 systems, 28, 168-188, 287 Humidification, 39, 221, 276. See also Air conditioning. Humidifier, 39, 221 Humidifying efficiency, 280 Humidity, absolute, 198, 199 Humidity, control of, 278, 279 measurement of, 200, 201 relative, 198, 199 standards of, 211, 212, 214 See also Air conditioning. Infiltration, 19, 20 Intermittent heating, 21, 22 Joule's equivalent, 8 K k, values of, 18 L Latent heat, 50, 51 Leaders, 40-44 M Mercury seal generator, 183, 184 Metering, 294 Mixing damper, 227 Mixtures of substances, 54-58 Moisture, in air. See Water vapor and Humidity. N Neon, 196 Nitrogen, 196, 207 O Odors, 214, 215, 218 Office buildings, ventilation of, 225, 226 330 INDEX One-pipe systems. See Single-pipe systems. Overhead system, steam, 117, 118, 144 water, 174, 175 Oxygen, 196, 207 Ozone, 196, 220 Partial pressures, law of, 198 Petterson and Palmquist apparatus, 197 Pipe, 127-129 coil heaters. See Heaters. coils, 156 covering, 134-136 dimensions of, 128 expansion of, 145, 146 fittings, 129-131 flanges, 131 hangers, 150, 151 Pipe, threads, 129 Pipes, hot-air, 39-46 size of, for steam, 159-164 water, 177-183, 185-188 Piping, for hot water systems, 183 steam, 143-167 Pitot tube, 240, 241 Plenum chamber, 227 Power plants, 165, 166 Pressure drop in steam pipes, 157- 159 gage, 109 Proximate analysis of coal, 93, 94 Psychrometer, 201 Psychrometric chart, 201, 202, 299- 301 formula, 200 Pumpage, 185 Pumps, circulating, 188 vacuum, 125 Pyrometer, 3 R Radiation, definition, 9 transmission of heat by, 9, 67-78 Radiators, 61-91 cast-iron, 61-64 classification of, 61 connections to, 154, 155, 163, 164 effect of enclosing, 71, 72 of length, 68, 69 of painting, 70 of shape, 68, 69 of width, 68, 69 heat transmission from, 67-78, 87,88 heating surface of, 64 indirect, 83-89 location of, 78-80 * , ' pipe, 67 pressed metal, 65, 66, 78, 79 semi-indirect, 89, 90 tappings, 65 wall type, 64, 65 Reducing valve, 141 Registers, 41, 42, 45 Regulation of temperature, 189-195 Relief system, 115 Retarder, 121 Return piping, 152, 164 Risers, 149, 151 hot-air, 40, 44, 45 Safety valve, 108, 109 Saturation, adiabatic, 200 School buildings, 226, 228, 229 Separator, 140, 141 Single-duct system, 226, 228, 248- 251 -pipe systems, steam, 113-115, 143 water, 175 Sling psychrometer, 201 Slip joint, 290 Smoke, 95, 96 Smokeless furnaces, 101-104 Specific heat, definition, 4 of substances, 6 of water, 298 of air, 205 INDEX 331 Split system, 224 Stacks, 110, 111 Static efficiency, 256 head, 239 Steam boilers. See Boilers. consumption of, 234-236 flow of, in pipes, 157-159 formation of, 49 -heating systems, 113-126 piping, 143-167 properties of, 49-60 table, 52, 53 saturated, 49, 50 superheated, 49 Stefan's law, 10 Stoves, 26 Synthetic air chart, 215-220 Tapping of radiators, 65 Temperature, absolute, 4 Temperature, colors, 4 control of, 189-195 definition of, 1 gradient, 14 inside, 18, 19 measurement of, 2-4 standards of, 211, 212 Theatres, heating of, 231-233 Thermodynamics, first law of, 8 Thermometer, 2, 3 wet- and dry-bulb, 199-201 Thermostatic control, 189-195 of fan systems, 272 Total efficiency, 256 heat, 52 Traps, bucket, 138 ; 139 float, 138, 139 radiator, 120, 121 thermostatic, 120, 121 tilting, 139, 140 Trunk duct system, 225, 226, 251, 252 Tunnels, 291, 292 Two-pipe systems, steam, 115-117 water, 172-174 U Underground piping, 287-290 Unions, 129, 130 Unit of heat, 5 Unit ventilator, 233, 234 Unwin's coefficient, 157-159 Vacuum pump, 125 system, 125, 126, 144, 152, 153 Valves, air-, 137, 138 air-line, 138 back-pressure, 166 check, 132 gate, 132 globe, 132 location of, 153, 154 Valves, radiator, 122, 123, 133 reducing, 141 Vapor, 50 system, 119-122, 123-125, 144, 152, 153 water. See Water vapor. Vaporization, heat of, 50 Velocity head, 239 Ventilation, 30-32, 206-223 heat required for, 20, 21 methods of, 30, 31, 221, 222 of auditoriums, 231-233 of schools, 226, 228, 229 of theatres, 231-233 requirements, 206, 207 tests, 215-220. See also Fan systems. Vento heaters. See Heaters. Volatile matter, 92, 94 W Walls, coefficients of heat trans- mission through, 13-18 flow of heat through, 12-17 Water column, 108, 109 pan, 39 specific heat of, 298 thermal properties of, 298 vapor, 197, 198. See also Hu- midity. 332 INDEX Wet- and dry-bulb thermometer, Wolpert method of CO 2 determina- 200, 201 tion, 197 -bulb temperature, 200 Wood casing, 288 -return system, 116, 117 Windows, air leakage through, 20 heat loss through, 18, 298 Zero, absolute, 4 THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. 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