UNIVERSITY OF CALIFORNIA ANDREW SMITH HALLIDIL: COMPEND OF Mechanical Refrigeration A COMPREHENSIVE DIGEST OF APPLIED ENERGETICS AND THERMODYNAMICS FOR THE PRAC- TICAL USE OF Ice Manufacturers, Cold Storage Men, Contractors, Engineers, Brewers, Packers and Others Interested in the Application of Refrigeration. FIFTH EDITION. BY J. E. SIEBEL, Director Zymotectinic Institute, Chicago, CHICAGO : H. S. RICH & Co. 1903. = : Entered according to act of Congress by H. S. RICH & CO., In the office of the Librarian of Congress at Washington, D. CT 1895, 1896, 1899, 1902 and 1903. All rights of translation reserved. PRESS OP ICE AND REFRIGERATION CHICAGO. PREFACE. WHILE in the third, fourth and fifth editions of the Compend the general arrangements of matter and the manner of treatment remain the same as in the first and second editions, it is nevertheless an entirely new book. Not only that the contents of the fifth edition covers nearly one hundred and fifty pages more than they did in the first edition, but also much of the former matter has been entirely rewritten and nearly every topic has received valuable additions. This will be especially noticed in the practical chap- ters on the "Compressor and Its Attachments,'' "Ice and Distilled Water Making," "Cold Storage," "Piping of Rooms," "Insulation and Heat Leakage," "Brewery Refrigeration," "Absorption Machine," "Management and Testing of Machines," etc. On "Liquefied Air, Its Pro- duction and Uses," and on "The Carbonic Acid Machine" entirely new chapters have been added. The cold storage temperature taWes and storage rates have again been thor- oughly revised, and many important tables and many prac- tical examples on various topics have been added to the book; and although it now covers over four hundred pages, it nevertheless retains its convenient shape, equally well adapted for pocket and table use. Special attention has been given to the preparation of the table of contents, and more particularly to the topical index, which contains some fifteen hundred refer- ences, so that whatever has been said in the book on any subject can be readily found under every possible appella- tion. Again, the hints and suggestions kindly offered by the engineering fraternity have been duly utilized in the present edition. Still many imperfections must neces- sarily remain, and for this reason the author solicits such further communications and criticism as may tend to render the work of the greatest possible utility to the profession. 116770 PREFACE TO FIRST EDITION. THE object for which this book has been compiled is a two-fold one. In the first place it is intended to pre- sent in a convenient form those rules, tables and formulae which are frequently needed by the refrigerating en- gineer. In the second place it is an attempt to present the subject in a simple yet systematic manner, so as to enable the beginner to acquire a more or less thorough insight into the matter and to understand the technical terms used in publications on the subject. This course has been suggested or rather prompted by constant inquiries addressed to the publishers, and in order to best subserve this purpose the different para- graphs and chapters have been framed in such a man- ner, that while each paragraph may be consulted for the individual information which it contains, the whole forms a continuous chain of reading matter calculated to digest the entire subject of Energetics and Thermodynam- ics and their application to mechanical refrigeration. Instead of making the futile attempt to describe the decorative details of the endless varieties of machines and appliances, the author has aimed to discuss the vari- ous methods of refrigeration and applications thereof for different purposes in such a manner as to enable every engineer, operator and owner of a plant to thoroughly understand all the vital points in the working of his machinery and in the handling of goods for cold storage, in the making of ice, in the refrigeration of breweries, packing houses, etc. In this way it is thought that the familiar questions as to temperatures, say of brine and storage rooms, as to what a machine is able to do under given conditions, 01 PREFACE. what it might be made to do under others, as to the proper dimensions of different parts, and most other problems relating to the operation of refrigerating works, can be readily answered by turning to a paragraph or a table, and in cases of greater accuracy by doing some plain figuring. The different amounts of space allotted to the differ- ent systems of refrigeration must not be construed into argument for or against the merits of one or the other system. The author is not interested in any one system in particular, and if his intention to be strictly impartial is not actually carried out in every respect, his judgment rather than his impartiality should be impeached. As regards the mathematical treatment of the sub- ject, it had to be strictly elementary and without the use of diagrams to subserve the desired purpose of a book for ready reference. In presenting the subject on this basis it has been the special object of the author to have the formula as plain and simple as they could be made with- out making an undue sacrifice in regard to accuracy. This is especially the case with all the formulas relating to ammonia refrigeration, which subject, like some others, has been treated altogether on the basis of articles pub- lished by the author in Ice and Refrigeration. In order to further enhance the usefulness of the book, and in forced recognition of the fact that many practical machinists have an aversion to even the sim- plest kind of a formula, a separate appendix has been devoted to the numerical solution of a number of varied examples, which it is thought will suffice to demonstrate that the formulae in these chapters can be handled by any one versed in the simplest forms of common figuring. Independent of the strictly practical issues, and in pursuance of the stated objects of the Compend, it has been sought to give so much of an elementary discussion of the terms and definitions of the science of energetics and of thermodynamics in particular, that its perusal will suffice to understandingly master the technical terms in PREFACE. treatises on refrigeration and kindred topics in Ice and Refrigeration and other publications. In this attempt those definitions and concepts which are of more recent coinage and which have not as yet been generally accepted in text books, have for this reason received rather more attention in these pages than their direct relation to the main subject would seem to call for at first sight. To those who possess the required practical and the- oretical knowledge, the book will doubtless prove a wel- come companion, as it contains in a very convenient form a prolific array of useful and indispensable tables, and a number of rules which are not usually committed to memory. Aside from the works quoted in Appendix III. the author is indebted to many of the ice machine building fraternity for much of the information here presented, and he may also be allowed to mention in this direction the valuable contributions to Ice and Refrigeration by Wood, Denton, Jacobs, Linde, Sorge, Starr, Eichmond, St. Clair, Post, Rossi, Kilbourn, Burns and others. There naturally must be many imperfections and shortcomings connected with an attempt like this, and special pains have been taken to draw attention to them in the body of the book, and any further suggestions or hints in this direction by those using the same will be thankfully received by its author with a view to further improve and perfect the contents of this publication. TABLE OF CONTENTS. PART I. GENERAL ENERGETICS. CHAPTER I.-MATTER. "MATTER General Properties of Matter, Constitution, Atoms, Molecules, Solid, Liquid, Gaseous Matter 5 Body, Mass, Unit of Mass, Mass and.Weight,iMeasurement of Space, Density, Specific Weights.: 6 Fundamental Units, Derived Units, C. G. S. Units 6 CHAPTER II. MOTION, FORCE. MOTION. Force, Measurement of Force, Dyne, Gravitation, Molecular Forces, Cohesion (table) 7 Adhesion, Chemical Affinity, Work, Unit of Work, Foot-Pound, Time, Power, Horse-Power, Velocity, Momentum 8 Inertia, Laws of Motion, Statics, Dynamics or Kinetics 9 CHAPTER III. ENERGY. ENERGY. Visible Energy, Kinetic Energy,Potential Energy, Molecular Energy 9 C. G. S. Unit of Energy, the Erg, the Dyne Centimeter, Con- servation of Energy, Transformation of Energy 10 Physics, Subdivision of Physics, Dissipation of Energy, Energy of a Moving Body, Mechanisms 10 CHAPTER IV HEAT. HEAT. Sources of Heat; Ether, RadiantJHeat and Light 11 Temperature, Thermometer, Thermometer Scales 12 Comparison of Thermometer Scales (table ) 13 Measuring High Temperatures 14 Absolute Zero, Unit of Heat H C. G. S. Unit of Heat, Capacity for Heat, Specific Heat 1& Tables on Specific Heat of Solids, Liquids and Water at Dif- ferent Temperatures - 16-16 Use of Specific Heat, Determination of Specific Heat, Tem- perature of Mixtures 16 Expansion by Heat of Solids (table), of Liquids IT Expansion of Water and Liquids (tables), Transfer of Heat.. 18 Insulators (table) 19 Conduction of Heat, Conductivity of Metals, Radiation of Heat, Theory of Heat Transfers, Absorption of Heat 20 Convection of Heat, Complicated Transfer, Convection 23 Comparative Absorption and Radiation (table) 25 Condensation of Steam in Pipes, Heat Emitted (tables) . . .24-2&-26 Non-conductive Coating for Steam Pipes (tables) 23-24 Cooling of Water in Pipes (tables) 24-25 Transmission of Heat through Plates from Water to Water and Steam to Water (tables) 27-28 Condensation in Pipes Surrounded by Water, Transmission of Heat through Pipes (tables) 29-30 Latent Heat, Latent Heat of Fusion (tables), Effect of Pres- sure on Melting Point, Latent Heat of Solution 31 Frigorific Mixtures (table ) . 32 lii TABLE OP CONTENTS, HEAT BY CHEMICAL, COMBINATION. Elementary Bodies, Chemical Atoms, Molecules., .* '.-. 33-34 Chemical Symbols, Atomicity, Tables of Properties of Ele- ments, Generation of Heat. , .' .33-34 Measure of Affinity, Total Heat Developed, Maximum Prin- ciple, Expressions for Heat Developed, Heat of Combina- tion with Oxygen ( table ) , 35 COMBUSTION. Air Required in Combustion, Gaseous Prod- ucts.. ; .^. i 36-37 Heat Generated, Coal, Coke, Lignite 38 Chimney and Grate ' % 39 Heat by Mechanical Mean's , <.'...:.... 3 CHAPTER v. FLUIDS, GASES, VAPORS. FLUIDS IN GENERAL. Viscosity, Pascal's Law, Buoyancy of Liquids, Archimedean Principle, Specific Gravity De- termination, Hydrometers 40 Comparison of Hydrometers, Specific Gravity, Twaddle, Baume" and Beck (tables), Pressure of Liquids 41 Water Pressure, Surface Tension of Liquids, Velocity of Flow 42 Flow of Water in Pipes, Flow through Pipes, Head of Water, . Water Power, Hydrostatics and Dynamics 45 CONSTITUTION OF GASES. Pressure and Temperature, Boyle's Law, Mariotte's Law, St. Charles Law, Unit of Pressure, Absolute and Gauge Pressure ........ 44 Comparison of British and Metrical Barometer, Action of Vacuum, Mano-Meters, Gauges, Weight of Gases..., 45 Mixture of Gases, Dalton's Law, Buoyancy of Gases, Lique- faction of Gases, Heat of. Compression, Critical Tempera- ture, Critical Pressure, Critical Volume ; & Table of Critical Data, Specific Heat of Gases (table) 47 Isothermal Changes, Adiabatic 'Changes, Free Expansion, * Latent Heat of Expansion, Volume and Pressure 48 Perfect Gas, Absolute Zero Again, Velocity of Sound Friction of Gas in Pipes, Absorption of Gases 49-50 VAPORS. Saturated Vapor, Dry or Superheated Vapor, Wet Vapor, Tension of Vapors ; . . ; 50 Vaporization, Ebullition, Boiling Point, Variation of Boiling Points, Retardation of Boiling, Latent Heat of Vaporiza- tion ... . ......'... 51 Befrigerating Effects, Liquefaction ' of Vapors, Distilling, Condensation,, Compression, Dalton's Law for Vapors, Vapors from Mixed Liquids, Sublimation, Dissociation. . . . 52 .CHAPTER VI. MOLECULAR DYNAMICS. MOLECULAR KINETICS. Rectilinear Motion of Molecules, Temperature of Gases, Pressure of Gases, Avogrado's Law ....; 63 Velocity of Molecules in Gases, Internal Friction, Total Heat Energy of Molecules.... 54 Law of Gay Lussac, Expansion of Gases, Volume and Tem- perature ...., ,. . 56 EQUATION FOR GASEOUS BODIES Equation for Perfect Gases, Connecting Volume, Pressure and Temperature.. . . 55 Van der Waal's Universal Equation for Gases : 5ft Critical Condition, of Gases, Critical Data ,. . . .66-51 Application of Universal Equation, Molecular Dimensions... 58-59 Absolute Boiling Point, Capillary Attraction, Gas and Vapor, Liq-uef action of Gases 60 CHAPTER VII. THERMODYNAMICS. THERMODYNAMICS.-First Law of Thermodynamics, Sec- ond Law of Thermodynamics, Equivalent Units, Mechan- ical Equivalent of Heat ( J), Second'Law Qualified 61 TABLE OP CONTENTS. ill Conversion of Heat into Work, Continuous Conversion, Work- ing Substance. Working Medium, Molecular Transforma- tion of Heat into Work, Work Done by Gas Expanding against Resistance, Vacuum, Heat Energy of Gas Mixtures 62 Dissipation of Energy, Adiabatic Changes, Adiabatic Com- pression, Adiabatic Expansion, Reversible Changes or Conversions, Isothermal Changes, Isothermal Compression 63 Maximum Conversion, Continuous Conversion, Passage of Heat, Its Ability to Do Work (Proportional to Differences in Temperature) . ., 64 Requirements for Continuous Conversion, Working Medium, Boiler or Generator, Refrigerator or Condenser, Compen- sation for Lifting Heat . .64-to Components of Heat Changes, Internal and External Work/ . Maximum Continuous Conversion of Heat 65 CYCLE OF OPERATIONS. Reversible Cycle, Ideal Cycle.... 66 Ideal Cycles Have the Same and the Maximum Efficiency 66 Influence of Working Fluid, Rate of Convertibility of Heat, Carnot's Cycle. 67 Synopsis of Proof of Second Law 67-68 Efficiency of Ideal Cycle, Description of Carnot's Cycle 68-69 Heat Engines, Available Effect of Heat 70 Consequences of Second Law, Absolute Zero of Temperature.70-7l Ideal Refrigerating Machine, Efficiency and Fall of Heat.... 71-72 COMPENSATED TRANSFER OF HEAT. Uncompensated Transfer, Entropy, Latent and Free Energy 72- Future Condition of Universe, Changes of Entropy 73 Increase of Entropy, Origin of Heat Energy 74 SPECIFIC HEAT OF GASES. -At Constant Volume, at Con- stant Pressure, Components of Specific Heat of Gases.. 75-76 AIR THERMOMETER. Thermodynamic Scale 76 Heat, Weight, Entropy, Thermodynamic Function, Carnot's Function, the Constant of the Gas Equation (R ) 77 Isentropic Changes, Latent Heat and Entropy , ,.' 77 CHAPTER VIII. MODERN ENERGETICS. NATURE OF MASS. System of Energetics, New Definition of Energy, Classification of Energy, Mechanical Energy, Heat, Electric and Magnetic Energy, Chemical or Internal Energy, Radiated Energy 78 Mechanical Energy, Kinetic Energy, Energy of Space, Energy of Distance ( force ), Energy of Surface, Energy of Volume . 78 Factors of Energy, Intensity Factor, Capacity Factor, Applied to Various Forces of Energy, Dimensions of Energy 79 The Intensity Principle, Compensation of Intensities, Differ- ences of Intensities, Regulative Principle of Energy, Maxi- mum Amount of Transformation, State of Equilibrium.. 80 Artificial and Natural'.Transf ers, Artificial Equilibrium, Dissi- pation of Energy, Radiant Energy 81 Transformation of Energy, Reversible Changes, Irreversible Changes, Perpetual Motion of First and Second Order, Con- servative System 82 Continuous Conversion of Energy, Maximum Convertibility, Intensity of Principle, Criterion of Changes 83 Justification of Modern Concepts, Uniform Units of Energy, Change of Absolute Zero , 84 PART II. PRACTICAL APPLICATION. CHAPTER I. REFRIGERATION IN GENERAL. MEANS FOR PRODUCING REFRIGERATION. Classifica- tion of Methods, Air Machines, Windhausen Machine 85 IV TABLE OF CONTENTS. Freezing Mixtures, Ice Machines, Construction of Machines, Vaporization, Vacuum and Absorption Machines 86 Continuous Absorption Machine, the Compression Machine Cycle of Operation , 87 AMMONIA MACHINES, Qualifications of Ammonia for Refrigerating Purposes, Perfect Compression System, the Reversible Cycle of Operations, Work to Lift Heat 88 Formula Expressing Work, Defect in Cycle, Choice of Circu- lating Medium, Discussion of Essential Qualities of Differ- ent Refrigerating Liquids ( table) ...*..,., 89 Comparison of Ammonia, Sulphurous Acid and Carbonic Acid for Refrigeration, Size of Ice Making Machines, Ex- pressions for Capacity, Refrigerating and Ice Making Capacity, Various Uses of 'Refrigeration 89-90 CHAPTER II. PROPERTIES OF AMMONIA. FORMS OF AMMONIA. Anhydrous Ammonia, Composition and Decomposition of Same, Compressibility and Com- bustibility, Non-Explosiveness of Ammonia 91 Handling of Drums Containing Ammonia, Suffocating Proper- ties of Same, Pressure and Temperature of Saturated Ammonia, Vapor Density of Amnionia and Volume of Vapor, Specific Heat -of Liquid and of Vapor (Negative Specific Heat) .:............... 92 Specific Volume of Liquid Ammonia, Latent Heat of Evapora- tion, External Heat, Weight of Ammonia Liquid and Vapor. 93 Woo&s Table for Properties of Saturated Ammonia Vapor. T . . '94 Van der Wall's Formula Applied to Ammonia, Values for Pressure of Saturated Ammonia by this Formula 95 Superheated Amnionia Vapor, Formulae for Superheated Vapor, Relation of Volume, Temperature arid Pressure. .96-97 AMMONIA LIQUOR. Strengths of Solution of Ammonia (table), Showing Specific Gravity and Degrees Baume 97 Siaar'* Table, Showing Relations between 'Pressure and Tem- perature of Ammonia Solutions of Different Strengths.. 98-99 Explanation of Baume" Scales or Hydrometers, Saturated Solution of Ammonia, Tables Showing Percentage of Am- monia in Saturated Solution at Different Temperatures, 100 -101 Heat Generated by the Absorption of Ammonia, Formula for Calculating the Same .101-102 Sim's Table, Showing the Solubility of Ammonia in Water at Different Pressures and Temperatures 102 Tests for Ammonia, Boiling Point Test, Nessler's Reagent, Different Systems of Ammonia Refrigeration 103-104 CHAPTER III. WATER, STEAM, ETC. PROPERTIES OF WATER. Composition, Formation of Ice, Freezing Point Depressed by Pressure. Properties of Ice, Steam, Volume of Steam, Pressure of Saturated Steam. .. 105 Total Heat in Steam, Latent Heat of Vaporization, Externaf Latent Heat, Internal Latent Heat, Specific Heat of Water and of Steam, Negative Specific Heat of Steam, Specific Heat of Ice, Specific Volume of Steam 106-107 Table Showing Properties of Saturated Steam 107 Volume and Weight of Water at Different Temperatures 108 PRODUCTION OF STEAM. Work Done by Steam, Heating Area of Boiler, Priming 108 Amount of Priming, Flow of Steam through Pipes 109 HYGROMETRY. Air Saturated with Moisture, Hygrometric State of Atmosphere, Absolute Moisture, Dew Point, Determination of Moisture, Wet and Dry Bulb Thermo- meter........ 110 Maximum Tension of Aqueous Vapor, Table Showing Tension of Vapor, Drying Air, Vaporization of Water into Air.. 11 1-113 Purity of Water. 113 TABLE OF CONTENTS. V CHAPTER IV. THE AMMONIA COMPRESSION SYSTEM. GENERAL FEATURES. The System a Cycle, the Compressor. 114 Refrigerating Effect of the Circulating Medium in General and of Ammonia in Particular : ...115 Work of Compressor per Pound of Ammonia Circulated 115 Heat to Toe Removed in the Condenser, Amount of Superheat- ing, Counteracting Superheating, Amount of Ammonia Required to Prevent Superheating 116 Net Theoretical Refrigerating Effect of One Pound of Am- monia, Volume of Compressor, Cubic Capacity of Com- pressor (per Minute), Clearance of Compressor 117 Formula for Clearance, Refrigerating Capacity of Compressor in Tons of Refrigeration and in Thermal Units 118 Ammonia Passing the Compressor, Net Refrigerating Ca- pacity 119 Horse Power of Compressor, Size of Compressor for a Given Refrigerating Duty. 119 Reduced Refrigerating Duty, Revolutions and Piston Area 120 Useful and Lost Work of Compressor, Determination of Lost Work, Indirect Determination of Actual Work 120-121 Horse Power of Compressor Engine, Water Evaporated in Boiler, Coal Required . 121-122 Efficiency of Compressor : 122 DIFFERENT KINDS OF COMPRESSORS.-The Linde Com- pressor . 123 The De La Vergne Compressor, the Water Jacket Compressor 124 Tables Showing the Relation between the Volume of Ammonia Gas Passing the System and the Theoretical Refrigeration under Different Back and Condenser Pressures 124-125 The St. Glair Compound Compressor, Amount of Water for Counteracting Superheating 125 The By-Pass, the Oil Trap ]26 THE CONDENSER. Submerged Condenser, Amount of Con- denser. Surf ace, Empirical Rules and Formulae 126-127 Amount of Cooling Water, Rule and Empirical Formulas, Economizing Cooling Water 128 Device for Economizing Cooling Water, Using Same for Boiler Feeding, Open Air Condenser, Pipe Required for Same 129 Empirical Rule for Piping, Water Required, Condenser Pressure, Liquid Receiver 130 Dimensions of Condenser, Forecooler, Purge Valve, Duplex Oil Trap, Wet and Dry Compression 131-133 Expansion Valve, Expansion of Ammonia, Direct and Indirect Expansion, Size of Expansion Coils, Piping Rooms, Usual Pipe Sizes, Circumstance Governing Amount of Pipe ... 134-135 Transmission of Heat or Refrigeration through Pipes, Discus- sion of the Problems Involved, Practical Rules for Piping. 135 Scope of Rules for Piping, Comparative Dimensions of Pipe.. I3tf Brine System, Size and Amount of Pipes in Brine Tank, Pipe for Brine Circulation, General Empirical Rule, Rule for Laying Pipes, Table for Equalizing Pipes 137-138 Table Showing Capacity of Single- Acting Pumps 139 The Brine Pump, Preparation of Brine, Table Showing Prop- erties of Solutions of Salt, Strength of Brine 140 Rules for Calculating Strength of Brine, Points Governing Strength of Brine 141 Salometer and Substitutes for Same, Table Showing Specific Gravity of Salt Solutions and Corresponding Hydrometer Degrees, Chloride of Calcium for Brine Preparation Table Showing Properties of Chloride of Calcium in Solutipn. 142 Brine Circulation vs. Direct Expansion, the Dryer Liquid Tra P- 142-14? Vi . TABLE OF CONTENTS. CHAPTER V. ICE MAKING AND STORING. SYSTEMS OF ICE MAKING.-Can and Plate System, Ice Making Capacity of Plant, Size of Cans in Can System, Temperature for Freezing 144 Dimensions of Ice Making Tanks (table) 145 Time for Freezing, Amount of Pipe in Freezing Tank 146 Arrangement of Brine Tank, Size of Brine Tank 14T The Brine Agitator, Harvesting Can Ice, Hot Well 148 Comparison of Plate and Can System, Size of Plates, Time for Freezing, Harvesting Plate Ice, Storage of Artificial Ice.. 149 Ice for Storage, Construction of Storage Houses for Ice, Ante- Room in Ice Storage House, Equivalent of Ton of Ice in Cubic Feet, Refrigerating Ice Houses, Rule for Same ...... 150 Packing Ice, Withdrawal and Shipping Ice, Selling of Ice.. 151-152 Weight and Volume of Ice, Cost of Ice, Coal for Making Ice v 153-155 Skating Rinks, Quality of Ice ; 156 WATER FOR MAKING ICE. Requirements of Same, Clear Ice, Boiling and Filtration of Water \ : ...... 157 Distilled Water, Cooling Water Required in Distillation, Size of Condenser, Discussion of Rules on Amount of Con- densing Surf ace, Filtration of Water 158 Re boiling and Filtering Distilled Water, Cooling the Distilled Water, Storage Tank 159 Intermediate Filter, Dimensions of Distilling Plant, Dimen- sions of a Ten-ton Distilling Plant, Dimensions of a Thirty-ton Distilling Plant 160 Skimmer, Brine Circulation, Arrangem ent of Plant 161 Defects of Ice, White or Milky Ice, White Core. Red Core, Taste and Flavor of Ice, Use of Boneblack and Fil- tration 162-164 Number of Filters, Rotten Ice, Purity of Water Test 165-166 Devices for Making Clear Ice, the Cell System, Remuner- abilityof Artificial Ice Making 167 CHAPTER VI. COLD STORAGE. COLD STORAGE. Storage Rooms, Their Construction and Size, Construction of Wood 168 Construction of Brick and Tiles, and Other Constructions.. 169-173 REFRIGERATION REQUIRED for Storage Rooms Expressed in Units per Cubic Foot : . . fi& Piping Cold Storage Rooms, Refrigeration Required Found by Calculation, Radiation through Walls, Transmission of Heat through Walls (tables) 174-182 REFRIGERATION OF GOODS for Cold Storage, Calculation of Amount, Specific Heat of Victuals (table)......., 182 Calculation of Specific Heat of Victuals, Freezing Goods in Cold Storage, Refrigeration Required 183 Conditions Obtaining in Cold Storage, Ventilation, Moisture, Dry Air for Cold Storage, Forced Circulation 184-188 COLD STORAGE TEMPERATURES. Storing Fruits, Table Showing Best Temperature for Different Fruits 188 Storing Vegetables, Onions, Pears, Lemons, Grapes, Apples, Liquors, etc 189-192 Storing Fish and Oysters (table), Freezing Fish, Storage of Butter, Cheese, Milk, Eggs and Similar Products 193-195 Miscellaneous Goods (Table of Storage Temperatures), Ven- tilation of Rooms, Lowest Cold Storage Temperatures 196 CHAPTER VII. BREWERY REFRIGERATION. OBJECTS OF BREWERY REFRIGERATION. Cooling Wort, Removal of Heat of Fermentation, Storage of Beer. Rough Estimate of Refrigeration, Specific Heat of Wort (table).. 197 TABLE OF CONTENTS. vii\ PROCESS OP COOLING WORT. Cooling Vat, Tubular Cooler, Refrigeration Required for Cooling Wort, Simple Rule for Calculation of Same 198 Size of Machine for Wort Cooling, Increased Efficiency of Ma- chine in Wort Cooling 199 HEAT PRODUCED BY . FERMENTATION. Calculation of Heat of Fermentation in Breweries, Simple Rule for Same 200 Refrigeration for Storage Rooms Expressed in Units per Cubic Foot and per Square Foot of Walls, Closer Calculations.. . 201 Different Saccharometers, Table of Comparison of Them 202 Cooling Brine and Sweet Water, Total Refrigeration, Distri- bution of Fermentation, Dimensions of Wort Cooler 203 Direct Expansion Wort Cooler , 204 Piping of Rooms in the Brewery, Amount Required, Temper- ature of Rooms, Heat of Fermentation Allowed for 204-206 REFRIGERATION FOR ALE BREWERIES. Amount Re- quired for Wort Cooling and for Storage, etc. Rule for Piping ..206-207 Attemperators, Chilling of Beer, Brewery Site, Storage of Hops.. 207-210 Refrigeration in Malt Houses, Actual Refrigerating Installa- tion in Breweries of Different Capacities 211 CHAPTER VIII. REFRIGERATION FOR PACKING HOUSES, ETC. AMOUNT OF REFRIGERATION REQUIRED. Theoretical Calculation of Same, Practical Rules for Same (Units per Cubic Foot), Calculation per Number of Animals, Freez- ing of Meaf . 212 Other Methods of Calculating Required Refrigeration, Rules for Piping of Rooms (Cubic Feet per Foot of Pipe) 213 Storage Temperatures for Meat (table), Official Views on Meat Storage, Freezing, etc. 214 Best Way of Freezing Meat, Circulation of Air in Rooms, Ship- ping Meat, Bone Stink, Defrosting Meat, etc 215-217 Refrigeration in Oil Works, Oleomargarine, Stearin and India Rubber Works,- Dairy Refrigeration, Refrigeration for Glue Works, Skating Rinks, etc 218-220 Refrigeration in Chemical Works 220-321 Concentration of Sulphuric Acid by Cold, Decomposition of Salt Cake, Pipe Line Refrigeration, Refrigeration and En- gineering ..., 221 CHAPTER IX. THE ABSORPTION SYSTEM. CYCLE OF.OPERATIONS.-A Compound Cycle, Application of First Law to Same, Equation of Absorption Cycle 222 Working Conditions of System, Heat Added in Refrigeration. 223 Heat Introduced by Pump, Amount of Rich Liquor to be Cir- culated ; 224 STRENGTH OF RICH AND POOR LIQUOR. Heat Removed in Condenser, Heat. Removed in Absorber 225 Heat of Absorption, Formula to Calculate Same, Table Show- ing Same, Heat Introduced by Poor Liquor 225-226 Negative Heat Introduced by Vapor, Heat Required in Gener- ator, Work by Pump, Anhydrous Ammonia Required.. .... 227 HORSE POWER OF AMMONIA PUMP. Amount of Con- denser Water Required, Water Required in Absorber 228 Economizing Water, Economizing Steam, Steam Required.. . 229 Actual and Theoretical Capacity, Heat Used in Still. 230 Expression of Efficiency, Comparable Efficiency of Compressor 231 CONSTRUCTION OF ABSORPTION MACHINE.-The Gener- ator, the Analyzer, Battery Generator, Size of Still, the Condenser ' 232-233 viii TABLE OF CONTENTS. The Rectifier, Liquid Receiver, etc., the Absorber, the Ex- changer 234-235 The Exchanger, the Heater, the Cooler, the Ammonia Pump, Miscellaneous Attachments , 236-237 Overhauling Plant. Compression vs. Absorption, Tabulated Dimensions 238-239 CHAPTER X. THE CARBONIC ACID MACHINE. General Considerations, Properties of Carbonic Acid Gas (table ),;.-. 240-241 Construction of Plant, Compressor, Stuffing Box, Glycerine Trap, Condenser, Evaporator, Safety Valve 242-243 Joints, Strength and Safety, Application of Machine, Effi- ciency of System 244-245 Comparisons of Efficiency, Practical Comparative Tests .. .246-247 CHAPTER XI.-OTHER COMPRESSION SYSTEMS. AVAILABLE REFRIGERATING FLUIDS. Table Showing Vapor Tension of Ether, Sulphur Dioxide/Methylic Ether, Carbonic Acid, Pictet Liquid and Ammonia 248 Methyl and Ethyl Chloride Machine 249 REFRIGERATION BY SULPHUR DIOXIDE. Properties of Sulphur Dioxide 24& Table of Properties of Saturated Sulphur Dioxide Gas, Useful Efficiency, Table of Comparison of Ammonia and Sulphur Dioxide Plant 250 ETHER MACHINES. Table Showing Properties of Saturated Vapor of Ether, Practical Efficiency of Ether Machines. 25 1-252 REFRIGERATION BY PICTET'S LIQUID. Table Showing Properties of Liquid, Anomalous Behavior of Pictet's Liquid, Explanations for the Anomaly 252-253 Bluemcke on Pictet's Liquid 253 Mottay and Rossi's System, Cryogene, Hydrocarbons as Re- frigerating Agents, Acetylene, Naphtha, Chimogene, etc.. 264 CHAPTER XII. AIR AND VACUUM MACHINES. COMPRESSED AIR MACHINE. Cycle of Operations, Work of Compression of Air 255 Temperature of Air after Compression, Cooling of Air after Compression, Amount of Water Required, Work Done by Expansion 256 Temperature after Expansion, Refrigeration Produced, Work for Lifting Heat, Equation of Cycle 257 Efficiency of Cycle, Size of Cylinders, Actual Efficiency 258 Experiments Showing Actual Performance on Cold Air Ma- chines (table) 359 Work Required for Isothermal Compression, Work Done in Isothermal Expansion, Other Uses of Compressed Air, Table Showing Friction by Compressed Air in Pipes 260 Calculated Efficiency of Compression Air Machine, Limited Usefulness 261 VACUUM MACHINES. - Refrigeration Produced by Them, Efficiency and Size 261-263 Compound Vacuum Machine, Expense of Operating, Objec- tions to Sulphurous Acid, Southby's Vacuum Machine.. 262-263 Southby's Vacuum Machine, Operating Same 284 CHAPTER XIII. LIQUEFACTION OF GASES. Historical Points, Self-intensifying Refrigeration 265 Linde's Simple Method, the Rationale of Linde's Device.... 266-267 Variable Efficiency, Hampson's Device, Other Methods 268 Tripler's Invention 269 TABLE OP CONTENTS. IX Uses of Liquid Air 270-271 Tabulated Properties of Gases 272 CHAPTER XIV. MANAGEMENT OF COMPRESSION PLANT. INSTALLATION OF COMPRESSION PLANT. Proving of Machine, Pumping a Vacuum, Charging the Plant 273 Charging by Degrees, Operation of Plant, Detection of Leaks, Amount of Ammonia Required, Waste of Ammonia 275 Ammonia in Case of Fire... 276 Condenser and Back Pressure in Different Cases 277 Table Showing Efficiency of Plant under Different Conditions. 278 Permanent Gases in Plant, Freezing Back 279 Origin of Permanent Gases, Clearance, Valve Lift 280 Packing Pistons, Pounding Pumps, etc., Cleaning Coils, etc.. . 281 Insulation, Lubrication, etc 282 CHAPTER XV. MANAGEMENT OF ABSORPTION PLANT. Management and Installation of Plant, Ammonia Required, Charging of Plant ; 283-284 Recharging Absorption Plant, Charging with Strong Liquor and Anhydrous Ammonia 285 Permanent Gases in Plant 286 Corrosion of Coils, Kinds of Aqua Ammonia '. . . . . 287 Leaks in Absorption Plant, Leak in Exchanger, Leak in Rec- tifying Pans, Strong Liquor Siphoned over 288-289 Tu.e "Boil-over," Cleaning the Absorber, Operating the Ab- sorber, Packing Ammonia Pump 290-292 Economizing Water, Operating Brine Tank, Leaks in Brine Tank... .293 Top and Bottom Feed Coils, Cleaning Brine Coils, Dripping Ceiling, Removing Ice from Coils, Cost of Refrigeration, Management of Other Plants 294-295 CHAPTER XVI. TESTING OF PLANT. Test of Plant, Fitting up for Test, Mercury Wells ,296 The Indicator Diagram, Maximum and Actual Capacity... 297-301 Commercial Capacity, Nominal Compressor Capacities (table), Actual Refrigerating Capacity 302 Friction of Compressor, Heat Removed in Condenser, Maxi- mum Theoretical Capacity, Correct Basis for Efficiency Calculation More Elaborate Test, Table Showing Data of Tests of Com- pression Plant. 304 Efficiency of Engine and Boiler, Test of Absorption Plant 305 Table Showing Results of Test, Estimate and Proposals 306 Contracts, How Made 307 Unit of Refrigerating Capacity, Test of Various Machines ... 308 APPENDIX L TABLES, ETC. Mensuration of Surfaces, Polygons 309 Properties of the Circle, Mensuration of Solids, Polyhedrons. 310 Table of Ammonia Gas ( Superheated Vapor) . . 311 Square Roots and Cubic Roots, 1-20. (table ) 312 Squares and Cubes and Roots, 1-100 (table) 313 Areas of Circles, Equivalents of Fractions of an Inch. . . . 314 Tables of Logarithms, 1-999 315-316 Rules for Logarithms '. 3^7 Tables of Weights and Measures, Troy Weight, Commercial Weight, Apothecaries' Weight, Long Measure . . 317 TABLE OF CONTENTS. Inches and Equivalents in Feet, Square or Land Measure, Cubic or Solid Measure, Liquid Measure, Dry. Measure.... 318 The Metric Measure, Measure of Length, of Liquids* Etc 319 Equivalents of French and English Measure 319 Specific Gravity and Weight of Materials (tables).......... 319-321 Cpntents of Cylinders, Table of Gallons 322 Comparison of Metric and United States Weights and Meas- ures, Comparison of Alcoholometers 323 Horse Power of Belting (table) .Horse Power of Shaftine (table) .7324 Capacity of Tanks in Barrels ( table) 325 Table of Converting Feet of Water into Pressure per Square' Inch, Table of Horse Power Required to Raise Water 32j5 Table Showing Loss of Pressure of Water, etc., while Run- ning through Pipes , ; , 327 Flow of Steam through Pipes, Horse Powers of Boilers 328 Tables Shoeing Properties of Saturated Ammonia ; 329-331 Humidity and Moisture in Air, Latent Heat of Fusion and Volatilization :.. ... 332 Cold Storage Rates .333-337 Description df Two-flue Boilers 337 Useful Numbers for Rapid Approximations 338 Weight of Castings , 338 Solubility of Gases in Water , .339 Dimensions of Double Extra Strong Pipe 339 Dimensions of Corliss Engines 340 Temperature of Different Localities '.341 Useful Data on Liquids, Measures, etc : .341-342 Table of Temperature, Fahr. and Cels 343 Specific Gravity Table (Baum) '.344 Table on Chloride of Calcium 345 Friction of Water in Pipes 346 Units of Energy (Comparison) 346-347 Mean Effective Steam Pressure .348-349 Relative Efficiency of Euel, Table on Tension of Water Vapor and on Boiling Points 350 Composition of. Water Constituents and Table on Grains and Grams, . . 351 APPENDIX II. PRACTICAL EXAMPLES. Introductory Remarks, Fortifying Ammonia Charge 358 Numerical Examples on Specific Heat, Evaporation Power of Coal, Capacity of Freezing Mixture, .-....- 854 Numerical Examples on Permanent Gases, Examples Show- ing Use of Gas Equation ....355 Work Required to Lift Heat, Refrigerating Effect of Sulphur- ous Acid, Refrigerating Capacity of a Compressor 356 Second Method of Calculation of Compressor Capacity, Third Method of Calculation, Cooling Beer Wort 857 Heat by Absorption of Ammonia. Water, Rich Liquor to be Circulated in Absorption Machine . ^ 358 Numerical Calculation of Capacity of Absorption Machine,, Heat and Steam Required for Same 359 Numerical Examples on Cold Storage, by Calculation, by an Appropriate Estimate 360 Calculation of Piping -Required , 361 Numerical Examples on Natural Gas with Reference to Re- frigerating Purposes, Temperature of Same after Expan- sion 36? TABLE OP CONTENTS. xi Refrigerating Capacity of Gas, Work Done by Expansion, Size of Expanding Engine . ^ 363 Expansion of the Gas without Doing Work, Refrigeration Ob- tainable by Expansion Alone, Calculation of Refrigerating Duty s 364-365 Calculating Ice Making Capacity, Volume of Carbonic Acid Gas < 366 Horse Power of Steam Engine 307 Calculation of Pump.. 368 Motive Power of Liquid Air 39 Moisture in Cold Storage 370 Carbonic Acid Machine 371 APPENDIX III. LITERATURE ON THERMODYNAMICS, ETC. a. Books. ... 372-373 b. Catalogues....;.... 374 TOPICAL INDEX 375-387 MECHANICAL REFRIGERATION. PART I. GENERAL ENERGETICS. CHAPTER I. MATTER. MATTER. Matter is everything which occupies space in three directions, and prevents other matter from occupying the same space at the same time. Matter is differen- tiated by its physical and chemical properties, color, hard- ness, weight, chemical changeability, etc. GENERAL PROPERTIES OF MATTER. The general properties of matter which are shared by all bodies are impenetrability, extension, divisibility, porosity, compressibility, elasticity, mobility and inertia. CONSTITUTION OF MATTER. To explain the different properties it is generally as- sumed that matter is ultimately composed of infinitely small particles called atoms, which aggregate or unite to form still infinitely small groups called molecules. At- tractive and repulsive forces acting between the atoms and molecules, and their respective motions are made to account for the various physical and chemical phenomena. SOLID MATTER. Matter is solid when the molecules possess a suffi- cient degree of immobility to insure the permanence of shape. LIQUID MATTER. If the molecules of a body are sufficiently movable to allow of its being shaped by the surrounding vessel, and if the same can be easily poured, it is called a liquid. GASEOUS MATTER. The gaseous state of matter is characterized by almost perfect freedom of motion of the molecules, an unlimited tendency to expand and a great compressibility. The term fluid covers both the liquid and the gaseous states. 6 MECHANICAL REFRIGERATION. BODY. A body is a limited amount of matter. MASS. Mass is the quantity of matter contained in a body. UNIT OF MASS. The unit of mass is the standard pound, which in the form of a piece of platinum is preserved by the gov- ernment. WEIGHT. Weight, or absolute weight, is the pressure of a body exerted on its support. The unit of weight is the force necessary to support one pound in vacuo, and it differs with the latitude, as the gravity or the earth's attraction. MASS AND WEIGHT. The relations between mass and weight are expressed by the equation in which M stands for mass, W for weight and g for the acceleration caused by the attraction of the earth. MEASUREMENT OF SPACE. The unit of measurement of space is the cubic foot and its subdivisions (see tables of weight and measures in appendix, etc). DENSITY. Equal amounts of matter do not necessarily occupy the same space; in other words, the density of different bodies is not the same . SPECIFIC WEIGHT. The relative density of different bodies is expressed by their specific gravity, which is the figure obtained when the weight of a body is divided by the weight of an equal volume of water. The specific weights used in the arts and industries are given in tables in Appendix 1. FUNDAMENTAL UNITS. The fundamental units of measurement are the units of distance, time and mass. DERIVED UNITS. From the fundamental units units for more complex quantities may be derived. As the fundamental units vary in different countries, the derived units vary also. FORCE. 7 C. G. S. UNITS. Besides our national units, the units derived from the French or metric system are also frequently em- ployed. They are designated as the centimeter-gramme- second units; abbreviated C. Gr -S. units, and are also called absolute units. CHAPTER II. MOTION;- FORCE. MOTION. The removal of matter from one place to another. FORCE. Any cause which changes or tends to change the condition of rest or motion of a body (in a straight line). MEASUREMENT OF FORCE. Force may be measured by the change of momentum it produces in a second. The unit of force is a dyne; it is based on the metric system, and represents that force which, after acting for a second, will give to a gram of matter a velocity of one centimeter per second. GRAVITATION. The tendency which is common to all matter, and according to which all bodies mutually attract each other with an intensity proportional to their masses and in- versely as the square of their distances, is called gravita- tion. The force of the earth attraction at its surface is equivalent to 981 dynes. MOLECULAR FORCES. The attraction and repulsion which exist between the minute and most minute parts or atoms of bodies are often referred to as the molecular forces. COHESION. Cohesion designates the attraction existing be- tween the minute parts of the same body; and for solids it is measured by the force expressed in pounds to tear apart by a straight pull a rod of one square inch area of section. This measure is also called the tenacity of a body (tons). The relative tenacities of the metals are given ap- proximately in the table below, lead being taken as the standard. Lead 1.0 Castiron 7 to 12 Tin 1.3 Wroughtiron 20to 40 Zinc 2.0 Steel 40 to 143 Worked copper 12 to 20 S MECHANICAL REFRIGERATION. ADHESION. Adhesion designates the attraction between the parts of dissimilar bodies. CHEMICAL AFFINITY. This expression generally stands for the relative at- traction existing between the smallest particles (atoms and molecules)]of different substances, which, if satisfied, brings about substantial or chemical changes. WORK. Work is the product of force by the distance through which it acts. The unit of work is the product of the units of its factors, force and space. Useful work is that which brings about a specific useful effect, and lost work is that which is incidentally wasted while producing such effect. UNIT OF WORK. The unit of work is the foot-pound, i. je.,.the work necessary to raise one pound vertically through a dis- tance of one foot. One pound raised vertically through a distance of ten feet, or ten pounds raised through one foot, or five pounds raised through two feet, all represent the same amount of work, i. e., ten foot-pounds. TIME. The interval between two phenomena or changes of condition. The unit of time is the hour and its sub- divisions. POWER HORSE POWER. Power is the rate at which work is done, and is there- fore equivalent to the quantity of work done in the unit of time, expressed in foot-pounds, kilogram- meters, etc., per hour, minute or second. The unit commonly employed is the horse power, which is defined as work done at the rate of 550 foot-pounds per second, or 1,980,000 foot pounds per hour. VELOCITY. The length, !, of path traversed by a moving body in the unit of time, t; therefore V standing for velocity. MOMENTUM. Momentum is the product of mass (in motion) mul- tiplied by its velocity or force multiplied by the time during which it acts. ENERGY. 9 INERTIA. Inertia expresses the inability of a body to change its condition of rest or motion, unless some force acts on it. LAWS OF MOTION. Newton propounded the following laws of motion: 1. A free body tends to continue in the state in which it exists at the time, either at rest or in uniform rectilinear motion. 2. All change of motion in a body free to move is proportional to the force applied, and it is in the direction of that force. 3. The reaction of a body acted upon by the im- pressed force is equal, and directly opposed to, that force. STATICS. Statics is that branch of science which treats of the relation of forces in any system where no motion results from such action. . DYNAMICS OB KINETICS. Dynamics or kinetics treats of the motion produced in ponderable bodies by the action of forces. CHAPTER III. ENEEGY. . ENERGY. Energy is the power or quality for doing work. We distinguish between different forms of energy, viz.: VISIBLE ENERGY. This is the energy of visible motions and positions, and is subdivided as follows: KINETIC ENERGY. Kinetic or actual energy is energy which a body possesses by virtue of its motion, such as the energy of winds, ocean currents, etc. POTENTIAL ENERGY. Potential or latent energy is that kind of energy which a body possesses by virtue of its position, a head of water, a raised weight, a coiled spring, etc. MOLECULAR ENERGY. The molecular energy comprises the energy of radi- ation or radiated matter, i. e, t electricity, light, heat, 10 MECHANICAL REFRIGERATION. etc.; molecular, potential energy or energy of chemical affinity, etc. C. G. S. UNIT OF ENERGY. The unit of energy is one-half of the energy pos- sessed by a gramme of mass when moving with a velocity of one centimeter per second. This unit is called the erg. The erg may also be defined as the work accom- plished when a body is moved through a distance of one centimeter with the force of one dyne, that is a "Dyne Centimeter." One million ergs is called a megerg. CONSERVATION OF ENERGY. The total amount of energy in the universe, or in any limited system which neither receives nor loses any energy to outside matter is invariable and constant. TRANSFORMATION OF ENERGY. The different forms of energy are convertible or transformable into each other, so that when one form of energy disappears, an exact equivalent of another form or kind of energy always makes its appearance. (See " Dissipation of Energy.") PHYSICS. Is the science which treats of the transformations and transference of energy, broadly speaking. SUBDIVISIONS OF PHYSICS. Physics, therefore, is subdivided into a science of op- tics or radiation, a science of heat, of mechanics, of electricity and of chemistry. Other distinct branches of science treat on the specific relations between two kinds of energies; for this reason we speak of thermodynamics, electro-chemistry, photochemistry, thermochemistry, electro-dynamics, etc. DISSIPATION OF ENERGY. In our efforts to transform one form of energy into another, a certain portion of the first energy always as- sumes a lower degree of tension; it is dissipated and now represents an amount of energy of less availability for useful purposes. ENERGY OF A MOVING BODY. The amount of kinetic energy possessed by a body by virtue of its motion may be expressed by the formula in which E stands for energy, M for mass and v for velo- city. HEAT. 11 MECHANISMS. A machine or a mechanism is a contrirance enabling us to transform mechanical energy, by changing the direction, power and velocity of available forces to make them serviceable for useful proposes. The energy sup- plied to a machine is partly employed to do the useful work required, and partly it is consumed in doing what is called internal work, by overcoming friction, etc. It is the lost work of the machine, and the less the latter the more perfect is the machine. CHAPTER IV. HEAT. HEAT. Heat Is a form of energy, and represented by the kinetic energy of the molecules of a body. SOURCES OF HEAT. As sources of heat we may quote: Friction, percus- sion and pressure, solar radiation, terrestrial heat, mo- lecular action, change of condition, electricity, chemical combination, more especially combustion. RADIANT HEAT. The foregoing definition, while it accounts for the phenomena of bodily and conducted heat, does not ac- count for the conditions which obtain when heat passes from one body to a distant other body without a ponder- able intervening~medium, or without perceptibly heating the intervening medium, i. e., the radiation of heat. To explain these conditions in harmony with the mechanical or molecular theory of physics, it is supposed that the radiant heat is in the nature of a wave motion propa- gated .by means of a hypothetical substance, the ether. ETHER. The hypothetical ether which is the supposed vehicle for the transmission of the supposed wave motion consti- tuting radiant energy (radiant heat as well as light), in order to accomplish such transmission in accordance with the present conceptions of these phenomena would have to possess the following properties: "Its density would have to be such that a volume of it equal to about twenty volumes of the earth would weigh one pound; its pressure 12 MECHANICAL REFRIGERATION. per square mile would be about one pound, and the heat required to elevate the temperature of one pound for 1 F would have to be equal to the amount of heat required to raise the temperature of about 2,300,000,000 tons of water for one degree. Such a medium would satisfy the require- ments of nature in being able to transmit a wave of light or heat 180,000 miles per second, and to transmit some 130 foot-pounds of heat energy from the sun to the earth, each second per square foot of heat normally exposed, and also be everywhere practically non-resisting and sensibly uniform in temperature, density and elasticity." (Wood.) RADIANT HEAT AND LIGHT. Kadiant heat follows the same laws regarding re- fraction, reflection, polarization, etc., as does light. TEMPERATURE. The temperature of a body is proportional to the average kinetic energy of its molecules, and is measured by the thermometer. THERMOMETER. The most prevalent form of thermometer consists of a body of mercury, enclosed in a glass tube so that slight variations of expansion due to change of temperature can be read of on the scale attached. Other substances, like alcohol, air, etc., are also used as thermometric sub- stances instead of mercury. THERMOMETER SCALES. Three different scales are in use for thermometers, the "Fahrenheit" in England and United States, the "Keaumur" in Germany and the "Celsius" or "Centi- grade " in France, and for scientific and technical pur- poses, more or less, all over the world. The scales of the different thermometers compare as follows: Freezing-point Boiling point of water. of water. Fahrenheit 32 2^ Centigrade 100^ Reaumur If we designate the scales by their initials the follow- ing rules apply for the conversion of the degrees in one another' C.=i(F.-32)=f B. E.=| (P. 32)=| C. HEAT. COMPARISON OF THERMOMETER SCALES. 13 B. 0. F. R. C. F. ~"+80 +100 +212 +23 +28.75 +83.75 79 98.75 209.75 22 27.60 81.50 78 ' 97.50 207.50 21 26.25 79.25 77 96.25 205.26 20 25 77 76 95 203 19 23.75 74.75 75 93.75 200.75 18 22.50 72.50 74 92.50 198.50 17 21.25 70.25 73 91.25 196.25 16 20 68 72 90 194 15 18.75 66.75 71 88.75 191.75 14 17.50 63.50 70 87.50 189.50 13 16.25 61.25 69 86.25 187.25 12 15 59 68 85 185 11 13.75 56.75 67 83.75 182.75 10 12.50 54.50 66 82.50 180.50 9 11.25 52.25 66 81.255 178.25 8 10 50 64 80 176 7 8.75 47.76 63 78.75 173.75 6 7.50 45.50 62 77.50 171.50 5 6.26 43.26 61 76.25 169.25 4 5 41 60 75 167 3 3.75 38.75 59 73.75 164.75 2 2.50 36.50 58 72.50 162.50 1 1.25 34.25 57 56 71.25 70 160.25 158 -1 1.25 32 29.75 55 68.75 155.75 2 2.50 27.50 54 67.50 153.50 3 3.75 25 25 53 66.25 151.25 4 5 23 52 65 149 5 6.25 20.75 51 63.75 146.75 6 7.50 18.50 50 62.50 144.50 7 8.75 16.25 49 61.25 142.25 8 10 14 48 60 140 9 11.25 11.75 47 58.75 137.75 10 12.50 9.50 46 57.50 ia5.50 11 13.75 7.25 45 56.25 133.25 12 15 5 44 55 131 13 16.25 2.75 43 53.75 128.75 14 17.50 0.50 42 52.50 126.50 15 18.76 1.76 41 51.25 124.25 16 20 4 40 50 122 17 21.25 6.25 39 48.75 119.75 18 22.50 8.50 38 47.50 117.50 19 23.75 10.75 37 46.25 115.25 20 25 13 36 45 113 21 26.25 15.25 35 43.75 110.75 22 27.50 17.50 34 '42.50 108.50 23 28.75 19.75 33 41.25 106.25 24 30 23 32 40 104 25 31.25 24.25 31 38.75 101.75 26 32.50 26.50 30 37.50 99.50 27 33.75 28.76 29 36.25 97.25 28 35 31 28 35 95 29 36.25 33.25 27 33.75 92.75 30 37.50 26 32.50 90.50 31 38.75 37! 75 25 31.25 88.25 32 40 40 24 30 86 MEASURING HIGH TEMPERATURES. Temperatures which are beyond the reach of tlie mercurial thermometers (over 500) are measured by pyrometers constructed to meet the wants of specific cases. High temperatures may be estimated approxi- 14 MECHANICAL REFRIGERATION. mateJy by heating a piece of iron of the weight w up to the unknown temperature T, and then immersing the same into a known weight, W, of water of the tempera- ture t. Then if t is the temperature of the water after immersion and s the specific heat of the iron or other metal, T is found after the formula: W S ABSOLUTE ZERO. The zero points on the scales of thermometers men- tioned are arbitrarily fixed, since the expressions of warm and cold have only a relative significance. The real zero point of temperature, that is, that point at which the molecules have lost all motion, the energy of which represents itself as heat, is supposed to be, and in all proba- bility is over 460 F. below the zero of the Fahrenheit thermometer. At that temperature there is an entire ab- sence of heat and demonstrations of heat phenomena, and above that the differences in temperatures are only such of degree, but not in kind. Hence the impropriety of speaking of heat and cold as such. If t is a given temperature in degrees Fahrenheit the corresponding degrees T expressed in absolute tem- perature are found after the formula UNIT OF HEAT. The quantity of heat contained in a body is the sum of the kinetic energy of its molecules. Heat is meas- ured quantitatively by the heat unit, which also varies in different parts like other standards. The unit used in the United States and England is the British Thermal Unit (abbreviated B.T.U.) and represents the amount of heat required to raise the temperature of one pound of water 1 F. The French unit is the calorie, and is the quantity of heat required to raise the temperature of one kilogram of water from to 1 Celsius. Some writers define the B. T. unit as the heat re- quired to raise the temperature of one pound of water from 32 to 33. Others make this temperature from 60 to 61, and still others define it as that amount of heat required to raise rf 5 pound of water from the freez- ing to the boiling point. The two last definitions give nearly the same result, and may be considered practically identical. HEAT. 15 C. G. S. UNIT OF HEAT. We have no unit for heat corresponding to the C. G. S. or absolute system. The small French calorie, being the heat required to elevate the temperature of one gram of water for 1 Celsius (from 17 to 18) is equivalent to 41,- 830,000 ergs. CAPACITY FOR HEAT. The number of heat units required to raise the tem- perature of a body for one degree is called its heat capacity. It gradually increases with the temperature. SPECIFIC HEAT. The ratio of the capacity for heat of a body to that of an equal weight of water is specific heat. Hence the figure expressing the capacity for heat of one pound of a body in B. T. U. expresses also its specific heat, and vice versa. SPECIFIC HEAT OF METALS. Antimony .0507 Manganese .1441 .0308 Mercury solid .0319 .0939 liquid... .0333 0951 Nickel .1086 Cymbal metal 086 PI at iiium, sheet .... .0324 Gold .0334 " SDOnfiTY .0329 Iridium .1887 Silver .0570 .1298 Steel .1165 " wrought .1138 Tin .0569 Lead .0314 Zinc .0959 SPECIFIC HEAT OF OTHER SUBSTANCES. STONES. Brickwork and masonry.. Marble .20 .2129 .2148 .2169 .2174 .2411 .2415 .2031 .2008 .2017 CARBONACEOUS Cont. .2019 .197 .1977 .504 .2503 .2311 .0872 .1966 .2026 of blast furnaces SUNDRY. Place Quicklime Magnesian limestone CARBONACEOUS. Coal Ice .... Phosphorus Soda Sulphate of lead Cannel coke ...... " of lime Anthracite... SPECIFIC HEAT OF LIQUIDS. .6588 Turpentine .4160 .3932 Vinegar 9200 0333 Water, at 32 F . . . . 1 0000 Olive oil .3096 212F 1 0130 Sulphuric acid: Density 1 87 3346 32 to 212 F Wood spirit . . 1.0050 6009 ' ' i 30 .6614 Proof spirit 973 16 MECHANICAL REFRIGERATION. SPECIFIC HEAT OF WATER AT VARIOUS TEMPERATURES. Heat to Raise Heat to Raise Tempe- rature. Specific Heat. lib. of Water from 32 F. to Given Tempe- rature. Specific Heat. 1 Ib. of Water from 32 F. to Given Temperature. Temperature. 'Fahr. Units. Fahr. Units. 32 1.0000 0.000 248 1.0177 217.449 60 1.0005 18.004 266 1.0204 235.791 68 1.0013 36.018 284 1.0232 254.187 86 1.0020 54.047 302 1.0262 272.628 104 1.0030 72.090 320 1.0294 291.132 122 1.0042 90.157 338 1.0328 309.690 140 1.0056 108.247 . 356 1.0364 328.320 158 1.0072 126.378 374 1.0401 347.004 176 1.0089 144.508 392 1.0440 365.760 194 1.0109 162. 686 410 1.0481 384.588 212 1.0130 180.900 428 1.0524 403.488 230 1.C153 199.152 446 1.0568 422.478 USE OF SPECIFIC HEAT. The amount of heat or cold necessary to elevate or lower the temperature of w pounds of a body having the specific heat c for t degrees is found after the follow- ing equation: 8 = c X t X w DETERMINATION OF SPECIFIC HEAT. The specific heat of various bodies can be found from the table, and it may also be determined experi- mentally as follows for solid substances (to find the specific heats of liquids the same principle is followed,care being taken that the liquids to be mixed have no chemical affinity for each other): Take a known weight, w, of the substance whose specific heat is to be determined, and let it have a known temperature, t (above that of the atmosphere), then immerse it in a known weight, v, of water having the temperature t' and now observe the temperature, 2, acquired by the mixture. From these quantities the specific heat, x, of the substance can be cal- culated after the formula v ( z t'} X = ^(t^] If the substance is soluble in water any other liquid whose specific heat is known may be used instead. This method, while it might answer for rough determinations, would have to be surrounded by special safeguards in order to allow for loss by radiation of the vessel, etc., in order to be applicable for exact determinations. TEMPERATURE OF MIXTURES. If two substances having respectively the weight w to t , the temperatures t and t lt and the specific heat s HEAT. 17 and !, are mixed without loss or gain of heat, the tem- perature, T, of the mixture is: W S--Wi S EXPANSION BY HEAT. When a body becomes warmer it expands,when it be- comes cooler it contracts, a rule of which ice, however, is one of the exceptions. EXPANSION OF SOLIDS. Amount of linear expansion of solids may be com- puted by the following formula for the Fahrenheit scale; (M-4) T 180 In which JD t is the length of a bar at any temperature, f t , knowing its length, L, at any other temperature, t, and a is a coefficient to be obtained from the following table: COEFFICIENT OF EXPANSION FROM 32 TO 210 F. Glass 0.000,861,30 Pine wood (length wise)... 0.000,3 Platinum 0.000,884,20 Oak wood 0.000,7 Steel, soft 0.001,078,80 Granite 0.000,8 Iron, cast 0.001,125,00 Limestone 0. 000,8 Iron, wrought 0.001,220,40 Antimony 0.001,1 Steel, hardened 0.001,239,50 Gold 0.001,4 Copper 0.001,718,20 Ebonite 0.001,7 Bronze 0.001,816,70 Nickel 0.0018 Brass 0.001,878,20 Silver... 0.001.B Tin 0.002,173,00 Aluminum .002,3 Lead 0.002,857,50 Pine wood (crosswise) . 005,8 Zinc 0.002,941,70 Mercury (in glass tube). ..0.016,2 EXPANSION OF LIQUIDS. The expansion of liquids by heat is expressed by the volume of a given quantity of liquid at different temper- atures, as is done in the following table for water, show- ing also that at the point of maximum density. The maximum density of water, as appears from this table, is between 32P and 46 F.; above 46 the volume increases, but below 32 it increases also. Apparently this is an exception to the general rule that all bodies expand by heat and contract when the temperature is lowered. This exception, however, may be accounted for when we assume that at 32, when the water passes from the liquid to the solid state, its molecular constitu- tion is changed also, which is also indicated by thf change in specific heat at this point. 18 MECHANICAL REFRIGERATION. EXPANSION AND WEIGHT OF WATER AT VARIOUS TEMPERATURES. Tem- pera- ture. Relative Volume by Ex- pansion. Weight of One Cubic Foot. Weight of One Imperial* Gallon. Tem- pera- ture. Relative Volume by Ex- pansion. Weight of One Cubic Foot. Weight of One Imperial* Gallon. Fahr. Pounds. Pounds. Pahr. Pounds. Pounds. 32 1.00000 62.418 10.0101 100 1.00639 62.022 9.947 35 .99993 62.422 10.0103 105 1.00739 61.960 9.937 f 62.425 ] 110 1.00889 61.868 9.922 39.1 . 99989 / surface per degree of difference of temperature of steam and air, per hour, at ordinary temperatures. , , t 114 = ~58~ ~T s = quantity of steam condensed in pounds. ji = quantity of heat emitted in units. h'= quantity of heat emitted, per degree of difference of temperature. i=difference of temperature, in Fahrenheit degrees. The latent heat of steam of 22 pounds total pressure per square inch, 950 units per pound, is employed as the heat factor, as an average value. The following table has been calculated by means of these formulae: MECHANICAL REFRIGERATION. STEAM CONDENSED IN BARE CAST IRON PIPES IN AIR, AND HEAT EMITTED, AT ORDINARY TEMPERATURES. Steam. Differ- ence or Excess of Tem- perature of Steam above 62 Fahr. Steam Condensed per Square Foot per Hour. Heat Emitted. per Square Foot per Hour. Total Pressure per Square Inch. Tempe- rature. Total. Per 1 F. of Differ- ence. Total. Per 1 F. of Differ- ence. Pounds. 14.7 18 21.5 26 31 36.5 43 51 Fahr. 212 222 S32 242 252 262 272 282 Fahr. 150 160 170 180 190 200 210 220 Pounds. 29 346 .405 .47 .54 .607 .682 .76 Pounds. .00193 .00216 .00238 .00261 .00284 .00303 .00325 .00345 Units. 276 329 384 446 513 577 648 722 Units. 1.84 2.05 2.26 2.48 2.70 2.89 3.08 3.28 For the increased rate of condensation induced by a draft of air, compared with that caused in the still air of a room, a bare steam boiler, in open air, was tested. Steam of 50 Ibs. absolute pressure per square inch was condensed at the rate of 1.25 pounds per square foot of external surface per hour; or, for a difference of 236 of temperature, .0053 pound per degree of difference; show- ing that 4.79 units of heat per degree was emitted, or a half more than from a pipe in still air. EXPERIMENTS NEEDED. The foregoing and following data relate nearly all to the emission of heat from pipes, etc., filled with water or steam. It would of course be also highly desirable to have similar data for ammonia, especially for anhydrous ammonia, at the temperatures of condenser, freezing tank, brine tank and cold storage rooms. But such ex- periments have not been made so far. Numerical data on this topic have been abstracted from practical experi- ence, and such as were attainable in this way have been mentioned in their place in the second part of this book, but are necessarily somewhat arbitrary. COOLING OP WATER IN PIPES EXPOSED TO AIR. Mr. Wm. Anderson experimented with 2-inch wrought iron pipes, ^ inch thick, galvanized, and 4-inch cast iron pipes, iV mc k thick, through which hot water was passed. HEAT. 27 Results are given in the following table. The ultimate results harmonize with those for the use of steam in pipes. . COOLING OF WATER IN PIPES EXPOSED TO AIR. Two-inch Wrought Iron Pipes. Four-inch Cast Iron Pipes. Number of exper- > iment ) 1 53 103.7 233.7 2.25 2 53 49. 4 104.4 c2.11 3 52.5 25 .4 46.45 1.83 4 52 14.3 19.7 1.39 1 60 62.3 99.5 1.59 2 60 45.8 69.9 1.53 3 60 33.9 49.5 1.46 4 59 27 .3 38.2 1.40 Temperature o f the atmosphere Fahr Average differ- ence of temper- aturesof the wa- ter and the air Fahr Total heat emit-' ted per square foot per hour. Units Heat emitted per' 1 P. difference of temperature Units... Tredgold experimented with small vessels of different materials, in which water was cooled from a temperature of 180 to one of 159, in a room at 58P. The heat emitted per square foot per hour per degree of mean difference of temperature was as follows: Tin plate 1.37 units. Sheetiron 2.24 tt Glass 2.18 - Also, in a 2^-inch cast iron pipe, % inch thick, water was cooled from 152 to 140 F., in a room at 67. The heat emitted per square foot per hour per degree of dif- ference of temperature was as follows: Ordinary rusty surface 1.823 units. Black, varnished 1.900 " White (two coats of lead paint) 1. 778 TRANSMISSION OF HEAT THROUGH METAL PLATES FROM WATER TO WATER. In a metal tubular refrigerator, hot wort was cooled by water at such a rate that, taking averages, 80 units of heat passed from the wort, and was absorbed by the water per square foot of cooling surface per 1 F. dif- ference of temperature. The water and the wort were moved in opposite directions. M. P4clet proved experimentally that the rate of transmission of heat was directly as the difference of temperature at the two faces of metal plates. 28 MECHANICAL REFRIGERATION. TRANSMISSION OF HEAT THROUGH METAL PLATES FROM STEAM TO WATER. The rate of transmission of heat from steam through a metal plate to water at the other side is practically uniform per degree of difference of temperature. The following table gives average results of performance, from which it appears that the transmission is much more effective for evaporating than for heating water, twice as much for flat copper plate, three times as much for copper pipe, one-fourth more for cast iron plate. Also, that pipe surface is one-fifth more effective than flat plate surface for heating, and more than twice as much for evapora- tionthe result of better circulation, no doubt. HEATING AND EVAPORATING WATER BY STEAM THROUGH METALS. Metal Surface. Per Square Foot per 1 F. Difference of Temperature. Steam Condensed. Heat Transmitted. Heating. Evaporat- ing. Heating. Evaporat- ing. Copper plate Copper pipe Pounds. .248 .291 .077 Pounds. .483 1.070 .105. Units. 276 312 82 Units. 534 1034 100 Mr. Isherwood experimented with cylindrical metal pots, 10 inches in diameter, 21^ inches deep; % inch, 34 inch and % inch thick; turned and bored. They were placed in a steam bath of from 220 to 320 F. Water at 212 was supplied to the pots, and evaporated. The rate of evaporation per degree of difference of temperature was the same for all temperatures; and the rate was the same for the different thicknesses. The respective weights of water, and heats consumed per square foot of inside surface per degree of difference were as follows: Copper Brass Wrought iron Cast iron Water at 212*. .665 Ib. .577 " .387 " .327 " - Heat. 642.5 units 556. 8 " 373.6 " 315.7 " The differences of results for the same metal evi- dently arise in part from the comparative activity of cir- culation, and in part from the condition and position of the heating surfaces. HEAT. 29 CONDENSATION OF STEAM IN PIPES OR TUBES BY WATER EXTERNALLY. From the results of experiments with surface con- densers, in which the steam was passed through the tubes, it appears that 500 units of heat by condensation were transmitted per square foot of tube surface per hour per 1 F. difference of temperature. The condensers were arranged in three groups of tubes successively trav- ersed by the condensing water. In another case, where the condenser was arranged in two groups, from 220 to 240 units were transmitted. Mr. B. G. Nichol experimented with an ordinary sur- face condenser brass tube, % inch in diameter outside, No. 18 wire gauge in thickness ; encased in a 3%-inch iron pipe. Steam of 32^ pounds total pressure per square inch occupied the interspace, while cold water at 58 F. initial temperature was run through the brass tube. Three experiments were made with the tubes in a vertical position, and three in a horizontal position. Vertical Position. Horizontal Position. 1, 2, 3, 4, 5, 6, Velocity of water through tube, in feet per minute, 81, 278, 390, 78, 307, 415 feet. Steam condensed per square foot of surface per hour, for 1 G F. difference of temperature, .335, .436, .457, .480, .603, 609 pound. Heat absorbed by the water, per square foot per hour, per 1 F. difference of temperature, 346, 449, 466, 479, 621, 699 units. The rate of condensation was greater in the hori- zontal position than in the vertical position. Also, the efficiency of the condensing surface was increased by an increase of velocity of the water through the tube, nearly in the ratio of the fourth root of the velocity for vertical tubes; and nearly as the 4. 5 root for horizontal tubes, TRANSMISSION OF HEAT THROUGH METAL PLATES OR TUBES, FROM AIR OR OTHER DRY GAS TO WATER. The rate of transmission of con vected heat is prob- ably from 2 to 5 units of heat per hour per square foot of surface per 1F. of difference of temperature. In a locomotive fire box, where radiant heat co-oper- ated with con vected heat, the following results have been 30 MECHANICAL REFRIGERATION. obtained in generating steam of 80 pounds pressure per square inch. The temperature of the fire is taken at 2,000 F. Heat Transmitted Water Evaporated per Square Foot per per Square Foot Hour perl F.Differ- per Hour. ence of Temperature. Burning coke, 75 pounds ) per square foot of [ 25% pounds. 14^ units. grate ) Burningbriquettes, ) 74^ pounds per [ 35 20 square foot of grate ) There are in practice little or no differences between iron, copper and lead in evaporative activity, when the surfaces are dimmed or coated, as under ordinary condi- tions. COMPARATIVE RATE OF EMISSION OF HEAT FROM STEAM PIPES IN AIR AND IN WATER. It appears that for equal total difference of tempera- ture, the rate of emission of heat from steam pipes in water amounts, in round numbers, to from 150 to 250 times the rate in air, according as the pipes are vertical or horizontal. COMPARATIVE RATE OF EMISSION OF HEAT FROM WATER TUBES IN AIR AND IN WATER AT REST AND IN MOTION. It appears that the rate of emission from water- tubes in water was about twenty times the rate in air. Mr. Craddock proved it experimentally to be twenty-five times. When the water tube was moved through the air at a speed of fifty-nine feet per second, it was cooled in one-twelfth of the time occupied in still air. In water, moved at a speed of three feet per second, the water in the tube was cooled in half the time. PASSAGE OF HEAT THROUGH METAL PARTITIONS. From eome recent observations made in Germany the following table, giving the transmission of heat through metal partitions per hour, per square foot and per one degree F. difference between each side, viz.: Smoke or air through metal to air 1.20 to 1.70B. T. U. Steam through metal to air 2. 40 to 8.40 Water through metal to air or reverse 2.15 to 3. 15 Steam through metal to water : 200.00 to 240.00 Steam through metal to hoiling water 1,000.00 to 1,200.00 Water through metal to water 72. 00 to W.OO LATENT HEAT. When a body passes from the solid to the liquid state, or from the liquid to the gaseous or vapor state, a HEAT. 31 certain amount of heat is required to bring about the change. As this heat is absorbed during the process of fusion or vaporization it is called latent heat of fusion and latent heat of evaporation (latent heat contained in the vapor). LATENT HEAT OF FUSION. The heat which becomes latent during the fusion or melting of a body is used or absorbed while doing the work of disintegrating the molecular structure, doing internal work as it is called. TABLE SHOWING LATENT HEAT OF FUSION. Thermal units. Ice 142.5 Nitrate of ammonia 113.2 Nitrate of soda 104.1 Phosphate of potash 85.1 Nitrate of potash 78.4 Chloride of calcium 64.3 Zinc 60.6 Platinum 48. 8 Silver 37.8 Thermal units. Tin 25.5 Cadmium 24.5 Bismuth 22.7 Sulphur 16.8 Lead 9.6 Phosphorus 9.0 D'Arcet's alloy 6.1 Mercury 0.1 MELTING POINTS, ETC. Fahr. Fahr. Aluminum -| Full red heat 1150 507 1690 1996 2156 2282 2012 108 32 45 112 109 to 120 Iron, cast, white } 1992 to 2012 2912 617 39 1873 2372 to 2562 442 773 120 239 92 14 142 154 " wrought . . . Lead Bismuth ....... Mercury Silver Copper......... Cfppl " pure. Tin Iron, cast, gray Zinc Ice Sulphur ... Tallow Phosphorus Turpentine Wax, rough " bleached EFFECT OF PRESSURE ON MELTING POINT. Substances which expand during solidification, like water, have their freezing points lowered by pressure, and those which contract in solidification have their freezing points raised by pressure. LATENT HEAT OF SOLUTION". When a body is dissolved in water or in any other liquid, or if two solid bodies (salt and snow, for an ex- ample) mix to form a liquid, a certain amount of heat becomes likewise latent; it is called the latent heat of fusion. Since the latent heat of fusion in the case of 32 MECHANICAL REFRIGERATION. such mixtures is taken from the mixture itself, the tem- perature falls correspondingly, as shown by the table on frigoriflc mixtures. For practical purposes the mixtures of snow and hydrochloric acid, or, where acid is objectionable, the mixture of snow and potash, is very serviceable to pro- duce refrigeration on a small scale. The mixture of sodium sulphate, ammonium nitrate and nitric acid is also recommendable. LIST OF FRIGORIFIC MIXTURES. Thermometer Sinks Degrees F. Ammonium chloride. Potassium nitrate Water 16 " ) i chloride 5 parts ) Potassium nitrate 5 " > From + 50 to + 10 Ammonium chloride 5 parts "! Potassium nitrate 5 " 1 Sodium sulphate 8 " f From + 80 to + 4 Water 16 " J Sodium nitrate 3 parts I Nitric acid, diluted 2 " f From + 50 to - 3 Ammonium nitrate 1 part ) Sodium carbonate. 1 > From -f 60 to 7 Water 1 ) Sodium phosphate 9 parts I Nitric acid, diluted 4 " f From + 50 to -12 Sodium sulphate 5 parts I ,, Sulphuric acid, diluted 4 " f From + 50 * + Sodium sulphate 6 parts 1 Ammonium chloride 4 L .*.. _i U *-, 10 Potassium nitrate 2 " f From 4- 50 to - 1 Nitric acid, diluted 4 ' j Sodium sulphate 6 parts ) Ammonium nitrate ... 5 V From + 50 to 40 Nitric acid, diluted 4 ) Snow or pounded ice 2 parts I - Sodium chloride 1 " J Snowor pounded ice 5 parts Sodium chloride. Ammonium chloride 1 Snow or pounded ice 24 parts Sodium chloride 10 Ammonium chloride 5 Potassium nitrate 6 Snow or pounded ice 12 parts Sodium chloride 6 Ammonium nitrate 5 3 to-l* to -18 to- 25 cXum chloride::::::':::::::::::::: 5 pa ts } From+32- to-4o Ca?cTum'cmorideVcryVtailized. .'.'.'.'.'.' 3 , S \ From + 32 to 5C HEAT, M HEAT BY CHEMICAL COMBINATION. As one of the chipf sources of heat chemical combina- tion has been mentioned, which may be defined as the process which takes place when the ultimate constituent parts (atoms) of one or more elementary bodies unite with those of another elementary body or bodies to form a substance essentially different in its properties from those of the original bodies. ELEMENTARY BODIES. Substances which cannot be resolved into two or more different substances are called elementary bodies, elements or simple bodies. CHEMICAL ATOMS. Chemically considered, an atom is the smallest parti- cle of matter entering into or existing in combinations. The atomic weight is a number expressing the ratio of the weight of the atoms of an element to the weight of an atom of hydrogen, the latter being taken as unit. MOLECULES. The smallest quantity of an elementary body, as well as of a compound body, which is capable of having an independent existence is called a molecule. A molecule, therefore, is a combination of several atoms of one and the same or of different elements. CHEMICAL SYMBOLS. The chemical elements are expressed by symbols which are the initial letters of their Latin or English name. The symbols also represent the relative quan- tity of one atom of an element. The composition of the molecule of a body is indi- cated by the symbols of its constituents. The num- ber of atoms of each element present is denoted by a number placed at the lower right hand end of the sym- bol. Thus H 2 represents a molecule of hydrogen which is composed of two atoms, and H 2 O represents a molecule of water, which is composed of two atoms of hydrogen and one of oxygen. The atomic weight of hydrogen being 1 and that of oxygen 16, it is readily seen how the formula II 2 O yields the percentage composition by a simple cal- culation. ATOMICITY. Atomicity or valence is that property of an element by virtue of which it can hold in combination a definite 34 MECHANICAL REFRIGERATION. number of other atoms, the atomicity of an elementary body is measured by the number of atoms of hyurogen which can be held in combination by an atom of the ele- mentary body in question, the atomicity of hydrogen being taken as unit. Thus by referring to the following table it is readily seen how one atom of chlorine will hold in combination one atom of hydrogen, one atom of oxygen two atoms of hydrogen, one atom of nitrogen three atoms of hydrogen, and one atom of carbon four atoms of hydrogen and form saturated compounds. For obvious reasons the rare and new elements, argon, helium, atherion, etc., are not mentioned. TABLE OF PROPERTIES OF ELEMENTS. Element. Sym- bol. Atom- icity. Atomic Weight. Specific Gravity. Al IV 27 *i 2KO Antimony Sb v 122 6 7 Arsenic As v 7K BrtK Barium Ba II 137 4 Bismuth . Bi y OAQ 8 75 Boron . ... B III Jl 2 68 Bromine Br I 80 2 Q Cadmium .. .... Cd II 112 1 58 Calcium Ca II 40 1 65 Carbon c IV 12 2 33 Chlorine Cl I 35 5 Cr VI 52 5 6 5 Cobalt Co VI 58 8 Cu II 63 5 8 958 Fluorine. F I 19 Gold Au in IQfi 7 19 26 H I 1 Iodine . I in 127 4 948 Iridium ... Ir VI 198 21 15 Iron Fe VI 56 7 79 Lead. Pb IV 207 11 36 Lithium Li i 7 594 Mg ii 24 1 70 Manganese Mn VI 55 8 03 Mercury Hff II 200 13 go Nickel Ni VI 58 8 Nitrogen N Y 14 Oxygen o II 16 Palladium . Pd IV 106 5 11 40 Phosphorus p v 31 1 g40 Platinum Pt IV 197 4 21 15 K I 39 865 Rhodium. ... . Rh VI 104 12 1 Selenium Se VI 79 4 28 Silicon Si IV 28 5 2 49 Silver. Air I 108 10 53 Sodium Na I 23 9722 Strontium Sr 11 87 5 2 543 g Vf 32 2 07 Tellurium Te VI 128 6 180 Tin Sn IV 118 Titanium. .. Ti IV 50 W VI 184 Uranium .... Ur VI 12i) 18.4 Vanadium v v 51 2 5 5 Zinc... Zn II 65 7.13 HEAT. 36 GENERATION OF HEAT. The generation of heat by chemical combination is explained by the fact that the resulting compounds pos- sess less energy than the constituent elements before they unite or combine. The difference of energy before and after combination appears in the form of heat, elec- tricity, etc. By the same token heat is absorbed during the decomposition of chemical compounds. MEASURE OF AFFINITY. The amount of heat or other form of energy devel- oped during a chemical change is a measure for the chemical work done or the amount of affinity displayed during the change. TOTAL HEAT DEVELOPED. The total amount of heat or energy developed dur- ing a chemical change depends solely upon the initial and final condition of the participating bodies (the initial or final condition of the system), and not on any intermedi- ate conditions. In other words, the heat developed dur- ing a chemical change is the same whether the change takes place in one operation or in two or more separate processes. MAXIMUM PRINCIPLE. Of all chemical change which may take place within a system of bodies, without the interference of outside energy, that change will take place which causes the greatest development of heat, as a general rule. According to the more modern conceptions it is held that that change will take place which will cause the greatest dissipation of energy, or by which the entropy of the system will suffer the greatest increase, or by which the greatest amount of energy will be dissipated. (For definitions of entropy see Chapters VII and VIII.) EXPRESSIONS FOR HEAT DEVELOPED. The amount of heat, expressed in units, developed or absorbed during a chemical process may be conveniently used in connection with the chemical symbols. Thus the formula P6 + 2/=P6/ 2 -h 7.1400 U signifies that 207 parts of lead combine with 254 parts of iodine to form 461 parts of iodide of lead, and develop thereby 7.1400 units of 36 MECHANICAL REFRIGERATION. HEAT OF COMBINATION OF SUBSTANCES WITH OXYGEN. Substances. Product. Units of Heat Evolved. By 1 Ib. of Substance. By 1 Ib. of Oxygen. By 1 Atom of Substance in Pounds. Hydrogen Wood charcoal Sulphate, native . . . Phosphorus(yellow) Zinc H 2 O ct> 2 SO 2 P20 5 Zn. F 3 0? CuO CO, CuO 60,986 14,220 3,996 10,345 2,394 2,848 1,085 4,325 561 7,623 5,332 3,996 8,017 9,703 7,475 4,309 60,986 170,640 127,872 320,683 156,610 159,466 68,947 121,111 32,947 Iron Carbonic oxide Cuprous oxide COMBUSTION. Combustion is the rapid combination of combustible material (fuel) with oxygen. SPONTANEOUS COMBUSTION. In order to start the combustion of a combustible body it is generally necessary to elevate its temperature or to bring it in contact with a burning body. In other words, it must be ignited. If a body undergoes com- bustion without ignition it is a case of spontaneous combustion ; and if combustion takes place without the appearance of a flame or light it is called slow combustion. INFLAMMABLE BODIES. Bodies which are able to undergo combustion as with the appearance of a flame are called inflammable. EXPLOSIVE BODIES. If combustion of a body takes place at once or sim- ultaneously throughout its whole mass, an explosion generally takes place, especially if the body is confined in a limited space and if the products of the combustion are of a gaseous nature. Therefore such bodies are called explosives. AIR REQUIRED IN COMBUSTION. The volume of air consumed chemically in the com- bustion of fuel is expressed by the formula: .40) A = volume of air as at 62 F., and under one atmos- phere of pressure, in cubic feet per pound of fuel A' weight of air as at 62 F. per pound of fuel. (7 = percentage of constituent carbon. H = percentage of constituent hydrogen. O = percentage of constituent oxygen. HEAT. 37 The weight of the air thus found by volume is equal to the volume divided by 13.14. Or it is found directly by the formula: ^'=.116(C+3If .40) In these formulae the heat evolved by the combus- tion of the sulphur constituent is not noticed, as it is trifling in proportion. GASEOUS PRODUCTS. The volume of the volatile or gaseous products of the complete combustion of one pound of a fuel, as at 62 F., at atmospheric pressure, is, by formula: V= 1.52 (7+ 5.52S" The weight of the gaseous products is, by formula: w = .1260+. 358 H y= volume of gaseous products, in cubic feet. tc == weight of gaseous products, in pounds. C =- percentage of constituent carbon. H= percentage of constituent hydrogen. The volume at any other temperature is found by tfce formula for expansion of gases, given elsewhere. The proportion of free or unconsumed air usual y present in the gaseous products is determined by mum- plying the percentage of oxygen , found by analysis, by 4.35. The product is the percentage of free air in parts of t/ whole mixture. HEAT GENERATED. The heat generated by combustion is as follows: Carbon ....................... 14,500 heat units per pound Hydrogen ...................... 62,000 S ulphur .............. ; ......... 4,000 The heating power of fuels containing carbon ar>d hydrogen is approximately expressed by the formula: h = 145 (C + 4.28H) in which h is the total heat of combustion. The evaporative efficiency for one pound of fuel is - e = .15(O+4.29.ff) e = weight of water evaporable from and at 21 2P, Jn pounds, per pound of fuel. The maximum temperature of combustion of carbon is about 5,000 F. ; and that of hydrogen is about 5,800 JP. 38 MECHANICAL REFRIGERATION. HEAT OF COMBUSTION OF FUELS. Fuel. Air Chemically Consumed per Pound of Fuel. Total Heat of Combus- tion of One Pound of Fuel. Equivalent Svaporative Power, from and at 212 F., Water per Pound of Fuel. Coal of average compo- 1 sit/ion Pounds. 10.7 10.81 8.85 11.85 6.09 4.57 9.51 7.52 5.24 9.9 4.26 14.33 17.93 Cub. Ft. at 62 F. 140 142 116 156 80 60 125 99 69 130 56 188 235 Units. 14,700 13,548 13,108 17,040 10,974 7,951 13,006 12,279 8,260 12,325 8,144 20,411 27,531 Pounds. 15.22 14.02 13.57 17.64 11.36 8.20 13.46 12.71 9.53 12.76 8.43 21.13 28.50 Coke Lignite Asphalte Wood desiccated Wood, 25 per cent ture mois- 1 Wood charcoal, cated desic- 1 Peat, desiccated. Peat, 30 per cent mois- ) Peat charcoal, desic- 1 Straw . . Petroleum oils Coal gras, per cubic foot | 630 .70 at 62 U F j COAL. Coal consists mainly of carbon, which varies from 50 per cent to 80 per cent, by weight, of the fuel. Lignite or brown coal contains from 56 to 76 per cent of carbon. The average composition of coal is, say, 80 per cent of carbon, 5 per cent of hydrogen, 1% per cent of sulphur, 1 per cent of nitrogen, 8 per cent of oxygen, and 4 per cent of ash. The fixed carbon or coke averages 61 percent. The average specific gravity is 1.279: average weight of a solid cubic foot, 80 pounds; and of a cubic foot heaped, 50 pounds; average bulk of one ton heaped, 44% cubic feet; equivalent evaporative efficiency, 15.40 pounds of water per pound of coal, from and at 212 F. Bituminous coals hold from 6 per cent to 10 per cent of water hygroscopically; Welsh coals from % per cent to 2M per cent. COKE. Coke contains from 85 to 97% per cent of carbon; from M to 2 per cent of sulphur, and from 1% to 14% per cent of ash. The average composition may be taken as 93% per cent of carbon, 1^ per cent of sulphur, 5% per cent of ash. It weighs from 40 pounds to 50 pounds per cubic foot solid, and about 30 pounds broken and heaped. The volume of one ton heaped is from 70 to 80 cubic HEAT. ^ 39 feet; average, 75 cubic feet. Coke is capable of absorb- ing from 15 to 20 per cent of moisture. There is or- dinarily from 5 per cent to 10 per cent of hygrometric moisture in coke. LIGNITE. Lignite or brown coal consists chiefly of carbon, oxy- gen and nitrogen; averaging in perfect lignite, 69 per cent of carbon, 5 per cent of hydrogen, 20 per cent of oxygen and nitrogen, and 6 per cent of ash. The weight is about 80 pounds per cubic foot. Imperfect lignite weighs about 72 pounds per cubic foot. CHIMNEY AND GRATE. The quantity of good coal, C,in pounds, that may be consumed per hour with a chimney having the height, If, above the grate bars, a sectional area, A, in square feet at the top, may be expressed by the formula C=16 A VI? and the total area of flre grate G in square feet 1071 HEAT BY MECHANICAL MEANS. Mechanical work is also a source of heat, and in nearly all cases where work is expended, the appearance of an equivalent amount of heat is observed.. The heat due to friction, percussion, etc., is an example of this kind, as also is the heat generated by the compression of gases and vapors (see Thermodynamics). The height of chimney for a given total grate area, the diameter at the top being equal to one-thirtieth of the height, is The side of a square chimney equal in sectional area to a given round chimney is equal to the product of the diameter by 0.886; the equivalent fraction of the height for the side of a square chimney is one-thirty-fourth. Conversely, the diameter of a round chimney equal in sectional area to a given square chimney is equal to the product of the side of the square by 1.13. When the top diameter of the chimney is one-thir- tieth of the height a good proportion the quantity of coal that may be consumed per hour is expressed by the formula 40 MECHANICAL REFRIGERATION, CHAPTER V. FLUIDS; GASES; VAPORS. FLUIDS IN GENERAL. Fluids may be generally defined as bodies whose molecules are displaced by the slightest force, which property is also called fluidity, and it is possessed in a much larger degree by gases than by liquids. Gases are eminently compressible and expansible, while liquids are so but in a slight degree. VISCOSITY. The property of liquid to drag adjacent particles a ong with it is called viscosity (Internal Friction). PASCAL'S LAW. Pressure exerted anywhere upon a liquid is trans- itted undiminished in all directions and acts with the same force on all equal surfaces in a direction at right angles to those surfaces. BUOYANCY OF LIQUIDS. The pressure which the upper layer of a liquid exerts on the lower layers, is consequently also exerted in an upward direction, causing what is termed the buoyancy ol! liquids. It is on account of the buoyancy of liquids tlhat a body weighed under liquid loses a part of its \reight, equal to the weight of the displaced liquid ( Archimedian principle). SPECIFIC GRAVITY DETERMINATION. By ascertaining the loss in weight of a body immersed under water its volume may be readily ascertained, it being equal to the volume of water corresponding to the lost weight. This principle is used to determine the specific gravities of bodies in various ways; for instance, for solid bodies, by dividing their weight in air by the loss of weight which they sustain when weighed under water. HYDROMETERS. From among the instruments frequently used to ascertain the specific gravity of liquids, and by inference their strength, we mention those called hydrometers as based on the Archimedian principle. They are generally made of a weighted body (usually of glass), having a thinner stem at the upper end provided with a scale di- vided in degrees. The degrees may be arbitrary or show specific gravities or the strength of some particular liquid FLUIDS; GASES; VAPOliS. 41 or solution in per cents; in the latter case the instru- ment is called Saccharometer, Salometer, Alcoholometer, Acidometer, Alkalimeter, etc., according to the liquid it is designed to test. Hydrometers for different liquids or purposes, provided they cover the same range of specific gravities, may be used for either liquid when the relation their degrees bear to each other is known. For some of the more current hydrometers, these relations are shown in the following table : TABLE SHOWING SPECIFIC GRAVITY CORRESPONDING TO DEGREES, TWADDLE, BEAUME AND BECK, FOR LIQUIDS HEAVIER THAN WATER. '1-1 Q) Corresponding Sp. Gr. It Corresponding Sp. Gr. sl 3Q Twaddle Beau me. Beck. if 3Q Twaddle Bcaume. Beck. 1.000 1.000 1.000 21 1.105 L1M .1409 1 1.005 1.007 1,0059 22 1.110 1.176 .1486 2 1.010 1.014 1.0119 23 1.115 1.185 .1565 3 1.015 1.020 1.0180 24 1.120 1.195 .1644 4 1.020 1.028 1.0241 25 1.125 1205 .1724 5 1.025 1.034 1.0303 26 1.130 1.215 .1806 6 1.030 1.041 1.0366 27 1.135 1.225 .1888 7 1.035 1.049 1.0429 28 1.140 1.236 .1972 8 1.040 1.057 1.0194 29 1.145 1245 .2057 9 1.045 1064 1.0559 30 1.150 1.256 1.2143 10 1.050 1.072 1.0325 32 1.160 1.278 1.2319 11 1.055 i.o;o 1.0692 34 1.170 1.300 1.2500 12 l.OfO 1.088 1.0759 36 1.180 1.324 1.2380 13 1.065 1.096 1.0828 88 1.190 1.349 1.2879 14 1.070 1.104 1.0897 40 1.200 1.375 .3077 15 1.075 1.113 1.0068 45 1.225 1.442 .3600 16 1.080 1.121 1.1039 50 1.250 1.515 1.4167 17 1.085 1.130 l.llll 55 1.275 1.596 .4783 18 1.090 1.138 1.1184 60 1.300 1.690 5454 19 1.095 1.147 1.1258 65 1.325 1.793 .6190 20 1.100 1.157 1.1333 7U 1.350 1.909 1.7000 There Is a slight difference between the indications of the Reaume scale in different countries. The manufacturing chem- ists of the United States have adopted the following formula for converting the Beaume degrees into specific gravity: Specific gravity^ which gives specific weight slightly higher than those in the fore- going table. (See also table in Appendix.) PRESSURE OF LIQUIDS. The pressure exerted by a column of liquid at its bottom or base is proportional to the vertical height of the column of liquid, its specific gravity and to the area of the bottom, and independent of the shape or thickness pf the column of liquid. 42 MECHANICAL REFRIGERATION. WATER PRESSURE. The pressure in pounds, P, of a column of water h feet high is P s= .4335 h per square inch, and P as 62.425 h per square foot. SURFACE TENSION OF LIQUIDS. The layer of a liquid which separates the same from a gas or vacuum has a greater cohesion than any other layer of the liquid, owing to the fact that the attraction exerted on this layer by the interior of the liquid is not counteracted by any attraction on the outside. The sur- face is, as it were, stretched over by an elastic skin which exerts a pressure on the interior, which pressure is termed surface tension. It increases with the co- hesion of the liquid. VELOCITY OF FLOW OF LIQUIDS. The velocity with which a liquid flows through an opening depends only on the height of the liquid above the orifice and is independent of the density of the liquid. The velocity, v, in feet per second is expressed by the for- mula V= V 2 g h =8 V h g being the acceleration per second due to gravity, and h the depth of the orifice below the surface, both expressed in feet. QUANTITY OF FLOW. The quantity of a liquid, say water, discharged through an opening depends on the area of the opening, A (in square feet), and also on the shape, etc., of the ori- fice. If the orifice is a hole in the thin wall of a vessel, the quantity, E (in cubic feet), discharged is expressed by A short cylindrical appendix to the opening woulc" increase the discharge to E 6.56 A */2h.- and an appendix haying the best form of a conic frus- trum will nearly discharge the theoretical amount E 8 A V h FLUIDS; GASES; VAPORS. 43 FLOW OF WATER IN PIPES. The mean velocity, v, of water in a cast iron pipe of the length, Z, and the diameter, d, under the head, h, is v = The velocity is affected by the surface of pipe, and the viscosity or interior friction of the liquid (hydraulic friction). QUANTITY OF FLOW THROUGH PIPES. Dawning's formula for the quantity, E, in cubic feet of water discharged by channel or pipe under the head, /i, in feet is as follows: E = 100 a t/ I being the length of pipe in feet; a, sectional area of current in square feet; c, wetted perimeter in feet. D = 1 -~ = hydraulic mean depth. HEAD OF WATER The head, h, approximately required to move water with a velocity of 180 feet per minute through a clean cast iron pipe, having a diameter D inches and the length I in feet, is WATER POWER. The theoretical effect of water power expressed in foot-pounds per minute, is equal to the weight of the water falling per minute, multiplied by the height through which the water falls. Divided by 33,000, it expresses horse powers. The practical effect depends on the efficiency of the motor (water wheel, turbine, engine, etc.). The power required to lift water is calcu- lated in the same manner. HYDROSTATICS AND DYNAMICS. The science which treats of the condition of liquids while at rest is called hydrostatics, and that which treats of the motion of liquids is called hydrodynamics. 44 MECHANICAL REFRIGERATION. CONSTITUTION OF GASES. In a general way the term gas has been defined in the foregoing. Speaking more specifically, a gas is a body in which the distance between the constituent atoms or molecules is so great that the dimensions of the mole- cules themselves may be neglected in comparison there- with. The atoms or molecules in a gas are constantly vibrating to and fro, and the average momentum or energy of this motion represents the temperature of the gas. The vehemence or force with which the atoms or molecules impinge on the walls of a surrounding vessel in consequence of this motion represents the pressure of the gas. PRESSURE AND TEMPERATURE. In accordance with the foregoing definition the pressure, volume and temperature of a gas are in direct connection, which is expressed by the laws of Boyle and St. Charles. BOYLE'S LAW. The law of Boyle or of Mariotte asserts that the vol- ume of a body of a perfect gas is inversely proportional to its pressure, density or elastic force, if its temperature remains the same. ST. CHARLES LAW. If a gaseous body is heated while the pressure re- mains constant, its volume increases proportionally with the temperature. The increase of volume for every degree F. is equal to ^3 of its volume at 32 F. UNIT OF PRESSURE. The general unit of pressure is the pressure of the atmosphere per square inch, which is equal to that of a column of water of about thirty feet, or that of a col- umn of mercury of about thirty inches, and also equiva- lent to a pressure of 14.7 pounds in round numbers fif- teen pounds per square inch. ABSOLUTE AND GAUGE PRESSURE. The pressure gauges in general- use indicate pressure in pounds above the atmospheric pressure; it is called gauge pressure. To convert gauge pressure into abso- lute pressure 14.7 has to be added to the former. Smaller pressures are designated by the number of inches of mercury which they will sustain, or, after the FLtTIDS; GASES; VAPORS. 45 F ranch system, by millimeters of mercury, which are compared in the following table for ordinary pressures of the surrounding atmosphere. COMPARISON OF THE BRITISH AND METRICAL BAROMETERS. Inches. Millimeters. Inches. Millimeters. Inches. Millimeters. 27.00 685.788 38.40 721.347 29.80 756.906 27.10 688.338 38.50 733.887 29.90 759.446 27.20 690.867 28.60. 736.437 30.00 761.986 27.30 693.407 38.70 738.967 30.10 764.536 27.40 695.947 28.80 731.507 30.20 767.066 87.50 698.487 28.90 734.047 30.30 769.606 87.60 701,037 39.00 736.587 30.40 773.146 17.70 703.567 39.10 739.127 30.50 774.686 27.80 706.107 29.20 741.667 30.60 777.226 87.90 708.647 39.30 744.306 30.70 779. 766 88.00 711.187 29.40 746.746 30.80 782.306 28.10 713.737 29.50 749.286 30.90 784.846 28.30 716.267 29.60 751.836 88.30 718.807 29.70 754.366 ACTION OF VACUUM. The pressure of the atmosphere is the cause of the raising of water by suction pumps, the air in the pumps being removed by the movement of the piston, and its space occupied by water forced up by the pressure of the outside atmosphere. For the same reason such a pump cannot lift water higher than thirty-two feet, a column of water of this height exerting nearly the same pressure as the atmosphere at the earth's surface. For the same reason the mercury in a barometer (or glass tube from -which the air is withdrawn) stands about twenty-nine inches high, vary ing with the pressureof the atmosphere, between twenty-seven and thirty inches at the earth's surface, but decreases with the height above the earth at the rate of 0.1 inch for 84 feet. MANOMETERS GAUGES. The instruments for measuring higher gaseous press- ures are usually called manometers or gauges. WEIGHT OF GASES. The weight of gases is determined by weighing a glass balloon filled with the same, and by subtracting from this weight that of balloon after the same has been evacuated by means of an air pump. One hundred cubic inches of air weighs 31 grains at a pressure of the atmos- phere of 30 inches, and at a temperature of 60 F.; there- fore the density of air is 0.001293 or y f $ that of water. 46 MECHANICAL UEFRIGERATION. One hundred cubic inches of hydrogen, the lightest of the common gases weighs 2.14 grains. MIXTURE OF GASES. Two or more gases present in vessels, communicat- ing with each other, mix readily, and each portion of the mixture contains the different gases in the same pro- portion. Mixtures of gases follow the same laws as simple gases. DALTON'S LAW. The pressure exerted on the interior walls of a vessel containing a mixture of gases is equal to the sum of the pressures which would be exerted if each of the gases occupied the vessel itself alone. BUOYANCY OF GASES. The Archimedian principle applies also for gases; hence a body lighter than air will ascend (air balloons, smoke, etc.). LIQUEFACTION OF GASES. If sufficient pressure be applied to a gas and the tem- perature is sufficiently lowered all gases can be com- pressed so as to assume the liquid state. HEAT OF COMPRESSION. When gases or vapors are being compressed, the energy or work spent to accomplish the compression appears in the form of heat. CRITICAL TEMPERATURE. There appears to exist for each gas a temperature above which it cannot be liquefied, no matter what amount of pressure is used. It is called the critical tem- perature. Below this temperature all gases or vapors may be liquefied if sufficient pressure is used. CRITICAL PRESSURE. The pressure which causes liquefaction of a gas at or as near below the critical temperature as possible, is called the critical pressure. Between these two tempera- tures that is, in the neighborhood of the critical point the transition from one state to another is unrecog- nizable. CRITICAL VOLUME. The critical volume of a gas is its volume at the critical point, measured with its volume at the freezing FLUIDS; GASES; VAPORS. 47 point, under the pressure of an atmosphere as unit. The critical temperature, pressure and volume are fre- quently referred to as critical data. TABLE OF CRITICAL DATA. Substance. Critical Press- ure in Atmos- pheres. Critical Tem- perature, Degrees C. Critical Volume. Ammonia, 115 130 Aethylen 61 10 0.00560 Alcohol 67 235 0.00713 Acetic acid 76.4 231.5 0.0110 Aethylic ether 37.5 200 01344 Acetate of aethyl. . 42.2 240 01222 Benzol 60 292 0.00981 Bisulphide of carbon.. Butyrate of amyl 77.8 23.8 275 332 0.0096 03809 Carbonic acid 77 31 0066 Cumol 31.8 347.2 0.0258 Hydrogen . 20 3 240 Nitrous oxide (N 2 O)... 75 50 35.4 118 0.00480 Propylic alcohol 63.3 256 0.00968 Sulphurous acid . . 79 155 4 Toluol 40 320.8 02138 Water 195 358 00187 SPECIFIC HEAT OF GASES. A gas may be heated while its volume is kept con- stant and also while its pressure remains constant. In the former case the pressure increases and in the latter the volume increases. Therefore we make a distinction between specific heat of gases at a constant volume or at a constant pressure. In the former case the heat added is only used to increase the momentum of the molecules, while in the latter case an additional amount of heat is required to do the work of expanding the gas against the pressure of the atmosphere. The specific heat of all permanent gases for equal volumes at con- stant pressure is nearly the same and about 0.2374 water taken as unity. TABLE OF SPECIFIC HEAT OF GASES. For Equal Weights. (Water = 1.) At Constant Pressure. At Constant Volume. Air . .2377 .2164 .2479 3.4046 .5929 .2440 .2182 .1688 .1714 .1768 2.4096 .4683 .1740 .1559 .3050 .3700 .1246 Carbonic acid (CO 2 ) " oxide (CO) Hydrogen . Light carbureted hydrogen Nitrogen Oxygen ^. Steam saturated Steam gas . . .4750 .1553 Sulphurous acid 48 MECHANICAL REFRIGERATION. ISOTHERMAL CHANGES. A gas is said to be expanded or compressed isother- mally when its temperature remains constant during expansion or compression, and an isothermal curve or line represents graphically the relations of pressure and volume under such conditions. ADIABATIC CHANGES. As gas is said to be expanded or compressed adiabat- ically when no heat is added or abstracted from the same during expansion or compression, an adiabatic line or curve represents graphically the relations of pressure and volume under such conditions. FREE EXPANSION. When gas expands against an external pressure much less than its own, the expansion is said to be free. The refrigeration due to the work done by such expansion may be used to liquefy air. (See Linde's method.) LATENT HEAT OF EXPANSION. When a gas expands while doing work, such 9 propelling a piston, an amount of heat equivalent to tb work done becomes latent or disappears. It is called the latent heat of expansion. VOLUME AND PRESSURE. The relations of volume pressure and temperature of gases are embodied in the following formulae in which V stands for the initial volume of a gas at the initial tem- perature t and the initial pressure p. F 1 , t t and j? stand for the corresponding final volume, temperature and pressure. For different temperatures = V t+461 For different pressures V 1 = V-2- i P 1 For different temperature and pressure pM* +461) If the initial temperature is 60 F. and ^he initial pressure that of the atmosphere, the final pressure may be found after the formula FLUIDS; GASES; VAPORS. 49 r l If the volume is constant P 1 35.58 If the temperatures in above formula are expressed degrees Fahrenheit above absolute zero, the figure 461 is to be omitted. PERFECT GAS. The above rules and formulae apply, strictly speak- ing, only to a perfect or ideal gas, that is a gas in which the dimensions of the molecules may be neglected as re- gards the distance between them. Therefore when a gas approaches the state of a vapor, these laws do no more hold good. ABSOLUTE ZERO AGAIN. The expansion of a perfect gas under constant pressure being ^ g of its volume at 32 F. (freezing point), it follows that if a perfect gas be cooled down to a temperature of 493 below freezing, or 461 below zero Fahrenheit, its volume will become zero. Hence this point is adopted as the absolute zero of temperature. (See also former paragraph on this subject.) VELOCITY OF SOUND. The velocity, v, of sound in gases is expressed by the formula In which formula g is the force of gravity, h the barometric height, d the density of mercury, d the density of the gas, t its temperature, c its specific heat at constant pressure, and c t its specific heat at con- * C stant volume. Hence the quotient, , for a certain gas ^i can be determined by the velocity of sound in the same. FRICTION OF GAS IN PIPES. The loss of pressure in pounds, P, sustained by gas in traveling through a pipe having the diameter d in inches, for a distance of I feet, and having a velocity of n feet, is p = 0.00936 !LiL 50 MECHANICAL REFRIGERATION ABSORPTION OF GASES. Gases are absorbed by liquids ; the quantities of gases so absorbed depend on the nature of the gas and liquid, and generally increase with the pressure and decrease with the temperature. During the absorption of gas by a liquid a definite amount of heat is generated, which heat is again absorbed when the gas is driven from the liquid by increase of temperature or decrease of pressure. Solids, especially porous substances, also absorb gases. Thus charcoal absorbs ninety times its own volume of ammonia gas. VAPORS. As long as a volatile substance is above its critical temperature it is called a gas, and if below that it is called a vapor. This definition, although the most definite is not the most popular one. Frequently a vapor is defined as rep- resenting that gaseous condition at which a substance has the maximum density for that temperature or pressure. Generally gaseous bodies are called vapors when they are near the point of their maximum density, and a distinction is made between saturated vapor, superheated vapor and wet vapor. SATURATED VAPOR. A vapor is saturated when it is still in contact with some of its liquid; vapors in the saturated state are at their maximum density for that temperature. Com- pression of a saturated vapor, without change of tem- perature, produces a proportional amount of liquefaction. DRY OR SUPERHEATED VAPOR. Vapors whieh are not saturated are also called dry or superheated vapors, and behave like permanent gases. WET VAPOR. A saturated vapor which holds in suspension parti- cles of its liquid is called wet or moist vapor. TENSION OF VAPORS. Like gases, vapors have a certain elastic force, by virtue of which they exert a certain pressure on sur- rounding surfaces. This elastic force varies with the nature of the liquid and the temperature, and is also called the tension of the vapor, FLUIDS; GASBS; VAPORS 51 VAPORIZATION. A liquid exposed to the atmosphere or to a vacuum forms vapors until the space above the liquid contains vapor of the maximum density for the temperature. EBULLITION. If the temperature is high enough the vaporization takes place throughout the liquid by the rapid produc- tion of bubbles of vapor. This is called ebullition, and the temperature at which it takes place is a constant one for one and the same liquid under a given pressure. BOILING POINT. The temperature at which ebullition of a liquid takes place is called its boiling point, for the pressure then ob- taining. When no special pressure is mentioned we understand by boiling point that temperature at which liquids boil under the pressure of the atmosphere. DIFFERENT BOILING POINTS. The boiling point varies with the nature of the liquid, and always increases with the pressure. It is not affected by the temperature of the source of heat, the temperature of the liquid remaining constant as long as ebullition takes place. The heat which is imparted to a boiling liquid, but which does not show itself by an increase of temperature, is called the latent heat of vaporization. ELEVATION OF BOILING POINT. Substances held in solution by liquids raise their boiling point. Thus a saturated solution of common salt boils at 214 and one of chloride of calcium at 370. The boiling point of pure water may also be raised above the boiling point; for water free from gases to over 260 without showing signs of boiling. This retardation of boiling sometimes takes place in boilers, and may cause explosions, if not guarded against by a timely motion produced in the water. LATENT HEAT OF VAPORIZATION. The heat which becomes latent during the process of volatilization is composed of two distinct parts. The one part is absorbed while doing the work of disintegrating the molecular structure while doing INTERNAL WORK, as it is termed. The other part of heat which becomes latent is 52 MECHANICAL REFRIGERATION. absorbed while doing the work of expansion against the pressure of the atmosphere, and is called the EXTERNAL WORK. In a liquid evaporized in vacuum, in which case no pressure is to be overcome, the external work becomes zero, and only heat is absorbed to do the internal work of vaporization (free expansion}. REFRIGERATING EFFECTS. If liquids possess a boiling point below the tempera- ture of the atmosphere the latent heat of vaporization is drawn from its immediate surrounding object, causing a reduction of temperature, i. e., refrigeration. LIQUEFACTION OF VAPORS. When vapors pass from the aeriform into the liquid state, that is, when they are liquefied, the heat which bo- came latent during evaporation appears again, and must I e removed by cooling. Vapors of liquids the boiling point i ^f which is above the ordinary temperature can be liquefied at the ordinary temperature without additional pressure (distilling condensation}. Permanent gases require addi- tional pressure, and in some cases considerable refrigera- tion, to become liquefied (compression of gases). D ALTON'S LAW FOR VAPORS. The tension and consequently the amount of vapor of a certain substance which saturates a given space is the same for the same temperature, whether this space contains a gas or is a vacuum. The tension of the mix- ture of a gas and a vapor is equal to the sum of the ten- sions which each would possess if it occupied the same space alone. VAPORS FROM MIXED LIQUIDS. The tension of vapor from mixed liquids (which have no chemical .or solvent action on each other) is nearly equal to the sum of tension of the vapor of the two separate liquids. SUBLIMATION. The change of a solid to the vaporous state without first passing through the liquid state is called sublimation (camphor, ice). DISSOCIATION. The term dissociation is used to denote the separa- tion of a chemical compound into its constituent parts, especially if the separation is brought about by subject- ing the compound to a high temperature. MOLECULAR DYNAMICS. 53 CHAPTER VI. MOLECULAR DYNAMICS. MOLECULAR KINETICS. It has already been stated that the laws of Boyle and St. Charles are in accordance with the molecular theory, by the consequent development of which a num- ber of other relations have been established which are of the utmost importance in all discussions of energy, es- pecially those of thermodynamical nature. Applied to gases, this theory means that the rectilinear progressive motion of the molecules, which constitutes the body of a gas, represents by its kinetic energy the temperature of a gas, and by the number of impacts of its molecules against the wall of the vessel containing the gas, its pressure. DENSITY OF GASES. If m represents the mass of a molecule and u the average velocity of its rectilinear progressive motion, the kinetic energy, E (i.e., the temperature), of the molecule is expressed by If the unit of volume, say a cubic foot of a gas, con- tains JV molecules of the mass, m, the density of the gas, p, is p= m N PRESSURE OF GASES. The number of molecules which collide with the inte- rior surf aces of a cube of above size is equal to N it, and hence the number which collide with one of the interior surfaces of the cube (one foot square): Nu 6 The number of impacts multiplied by the momentum of the impact of each molecule, 2 ra it, yields the pressure: p = -^-Nmu 2 = ^-pu z o o AVOGADRO'S LAW. At the same temperature and pressure equal volumes of different gases contain the same number of molecules. Hence the molecular weights of gases are proportional to their densities, 54 MECHANICAL REFRIGERATION. MOLECULAR VELOCITY. The average velocity of the molecules, u t is accord- ingly For hydrogen we find u = 1,842 meters per second. If M is the molecular weight of a gas referred to hydrogen as unit (p being proportional to M) the aver- age velocity of the molecules is expressed by u = 1,842 -* / -_ meters per second. \ M The average distance, L, which a molecule travels in rec- tilinear direction before it meets another molecule is ex- pressed by the formula L== 1.41 ics* in which \ is the average distance of the molecules, and therefore A. 3 the size of the cube which contains one molecule on an average. L accordingly has been found to be for hydrogen 0.000185 millimeter; for carbonic acid, 0.000068mm.; for ammonia 0.000074 mm. INTERNAL FRICTION OF GASES. The internal friction, 77, of a gas is expressed by the equation The velocity of sound in different gases is inversely proportional to the square root of their molecular weights (see page 49). TOTAL HEAT ENERGY OF MOLECULES. The total heat energy of a body is composed of the energy due to the progressive motion of its molecules, and the interior energy which is represented by possible rotatory motions of the molecules, or by motions of the atoms composing the molecule. In gases, and probably also in liquids and solid bodies, the former portion of energy is proportional to the absolute temperature, so that at the absolute zero 461 F. the progressive mo- tion of the atoms would cease. MOLECULAR DYNAMICS. 55 LAW OF GAY LUSSAC. Since chemical combinations between different ele- ments take place in the proportion of their molecular weights, and since equal volumes of gases contain equal numbers of molecules, the chemical combination between gaseous elements must take place by equal volumes or their rational multiples, and the volume of the combina- tion if gaseous bears equally a simple numerical relation to that of the elements. EXPANSION OP GASES. Since the same number of molecules of different gases occupy the same volume at equal temperatures and pressure, the expansion by heat of all gasec under con- stant pressure must be the same, and for perfect gases it is the same for all temperatures, being equal to the ^ 5 part of the volume of a gas at the freezing point and at the pressure of one atmosphere. This is tantamount to saying that the volume of gas under constant pressure is proportional to its absolute temperature, T= 461 -f- * EQUATION FOR PERFECT GASES. The increase of pressure of a gas heated at constant volume being likewise proportional to the absolute tem- perature and equal to ^ of its volume at the freezing point, the product of pressure and volume, p v, must be likewise, and hence it can be expressed by the equation p v = E T in which R is a constant factor, depending only upon the units used. T standing for absolute temperature, it may be written p and v standing for pressure and volume at the tem- perature of 32 F., both being unit. GENERAL EQUATION FOR GASES AND LIQUIDS. . Tnis formula answers for a perfect gas in which the dimension of the molecules and their mutual attraction disappear in comparison with their volume and the expansive force due to the temperature. If the dimen- sions and mutual attraction are taken into consideration, the formula according to Van der Waals reads: 56 MECHANICAL REFRIGERATION. In this formula the signs have the same meaning as in the former equation, except the two constants a and 6, which differ with the nature of the gas ~\ atoning for the influence of the molecular attraction which may be derived from the deviation of the gas from Boyle's law; b stands for the influence of the volume of the molecule; it is equal to four times the volume of the molecules. Its value may be ascertained by inserting the value found for a into the formula of Van der Waals. How- ever, it is generally more convsnient and of more prac- tical application to derive the values a and b from the critical data, as will be shown later on. The formula of Van der Waals answers not only for all gases, but for the liquid condition as well, as far as changes of volume, pressure and temperature are con- cerned, provided, however, that the changes take place homogeneously and that the molecular constitution of the substance is not altered during the change. CRITICAL CONDITION. If this formula is elaborated numerically as to vol- ume for given temperatures and pressures, we always obtain one real positive expression for volume except for pressures near the point of liquefaction at tempera- tures below the critical point. Here the formula does not apply on account of the so-called critical condition (partly gas and partly liquid) which the substance maintains at this stage. These conditions become readily apparent by an elaboration of the equation of Van der Waals, for if the equation which may also be written is developed after powers of v ( p and v = unit), we obtain This equation being a cubical one, it may be satisfied by three values, which may all be real or one of which may be real and the other two imaginary. Accordingly, we MOLECULAR DYNAMICS. 57 find for all temperatures above the critical point for any given pressure only one value for volume ; except for temperatures below the critical point for certain values of p, i.e., for pressures near the point of lique- faction for that temperature, or nearing the boiling point for that pressure. At these stages the substance is under so-called critical conditions, and here we find three different values for v, one of which may stand for the volume of the substance in its gaseous form, another for its volume as a liquid, and the third for an inter- mediate volume CRITICAL DATA. When, on increasing temperature and pressure these three values for volume converge into one, that is, if the three real roots of the equation become equal, we have reached the critical volume, that is, that volume which corresponds to the critical pressure and to the critical temperature. At this, the critical point, the substance passes gradually and without showing a separation into liquid and gas, that is to say homogeneously, from the gaseous into the liquid state; there is no intermediate stage at this temperature between the volume of the liquid and the volume of the gas, as is the case at tem- peratures below the critical point and at pressures cor- responding to the boiling point. The values of temperature pressure and volume at which the three roots of the above equation become equal is found by the following considerations: If in a cubical equation of the form the three roots become equal to each other = x t the fol- lowing relations obtain : Applying this to the above equation, which may also be written by inserting the signs, q>, n and 5 to stand for volume, pressure and temperature at the critical point we find 68 MECHANICAL BEFKIGERATION. *~ which may be simplified thus: ^=3 6 ^ __ 8 o 493 27 (1 + a) b (16) We see from these formulae how the two constants, a and 6, which may be deduced from the deviations from Boyle's law, determine the critical pressure, temperature and volume. APPLICATION OF GENERAL EQUATION. On the other hand (and which is practically of more importance), it is readily seen how the two constants, a and 6, and therefore the behavior of a homogeneous gas or liquid as to volume, temperature and pressure, may be derived from the critical data, viz. : 3 S _ it

and p = e it and T m , the general equation may be written If the values for TT,

46). If v is smaller than 4 b the formula may possibly give correct results, but when it does not such a result does not vitiate the admissibility of the theory in other re- spects, as Van der Waals has shown. OTHER MOLECULAR DIMENSIONS. In accordance with the foregoing the average space, Y, occupied by each molecule of a gas is expressed by y- JL ** 4 32 X 273 it and the specific weight, w, of a gas (water at 39 F. = 1): M 22350 y M being the molecular weight in grams, and 22,350 c. c. the volume occupied by the same at 32PF., and at the pressure of one atmosphere. If the molecules are supposed to be of spherical form their diameter, s, is expressed by the formula s = 6 V~2~I, y = 8.5 L y L being the average distance which a molecule travels, as stated above, viz. : L -- _ V2 7TS 2 60 MECHANICAL REFRIGfiRATloK. ABSOLUTE BOILING POINT. The definition of the boiling point as given hereto- fore fits only for a certain pressure, but in accordance with the critical conditions we can define an absolute boiling point as the temperature at which a liquid will assume the aeriform state, ho matter what the press- ure is, viz., the critical temperature. CAPILLARY ATTRACTION. Since capillary attraction (in consequence of which liquids rise above their surface in narrow tubes) and also the surface tension of liquids are both functions of the cohesion of liquids, and since the cohesion diminishes with the temperature, the capillary attraction must do likewise; and it has been shown that it becomes zero at the critical temperature or at the absolute boiling point. CRITICAL VOLUME. At the critical temperature the change from the liquid to the gaseous condition requires no interior work, and therefore the latent heat of vaporization at this temperature must be equal to zero. The volumes of a certain weight of liquid or vapor of a substance at the critical temperature must likewise be the same. GAS AND VAPOR. If, with Andrews, we confine the conception of vapor to a fluid below its critical point, and that of a gas to a fluid above its critical point, we can also define as vapor such aeriform fluids as may be compressed into a liquid by pressure alone without lowering temperature; and by the same token a gas is an aeriform fluid which cannot be compressed into a liquid by pressure alone without lowering the temperature. By liquefaction we designate the production of a liquid separated from the vapor by a visible surface. LIQUEFACTION OF GASES. After the significance of the critical temperature had been duly understood and appreciated it became also possible to liquefy the most refrangible gases by pressure when cooled down below their critical tempera- ture. A novel way for the liquefaction of such gases, more especially air, has been devised by Linde, and the process employed by him is so simple and successful that it will doubtless become of practical value in many re- spects, more especially also practical refrigeration. THERMODYNAMICS. 6l CHAPTER VII. THERMODYNAMICS. THERMODYNAMICS. Thermodynamics as the science which treats of heat in relation to other forms of energy, and more especially of the relations between heat and mechanical energy. FIRST LAW OF THERMODYNAMICS. This law is a special case of the general law express- ing the convertibility of different forms of energy into one another. The first law of thermodynamics asserts the equivalence of heat and work or mechanical energy, and states their numerical relation. Accordingly heat and work may be converted into each other at the rate of 778 foot-pounds for every unit of heat, and vice versa. SECOND LAW OF THERMODYNAMICS. The foregoing law holds good without any limitation as far as the conversion of work or mechanical energy into heat is concerned. It must be qualified, however, with respect to the conversion of heat into work. It amounts to this, that of a certain given amount of heat at a given temperature only a certain but well defined portion can be converted into work, while the remaining portion must remain unconverted as heat of a lower temperature. This outcome is a natural consequence of the condition that heat cannot be directly transferred from a colder to a warmer body. EQUIVALENT UNITS. In accordance with the first law, we can measure quantities of heat by the heat unit or by the unit of work (foot-pound) and we can also measure it by its equivalent in heat units as well as by the units of work. The figure designating the number of foot-pounds equivalent to the unit of heat (778), i. e., the mechanical equivalent of heat, is frequently referred to by the letter J. When quantities of work and heat are brought in juxtaposition in equations, etc., it is always understood that they are expressed by the same units, i. e., in either heat or work units. SECOND LAW QUALIFIED. In a system in which the changes are only such of heat and such of mechanical energy (work), the appear- ance of a certain amount of work is always accompanied by the disappearance of an equivalent amount of heat, 62 MECHANICAL REFRIGERATION. and the appearance of a certain amount of heat is always accompanied by the expenditure of an equivalent amount of mechanical energy. From this, however, it must not be concluded that by withdrawing a certain amount of heat from a warmer body we can convert it into its equivalent amount of mechanical energy. This is only the case under exceptional conditions ; but when, as in the case of practical requirements, the conversion of heat into work must be done by a continuous process it cannot be accomplished under conditions practically available. CONVERSION OF HEAT. The conversion of heat into mechanical work, and work into heat, takes place in many ways. Generally the change of volume or pressure brought about by heat changes mediates the conversion. The substance which is used to mediate the conversion is called the working medium or the working substance. MOLECULAR TRANSFER OF HEAT ENERGY. The manner in which heat is converted into mechan- ical work is readily understood on the basis of the molec-' ular theory, when the working fluid is a gas, the pressure of which, due to its molecular energy (heat) is employed to propel a piston. The molecules of the gas by colliding with the piston impart a portion of their molecular energy to the piston, moving the same forward; at the same time the energy of the molecules grows less, and indeed the temperature of the gas decreases as the piston moves ahead. If the work done by the piston and the heat lost by the gas were measured in the same units, it would be found that they were practically alike (pre- supposing we employ a perfect gas, consisting of simple molecules, undergoing no internal changes). GAS EXPANDING INTO VACUUM. If there had been no pressure on the piston (and the piston supposed to have no weight) in the foregoing experiment, the piston would have been moved by the expanding gas, without doing work during the expansion, and hence the temperature of the gas, while expanding under such conditions (against a vacuum), remains con- stant and unchanged, at least practically so. HEAT ENERGY OF GAS MIXTURES. The same would happen if two vessels, containing the same or different gases at different pressures, are THERMODYNAMICS. 63 brought in communication ; no change of heat takes place, while the pressures equalize themselves. Hence, the heat energy of a gas is independent of its volume, and the energy of a mixture of gases is equal to the sum of the energy of its constituents. DISSIPATION OF ENERGY. Accordingly we may allow a gas under pressure to dilate in such a way as to do a certain amount of work at the expense of an equivalent amount of heat, and we may allow it to expand without doing work. In the latter case the availability of the gas to mediate a cer- tain amount of work has not been utilized, has been dis- sipated, as it were, since the original condition of the gas cannot be re-established again without the expendi- ture of outside energy. ADIABATIC CHANGES. In the former case, when the gas was allowed to ex- pand while doing work, the greatest possible amount of work obtainable is produced when the pressure of the piston is always kept inflnitesimally less than that of the gas. If this is being done the original condition of the gas can be established by making the pressure on the piston only infinitesimally more than on the gas, when the gas will be compressed to its original volume and temperature (no heat having, been added to or ab- stracted from the gas during the operation). Both the operations of expansion and compression of the gas as conducted (without addition of heat, etc.) are therefore adiabatic changes, they are both reversible changes, and neither of them involves any dissipation of heat or energy. In the one change we have converted heat energy into work, and in the other work into heat. ISOTHERMAL CHANGES. The expansion of the gas while propelling a piston may be allowed to proceed while the energy imparted to the piston is replaced by heat supplied to the expanding gas from without. In this case the expanding gas is kept at the same temperature, and therefore it is said that the expansion proceeds isothermically. This operation may also be reversed and work converted into heat by apply- ing the power gained by raising the piston, to push the piston back, and withdrawing the beat liberated by 64 MECHANICAL REFRIGERATION. the work of compression as fast as it appears, so that the gas is always at the same temperature. (Isothermic compression.) If, during expansion, the temperature of the gas is always only inflnitesimally smaller, and dur- ing compression infinitesimally greater than the out- side temperature, both operations are considered to be reversible, and no dissipation of energy takes place dur- ing the performance of either of them. MAXIMUM CONVERSION. In conducting the operations in the foregoing (re- versible) manner we obtain the maximum yield of mutual conversion of work and heat obtainable by the expansion or compression of the gas in question. CONTINUOUS CONVERSION. While a body of gas may be used in the above way to convert a certain amount of heat into work, and we versa, it would not answer for the continuous conversion of work into heat, for if the operation of work produc- tion is reversed we simply re-establish the original con- dition without having accomplished any outside change whatever. PASSAGE OF HEAT. The fact that heat cannot of itself pass from a colder to a warmer body is also in harmony with the, molecular theory. The molecules of bodies having the same tem- perature possess also the same average energy, and therefore cannot impart energy to one another; much less can energy of heat pass from a colder to a warmer body. The ability of heat to do work is due to its nat- ural tendency to pass from a warmer to a colder body, and therefore, other circumstances being equal, is di- rectly proportional to the difference of temperature be- tween the warmer and colder body. REQUIREMENTS FOR CONTINUOUS CONVERSION. As stated, for the practical conversion of heat into work, we need a working medium that is a substance of some kind which mediates the conversion. As the heat which is communicated to this medium for the purpose of doing work is never entirely available for this purpose, but a portion of the heat always remains as heat of a lower temperature (not available for mechanical work except when it can pass to a temperature still lower), it fol- lows as a matter of course and also of necessity, that when THERMODYNAMICS. 65 we desire to convert heat into work by a continuous pro- cess we need not only a working substance but also a warm body, a source of heat (boiler, generator, etc.), and a body of lower temperature, to which the heat not avail- able for work in the operation may be discharged. The latter device is generally called a refrigerator or con- denser; in the case of many heat engines it is the atmos- phere. The same requirements, only in a reversed order, obtain for the continuous conversion of work into heat, i. e., when heat is to be transferred from a colder to a warmer body, the work expended compensating for the transfer (lifting heat). COMPONENTS OF HEAT CHANGES. The changes produced in a body by heat may be divided in several parts, viz., the elevation of tempera- ture, i. e.,the increase of energy of the molecules, the change produced by overcoming the interior cohesion, and by rearranging the molecular constitution of the body, and the change required to do outside work, overcoming pressure. MAXIMUM CONTINUOUS CONVERSION OF HEAT. The question as to the maximum amount of work which can be obtained from a certain amount of heat by continuous conversion, and the maximum amount of heat which can be obtained by or lifted by a certain amount of work, is one of the most important in ther- modynamics. It has been solved with the same result in various ways, the following giving the outlines of one of them. CYCLE OF OPERATIONS. The contrivances which are required to perform the operations, by which through the aid of the working medium, etc., heat is continuously transformed into work, or work into heat, come under the general head of machines. A series of operations of the kind mentioned which are so arranged that the working substance returns periodically to its original condition is also called a cycle of operations. REVERSIBLE CYCLE. If a cycle of operations is conducted in such a manner that all the changes or operations can be carried out in the opposite direction the cycle is what is called a revers- ible cycle. Operations can generally be made revers- OF THE Mkil\/r-r->.~ 66 MECHANICAL REFRIGERATION. ible, at least in theory, if the transfers of heat follow only infinitesimally small differences in temperature and the changes in volume take place under but infinites- imally small differences of pressure. Not all changes can be performed in a reversible manner, however. IDEAL CYCLE. For the continuous conversion of heat into work we require the performance of a cycle, so that the work- ing substance, which is generally not unlimited, may return periodically to its original condition, and may be used continuously over and over again. If at the same time the operations of the cycle are carried on re- versibly the conversion of heat into work takes place at the greatest possible rate. In other words, the maximum amount of work obtainable from a given amount of heat is realized if the working substance is passed through the operations of a reversible cycle. Practically we can only approach the conditions of a reversible cycle, for which reason it is also called an ideal cycle of operations. IDEAL CYCLES HAVE THE SAME EFFICIENCY. The proof that a cycle of reversible operations for the transformation of heat into work yields the greatest return of work for a given amount of heat, and vice versa, may be based on the axiom that no energy can be created, or on the fact that heat cannot pass from a colder to a warmer body. For if one cycle of reversible opera- tions would yield a greater amount of work for a certain amount of heat than another reversible cycle, the latter would also by reversing it require a lesser amount of work to produce that given amount of heat. Hence we could operate the first cycle to convert a given amount, C, of heat to produce a certain amount of work, B, and the second cycle, being operated in the reverse manner, would only need a portion of the workB, say J5 t , to reproduce the heat C, which could be employed in the first cycle to again produce the work B. Therefore both devices or cycles co-operating in the manner indicated would during each co-operative performance create the work.B B t , or rather, transfer an equivalent amount of heat from a colder to a warmer body, which is impossible. Hence both devices must operate with the same efficiency, and all reversible cycles devised for the mutual conversion of heat into work must, theoretically speaking, have the same efficiency, and the maximum efficiency at that. THERMODYNAMICS. 67 INFLUENCE OF WORKING FLUID. In the same manner it may be demonstrated that the nature of working substance has no influence upon the amount of work which can be obtained from a given amount of heat in a reversible cycle. For if one sub- stance could be employed to yield a greater amount of work from the same amount of heat than another sub- stance, and vice versa, a combination between two cycles, each one employing one of the two substances, could be formed like the above, which would create the same im- possible results. It should be noted that this deduction holds good only when the two cycles work between the same limits of temperature, and when no molecular changes take place in the working fluid, the mass of the latter remain- ing constant. RATE OF CONVERTIBILITY OF HEAT. The maximum amount of work derivable from a given amount of heat in a continuous cycle of operations, being accordingly independent of the nature of the work- ing substance, and obtainable by every ideal reversible cycle, the rate of maximum conversion may be deduced from the working of any such cycle of operations. To do this we select as the working substance in our ideal cycle a perfect gas, since the laws governing the relation of pressure, temperature and volume in this case are not only well known but also comparatively simple. The first ideal reversible cycle of operations to determine the maximum convertibility of heat has been devised by Carnot, to whom the original elaborations of this subject are due. Of course any reversible cycle answers also. For simplicity's sake, following the example of Nernst, we use a cycle which is to be considered re- versible when working between very small differences of temperatures (between boiler and refrigerator). SYNOPSIS OF NUMERICAL PROOF. Consequently we assume that the absolute tempera- ture, T lt of the boiler or generator is only a little higher than the temperature, T , of the refrigerator, when the working of our ideal cycle and its numerical theoretical result may be delineated as follows: The mechanical de- vice consists of an ideal cylinder provided with a movable piston containing a certain amount of a permanent gas of 68 MECHANICAL REFRIGERATION. the volume y x . The cylinder is immersed in the refrig- erator of the temperature T Q , and by forcing down the piston (reversibly) is compressed to the smaller volume v z . The work, A, required to perform this change is ex- pressed by . _ p j, v, R being the constant of the gas formula as above de- fined, and In standing for natural logarithm. As the temperature is to remain constant, an amount of heat, Q, equivalent to the work done must be imparted to the condenser, i. e.: Q being expressed in the same units as A. Now the cylinder is immersed into the generator or boiler and allowed to assume the temperature T,, while the volume remains constant, v 2 . The heat which is hereby con- veyed to the gas is c(T,-T ) c being the specific heat of the gas at constant vol- ume. At this juncture the gas is allowed to expand from the volumeu 2 to the volume v t , and the work A, which is done on the piston, is expressed by A, = while at the same time an equivalent amount of heat passes from the generator to the gas in the cylinder, i. e.: Now the cylinder is brought back to the refrigerator, where, while the volume remains constant, the temper- ature is again reduced to T , the amount of heat, e(7\ T ), being transferred from the gas in cylinder to the refrigerator or condenser. The gas is now again in its initial condition, and the operations for one period of the cycle are completed. The useful work, W, gained by this operation is while the amount of heat, H, which luis been with- drawn from the boiler or source is equal to THERMODYNAMICS. 69 If we call W the total amount of work gained, and H the total amount of heat expended by the heat source to obtain the heat source, we can write H If we take T t T , infinitesimally small, we can neg- lect the term c (2\ T )> as against the infinitely greater quantity E T In , and we can write V 2 W_ T t T H~ T, EFFICIENCY OF IDEAL CYCLE. W The term - n -, i. e.. the work obtained divided by the _rz amount of heat (expressed in the same units) expresses what is termed the efficiency of the cycle. Generally speaking, therefore, the convertibility of a certain amount of heat into work is the greater, the greater the difference of temperature between boiler and condenser, i. e., the greater T 7 , T , and the lower this difference is located on the absolute scale of temperature, that is, the smaller 7\ under otherwise equal conditions. The limit is reached when T becomes zero (absolute)^ 493 F., and W = H, a condition which cannot even be approached in practical working. CARNOT'S IDEAL CYCLE. The ideal cycle originally devised by Carnot embraces four such operations. First, the cylinder with piston con- taining a given volume of a permanent gas is brought in contact with the heat source or boiler, and after it has attained that temperature and the pressure correspond- ing thereto, the piston is allowed to move forward against a resistance which is continually infinitesimally less than the pressure within (i. e., reversibly). An amount of heat equivalent to the work done by the piston passes from the source of heat to the cylinder, so that the gas always maintains the temperature of the source, Aence the expansion is isothermal. Now the cylinder is removed from the source ot heat to conditions which are supposed to be so that it cam neither take In nor give out heat, and while under such 70 MECHANICAL REFRIGERATION. conditions the piston is allowed to move forward again with the same precaution as to pressure. The expansion in this case is adiabatic, and it is allowed to proceed until the gas in the cylinder has attained the temperature of the colder body the refrigerator, to which the cylinder is then removed. The piston is now forced inward reversibly, the heat of compression being withdrawn by the refrig- erator; the temperature remains the same, thus constitut- ing an isothermal compression. After this isothermal compression the cylinder is again brought under condi- tions where it can neither absorb nor discharge heat, and under these conditions is further compressed reversibly, until the gas within has acquired the temperature of the source of heat or boiler. With this fourth adiabatic operation, the cycle is completed, the working substance having been returned to its original condition, and each and all operations may be performed in the re versed order. HEAT ENGINES. A heat engine is a contrivance for the conversion of heat into mechanical energy, and in accordance with the above laws the efficiency of such a machine does not depend on the nature of the working substance (steam, hot air, exploding gas mixtures, etc.), but only on the temperature which the working substance has when ib enters and when it leaves the machine. AVAILABLE EFFECT OF HEAT. The relation between a given amount of heat (H) employed in a heat engine and the greatest amount of work ( W) which can be derived from same (expressed in units of the same kind) finds its expression in the said equation: w 'H in which T t is the temperature at which the heat is fur- nished to the engine, and T the temperature of the re- frigerator or condenser at which the heat leaves the en- gine. The temperatures are expressed in degrees of ab- solute temperature. CONSEQUENCE OF SECOND LAW. The above equation is a concise mathematical ex- pression of the second law of thermodynamics. If in the same, T becomes zero If will become W; in other words, THERMODYNAMICS. 71 in a machine in which the refrigerator or condenser temperature is absolute zero, the whole amount of the heat employed can be converted into mechanical energy, and it furnishes an important additional proof for the reality of an absolute zero of temperature, which is fre- quently looked upon as a mere scientific fiction. IDEAL REFRIGERATING MACHINE. A similar deduction can be made when the opera- tions of the above cycle are reversed, the gas being allowed to expand at the lower temperature, taking heat from the refrigerator and its compression being performed at the higher temperature, discharging heat into the boiler. Instead of heat engine we have now a refrigerating ma- chine, and one representing conditions of maximum efficiency which must find its expression in the same equation reversed, viz.: 1L y o w T t r c EFFICIENCY OF REFRIGERATING MACHINE. The above equation signifies that by expending the amount of work TT, we can withdraw the amount of heat H from a body (refrigeration) of the temperature T , and transfer the same to a body (boiler called con- denser in the refrigerating practice) of the temperature 2\. The equation also shows that the efficiency of a refrigerating engine depends on conditions quite opposite to those applying to the efficiency of a heat engine, the conditions being, that the refrigeration which can be obtained by expending a certain amount of work is the greater the smaller 2 1 ! T , and the larger T lf that is the higher T t T is on the scale of temperature. FALL OF HEAT. In analogy with the conversion of the energy of falling water into mechanical energy and still following Carnot, it is sometimes stated that the amount of heat W while falling from the temperature T t to T is capable of doing the work H. We see now that this expression is not correct; the amount of heat W leaves the source or boiler haying the temperature T t , but only the amount TP IT enters the refrigerator or falls to the temperature T mm reversible beat engine. 72 MECHANICAL REFRIGERATION. On the other band, in a reversible refrigerating ma- chine the amount of heat W leaves the refrigerator at the temperature T and the amount JF-j- H is brought over to the warmer body having the temperature 2\. COMPENSATED TRANSFER OF HEAT. When a certain amount of heat passes from a warmer to a colder body a portion of the same can be intercepted, as it were, to be converted into mechanical energy or work. If the maximum amount of work obtainable in this manner in accordance with the above equation has beea produced, the transfer of heat from the warmer to the colder body is said to be fully compensated. The availa- bility of the energy of the whole system participating in the transfer has not been changed, since the process is reversible and the former condition can be fully re-estab- iished, theoretically speaking. TJNCOMPENSATED TRANSFER. When, however, heat passes from a warmer to a colder body without doing any work (as is the case in radiation of heat) or without doing the maximum amount of work obtainable, a corresponding amount of the availability of energy is wasted or dissipated, the heat at the lower temperature being lower on the scale of availability than it was before the transfer. In this case the transfer of heat is said to be not compensated, or only partially com- pensated. In the same way mechanical energy may be dissipated when expended without transferring the max- imum amount of heat from a colder to a warmer body, as it is expected to do in the refrigerating practice. ENTROPY. This term is used to convey different meanings by different writers. It was originated by Clausius to stand for a mathematical abstraction expressing the degree of non-availability of heat energy for the production of me- chanical energy under certain conditions. LATENT AND FREE ENERGY. That portion of energy present in a system which may be converted into its equivalent Of mechanical work is called free energy, and the remaining energy is called latent energy. Hence when a transfer of heat takes place in a system without due compensation, the free energy decreases, and the latent energy of the system THERMODYNAMICS. 3 increases correspondingly. In accordance with this con- ception the latent energy of a body divided by the tem- perature is the entropy of the body; the increase of the lament energy in a body, divided by the temperature at which it takes place, yields the amount of increase of en- tropy, and vice versa. FUTURE CONDITION OF UNIVERSE. Only the changes of the entropy can be determined, not its absolute amount. As most changes take place w thout full compensation, not reversibly, it has been ec ncluded that the entropy of the universe is constantly increasing, tending toward a condition when all energy will be latent, i.e., not available for further conversion cr changes. In reversible changes the entropy remains unchanged. CHANGES OF FREE AND LATENT ENERGY. The equation expressing the efficiency of an ideal ieversible cycle of operations, viz.: W_ T,-T H~ T t may a?so be written This equation furnishes also an expression for the change of free and latent energy in a system in which transfer of heat without compensation, or with only partial compensation, takes place. If the compensa- TT I fTI _ /TT \ tion is complete the expression -^ -- & W is sero, and the amount of free and latent energy remains thesame;butif H(r ^~ To) TF>0 that is, if TFissmall- J- 1 TT / /7T _ rp \ or than -' l ^ -- , the equation covers all cases in which the changes are not reversible, and the con- version is incomplete. The free energy of the sys- tem has been decreased correspondingly in accordance with this equation. As W can never become larger ft I Ji _ rp \ than - ^ , the above difference can never be neg- ative, which means that the free energy of a system can 74 MECHANICAL REFRIGERATION. never increase. If in the equation, W= ^ *~ , J. * T is equal to 1, the equation becomes which means that the convertible energy of the amount of heat, J?, while passing from one temperature to an- other one degree lower, with full compensation, is equal to that amount of heat divided by its absolute tempera- ture. INCREASE OF ENTROPY. If an amount of heat, JT, in a system is transferred from a higher temperature, T 1} to a lower temperature, T ,without compensation, the free energy decreases, and the latent energy increases by an amount? and the increase of entropy, in accordance with a former definition, is expressed by the term Keversing the above argument, we can also say: If an amount of heat, H, leaves a body of the temperature T the entropy of that body decreases by the amount TT Tfrj and when this same amount of heat enters another 4 i body of the temperature T (transfer without compen- sation), the entropy of the second body is increased by the Tf amount - -. The increase of the entropy of the system -*o comprising the two bodies is therefore, as above H_ H_ -g(T t -T ) TO T t - 2\ T ' ORIGIN OF HEAT ENERGY. The source of nearly all, if indeed not of all, forms of energy applicable for the production of heat and power, is traceable to the sun, the radiant energy of whose rays has been converted into potential or chemical energy in the plants, whence it found its way into the deposits of coals, etc. The heat of the sun's rays also produces the vapors which reappear as water falls, etc. ; it also brings THERMODYNAMICS. 75 about the commotion in the atmosphere which appears in the force of waves and in the useful applications of the wind as well as in the devastations of the storm. SPECIFIC HEAT OF GASES AT CONSTANT VOLUME. In accordance with the molecular theory, the specific heat or the increase of heat energy for an increase of one degree in temperature for a molecule of a gas, or a propor- tional quantity of the same of the weight, Jf, is expres- in which CV is specific molecular heat at constant volume, Tthe absolute temperature, ./"the mechanical equivalent of heat, and E the heat required to increase the motion within the molecule, u the velocity of the molecule as above defined. SPECIFIC HEATUOTER CONSTANT PRESSURE. If a gas is heated under constant pressure the volume increases, and a certain amount of work is done, the equivalent of which in heat must also be furnished to the gas when its temperature is elevated. If we express the work done by pv __ I Mu* T = 8 T the specific heat of a molecule (expressed in units of weight) of gas under constant pressure, Cp, is Mu* hence IT must always be smaller than f = 1.6667, since E must always be positive, and when it is very small, K ap- proaches this value, as for vapor of mercury (1.666), in which the molecule is probably composed of only one atom, while in gases of presumably very complex mole- cules, the value for K approaches the other limit, viz., 1, as for ether, K=1.Q2Q. COMPONENTS OF SPECIFIC HEAT OF GASES. From the foregoing we know that the heat required to do the work of expansion, when a gas is heated under 76 MECHANICAL REFRIGERATION. constant pressure, is always equal to two-thirds of the heat necessary to increase the energy of the molecule. We find the specific heat, c t , for equal volumes of gases under constant pressure, to be composed as follows: Heat to increase molecular motion = 3 x 0.034 Heat to do work of expansion = 2 x 0.034 Heat to do internal work (in molecule)... =n x 0.034 Specific heat = (n -f 5) 0.034 n being the number of atoms composing the molecule. As for perfect gases, we can substitute equal volumes for equal number of molecules (since the same volumes of different gases contain an equal number of molecules), we can also say that for equal volumes of practically per- fect gases, the specific heat is the same (see page 47). NEGATIVE SPECIFIC HEAT. When the heat equivalent of the work required to compress a saturated vapor from a lower to a higher pressure is greater than the heat required to increase the energy of the molecules of that vapor, from the temper- ature corresponding to the low pressure to the temper ature corresponding to the higher pressure of the satur- ated vapor, then the specific heat of such saturated vapor is said to be negative. For heat must be abstracted during compression to keep it in a saturated condition, and when allowed to expand a portion of the saturated vapor will condense for the same reason. AIR THERMOMETER. As the expansion of liquids and solids by heat is not uniform throughout the thermometric scale, this con- stitutes a serious defect in all thermometers constructed by their aid. This difficulty does not exist when air or another gaseous body is used as the thermometric sub- stance. Hence the air thermometer is used for exact determinations. THERMODYNAMIC SCALE OF TEMPERATURE. If a thermometer be graduated in such a way that each degree increase in temperature of the thermometric substance adds equal amounts of free heat energy or equal amounts of heat available for -mechanical conver- sion to the thermometric substance, we have a thermo- dynamic scale of temperature as devised by Thomson. The degrees of such a scale agree very nearly with those of the air thermometer. THERMODYNAMICS. 77 HEAT WEIGHT. In accordance with the terminology adopted by Zeuner, the "weight" or "heat weight" of a certain amount of heat, H, transferable at the absolute temper- ature T, is that portion or fraction of said amount of heat which is convertible into mechanical energy, viz.: --. If the same amount of heat, H, enters a body at the constant absolute temperature T (without compen- sation), the entropy of that body is said to increase by TT an amount --. Hence entropy and heat weight are ex- jv/essions which are numerically synonymous. The terms thermodynamic function (Rankine), and Carnot's func- tion are used in the same connection. Thomson's ther- modynamic scale of temperature shows equal heat weights from degree to degree. Thermodynamics also teaches that the difference be- tween the specific heat of a gas at constant pressure, c p , and that at constant volume, c v , is a constant quantity, and equal to the constant R of the gas equation, viz.: ISENTROPIC CHANGES. Adiabatic changes which are at the same time revers- ible are also called isentropic changes, because such changes do not alter the entropy. LATENT HEAT AND ENTROPY. The heat which enters a body at the same or at con- stant temperature is called latent heat. Hence entropy may also be defined as latent heat divided by the corre- sponding temperature. Accordingly during vaporization or fusion of a body its entropy is increased. The amount of increase may be expressed by -j~ when I stands for the latent heat of vaporization or fusion, and T for the boil- ing or melting point expressed in absolute degrees F. If a gas expands at constant temperature while do- ing work, it absorbs an amount of heat equivalent to the amount of work done, and its entropy increases corre- spondingly. Chemical changes taking place at constant temperature with transferences of heat cause correspond- ing changes of entropy. 78 MECHANICAL REFRIGERATION. CHAPTER VIII-MODERN ENERGETICS INTRODUCTORY REMARKS. In the foregoing paragraphs mass has been treated as one of the fundamental units, and as the vehicle not only of mechanical energy, but also of molecular energy according to the atomistic or mechanical theory of natural phenomena, which is still more or less generally accepted, and therefore followed in this compend. SYSTEM OF ENERGETICS. More recently following the example of Ostwald, Gibbs and others, it has been found expedient to consider energy not as a function of mass, but as something real, tangible and unchangeable in itself, thus creating a new series of scientific conceptions in accordance with which mass appears in the role of a factor in mechanical energy. The terminology of this system places many defini- tions in a plainer and clearer light, and is frequently used in discussions on questions of energy, so that a synopsis of its tenets will be welcome to those who desire to study them. NEW DEFINITION OF ENERGY. Energy may also be defined as that immaterial quantity which, while it causes the greatest variety of changes or phenomena between different objects, always maintains its value. This definition involves the princi- ple of conservation of energy. CLASSIFICATION OF ENERGY. The different forms of energy may also be classified in the following groups: 1. Mechanical energy. 2. Heat. 3. Electric and magnetic energy. 4. Chemical or internal energy. 6. Radiated energy. MECHANICAL ENERGY. The mechanical energy may be subdivided into two classes, viz.: The energy of motion or kinetic energy, and the energy of space, with the following subdivisions: 1. Energy of distance (force). 2. Energy of surface (surface tension). 8. Energy of volume (pressure). MODERN ENERGETICS. 79 ENERGY FACTORS. According to Helm, etc., the different kinds of energy are expressible by two factors one of intensity and the other of capacity. -Equal increases or decreases of energy in a given system or configuration of bodies correspond to equal increases or decreases of intensity, or, in other words, the energy of a system is proportional to its in- tensity. This may be expressed by the formula in which E represents energy, i the intensity and c the factor of capacity which is a measure for the amount of energy which is present in a system at a given intensity, i, the latter being counted from E = 0. In other words, the capacity factor for energy, c, may also be termed the capacity of the system for energy. The capacity and intensity factors of some of the various forms of energy are given as follows: ENERGY. CAPACITY. INTENSITY. I Mass (m) . Square of velocity A. Kinetic energy. -{ v 9 | Quantity of motion Velocity I (mv). 2 B. Energies of space. a. Energy of distance, b. Surface en- ergy, c. Energy of volume. C. Heat. D. Electricity. E. Magnetism. F. Chemical energy. Length. Surface. Volume. Capacity for heat. Quantity of elec- tricity. Quantity of mag- netism. Atomic weight. Force. Surface tension. Pressure. Temperature. Potential. Magnetic potential. Affinity. DIMENSIONS OF ENERGY. The definitions of the conceptions relating to energy, by means of algebraical expressions, or their dimensions are rendered in the following manner: If e stands for the unit of energy, t for time, I for length or distance and m for mass the dimensions of the different mechanical conceptions may be expressed as follows: OLD UNITS. NEW UNITS. 1. Energy, m I 2 t~* e 2. Mass, m r~t* 3. Quantity of motion, m 1 1 * e I * t 4. Force, m 1 t~* e Z 5. Surface tension, _m r~* e l~* 6. Pressure, n I 1 <~ 2 e l~ 7. Effect, m I 2 t~ 3 e * 80 MECHANICAL REFRIGERATION. The first three definitions belong to the domain of kinetic energy, 4, 5 and 6 represent potential energies, and 7 the effect corresponding to the mechanical concep- tion of a horse power. The dimensions as given in the second column differ from those in the first column in that the third funda- mental unit energy is substituted for mass, in accord- ance with the foregoing definition of energy factors. THE INTENSITY PRINCIPLE. Energy will pass from places of higher intensity to such of lower intensity; but energy of a certain intensity cannot pass to such of the same or of higher intensity. A system containing but one kind of energy is in equili- brium if the intensity of energy is the same throughout the system. If the intensity is not the same changes will occur until the differences in intensity have be 02 a m Per Ct. Sulphurous acid 10 171 2 7 35 41 23.3 61 70 0.24 Carbonic acid . . 310 123 2 277 1 00 447. 3 24 81 Ammonia 30 555.5 9.10 1.02 61.7 23.3 0.18 90 MECHANICAL REFRIGERATION. This table explains itself and readily accounts for the preference generally given to ammonia as the circu- lating fluid. The loss due to the cooling of the liquid as shown in percentage for every degree difference in tem- perature of condenser and refrigerator, is less than in case of the other liquids, and the total refrigerating effect per pound of liquid is largest. The only instance speak- ing more in favor of sulphurous acid is the lower press- ure of its vapor, while the compressor is smallest in case of carbonic acid, but the pressure and the loss due to heating of liquid is very large in the latter case. SIZE OF ICE MACHINES. The heat unit; as already stated, is used for measur- ing both heating and refrigerating effects. As a matter of convenience, however, the capacity of large refrig- erating plants is expressed in tons of ice. By a ton of refrigerating capacity used in the above connection is meant a refrigerating capacity equivalent to a ton of ice at the freezing point while melting into water at the same temperature. This refrigerating capacity is equal to 284,000 units. ICE MAKING CAPACITY. The refrigerating capacity of a machine is different from the actual ice making capacity of a plant; the lat- ter is considerably less, fifty per cent and upward, of the refrigerating capacity, according to temperature of wa- ter, etc. USES OF REFRIGERATION. The practical uses of mechanical refrigeration are so manifold that it is impossible to enumerate them all in a small paragraph. Foremost among them is cold storage, that is, the preservation of all kinds of articles of food and drink by the application of low temperature. Slaugh- tering, packing and shipping of meat can hardly be car- ried on nowadays without the use of mechanical refrig- eiation, and the days of the few breweries still working without this artificial appliance may be said to be num- bered. Since ice has become an article of daily necessity, there are few towns that have not or will not have their artificial ice factory or factories. Artificial refrigeration is or will be used for a great many other purposes, some of which will be mentioned later on. PROPERTIES OF AMMONIA. 91 CHAPTER II. PROPERTIES OF AMMONIA. FORMS OF AMMONIA. The ammonia occurs in practical refrigeration in thiee different forms, as the liquid anhydrous ammonia, the gaseous anhydrous ammonia and solutions of ammo- nia in water of various strengths. ANHYDROUS AMMONIA. Ammonia is a combination of nitrogen and hydrogen expressed by the formula NH 3 which means that an atom of nitrogen (representing 14 parts by weight) is combined with three atoms of hydrogen (representing fchree parts by weight). At ordinary temperatures the am- monia, or anhydrous ammonia, as it is called in its nat- ural condition, is a gas or vapor. At a temperature of 30 F. it becomes liquid at the ordinary pressure of the atmosphere, and at higher temperatures also if higher pressures are employed. The anhydrous ammonia dis- solves in water in different proportions, forming what is called ammonia water, ammonia liquor, aqua ammonia, otc. At a temperature of 900 F. ammonia dissociates, >.hat is, it is decomposed into its constituents, nitrogen and hydrogen, the latter being a combustible gas. It appears that partial decomposition takes place also at lower temperatures, but probably not to the ex- tent frequently supposed. The liquid ammonia turns into a solid at a tempera- t jre of about 115 F. In this condition it is heavier than tje liquid, and is almost without smell. At a tempera- tare of 95 F. the chemical affinity between sulphuric acid and ammonia is zero, no reaction taking place be- t ;veen the two substances when brought in contact at or below this temperature. Ammonia is not combustible at the ordinary tem- perature, and a flame is extinguished if plunged into the gas. But if ammonia be mixed with oxygen, the mixed gas may be ignited and it burns with a pale yellow flame. Such mixtures may be termed explosive in a certain sense. If a flame sufficiently hot is applied to a jet of ammo- nia gas, it (or rather, the hydrogen of the same) burns as long as the flame is applied, furnishing the heat required for the decomposition of the ammonia. Ammonia is not explosive, but when in drums con- taining the liquid ammonia not sufficient space is left for 92 MECHANICAL REFRIGERATION. the liquid to expand when subjected to a higher tempera- ture, the drums will burst, as has happened frequently during the hot season. The ammonia vapors are highly suffocating, and for that reason, persons engaged in rooms charged with am- monia gas must protect their respiration properly. PRESSURE AND TEMPERATURE OF AMMONIA. The relation between pressure and temperature of saturated ammonia vapor is expressed by the formula : 21 Qfi log. 10 p = 6.2495 ! . T in which p is the pressure in pounds per square inch, and T the absolute temperature . DENSITY OF AMMONIA. The density d of liquid anhydrous ammonia at different temperatures, water being 1, is approxi- mately expressed by the formula : (2 = 0.6502 0.00077 t, t being temperature in degrees Fahrenheit. The density of the gas is 0.597 at 32 F., and at 760 mm. pressure. The volume, v, of the saturated vapor per pound may be calculated by the formula : " 6.4993 p+" t cubic feet, in which P is the pressure in pounds per square foot, T the absolute temperature, h the latent heat of vaporiza- tion. SPECIFIC HEAT OF AMMONIA. The specific heat of liquefied ammonia is variously stated from 1 to 1.228. The specific heat of ammonia gas is given at 0.508 at constant pressure, and 0.3913 at constant volume. The coefficient of expansion of liquid ammonia is 0.00204. The specific heat, s, of saturated vapor of ammonia is expressed by the formula: _ -, 555.5 ~^r This value is negative for all values of T less than 555 absolute, which means that if saturated ammonia vapor is expanded adiabatically a portion of it will con- dense, giving up its heat to the remainder of the vapor, PROPERTIES OP AMMONIA. 93 thus maintaining the temperature corresponding to the pressure of saturation, and when compressed heat must be abstracted, if the temperature and pressure are continu- ally to correspond .to those of the state of saturation, otherwise it will become superheated. SPECIFIC VOLUME OF LIQUID. The specific volume, v 1 of liquefied ammonia may be found after the following rule: Cubicfeet - LATENT HEAT. The latent heat, h, of evaporation of ammonia is h = 555.5 0.613 1 0.000219 2 , in which formula t stands for degrees F. EXTERNAL HEAT. That portion of the latent hpat required to overcome external pressure or the external latent heat, E, is ex- pressed by J in which formula P stands for external pressure in pounds per square foot, v for the volume of the vapor, and v t for the volume of the liquid (which is neglected in the calculations given in the accompanying table), and J the mechanical equivalent of heat. WEIGHT OF AMMONIA. The weight, w, of a cubic foot of the saturated vapor is- 1 w = V And the weight, w lt of a cubic foot of the liquid is The weight of one cubic foot of liquid ammonia at a temperature of 32 F. is 39.017 pounds. TABULATED PROPERTIES OF SATURATED AMMONIA. The physical properties of anhydrous ammonia, both in the vapor and liquid state, which are of special use in the refrigerating practice, are laid down in the follow- ing table prepared by De Volson Wood, calculated by the above formulae which have been elaborated by him also. 94 MECHANICAL REFBIGERATION. PROPERTIES OF SATURATED AMMONIA. TEMPERA- TURE. PRESSURE, ABSOLUTE. !_, B External Heat. Thermal Units. Internal Heat, Ther- mal Units. fs ^ "o r it II fa Absolute. 5 6* GO ? 40 35 30 420.66 425.66 430.66 1540.9 1773.6 2035.8 10.69 12.31 14.13 579.67 576.69 573.69 48.23 48.48 48.77 531.44 628.21 524.92 24.37 21.29 18.66 .0234 .0236 .0237 .0410 .0467 .0535 25 20 15 435.66 440.66 445.66 2329.5 2657.5 3022.6 16.17 18.45 20.99 570.68 667.67 564.64 49.06 49.38 49.67 521.62 518.29 514.97 16.41 14.48 12.81 .0*38 .0240 .0242 .0609 .0690 .0779 10 6 450.66 455.66 460.66 3428.0 3877.2 4373.5 23.77 26.93 30.37 561.61 658.56 555.50 49.99 50.31 50.68 511.62 508.25 504.82 11.36 10.12 9.04 .0243 .0244 .oaie .0878 .0988 .1109 + 6 T 10 + 15 465.66 470.66 475.66 4920.5 5522.2 6182.4 34.17 38.65 42.93 552.43 549.35 646.26 60.84 51.13 51.33 601.69 498.22 494.93 8.06 7.23 6.49 !0249 .0250 .1241 .1384 .1540 + 20 + 25 + 30 480.66 485.66 490.66 6905.3 7695.2 8566.6 47.96 53.43 59.41 543.15 540.03 536.92 51.61 61.80 52.01 491.54 488.23 484.91 5.84 5.26 4.75 .0252 .025:5 .0254 .1712 .1901 .2105 + 35 It 495.66 600.66 506.66 9493.9 10512 11616 65.93 73.00 80.66 533.78 530.63 527.47 52.22 52.42 52.62 481.56 478.21 474. 85 4.31 3.91 3.56 .0256 .0257 .0260 .2320 .2583 .2809 + 50 + 55 + 60 510.66 515.66 620.66 12811 14102 15494 88.96 97.93 107.60 524.30 521.12 517. 93 52.82 53.01 53.21 471.48 468.11 464.72 3.25 2.96 2.70 .0260 .0260 .0265 .3109 .33,9 .3704 + 66 + 70 + 75 525.66 530.66 536.66 16993 18605 20336 118.03 129.21 141.25 514.73 511.52 508.29 53.38 53.57 53.76 461.35 457.85 464.63 2.48 2.27 2.08 .0266 .0268 .0270 .4034 .4405 .4808 + 80 + 85 + 90 540.66 545.66 550.66 22192 24178 26300 154.11 167.86 182.8 504.66 501.81 498.11 53.96 54.15 54.28 450.70 447.66 443.83 .91 .77 .64 .0272 .0273 .0274 .5262 .5649 .6098 + 90 + 100 + 105 555.66 560.66 565.66 28565 30980 33660 198.37 215.14 232.98 495.29 491.50 488.72 54.41 54.54 54.67 440.83 436.96 434.08 .51 .39 .289 .0277 .0279 .0281 .6622 .7194 .7757 JUO 115 120 570.66 675.66 580.66 36284 39188 42267 251.97 272.14 293.49 485.42 482.41 478.79 54.78 54.91 55.03 430.64 427.40 423.75 .203 .121 1.041 .0283 .0285 .0287 .8312 .8912 .9608 + 126 + 130 + 135 585.66 590.66 595.66 45528 48978 52626 316.16 340.42 365.16 475.45 472.11 468.75 55.09 55.16 55.22 420.39 416.94 413.53 .9699 .9051 .8457 .0289 .0291 .0293 1.0310 1 1048 1.1824 + 140 + 145 + 160 600.66 605.66 610.66 66483 60550 64833 392.22 420.49 460.20 465.39 462.01 458.62 55.29 65.34 56.39 410.09 406.67 402.23 .7910 .7408 .6946 .0295 .0297 .0299 1.2642 1.3497 1.4396 + 165 + 160 + 165 615.66 620.66 625.66 69341 74086 79071 481.54 614.40 549.04 455.22 451.81 448.39 55.43 65.46 55.48 399.79 396.35 392.94 .6511 .6128 .5765 .0302 .0304 .0306 1.5358 1.6318 1.7344 The critical pressure of ammonia is 115 atmospheres, the critical temperature at26oF. (Dewar), critical volume .00482 (calculated). PROPERTIES OF AMMONIA. 95 VAN DEB WAALS' FORMULA FOR AMMONIA. As has been shown (page 56), the constants a and b of Van der .Waals' formula can be derived from the critical data, which gave me the following values for am- monia : a = .0079; & = .0016. If the values for a and b thus found for ammonia are introduced in the general equation (page 56), setting p and v equal unit, the equation will read : (-0.0018)=(l + . 0.0079 ) 1.00627 X (461 + or This equation may be used to establish the relations between pressure, volume and temperature for anhydrous ammonia, and in order to test the same we may compare the results so obtained with those derived from actual ex- periments for saturated ammonia vapor, the volume of which ought to satisfy one of the three values for v which are possible below the critical temperature at the pressure of liquefaction. On this basis the values, p t , for the pressure of am- monia gas for given volumes at given temperatures have been calculated in the following table: t p v V I=T? Pt 40 0.71 24,37 1.282 0.66 15 1.38 12.81 0-674 1.33 + 32 3.96 4.57 0.24 4.02 + 60 7.17 2.7 0.142 7.24 +122 20.3 1.0 0.052 20.4 +165 36.6 0.57 0.030 36.4 In this table the values forp and i^ for the tempera- ture t are in accordance with Wood's interpretation of Regnault's experiments for saturated ammonia vapor, and the values, p lt are derived from the above formula for ammonia by inserting the value, w t , obtained in measuring the volume by the volume of. an equal weight of ammonia gas at the pressure of one atmosphere at 32 F. It will be noticed that p t agrees pretty closely with p between 15 and 165, thus proving the approximate correctness of Waals' formula for saturated ammonia within these temperatures, and therefore the formula may doubtless also be safely used for superheated vapor of this substance within these limits for approximate 96 MECHANICAL REFRIGERATION. estimation. Indeed, the agreement between the two sets of pressures obtained by entirely different experiments, and by an entirely different course of reasoning, is suffi- ciently close to inspire the greatest confidence in the ex- periments of Regnault and Dewar, as well as in the mathematical deductions of Van der Waals. SUPERHEATED AMMONIA VAPOR. Below its critical temperature (130 F.) ammonia in its volatile condition is to be termed a vapor, strictly speaking; but when it is not in a saturated condition, but in the condition of a superheated vapor, as it were, it be- haves practically like a permanent gas and is also termed ammonia gas. In this condition one pound of ammonia gas, under a pressure of an atmosphere, and at the tem- perature of 32 F. occupies a volume of 20.7 cubic feet (one cubic foot of air weighing 0.0806 pound, and the specific gravity of ammonia being 0.597 of air under these conditions). FORMULAE FOR SUPERHEATED VAPOR. On this basis the relations of volume, weight, press- ure and temperature of ammonia gas or superheated am- monia vapor can be calculated after the general equation of gases on pages 46 and 51. The volume v in cubic feet of one pound of ammonia gas at any temperature, , and for any pressure, p, expressed in pounds per square inch below that which corresponds to the pressure of saturated vapor at that temperature, or for any pressure and for any temperature above that which corresponds to the temperature of saturated vapor at that pressure, can be found approximately after the formula 20.7 (461 -f 1) 14.7 20.7 (461 -f t) 62 (461 -f t) 493 X p 33.5 p p If the volume, u, in cubic feet of one pound of am- monia gas at a certain temperature, i, is known, the press- ure can be found after the equation _ 20.7(461'+*) 0.62(461 +t) P = 33.5 v v And if the volume, v, and the pressure, p, are known the temperature may be determined approximately after the equation t = 1.62 > v 461 PROPERTIES OF AMMONIA. 97 As stated above, the formula of Van der Waals may also be used in this connection, but it is rather too cumber- some for this purpose. However, if the value of 20.7 in the foregoing formulae is substituted by 19, which is the figure found in accordance with Van der Waals' equation, the results agree closer with the figures obtaining for vapor just saturated. The table on " Properties of Am- monia Gas or Superheated Vapor of Ammonia " in the appendix agrees practically with the formula given forv, on page 96, and for this reason gives only approximate values, since said formula considers ammonia a perfect gas, which it is not, as indicated by Van der Waals. AMMONIA LIQUOR. The solutions of anhydrous ammonia in water are employed in the so called absorption machines, and the properties of such solutions vary with their strength or the percentage of ammonia which they contain. The strength of such solutions, "ammonia liquor," as they are commonly called, is approximately determined by spe- cific gravity scales or hydrometers, those of Beaume be- ing usually employed for this purpose. STRENGTH OF AMMONIA LIQUOR. Percentage of Ammonia by Weight. Specific Gravity. Degrees Beaume Water 10. Degrees Beauine" Water 0. 1.000 10 1 0.993 11 1 2 0.986 12 2 4 0.979 13 3 6 0.972 14 4 8 0.966 15 5 10 0.960 16 6 12 0.953 17.1 7 14 0.945 18.3 8.2 16 0.938 19.5 9.2 18 0.931 20.7 10.3 20 0.925 21.7 11.2 22 0.919 22.8 12.3 24 0.913 23.9 J3.2 26 0.907 24.8 14.3 28 0.902 25.7 15.2 30 0.897 26.6 16.2 32 O.H92 27.5 17.3 34 0.888 28.4 18.2 36 29.3 19.1 38 0.8BO 30.2 20.0 PROPERTIES OF AMMONIA LIQUOR. On the following pages we publish a table prepared by Starr, and based on experiments made by him, which shows the relations between pressure and temperature for solutions of ammonia in water of different strengths. MECHANICAL REFKIGEBATION. ga he n a 0)73^ .o on 3 .2 ld o"* fl SSI fl ? a iP |Sir ^"0 O ** i* f 5iS ^ bee *a 5^2 ^ d | 0) 03 -2 s.a ! sl !: iic o if* ^^ 32= .HIS 3*8 -II 1*5 ^ a S^^ c as* .t gfs .? ap 5s.. 43 0) M fl^: 3 -uja l^;- S'^a =n^^ 2^3 i 5 II ^s it v y a u S; sr s i Ij ^s- ^ts S" 5 ^s If f: -I* li 14* i a i-? PROPERTIES OF AMMONIA. 99 Cfi- -L T ^rJ ^ Z <; -j 3^ O^ a S | ? s * a ) ? 1 S a i d t ; j 5 J 2 ^ s S o * 2 ; : s a s R. .3- | 3 z, 2 C | t * ( S 3 S ; a " s s, r^ 5T S > ^2 K r & ^ 5 i f t S : s S; s > ; I a | s ft f g x- S Sr i 5 a j S c I 5 J 5 r t y ~ \ 3 * 1 JN s r~ 1 5 a i r; -A s 5 1 S ,1 -2 & g 7 i 1 X a- | s )3>|j3f4U2 m l ? ! S f I ? | IT fr g. | 1 I i | * 1 S 5 1 | 1 s I \ r; t; I j a ^ 2 5 ; S h ; g. Sr i i -S S g $ I * S S 2 5 S i s I I t = s s 2 j ~ s ol 1 | 3 3 i S I If $ 5 s 8 S 5 a S 5 s 3 i i s S s- ^ j J c5 i R 1 $ s * 5" S i S 1 & a s 1 s ^. s : -^ t | q 1 I i ul tf z i I fi 5 i a S fl I f ! n S P 5 | I 3 i j s 1 I f. s g ? \ 2 i s o | 5 i i i 1 4- I s s- s a s cs n S- 1 1 5 1 2 1 i a & ^ T ? ^ i 3- Jj ^ 5 i i S * fr S | s 5 5 s s S 1 s a 1 1 5 3 5- s 1- 2- 5- 5~ V 1 ) 1 G S s s I g 1 5 i j s | | a s- 1 S ^ 1 i 5- i i - ? f uJ i 5 $ | s | S 5 a 1 I 1 2 5 i a- i- i t ? .fe & > i X 5 s 1 $ ^ ?" 1 I I 1= H- i a- s s 9 ~ | S ul 00 s s 1 5 S" si 1 1 r | 3T | i | I ? - s 5 S R. K K* 3 & a 3 s a- S i 3 s | i | s- 1 5 g ~ t- ? S, t- Ic * fr 3 I a ? js | r ^ i 1. 1 | a '- s K ft _ 5 R. ft. | kl iS 5 1 i 5 9 | ^ 5 J S: i I 5 a i | R. | R f * - i a 3 3 a i = | ^ i 2- S- 1 1 V, l t s- 5" 3 * 1 ? * i in Q o S - r. 1 s 1 i S 1 'S 1 i r 5 ? c i f ?- 1 -5 i- i 1 -s 1 5" s i 3 4 i ^ s I 5 ^ i 1 ^ 1 ?. | s. | * 5 5 -s 5~ ^ * * s {? | r I i i s- i fj I H 2: *. | n s. i i 2 -a 5? D; 5 I ^ ? S s r I 2 g i 1 1 s- i r i; -a fe, 1 a. J 3 i 2 I ^ | E ^ f s- ^ ? ? S 1 1 ir i i 1 I | P 1. 1 | 4 i ? 5- g s r 5 i S g 5 I s g. i- g- & x 5 i S. r- "t S * r ft s 5 s i CJ 3 i 5 1 ^ S S I s 1 I 5 c 5. | | P. 1 1 3 J a 5 1 i f f | 1 s i 5 p S 1 C-4 1 CN/ i 5 S 1- I, I 1 ^ ^ i | 5 e S: 1 1 * I <^ | 1 1 ? 1 i 3 5 1 5 s s A 1 I s -2 ^ i: a 3 i 3 i sc 4 ^ | 5 s s w 5 S t- ? 5 I ^p 5 5 5 I 5 e, 5T I S 5 S 1 ^ S I ~ 5 i f i i V S s f 5 O Sr 5 g p - 5 i | 5 a 5 s c i 5 I i s 1 g: S- ^ - ^ 5- 1 s S i i- K 5 s ? ~ | 2 5 1 i ^ -S- 5- ^ g_ S 2. 2 s l I 1 S 2" tt 5" ^ 5 ^ 3 5 il ^ S- S s- in s f-? c =i i S Pl 3 ^ vij *r 1 1 i 2 Jt 2* S ^ ! * S "S SJ ^ T *j K 9&-W\\ 00 s; I d 13 c. 3 OQ % SH ^ 4 ^ 3 ^ 00 I 100 MECHANICAL REFRIGERATION. BEAUME SCALES. It should be noted that there are three BeaumS spe- cific gravity scales, or hydrometers; one of liquids which are heavier than water, and two for liquids lighter than water. Of the latter two the scale of the one designates pure water 10, and the other designates pure water zero. As ammonia liquor (comprising mixtures of water and ammonia in all proportions) is lighter than water, only the latter two Beaume scales come into question in this respect, and generally the one which designates pure water 10 is referred to when mentioned in connection with ammonia liquor, and the degrees given in this con- nection correspond to a certain specific gravity, i. e., to a certain percentage of water and ammonia contained in the ammonia liquor as shown in the table on page 97, SATURATED SOLUTION OF AMMONIA. The amount of ammonia which can be absorbed by water decreases with the temperature, as is shown in the following table. SOLUBILITY OF AMMONIA IN WATER AT DIFFERENT TEMPERATURES (ROSCOE). Pounds of Pounds of Degrees Celsius. Degrees Fahrenheit. NH 3 to one pound Degrees Celsius. Degrees Fahrenheit. NH 3 to on* pound water. water. 32. "*' 0.875 28 83.4 0.426 3 4 35.6 39.2 0.833 0.792 30 32 86. 89.6 0.403 0.382 6 42.8 0.751 34 93.2 0.362 8 46.4 0.713 36 96.8 0.343 10 50. 0.679 38 100.4 0.324 12 63.6 0.645 40 104.0 0.307 14 57.2 0.612 42 107.6 . 0.290 16 60.8 0.582 44 111.2 0.276 18 64.4 0.554 46 114.8 0.259 20 68. 0.526 48 118.4 0.244 22 71.6 0.499 60 122. 0.229 24 75.2 0.474 52 125.6 0.214 26 78.8 0.449 54 129.2 0.200 56 132.8 0.18G The heat H n developed when one pound of ammonia is dissolved in as much poor liquor containing one pound of ammonia to n pound of water, in order to obtain a rich liquor which will contain 6 + 1 pound of ammonia for each n pound of water (see pages 99 and 100) is 284 + 1426 n Hn = 925 units. PROPERTIES OF AMMONIA. 101 The figures in the following table on the solubility of ammonia in water at different temperatures have been obtained by Sims: Degrees Fahr. Lb.ofNH 8 to lib. of Water. Volume of NH 8 in 1 Volume of Water. Degrees Fahr. Lb.ofNH 8 to 1 Ib. of Water. Volume of NH s inl Volume of Water. 32.0 0.899 1,180 125.6 0.274 359 35.6 0.853 1,120 129.8 0.265 348 39.2 0.809 1,062 133.8 0.256 336 42.8 0.765 1,005 136.4 0.247 324 46.4 0.724 951 140.0 0.238 312 50.0 0.684 898 143.6 0.229 301 53.6 0.646 848 147.2 0.2?0 289 67.2 0.611 802 150.8 0.211 277 60.8 0.578 759 154.4 0.202 265 64.4 0.546 717 158.0 0.194 254 68.0 0.518 683 161.6 0.186 244 71.6 0.490 643 165.2 0.178 234 75. 2 0.4G7 613 168.8 0.170 223 78.8 0.446 585 172.4 0.162 218 82.4 0.426 559 176.0 0.154 202 86.0 0.408 536 179.6 0.146 192 89.2 0.393 516 183.2 0.138 181 93.2 0.378 496 186.8 0.130 170 96.8 478 190.4 0.122 160 100.4 350 459 194.0 0.114 149 1U4.0 0'.338 444 197.6 0.106 139 107.6 0.326 428 201.2 0.098 128 111.2 0.315 414 204.8 0.090 118 114.8 0.303 399 208.4 0.082 107 118.4 0.294 386 212.0 0.074 97 122.0 0.284 373 HEAT GENERATED BY ABSORPTION OF AMMONIA. The questions regarding the heat generated by the absorption of ammonia in water, as well as in water con- taining a certain percentage of ammonia, have been ex- perimentally studied by Berthelot, whose results may bo expressed by the following formula : /-> 142 O = units. n in which Q stands for the units of heat (pound Fahren- heit) developed when a solution containing one pound of ammonia in n pounds of water is diluted with a great amount of water. This equation fully suffices to solve the different problems arising in refrigerating prac- tice. Assuming 925 units (the values of different ex- perimenters differ) of heat to be developed when one pound of ammonia is absorbed by a great deal (say 200 pounds) of water, the amount of heat, Q, developed in making solutions of different strengths (one pound of ammonia to n pounds of water) may be expressed by tbe formula- ^ = 925 __ 142 102 MECHANICAL REFRIGERATION. The heat, 2 , developed when 6 pounds of ammonia are added to a solution containing one pound of am- monia to n pounds of water, is expressible by the formula : i A Let the poor liquor enter the absorber with a strength of 10 per cent, which is equal to one pound of ammonia to nine (n) pounds of water. Let the rich liquor leave the absorber with a strength of 25 per cent, which is three (i+&) pounds of ammonia per nine (n) pounds of water. Inserting these values, n = 9 and 6 = 2, in the above equation, we have 142(4+4) 9 1724 units. Hence by dissolving two pounds of ammonia gas or vapor in a solution of one pound of ammonia in nire pounds of water, we obtain twelve pounds of a 25 percent solution, and the heat generated is 1,724 B. T. units. SOLUBILITY OF AMMONIA IN WATER AT DIFFERENT TEM- PERATURES AND PRESSURES. (SIMS.) One Pound of Water (also Unit Volume], Absorbs the Following Quan- tities of Ammonia. Absolute Pr's'ure in Lbs. per Sq. Inch. 32 Lbs. P. Vols. 68 F. 104 F. 212 F. Lbs. Vols. Lbs. Vols. Gr'ms. Vol 14.67 0.899 .IbO 0.618 .683 0.338 .443 0.074 .97 15.44 0.937 ,5531 0.635 .703 0.349 .458 0.078 .102 16.41 0.980 .287 0.566 .730 0.363 .476 0.083 .109 IV. 37 .02it .351 0.574 .754 0.378 496 0.088 .115 18.34 .077 .414 0.594 .781 0.391 .513 0.092 .120 19,30 .128 .478 0.613 .805 0.404 .531 0.096 .126 20,27 .177 .546 0.632 .830 0.414 .543 0.101 .132 21.23 .236 .616 0.651 .855 0.425 .558 0.106 .139 22.19 .283 .685 0.669 .878 0.434 .570 0.110 .140 23.16 1.336 .754 0.685 .894 0.445 .584 0.115 .151 24.13 1.388 .823 0.704 .924 0.454 .596 0.120 .15Y 25.09 1.442 .894 0.722 .948 0.463 .609 0.125 .164 26.06 1.496 .965 0.741 .973 0.472 .619 0.130 .170 27.02 1.549 2.034 0.761 .999 0.479 .629 0.135 .177 27.99 1 603 2.105 0.780 1.023 0.486 .638 28 95 1 656 2 175 0^801 1.052 0.493 .647 30.88 1.758 2.309 0.842 1.106 0.511 .671 32 81 1 861 2 444 881 1.157 Q.K.O .696 34.74 l!966 2^582 0.919 1 207 o!547 .718 36.67 2.070 2.71 0.955 1.254 0.565 .742 88.60 0^992 l!302 579 764 40.63 0.594 .780 The ammonia does not follow the absorption laws of Dalton, inasmuch as the quantity of ammonia absorbed by water does not vary directly with the pressure. PROPERTIES OP AMMONIA. 103 DIFFERENT SYSTEMS OF REFRIGERATION. Both the anhydrous liquor and the ammonia are used in refrigeration, the former in what is known as the Linde or compression system, and the latter in the Carre or absorption system. TESTS FOR AMMONIA. As the boiling point of pure anhydrous ammonia is at 29 below zero -at a pressure of the atmosphere (30 inches of mercury), the purity of anhydrous ammonia may be tested by means of an accurate thermometer. The same is inserted into a flask containing the ammonia in a boiling condition, and provided with a tube to carry off the obnoxious vapor. If the boiling temperature differs materially from the above (allowance being made for the barometric pressure), it demonstrates that the ammonia is not pure. If after the ammonia is evapo- rated, an oily or watery residue is left in the flask, the name is also attributable to impurities. Ammonia leaks are generally easily detected by the smell or by the white fumes which form when a glass rod moistened with hy- drochloric acid is passed by the leak. If traces of ammonia are to be detected in water or in brine it is best to use "Nessler's Reagent," which is prepared as follows : Dissolve 17 grams of mercuric chloride in about 300 cc. of distilled water ; dissolve 35 grams of potassium iodide in 100 cc. of water ; add the former solution to the latter, with constant stirring, until a slight perma- nent red precipitate is produced. Next dissolve 120 grams of potassium hydrate in about 200 cc. of water ; allow the solution to cool ; add it to the above solution, and make up with water to one liter, then add mercuric chloride solution until a permanent precipitate again forms; allow to stand till settled, and decant off the clear solution for use ; keep it in glass stoppered blue bottles, and set away in a dark place to keep it from decomposing. The application of this reagent is very simple, a few drops of the same being added to the water or brine in question, contained in a test tube or a small glass of any other kind. If the smallest trace of ammonia is present a yellow coloring of the liquid will take place, which turns to a full brown when the quantity of ammonia present is larger- 104 MECHANICAL REFRIGERA? MX. TESTING AMMONIA. The purity of anhydrous ammonia is practically tested by allowing the same to evaporate from a flask placed in water and provided wifch a cork and bent tube to carry off the obnoxious water. If after the evapora- tion a notable oily or watery residue is left it is attribut- able to impurities. The boiling point may be observed at the time (it is 29-30 F. below zero), and if any perma- nent gases are given off when the tube carrying off the ammonia vapor is discharged into water they may be tested for their inflammability. However, these latter two tests will hardly prove satisfactory except in the hands of an experienced chemist. In order to test the liquid residue in anhydrous am- monia, Faurot used a glass tube about six and one-half inches deep and one and one-eighth inches in diameter, and drawn out to a narrow tube at the bottom, the latter being divided in fractions of a centimeter, while the whole tube contains about 100 cubic centimeters. The open top may be closed with a rubber cork having a vent tube of glass, the outer portion of which is bent down close to the large tube, so that the whole may be placed in a glass of water after the tube has been filled to about half with the anhydrous ammonia to be tested. The ammonia will now boil away and be absorbed by the water in which the vent tube dips, and the amount or percentage of any residue that may be left can be readily estimated by the readings on the graduated portion of the tube. Permanent gases in the ammonia will manifest themselves by bubbles passing through the water. Ammonia liquor is tested for its strength by the hydrometer, as shown. For chemical tests it should be diluted with two times its volume of distilled water when, after acidification with hydrochloric acid, the addition of chloride of barium solution will show the presence of sulphates by a white precipitate. In the same diluted ammonia liquor clear lime water will show the presence of carbonates by a similar precipitation. Chlorides may be detected by acidifying the diluted am- monia solution with nitric acid and the addition of nitrate of silver solution by the formation of white pre- cipitate. If on the addition of nitric acid to the ammo- nia a red color appears it indicates traces of organic bases. WATER, STEAM, ETC. 105 CHAPTER III. WATER, STEAM, ETC. Water is a combination of one atom of oxygen with two atoms (one molecule) of hydrogen, consequently to be designated by H 2 O, which means that two parts by weight of hydrogen are combined with sixteen parts by weight of oxygen to form eighteen parts (one molecule) of water. FORMATION OF ICE. Water solidifies at 32 F., but in very fine capillary tubes the freezing point may be depressed for 20 or more. If rigidly confined or placed under pressure, the freezing point is depressed likewise. For a pressure of n atmospheres the freezing point is depressed for n X 0.0135 F. Latent heat of ice, 142 B. T. units. PROPERTIES OF ICE. The ice which freezes out of solutions of salt or other substance, consists of pure water, the impurities remain- ing in the unfrozen portion. Ice melts at 32 F., but by a, pressure sufficiently high it can be converted into liquid at a temperature of 4 F. One cubic foot of ice weighs 998.74 ounces, avoirdupois. STEAM. Water volatilizes like any other liquid in accordance with the tension of its vapor, which at a temperature of 212 is equal to the tension of the atmosphere when the water boils, and is converted into steam, which occupies about 1,700 times the volume of the water. The water dis- eociates completely at a temperature of about 4.500, but a partial decomposition takes place at a lower tem- perature. SATURATED STEAM. When steam is still in connection with water, or if it is in such condition that a slight decrease of tempera- tare will cause liquefaction of some of the steam, it is called saturated steam. The pressure of saturated steam depends on its tem- perature in a manner approximately expressed by Ran- kine's formula: In which p is the pressure in pounds per square inch at the absolute temperature T in degrees F., the value of constants being: A = 6.1007, log. B = 3.43642, log. (7=5.- 69873. 106 MECHANICAL REFRIGERATION. TOTAL HEAT. By total heat of steam we understand that quantity of heat required to raise the temperature of unit weight of water from the freezing point to any given tempera- ture, and to entirely evaporate it at that temperature. The total heat, I, for any temperature, <, may be expressed by the formula: I =1091,7 -f 0.305 (t 32) LATENT HEAT OF VAPORIZATION. If the heat of the liquid, g (i. e., the amount of heat required to raise the temperature of unit weight of water from the freezing point to the temperature t) is sub- tracted from the total heat, I, at that temperature, we find the heat of volatilization, 7i, viz. : h = l g EXTERNAL LATENT HEAT. That portion of the latent heat required to overcome external pressure, or the external latent heat, J7, is expressed by *(-.) ~7~ In which formula P stands for external pressure, v for the volume of the saturated vapor, v for the volume of the liquid,.and /for the mechanical equivalent of heat. INTERNAL LATENT HEAT. The heat required to bring about the change from the liquid to the gaseous state, t. e., to perform the work of disintegration, or the so-called internal latent heat, F, is expressed by the equation F=h-E SPECIFIC HEAT OF WATER. The specific heat, c, of water at any temperature, t (expressed in degrees Celsius), is c = 1 + 0.00004 t + 0.000000 t z See also table, page 16. SPECIFIC HEAT OF STEAM. The specific heat of superheated steam is 0.3643 at constant volume and 0.475 at constant pressure. The specific heat of saturated steam, s, is expressed by the equation WATER, STEAM, ETC. 107 Which is negative for all values of T less than 1436 F., above absolute zero. SPECIFIC HEAT OF ICE. The specific heat of ice is about half of that of water, or 0.504. PROPERTIES OF SATURATED STEAM, AT PRESSURE FROM ONE POUND TO 200 POUNDS ON THE SQUARE INCH. PRESSURE ABSOLUTE. HEAT, IN DEGREES, FAHR. &*t 11 a~ s"*$$ s^*(5 3 f| g ! In Inches of ~f^ o^la 'sal O "p/*-? > Mercury at 32. Temperature. Latent Heat. Total Heat. SS31 IiJ IK bo iii Dif. Dif. prlb prlb i 2.0375 102. 1,043.05 1,145.05 20,890 .0020 .037 5 10.1875 162.37 9i26 1,001.9 1,163.46 82 4,627 .0135 .167 10 20.375 193.29 4.93 979.60 1,172.89 1.50 2,429 .0257 .318 15 30 5625 213.07 3.47 965.85 1,178.92 1.05 1,669 .0373 .463 eo 40.75 228. 2.8 955.5 1,183.5 .8 1,880 .0487 .604 25 50.9375 240.2 2.3 947. 1,187.2 .7 1,042 .0598 .742 30 61.125 250.4 2. 939.9 1,190.8 .6 881 .0707 877 35 71.3125 259.3 1.7 933.7 1,193. 764 .0815 1.012 40 81.5 267.3 1.5 928.1 1,195.4 ) 676 0921 .142 45 91.6875 274.4 1.4 923.2 1,197.6 608 .1025 .272 50 101.875 281. 1.3 918.6 1,199.6 | 652 .1129 .402 55 112.0625 287.1 1.2 914.4 1,201.5 506 .1232 .529 60 122.25 292.7 1 1 910.5 1,203.2 '.3 467 .1335 .654 65 132.4376 298. 1.1 906.8 1,204.8 .3 434 .1436 1.779 70 142.625 302.9 1. 903.4 1,206.3 .3 406 .1536 1.904 75 152.8125 307.5 .9 900.3 1,207.8 .3 381 .1636 2.029 80 163. 312. .9 897.1 1,209.1 .2 359 .1736 2.151 85 173.1875 316.1 .8 894.3 1,210.4 .3 340 .1833 2.271 90 183.375 320.2 .8 891.4 1,211.6 .2 323 .1930 2.391 95 193.5625 324.1 .8 888.7 1,212.8 .3 807 .2030 2.511 100 203.75 327.8 886.1 1,213.9 .2 293 .2127 2.631 105 213.9375 331.3 i7 1,215.0 .2 281 .2224 2.751 110 224.125 334.6 .6 881 .'4 1,216.0 .2 269 .2319 2.871 115 234.3125 338. .6 879. 1,217.0 .2 259 .2410 2.990 120 244.5 341.1 .6 876.9 1,218.0 .2 249 .2503 3.105 125 254.6875 344.2 .6 874.7 1,218.9 .2 239 .2598 3.227 130 264.875 347.2 .6 872.6 1,219.8 .2 231 .2693 3.347 135 275.0625 350. .5 870.7 1,220.7 .1 223 .2788 3.467 140 285.25 352.9 .6 868.6 1,221.5 .1 216 .2883 3.582 145 '295.4375 .6 866.8 1,222.4 .2 209 .2978 8.697 150 305.625 358^3 .5 864.9 1,223.2 .2 203 .3073 3.809 156 315.8125 360.9 .5 863.1 1,224. .2 196 .3168 3.927 130 326. 363.4 .5 861.4 1,224.8 .2 191 .3263 4.042 765 336.1875 365.9 .5 859.7 1,225.6 .2 186 .3353 4.157 170 346.375 368.2 .4 858.1 1,226.3 .2 181 .3443 4.270 175 356.5625 370.6 .5 856.4 1,227. .1 176 .3633 4.383 180 366.75 372.9 .4 854.8 1,227.7 .1 172 .3623 4.495 185 376.9375 375. 3 .5 853.1 1,228.4 .1 168 .3713 4.607 190 387.125 377.5 .4 851.8 1,229.1 .1 164 .3800 4.720 195 396.3125 379.7 .4 850.1 1,229.8 .2 160 .3888 4.832 ?00 407.5 381.7 .3 848.6 1,230.3 .1 157 .3973 4.945 SPECIFIC VOLUME OF STEAM. The specific volume v, of steam, in accordance with the experiments of Tate and Fairbairn, may be expressed by the formula- 25 62 ,_ 49513 r />-j-0.72 108 MECHANICAL REFRIGERATION. VOLUME AND WEIGHT OF WATER. The volume of water does not change in direct propor- tion with the temperature, its greatest density being at 39 F., at which one cubic foot weighs 62.425 pounds. At 32 it weighs 62.418, at 62 it weighs 62.355, and at the boiling point it weighs 59.640 pounds. One cubic foot of water is generally taken at 62.5 pounds = 7. 48 U. S. gal- lons ; one cubic inch of water = .036 pounds ; one cubic foot of water = 6.2355 imp. gallons, or 7.48 U. S. gallons; one U. S. gallon of water = 8.34 pounds; one U. S. gallon of water = 231 cubic inches. PRODUCTION OF STEAM. The economical production of steam for industrial purposes is chiefly a question of fuel and the proper con- struction of boilers, grates, etc., and has been alluded to in the chapter on heat under the headings relating to fuel. For satisfactory arrangements as to boilers, etc., it may be assumed that one pound of fair average coal will produce about eight pounds of steam, more or less. WORK DONE BY STEAM. The theoretical ability of steam to do a certain amount of work is governed by the laws of thermody- namics above set forth, and the practical yield depends on a great many details in the mode of applying the force of steam practically, the consideration of which is beyond the limits of this treatise. For rough estimates, it is assumed that it requires from fifteen to thirty pounds of steam to produce a horse power, according to per- fection of engine, per hour. HEATING AREA OF BOILER. If H is the nominal horse power of a boiler and A the effective heating area of the same, Box finds that A nominal horse power requires from 0.6 to 1.2 square feet of grate surface between the limits of sixty and three horse powers. PRIMING. The water which is mechanically drawn over from the boiler with the steam is called priming, and may be determined in the following manner given by Clark. Blow a quantity of the steam, the amount of priming in which it is desired to ascertain, into a vessel holding a WATER, STEAM, ETC. 109 given weight of cold water, noting the pressure and the weight of the steam blown in, and the initial and final temperatures of the mixture. An addition is to be made to the initial weight of water, to represent the weight of water equivalent to that of the vessel containing the water, in terms of their respective specific heats. A cor- responding addition is to be made for such portion of the apparatus as is immersed in the water. Let W= weight of condensing water, plus the equiva- lent weight of the receiver and apparatus immersed in the water. w = weight of nominal steam discharged into the vessel under water. W + w = gross weight of mixture of nominal steam and condensing water. H = total heat of one pound of the steam, reckoned from the temperature of the condensing water. Hw = total heat delivered by the gross weight of nominal steam discharged, taken as dry steam. t = initial temperature of condensing water. t' = final temperature of condensing water. s = augmentation of specific heat of water due to rise of temperature. L== latent heat of one pound of steam of the given initial pressure. Lw = latent heat of steam discharged into the vessel, taking it as dry steam. P= weight of priming or moisture in percentage of the gross weight of nominal steam. P _ 100 .gw [(W+w)X(t f t + s)] Lw FLOW OF STEAM. The flow of steam through pipes takes place accord- Ing to Babcock after the following equation: In which formula W is the weight of steam in pounds which will flow per minute through a pipe of the length L in feet and the diameter d in inches, when p t is the initial pressure, p 2 the pressure at end of pipe, and D the density or weight per cubic foot of the steam. 110 MECHANICAL REFRIGERATION. Steam of a pressure of fifteen pounds per square inch (gauge pressure) flows into vacuum with a speed of 1,550 feet per second, and into air with a speed of 650 feet per second. , HYGROMETRY. Hygrometry is the art of measuring the moisture con- tained in the atmosphere, or of ascertaining the hygro- metric condition of the latter. AIR SATURATED WITH MOISTURE. The amount of aqueous vapor which can be held by a given volume of air increases with the temperature and decreases with the pressure. The air is called satu- rated with moisture when it contains all the moisture which it can contain at that temperature. The degree of saturation or hygrometric state of the atmosphere is ex- pressed by the ratio of the aqueous vapor actually present in the air to that which it would contain if it were satu- rated. In accordance with Boyle's law the degree of saturation may also be expressed by the ratio of the elastic force of the aqueous vapor which the air actually contains to the elastic force of vapor which it would con- tain if saturated. ABSOLUTE MOISTURE. The absolute moisture is the quantity of aqueous vapor by weight contained in unit volume of air. DEW POINT. When the temperature of air containing moisture is lowered a point will be reached at which the air is satu- rated with moisture for that temperature, and a further lowering of temperature will result in the liquefaction of some of the moisture. This temperature is called the dew point. DETERMINATION OF MOISTURE. The moisture in the atmosphere may be determined by a wet bulb thermometer, which is an ordinary ther- mometer, the bulb of which is covered with muslin kept wet, and which is exposed to the air the moisture of which is to be ascertained. Owing to the evaporation of the water on the muslin the thermometer will shortly acquire a stationary temperature which is always lower than that of the surrounding air (except when the latter is actually saturated with moisture). If t is the temper- WATER, STEAM, ETC. Ill ature of Uie atmosphere and i t the temperature of the wet bulb thermometer in degrees Celsius, the tension, e, of the aqueous vapor in the atmosphere is found by the formula e = e t 0.00077 (t-tj h^ e^ being the maximum tension of aqueous vapor for the temperature t t as found in table, and h the barometric height in millimeters. If e z is the maximum tension of aqueous vapor for the temperature t, the degree of saturation, H, is ex- pressed by H and the dew point is also readily found in the same table, it being the temperature corresponding to the tension e. TABLE SHOWING THE TENSION OF AQUEOUS VAPOR IN MILLIMETERS OF MERCURY, FROM 30 C. TO 230 C. Temp. Ten- sion. Temp. Ten- sion. Temp. Ten- sion. Temp. Ten- sion. ^30 .39 21 18.5 94 610.4 105 907 -25 .61 22 19.7 94.5 622.2 107 972 10 .9 23 20.9 95 633. H 110 1,077 15 1.4 24 22.7 95.5 645.7 115 1,273 10 2.1 25 28.6 96 657.5 120 1,491 5 3.1 26 25.0 96.5 669.7 125 1,744 2. 4.0 27 26.6 97 682.0 130 2,030 1 4.3 28 28.1 97.5 694. G 135 2,354 4.6 29 29.8 98 707.3 140 2,717 1 4.95 30 81.6 98.5 721.2 145 3,125 2 5.3 35 41.9 99 732.2 150 3,581 3 5.7 40 55.0 99.1 735.9 155 4,088 4 6.1 45 71.5 99.2 738.5 160 4,551 5 6.5 50 92.0 99.3 741.2 165 5,274 6 7.0 55 117.5 99.4 743.8 170 5,961 7 7.5 60 148.Q 09.5 746.5 175 6,717 8 8.0 65 186.0 99.6 749.2 180 7,547 9 8.6 70 232.0 99.7 751.9 185 8,453 10 9.1 75 287.0 99.8 754. fi 190 9,443 11 9.7 80 354.0 99.9 757.3 195 10,520 12 10.4 85 432.0 100 760 200 11,689 13 11.1 90 525.4 100.1 762.7 205 12,956 14 11.9 90.5 535.5 100.2 765.5 210 14,325 15 12.7 91 545.8 100.4 772.0 216 15,801 16 13.5 91.5 556.2 100.6 776.5 220 1?,39T 17 14.4 92 566.2 101 787.0 225 19,097 18 15.3 92.5 577.3 102 816 230 20,926 19 16.3 93 588.4 103 845 20 17.4 93.5 599.5 104 876 Degrees C Atmospheres. 120 134 144 152 159 171 180 199 213 226 2 3 4 5 6 8 10 15 20 25 PSYCHROMETERS. Instead of the wet bulb thermometer alone it is more convenient to use two exact thermometers com- bined (one with a wet bulb and the other with a dry bulb, to give the temperature of the air) to determipe 112 MECHANICAL REFRIGERATION. the hygrometric condition of the atmosphere or of the air in a room. Instruments on this principle can be readily bought, and are called psychrometers. If they are arranged with a handle, so that they can be whirled around, they are called "sling psychrometers." These permit a quicker correct reading of the wet bulb ther- mometer than the plain psychrometer, in which the thermometers are stationary and are impracticable at a temperature below 32 F., while the sling instrument can be read down to 27 F. The following table can be used to ascertain the de- gree of saturation or the relative humidity : RELATIVE HUMIDITY PER CENT. t (Dry Ther.) Difference between the dry and wet thermometers (t t'). t (Dry Ther.) 0.5 1.0 1.5 2.0 2. 5 3.0 3. 5 4.0 4. 6 5.r5.5tJ.0 28 94 88 82 77 71 65 60 54 49 43 38 33 28 29 94 89 83 .77 72 66 61 56 50 45 40 35 29 30 94 89 84 78 73 67 62 57 52 47 41 36 30 31 95 89 84 79 74 68 63 58 53 48 43 38 31 32 95 90 84 79 74 69 64 59 54 50 45 40 32 33 95 CO 85 80 75 70 66 60 56 51 47 4i 33 34 95 91 86 81 75 72 67 62 57 53 48 44 34 35 95 91 86 82 76 73 69 65 59 54 50 45 35 36 96 91 86 82 77 73 70 66 61 56 51 47 36 3T 96 91 87 82 78 74 70 66 62 57 53 48 37 38 96 92 87 83 79 75 71 67 63 58 51 50 38 39 96 92 88 83 79 75 72 68 63 59 5o 52 39 40 96 92 88 84 80 76 72 68 64 60 56 53 40 The hygrometer of Marvin is a sling psychrometer of improved and approved construction. HYGROMETERS. While the term hygrometer applies to all instruments calculated to ascertain the amount of moisture in the air, it is specifically used to design instruments on which the degree of humidity can be read off directly on a scale without calculation and table. Their operation is based on the change of the length of a hair or similar hygro- scopic substance under different conditions of humidity. DRYING AIR. To remove moisture from air more or less saturated with it, certain so called hygroscopic substances which have a great affinity for water may be applied. Chloride of calcium, dried at a dul) red beat and powdered, may be WATER, STEAM, ETC. 113 used for this purpose, and when spread in a layer %-inch thick and exposed to air at 48 F., with a humidity of 0.75, will absorb per square foot surface in each one of seven succeeding days the following amounts of moist- ure: 1,368, 1,017, 958, 918, 900, 802 and 703 grains respect- ively (Box). VAPORIZATION. The vaporization of water into the airxlepends on the hygrometric state of the atmosphere, and its amount in grains, It, per square foot and per hour with air per- fectly calm, may be expressed according to Box by the following rule: B = (e 2 e)\5 When the air into which the water evaporates is in motion the evaporation proceeds much faster, thus : For a fresh breeze R=(e 2 e)QQ for a strong wind R=(e 2 e)l32 and for a gale E=(e 2 e)188. The refrigeration which is produced by the vaporiza- tion of water into the air is about 900 B. T. units for each pound of water evaporated, or 0.117 units per grain of water evaporated. PURITY OF WATER. As natural water is never absolutely pure it is fre- quently of importance to ascertain the degree of purity of a water for certain purposes. The requirements to be made in regard to the purity of a water vary with the purposes for which it is to be used ; water may be very good for drinking purposes, but at the same time it may be too hard for boiler feeding ; and on the other hand a water may be good for boiler feeding, yet it may be too impure (bacteriologically) for drinking purposes. Similar dis- tinctions obtain in other respects, so that it is impracti- cable to give general rules for the valuation of a water, unless they are based on an exact chemical analysis of the same. The crude chemical tests which are fre- quently recommended in this connection are of little or no value in most cases, and more frequently they are misleading. They generally only give qualitative indi- cations, but in order to be able to judge a water correctly the relative quantities of its constituents must be known. 114 MECHANICAL REFRIGERATION. CHAPTER IV.-THE AMMONIA COMPRESSION SYSTEM. GENERAL FEATURES. The refrigeration in this system is brought about by the evaporation of liquid anhydrous ammonia, which takes place in coils of pipe termed the expander or refrig- erating coils. These coils are either placed in the rooms to be refrigerated, or they are immersed in a bath of salt brine, which absorbs the cold. The salt brine is circu- lated in pipes through the rooms to be refrigerated by means of a pump. The ammonia, after having expanded, is compressed again by means of a compression pump called the compressor into another system of pipes called the condenser. The condenser -is cooled off by running water, which takes away from the ammonia in the coils the heat which it has acquired through the compression, as well as the heat which it has absorbed while having evaporated in the expander. Owing to both pressure and withdrawal of heat, the ammonia assumes its liquid form again to pass again into the expander, thus repeatirv# its circulation over and over again. THE SYSTEM A CYCLE. The refrigerating contrivance above described em- bodies a perfect cycle of operations. The working sub- stance, ammonia in this case, returns periodically to its original condition. During each period a certain amount of heat, partly in the refrigerator and partly during com- pression (from work converted into heat), is added to the working substance and an exactly equivalent amount is abstracted from the working substance in the condenser by the cooling water. THE COMPRESSOR. The compressor is a strongly constructed cylinder in which a piston moves to and fro, having a valve through which the expanded ammonia from the refrigerating coils enters and another through which it is forced into the con- denser. A double-acting compressor has two valves at each end of the compressor cylinder, and the packing for the piston rod must be made sufficiently long and tight to withstand the pressure of the ammonia. The com- pressor, like all other parts of the ammonia system, must be made of steel and iron, no copper or brass being admissible, THE AMMONIA COMPRESSION SYSTEM. H5 During the compression stage a certain amount of heat is evolved. If not otherwise stated, it is assumed in the following discussion, that enough heat is removed during compression to keep the vapor always in a satu- rated condition. REFRIGERATING EFFECT OF CIRCULATING MEDIUM. To arrive at numerical values of the quantities in- vol ved in the refrigerating process we may first determine the theoretical refrigerating effect, r, of the circulating medium. If t be the temperature of the condenser, that is, the temperature of the cooling water leaving the condenser; if tj be the temperature of the refrigerator, that is, the temperature of the brine leaving the refrigerator; if s is the specific heat of the circulating liquid, and if /i t is the latent heat of vaporization of one pound of the circulating medium in thermal units at the temperature t lt we find the refrigerating effect, r, of one pound of the circulating fluid, expressed in thermal units after the following formula: r=7i 1 (t t ) s The term (t t t ) s represents the refrigeration re- quired to reduce the temperature of the circulating fluid from the temperature t to the temperature t . Practically speaking, the temperature of the ammonia in condenser will always be a few degrees higher than the water leaving the condenser, and the ammonia in refriger- ating coil will always be a few degrees (5 to 10) lower than the outgoing brine. WORK OF COMPRESSOR. If the cycle of operation was a perfect reversible one, the work required from the compressor for every pound of the liquid circulating would be to lift the amount of heat, r, from the temperature t to the temperature t. As explained already, this is not the case, and the whole amount of heat as represented by the latent heat of vap- orization, namely, /i t , is to be lifted by the compressor through the range of temperature indicated. Hence the work theoretically required from the compressor ex- pressed in thermal units, TF, is therefore X T representing the temperature of the refrigerator ex- pressed in degrees of absolute temperature ( t v -f 460 ), 116 MECHANICAL REFRIGERATION. HEAT TO BE REMOVED IN THE CONDENSER. The theoretical number of heat units, D, which would have to be removed by the condenser water per pound of refrigerating fluid in circulation in the system, if the circulating fluid in compressor were always kept in a saturated condition from without by removing the surplus heat, could be expressed as follows: D = h, h being the latent heat of volatilization of one pound of the circulating liquid at the temperature of condenser (t). The whole amount of heat, Dj, to be removed when including that which would cause superheating of the fluid in compressor, may be theoretically expressed as follows: - tt< -Pi= T fri+fei-g(* *i). AMOUNT OF SUPERHEATING. The amount of heat, , liable to cause superheating may therefore be expressed by the formula S=D 1 D, or fc.fc COUNTERACTING SUPERHEATING. The surplus heat in compressor is removed in various ways : by injecting refrigerated oil, by surrounding the compressor with a cold water jacket, or by carrying liquid ammonia into the compressor, etc. While there is no doubt as to the advisability of preventing super- heating as much as possible, the theoretical discussions regarding the relative merit of these expedients do not quite agree among themselves, nor with practical expe- rience, and it would appear that besides theoretical con- siderations certain practical points have some bearing on this question, especially the degree to which the preven- tion of superheating is effected. AMOUNT OF AMMONIA IN COMPRESSOR. The additional amount of liquid ammonia that would have to be carried into the compressor with every pound of ammonia vapor entering the same, in order to keep the latter saturated during compression, may be ex- pressed by the formula P =F- /i, in which P stands for pounds of liquid ammonia so re- quired. THE AMMONIA COMPRESSION SYSTEM. 117 NET THEORETICAL REFRIGERATING EFFECT. The ammonia required to keep the vapor saturated in compressor has to be cooled down from the tempera- ture t to the temperature t}, and the refrigeration is re- duced to that extent. Accordingly the net refrigerating effect, r t , of every pound of circulating liquid volatilized in refrigerator, in case of wet compression is expressed by the formula: or r t = h t (t t )s T s(t t t ). ftj VOLUME OF THE COMPRESSOR. The* volume of the compressor is expressed by the amount of space through which the piston travels each stroke. If r be the radius of the compressor and b the length of stroke in feet, the active volume of the com- pressor, V, is V= r 2 X b X 3.145 cubic feet. If r and b are expressed in inches the formula would become ,,, r 2 bX 3.145 ,. . cubic feet. CUBIC CAPACITY OF COMPRESSOR. The cubic capacity of a compressor may be expressed by the amount of space which the piston travels through in one minute, only one way being counted in a single- acting, and both ways being counted for each revolution in a double-acting compressor. If m is the number of revolutions per minute, r the radius and 6 the length of stroke in feet of a compressor, the capacity of the same, C, if single-acting, is expressed by the formula : C = r 2 x3.145x&Xm cubic feet per minute; if double-acting, it is twice that. If r and b are given in inches, the product must be divided by 1,728 to find (7. CLEARANCE. As the piston does not exactly touch the cylinder ends, leaving always more or less dead space called clear- ance, the whole of the above capacity is not available on this account, and from 5 per cent to 7 per cent may be deducted from it for clearance. This may be called the reduced capacity of the compressor. 118 MECHANICAL REFRIGERATION. The exact percentage of clearance depends on a number of conditions, and may be approximately deter- mined after the following equation: V In this equation (7 is the theoretical capacity of a compressor, and C the corrected or reduced capac- ity in accordance with clearance. V is the volume traversed by piston in each stroke in cubic feet, n the actual clearance space left between piston and cylinder in cubic feet, w and w t the weights of equal volumes of ammonia at the pressure in condenser and refrigerator respectively. REFRIGERATING CAPACITY OF COMPRESSOR. The refrigerating capacity of a compressor does not alone depend on its cubic capacity, but also on surround- ing circumstances, especially the temperature in con- denser and refrigerator coils, and can, therefore, not be exactly determined without these data. For rough esti- mates it may be assumed, however, that under quite frequently prevailing conditions a cubic compressor capacity per minute of four feet will be equivalent to a capacity of one ton refrig. in twenty-four hours. (Fifty- six inches double-acting compressor capacity sixty revo- lutions. ) If GI is the reduced compressor capacity per minute (that is, G less clearance) the corresponding re- frigerating capacity, jK, expressed in tons of refrigera- tion in twenty-four hours, may be found after the follow- ing formula: p __ O t X 36 X r : vX 7,100 or approximately -R = 200 ^ ton8 ' In this formula v stands for the volume of one pound of ammonia vapor in cubic feet at the temperature of the refrigerator ; the sign r stands for the maximum theoretical refrigerating capacity for 'each pound of am- monia passing the compressor. The refrigerating capacity of a compressor, expressed in thermal units, B lt per hour, is THE AMMONIA COMPRESSION SYSTEM. H9 AMMONIA PASSING THE COMPRESSOR. The amount 'of ammonia, K, in pounds passing the compressor per minute is expressible thus: K G! X w pounds, in which C^ stands for the reduced compressor capacity per minute and w for the weight of one cubic foot of ammonia vapor at the temperature of the refrigerator or expansion coils. NET REFRIGERATING CAPACITY. As the last four formulae allow for clearance, but not for other losses, it is more convenient and practically sufficiently correct in most cases to substitute in these formulae Cfor d, and reduce the refrigerating capacity so found by 15 per cent, which should be ample for all losses, and give net refrigerating capacity. HORSE POWER OF COMPRESSOR. If W= rp^hi (in thermal units) is the power re- quired by the compressor to lift the heat which became latent by the evaporation of one pound of ammonia in refrigerator, as shown before, and if K represents the amount of ammonia vapor entering the compressor per minute, the work to be done by the compressor per min- ute, Wi t expressed in thermal units, is W l =WxK units. If expressed in foot-pounds, TF 2 , it is W* =778 WX K foot-pounds. And if expressed in horse powers, W 3 , it is ITQQ W * = ~33W WX K= " 0> 234 WK h rse P Wer * W 3 = 0.0234^^/1, x C X w horse power. SIZE OF COMPRESSOR. In order to determine the size of a compressor for a given refrigerating duty it is advisable to reduce the latter to an expression of heat -units to be removed per hour; and if the same is understood to represent actual refrigerating capacity, some 15 per cent or more, ac- cording to circumstances, should be added for clearance and other losses, and in case the refrigerating capacity is r equired in the form of manufactured ice it should at 120 MECHANICAL REFRIGERATION, least be doubled. The reduced refrigerating duty so obtained we will callr 2 , o the volume *of one pound of ammonia gas at the temperature of the outgoing brine, r t the refrigerating effect of one pound of ammonia for the temperatures employed, Fthe active volume swept over by the piston in each revolution (two times the volume of compressor if the same is double-acting), and m the number of revolutions per minute. Signs having this meaning, the following equations obtain: In this case Vm signifies the compressor capacity per minute. If m is given If F is given m " 60Xr,F revolutions - NUMBER OF REVOLUTIONS AND PISTON AREA. The number of revolutions of compressor varies with its size from forty to eighty revolutions per minute. When the compressor is worked directly by a steam en- gine, as is generally the case, the number of revolutions of the compressor is governed by those of the engine, and the area of the compressor piston must be in ac- cordance with that of engine piston. The product of average pressure on engine piston with the area of the latter must always be greater than the product of the compressor piston area multiplied by the pressure in con- denser coil if both the engine and compressor piston have the same length of stroke. If the stroke of com- pressor piston is shorter than that of engine piston its area can be made correspondingly larger. USEFUL AND LOST WORK OF COMPRESSOR. That part of the work of the compressor which is ex- pressed by the foregoing equations -for W^, W 2 or W 3 may be considered as useful work of the compressor, while what work is done by the compressor in excess of that amount, due to superheating, friction and other causes, may be considered as lost work. The smaller the lost work the more perfect is the operation of the com- pressor. AMMONIA COMPRESSION SYSTEM. 121 DETERMINATION OF LOST WORK. The lost work of a compressor may be determined in various ways, directly by interpretation of the indicator diagram and also indirectly in some cases. The lost work is the difference between the actual work done by the compressor and that theoretically required of the same, or expressed by formula, L standing for lost work in thermal units and W 6 for actual compressor work in thermal units: L= W Q Wi INDIRECT DETERMINATION OF ACTUAL WORK. In a machine with submerged condenser, the actual work, TF 6 , of the compressor may be approximately de- termined in T. U. per hour after the following formula: W 6 = (TT 1 )p (t t l )gs 1 in which formula T is the temperature of outgoing, T t the temperature of incoming condenser water, t the tempera- ture of cold brine, t t the temperature of returning brine, p the number of pounds of condensing water used per hour, g the number of pounds of brine circulated per hour, and s 1 the specific heat of the brine. The actual compressor work found in this manner will be somewhat larger than that found from the indi- cator diagram, since it includes the lost work due to fric- tion in the compressor. . Allowance must also be made for amount of superheating neutralized otherwise than by condenser water. HORSE POWER OF ENGINE. The work required to operate the compressor, whether furnished by engine direct or by transmission and gear- ing, must be equal, or rather somewhat greater than the actual work of the compressor. It must exceed the work shown by the indicator by at least the amount due to friction of piston, etc. It is safe to assume that the in- dicated horse power of an engine, JF 7 , necessary to pro- pel a compressor of a theoretical horse power, W 3 , is at least about W 7 = 1.4 W 3 horse power. In defective machines it may be more; seldom, how- ever, it will be less. WATER EVAPORATED IN BOILER. The amount of w.iter evaporated in boiler (for non- condensing engine) may be approximately estimated on 122 MECHANICAL REFBIGERATION. the basis that twenty-five pounds of water are needed per hour per horse power in a well regulated boiler. The amount of water, J., evaporated f or twenty-four hours is, therefore A = 25 X 24 X W 7 pounds. COAL BEQUIBED. If one pound of coal evaporates n pounds of water the amount of coal, F, required in twenty-four hours is ap- proximately In a condensing engine about fifteen pounds of water are used per horse power per hour, and the foregoing formula in that case reads ,, 15 X 24 X W 7 n P unds ' n differs for various kinds of fuel, but may be assumed equal to 8 for fair average coal. EFFICIENCY OF COMPRESSOR. The term efficiency covers a variety of meanings, and the meaning ought to be expressed clearly in each case. Generally efficiency is expressed by the number of units of heat removed from the refrigerator for every thermal unit of work done by compressor, which is also expressed by the quotient _, Heat removed in refrigerator Work done by compressor in T. U. This may be called the actual efficiency for a given case. As it varies not only with the machine, but also, and most decidedly so, with the local condition under which it works (temperature of refrigerator and con- denser) it affords no criterion as to the lost work done by the compressor, i. e., it is not an expression for the degree of perfection of the compressor. In order to obtain an expression for this quality we must, according to Linde, compare the actual efficiency of a plant with the maximum theoretical efficiency of Uje plant when working under the same condition. The maximum theoretical efficiency, E 2 , is expressed by Linde through the formula T E 2 = Ti _ T TflE AMMONIA COMPRESSION SYSTEM 123 As we have seen above, this should more properly be substituted by the maximum theoretical efficiency, E^ as explained in the above, at least if machines with the same circulating medium are to be compared, viz.: i-*i) If R stands for the heat actually removed in refrig- eration and Q for work actually performed by compressor, as ascertained by actual observation or test, we have for the actual efficiency, E % the expression The ratio or proportion, w, between the actual and the theoretical capacity is therefore E n = -E[ or if we insert the expressions found abore ,_. -RM<-*i) QT^-s(t-tJ} DIFFERENT KINDS OF COMPRESSORS. There are many constructive details in valves, etc., in the different makes of compressors which it is impracti- cable here to discuss. The principal difference, how- ever, is due to the different methods in which super- heating of the gas during compression is prevented or to whether the compressor is horizontal or vertical, double or single-acting, etc. By way of example we mention only a few typical ones. THE LINDE COMPRESSOR. This compressor is principally used for wet compres- sion, the peculiarities of which have been mentioned above ; it is a horizontal double-acting compressor with a deep packing, having a length of twelve inches or more in order to withstand the pressure of some 150 to 180 pounds. Since ammonia attacks India rubber, the best rubber packings for compressors are inlaid with cotton. Selden's, Oarlock's and Common Sense packing are also used. 124 MECHANICAL REFRIGERATION. The Boyle compressor is vertical and single-acting, compressing only on the up stroke. The gas has free en- trance to and exit from the cylinder below piston, calcu lated to keep cylinder and piston cool. The extreme lower portion of the pump forms an oil chamber to seal the stuffing box around piston. THE DE LA VERGNE COMPRESSOR. This compressor is also a vertical compressor, and superheating is counteracted by means of refrigerated oil, which is circulated through the compressor by means of a small pump. Another object of the oil is that its presence ahead and behind the piston abolishes the evil effects of clearance, or at least lessens the same mate- rially. It furthermore affords excellent lubrication of the moving parts and helps to make the piston tight. THE WATER JACKET COMPRESSOR. This form of compressor is mostly vertical, its pecul- iarity being that the superheating is prevented by circu- lating cold water or brine through a water jacket which surrounds the compressor. These compressors are frequently single-acting; in this case a shorter stuffing box (causing less friction) for piston rod may be used, since the pressure on the stuffing box is seldom more than thirty pounds. TABLE SHOWING REFRIGERATING EFFECT OF ONE CUBIC FOOT OF AMMONIA GAS AT DIFFERENT CONDENSER AND SUCTION (BACK) PRESSURE IN B. T. UNITS. i fd Temperature of the Liquid in Degrees P. to II! 65 70 75 80 85 90 95 100 105 43 Q u * Correspg. Condenser Pressure (gauge) Ibs. per sq. in. OQ 103 115 127 139 153 168 184 200 218 g G. Pres 27 1 27.30 27.01 26.73 26.44 26.16 25.87 25.59 25.30 25.02 20 4 33.74 33.40 33.04 32.70 32.34 31.99 31.64 31.30 30.94 -15 6 3ti.36 36.48 36.10 35.72 35.34 34.96 34.58 34.20 33.82 10 9 42.28 41.84 41.41 40.97 40.54 40.10 39.67 39.23 38.80 5 13 48.31 47.81 47.32 46.82 46.33 45.83 45.34 44.84 44.35 16 54.88 54.32 63.76 63.20 52.64 52.08 61.52 50.96 50.40 5 20 61.50 60.87 60.25 59.62 59.00 58.37 67.75 57.12 56.50 10 24 68.66 67.97 67.27 66.58 65.88 65.19 64.49 63.80 63.10 15 28 75.88 75.12 74. 3 1 73.59 72.82 72.06 71.29 70.53 69.76 20 33 85.15 84.30 83.44 82.59 81.73 80.88 80.02 79.17 78.31 25 39 95.50 94.54 93.59 92.63 91.68 90.72 89.97 88.81 87.86 80 45 106.21 105.15 104.09 103.03 101.97 100.91 99.85 98.79 97.73 51 115.W, 114.54123.39 112.24 111.09 109.94 108.79107.64 106.49 THfi AMMONIA COMPRESSION SYSTEM. 125 TABLE GIVING NUMBER OF CUBIC FEET OF GAS THAT MUST BE PUMPED PER MINUTE AT DIFFERENT CONDENSER AND SUCTION PRESSURES, TO PRODUCE ONE TON OF REFRIGERATION IN 24 HOURS. a be a Temperature of the Gas in Degrees F. ^ o> & Ili 65 70 75 80 85 90 95 100 105 S2 g_^ tJ tiC rf o ! o"o- Q Correspg. Condenser Pressure (gauge) Ibs. per sq. in. OSH^ 01 103 115 127. 139 153 168 184 200 218 27 G. Pres 1 7.22 7.3 7.37 7.46 7.54 7.62 7.70 7.79 7.88 20 4 5.84 5.9 5.96 6.03 6.09 6.16 6.23 6.30 6.43 15 6 5.35 5.4 ,^.46 5.52 5.58 5.64 5.70 5.77 5.83 10 9 4.66 4.73 4.76 4.81 4.86 4.91 4.97 5.05 5.08 5 13 4.09 4.12 4.17 4.21 4.25 4.30 4.35 4.40 4.44 16 3.59 3.63 3.66 3.70 3.74 3.78 3.83 3.87 3.91 20 3.20 3.24 3.27 3.30 3.34- 3.38 3.41 3.45 3.49 10 24 2.87 2.9 2.93 2.96 2.99 3.02 3.06 3.09 3.12 15 28 2.59 2.61 2.65 2.68 2 71 3.73 2.76 2.80 2.83 20 33 2.31 2.34 2.36 2.38 2. 41 2.44 2.46 2.49 2.51 25 39 2.06 2.08 2.10 2.12 2.15 2.17 2.20 2.22 2.24 30 45 1.85 1.87 1.89 1.91 1.93 1.95 1.97 2.00 2.01 36 51 1.70 1.72 1.74 1.76 1.77 1.79 1.81 1.83 1.85 THE ST. CLAIR COMPOUND COMPRESSOR. This is a combination of two or more single-acting compressors after the principles of compound engines, in such a way that the ammonia is compressed part way at a lower pressure in one compressor and then transferred to another compressor, in which the higher compression is applied after the ammonia has passed an intermediate condenser. WATER FOR COUNTERACTING SUPERHEATING. The amount of refrigeration, U, required to counter- act the superheating of ammonia in the case of dry com- pression may be expressed by U=SxKX 1440 units in twenty -four hours. In accordance with the above described devices, it is removed either by cooling the oil or by introducing water into the water jacket. The amount of water in gallons, i 5 5 7 7 7 7 7 in. in. 1 1 1 1* 1 '1 Pipe Ptpe 17 21 21 21 21 21 24 per per 3,680 4,440 7,750 7,750 13,950 12,400 14,080 ton, ton, 294.4 222. 258. a 193.75 279. 206.6 176. 147.2 126.8 155. 103.3? 139.5 99.2 93.86 263.42142.12 192.12) S8.79 SUBMERGED CONDENSERS. bp Tar iks. Ld '. .- i> Ilce Making Capacity. In Tons. IRefrigeratiE Capacity. In Tons. 1 Length. Feet. Width. Feet. 8 1 Thickness of Iron. Inches. Number of Coils. ' Pipes High. Feet LTmg. 2a |s| Total Feet o Pipe in Condenser. Feet of Pipe p Ton, Ice Mat ing Capacitv Feet of Pipe p Ton, Refrige ating Capacit 5 10 .10 31^ 6'/ 2 3-16 9 12 74 855 171. 85.5 10 20 10 i*-A 6J4 3-16 20 12 7V 1,900 190. 95. 12J4 25 10 1 1 A 6|/ 2 3-16 22 12 7/j 2,090 167. 83.6 15 30 10 8^3 3-16 25 12 2,375 151.6 79.16 20 35 10 10 6V4 3-16 27 12 7j| 2,565 128.25 73.28 30 50 10 10 /4 27 24 5,130 171. 102.6 40 75 14 10 13/4 % 27 24 ll 1 ^ 7,695 191.1 102.6 60 110 14 13 13'/ 2 % 35 24 "H 9,975 166.25 90.68 Aver age, 167. 89. THE FORECOOLER. In order to save power and cooling water many plants are provided with supplementary condensers, or forecoolers, which consist of a coil or series of coils through which the compressed ammonia is made to pass before it enters the condenser proper. The forecooler is cooled by the spent or overflow water of the condenser. 132 MECHANICAL REFRIGERATION. If consisting of one coil, the forecooler should have the same size as the discharge pipe from the compressor ', if consisting of a number of coils, the manifold pipe and the aggregate area openings of small pipes should equal that of the discharge pipe. NOVEL CONDENSERS. Condensers are now also built, in which the com- pressed gas, instead of entering a system of coils im- mersed in water, enters a cylinder or shell while the cooling water circulates through coils located within the cylinder. Such a condenser is described by Hendrick as to con- sist of a heavy cast iron shell standing upright on a channel iron frame ; it contains two or more spiral coils of 1^-inch extra heavy pipe, the tails of which project through the heads of the shell and are united by mani- folds. The ammonia gas, as discharged by the com- pressor, is delivered into the shell at the top, and as it becomes liquefied under the influence of pressure and by contact with the coils through which the condensing water is circulated (entering the lower ends of the coil), the liquid anhydrous ammonia collects in the bottom of the shell, which thus constitutes the liquid anhydrous receiver, and which is provided with suitable level and gauge. It will be seen that in this construction the water is subdivided into two or more separate and dis- tinct streams, traveling through coils which vary in length from 100 to 175 feet, according to the size of the condenser. This is said to give a much better utiliza- tion of the cold in the water than the ordinary methods, where the condensing coils are submerged in a water tank, or where the coils are arranged so that the water trickles over them ; in both cases the water simply traveling upward or downward ten to twenty feet. All coils are continuous from end to end. On a similar principle brine coolers are made in which the brine circulates through systems of pipps, while the ammonia expands in a shell or cylinder sur- rounding the brine pipes. PURGE VALVE. At the highest point of the condenser, or on the discharge line next to the condenser, a purge valve should be provided for, to let off permanent gases. THE AMMONIA COMPRESSION SYSTEM. 133 DUPLEX OIL TRAP. Frequently two oil traps are used, one of which, gen- erally a larger one, is placed near the machine, and the other, the smaller one, near the condenser. When a forecooler is used the smaller trap is placed between it and the main condenser. The following table shows the sizes of traps that may be used : Tons refrigeration 2 to 15 15 to 50 51 to 60 61 to 100 8"X3' 10" X 3' 12"X3' 12" X 4' Large trap 8"X5' 10" X 6' 12"X6' 12"X8' WET AND DRY COMPRESSION. If superheating is prevented by carrying liquid am- monia into the compressor to keep the vapor always in a saturated condition, we say that we are working by wet compression; and if, on the other hand, the ammo- nia gas becomes superheated during compression, we are working by what is called dry compression. Some forms of compressors are specially adapted for wet compres- sion; others for dry compression. Opinions are much divided as to the relative merits of these two systems of compression. The theory shows a gain of economy in favor of wet compression, and the practical results do not contradict this, although the difference is not very great. POWER TO OPERATE COMPRESSOR. The power actually required to operate a compressor in order to produce a ton of refrigeration varies from one to two horse power, according to size of machine, other circumstances being equal. Very large machines may be operated with one horse power per ton of refrigerating capacity (in twenty-four hours), but gen- erally one and one-third to one and one-half horse powers are required per ton for machines of over forty tons re- frigerating capacity. Machines from ten to forty tons refrigerating capacity will require from one and one-half to two horse powers per ton, and still smaller machines will require up to two and one-half horse powers, and sometimes still more, per ton of refrigeration. EXPANSION VALVE. This valve is placed between the condenser, or rather, the liquid receiver, and the expansion or refrigerating coils. It is a peculiar valve, admitting of very fine adjust- 134 MECHANICAL REFRIGERATION. ment, so as to enable the engineer to admit the required amount of liquid to the expander, and no more. EXPANSION OF AMMONIA. The expansion or volatilization of the liquid am- monia, by which the refrigeration is effected, takes place within series or coils of iron pipes. These pipes may be located in the rooms to be refrigerated (direct expansion system) or they may be placed in a bath of salt brine, which, after having been cooled in this way, is circulated in turn through the rooms to be refrigerated, (indirect expansion, or brine system.) SIZE OF EXPANSION COILS. The surface or the size and length of expansion coils to be placed in the rooms to be refrigerated, or in the brine tank, like nearly all the pipe work in the refrigerating practice, is based on empirical rules. There are no concise formulae on these subjects, as exact experiments on the transmission of heat under circumstances obtaining in the refrigerating practice aro almost entirely wanting. Besides this, the conditions are very variable, owing to the change of pipe surface by atmospherical condi- tions, or by the deposit of ice and snow or by the de posit from the water, as in case of the condenser, differ ence in insulation, etc. For these reasons every manu- facturer has his own rules; and whatever is said in this compend on this subject is abstracted from practical ex- perience and subject to modifications in individual cases. PIPING ROOMS. The size of pipe usually employed for piping rooms varies from one to two inches, and the length required varies according to circumstances, more especially with the temperature or the back pressure of the expanding ammonia and the temperature at which the rooms are to be held. If a room is to be held at a temperature of 34, and the temperature of the expanding ammonia is 10, it will take only half as much pipe to convey a certain amount of refrigeration as it would take if the tempera- ture of the expanding ammonia were at 22 F. In the latter case, however, the machine works under conditions far more economical, and for this reason it is advisable to use the larger amount of pipe in order to be enabled to work with a higher back pressure. THE AMMONIA COMPRESSION SYSTEM. 135 TRANSMISSION PER SQUARE FOOT. In allowing a difference of 8 to 15 between the temperatures inside arid outside of the pipes it is va- riously assumed that one square foot of pipe surface will convey 2,500 to 4,000 units of refrigeration in twenty-four hours in direct expansion. This figure nearly agrees with a transmission of heat at the rate of 10 B. T. units per hour, per square foot sur- face, for each degree F. difference between temperature inside and outside of pipe, in case of direct expansion. In the case of brine circulation the brine with the same back pressure has, of course, a much higher temperature than the ammonia, and for this reason the above difference will be much less, which explains the fact that from one and one-half to two times as much pipe is used with brine circulation as in direct expansion. If the amount of piping is calculated on this basis, allowing a refrigeration of a certain number of B. T. units per cubic foot of space to be refrigerated, the re- sult will generally fall short of the piping required after the rules lai'd down in the following paragraph. This is to be explained by the fact that the latter rules are given on a very liberal basis calculated to cover unfavorable cases as regards insulation, size of rooms, etc., it being understood that any possible surplus in piping will tend to increase the efficiency of machine. This remark ap- plies not only to the rules for piping in following para- graph, but to rules on piping in most cases. PRACTICAL RULE FOR PIPING. Practically the matter, however, is not often calcu- lated on this basis, but after a rule of thumb it is assumed (allowing for difference in insulation and size of rooms) that about one running foot of 2-inch pipe (direct expan- sion) will take care of ten cubic feet of space in houses which are to be kept below freezing down to a tempera- ture of 10 F. About one running foot of 2-inch pipe will take care of forty cubic feet of space in rooms to be kept at or above the freezing point, 32 F., or thereabouts. About one running foot of 2-inch pipe will take care of sixty cubic feet of space in rooms to be kept at 50 F., and above, as in the case of ale storage. In conformity with the remarks in preceding para- 130 MECHANICAL REFRIGERATION. graph, we take it that these rules are intended to cover cases of rooms of 50,000 cubic feet capacity and less, poorly insulated, and operated with small differences in temperature. On a similar basis it is frequently assumed that one ton refrigerating capacity will take care of 4,500 cubic feet cold storage capacity to be held at 32 to 35 F., and that from 260 to 300 feet of IM-inch pipe will properly distribute one ton of refrigeration. Relating to the question of piping rooms, condensers and brine tanks, it may be understood once for all that there are two sides to this also. One contemplates a less expensive plant by reducing piping to a minimum fre- quently at the expense of economical working. The other side aims at increasing the capacity by ample pipe surface, and therefore the first outlay for a plant will be greater, but probably will pay better in the end. DIMENSIONS OF PIPE. One running foot of 2-inch pipe is equal to 1.44 feet of 1^-inch pipe, and 1.8 feet of 1-inch pipe, as regards surface. For similar comparisons and calculations the following tables will be found convenient: DIMENSIONS OF STANDARD PIPE. < o a a (DH g vv 1 1 J} 2 3 1 ^| i 4 S L 1 i 1 ^ "^S i 5 . . *0 . < o-2 la o> 3S 2g 0) 1 3| c 9 i gg 5^1 a fl | ,af o gj 15 fc S3 oQ < M 2 X) H h ? p t-i s s* G ^ 0) P8.277 30.433 0.398 63.633 73.715 2.26 34.677 10 10.019 10.65 0.336 31.475 33.772 0.355 78.838 90.792 1.80 40.641 THE AMMONIA COMPRESSION SYSTEM. DIMENSIONS OF EXTRA STRONG PIPE. A table giving dimensions of extra strong pipe will be found in the Appendix. BRINE SYSTEM. In the brine system the expansion coils, as stated, are placed in separate vessels containing salt brine, which is cooled down to the desired degree. The brine so cooled is then conducted through pipes located in the rooms to be refrigerated by means of force pumps. In ice making the cells or boxes containing the water for ice making are suspended in the brine tank. SIZE OF PIPE IN BRINE TANK. The amount of piping allowed in brine tank is also a matter of practical experience. Generally 120 to 150 running feet of 1^-inch pipe are allowed per ton of re- frigerating capacity (in 24 hours) in brine tank for gen- eral refrigeration. In case of ice making 250 to 300 running feet of 1^- inch pipe are allowed in brine tank per ton of ice to be manufactured in twenty-four hours. TABLE OF BRINE TANKS AND COILS. The following table shows the dimensions of some brine tanks and coils for different capacities, expressed in tons of refrigerating capacity (not ice making capacity). Capacity In Tons Refrigera- tion. 25 tons.... 35 " .... 60 " .... 75 " . . Average per ton. p 1,664 2,080 2,730 4,785 * o fa 2 04 ' 3.41 2.90 2.58 2.36 2.20 2.07 1.96 1.87 1.79 5 ' 3.79 3.22 2.87 2.63 2.44 2.30 2.18 2.08 1.99 6 4.55 3.87 3.45 3.15 2.93 2.75 2.61 2.49 2.39 7 5.30 4.51 4.02 3.68 3.42 3.21 3.05 2.91 2.79 8 6.06 5.16 4.59 4.20 3.91 3.67 3.48 3.32 3.18 9 6.82 5.80 5.17 4.73 4.40 4.13 3.92 3.74 3.58 10 ' 7.58 6.44 5.74 5.25 4.88 4.59 4.35 4.15 3.98 12 ' 9.08 7.73 6.89 6.30 5.86 5.51 5.22 4.98 4.78 In brine circulation the brine should also be pumped through series of pipes running in the same direction, and connected by manifolds to decrease friction. Further information in regard to piping rooms, etc., will be found in the chapters on Cold Storage, Brewery Refrigeration, etc. THE AMMONIA COMPRESSION SYSTEM. 139 6 s B H III! ?- M . <3> V! 83 Iff? *> -i -l O B -. R P ss lag n> a, CL >T- CD Diameter of Pump Barrel, in Inches. 3*1 ^OGCWlSotOOS^IOSCAW^rf'-OJWtatSMH-MI-i I } H--J*- CC 111! 5 OX (f>. CO 13 l-l l-i J^eoi-^coo * So 8J So ^ ^ co p ao p w * co to to H^ M> . S 05 O *2 ^i JS p S p 00 OS Ol ** CO b J-> I BS ^2 to > g z 140 MECHANICAL REFRIGERATION. THE BRINE PUMP. The circulation of the refrigerated brine through the refrigerating coils in storage rooms, etc., is accomplished by the brine pump. The size of the brine pump may be estimated on the basis that the brine should not travel faster than sixty feet per minute. The table on opposite page will be found convenient in this connection. PREPARING BRINE. The brine is a solution of some saline matter in water, in order to depress the freezing point of the latter. Gen- erally chloride of sodium or common salt is-used for this purpose. To make the brine it is well to use a water tight box, 4X8 feet, with perforated false bottom and com- partment at end, with overflow pipe for brine to pass off through a strainer. The salt is spread on false bottom, and the water fed in below the false bottom as fast as a solution of the proper strength will form. A wooden hoe or shovel may be used for stirring to accelerate solution. TABLE SHOWING PROPERTIES OF SOLUTION OF SALT. (Chloride of Sodium.) bt>> . ce,o^ oc 3* O .j O ftrto o3? 60 ** * su- Percent of Salt Weigh en 9? o H! |-3l 4> O>o ga 3l2' a^ce 03 Man *= fl"J 1 if '3 a % $88 fi^-S fa fal |S| 1 0.084 4 8.40 1.007 0.992 30.5 0.8 2 0.169 8 8.46 1.015 0.984 29.3 1.5 2.5 0.212 10 8.50 1.019 0.980 28.6 1.9 3 0.256 12 8.53 1.023 0.976 27.8 2.3 3.5 0.300 14 8.56 1.026 0.972 27.1 2.7 4 0.344 16 8.59 1.030 0.968 26.6 3.0 5 0.433 20 8.65 .037 0.960 25.2 3.8 6 0.523 24 8.72 .045 0.946 23.9 4.5 7 0.617 28 8.78 .053 0.932 22.5 -5.3 8 0.708 32 8.85 .061 0.919 21.2 6.0 9 0.802 36 8.91 .068 0.905 19.9 6.7 10 0.897 40 8.97 1.076 0.892 18.7 7.4 1.092 48 9.10 1.091 0.874 16.0 8.9 15 1.389 60 9.26 1.115 0.855 12.2 11.0 20 1.928 80 9.64 1.155 0.829 6.1 14.4 24 2.376 96 9.90 1.187 0.795 1.2 17.1 25 2.488 100 9.97 1.196 0.783 0.5 17.8 26 2.610 104 10.04 1.204 0.771 1.1 18.4 STRENGTH OF BRINE. Generally speaking, the brine must contain sufficient salt to prevent its freezing at the lowest temperature in freezing tank, and by referring to the accompanying table one can answer the question for himself on this basis very readily. THE AMMONIA COMPRESSION SYSTEM. 141 To determine the weight of one cubic foot of brine multiply the values given in column 4 by 7.48. To determine the weight of salt to one cubic foot of brine multiply the values given in column 2 by 7.48. POINTS GOVERNING STRENGTH OF BRINE. Therefore if the temperature in the freezing tank does not go below 15 F., it would be quite sufficient to use a brine containing 15 per cent of salt (salometer de- grees 60), as from the above table it appears that such a solution does freeze below that temperature. On the other hand, if the temperature of freezing does not go below 20 F., a brine containing only 10 per cent salt would be sufficient for the same reason, etc. This table also ex- plains why it would be irrational to use stronger solutions of salt than these, for, as we see from the column show- ing specific heat, the same grows smaller as the concen- tration of the brine increases, and consequently the stronger the brine the less heat a given amount of brine will be able to convey between certain definite tempera- tures. There is another danger connected with the use of too strong, especially of concentrated, brine in refrig- eration. Such brine may cause clogging of pipes, etc., on account of depositing salt. This danger, however, is not so great as that of having the solution too thin, for while it may be concentrated enough not to freeze in the brine tank, it may be still too weak to withstand the tempera- ture obtaining in the expansion coil, so that a layer of ice will form around the latter which interferes with the prompt absorption of heat from the brine. For this rea- son the surface of the expansion coils in brine tank should be inspected from time to time to see if any ice has formed on them. SIMPLE DEVICE FOR MAKING BRINE. An ordinary barrel with a false bottom three inches above the real bottom, perforated with j^-inch holes, is a practical contrivance for making brine. The space above the false bottom is filled with salt nearly to the top of the barrel. Ordinary water is admitted below the false bottom, and the ready brine runs out at the top through a pipe, which is best inclosed in a wire screen filled with sponges. The pipe carrying off the brine should be about larger than the pipe admitting the water. 142 MECHANICAL REFRIGERATION. SUBSTITUTE FOR SALOMETER. In case one is unable to readily obtain a salometer, a Beaume hydrometer, or a Beck hydrometer scale, both of which are in quite general use for taking the strength of acids, etc., can be used as well. Their degrees compared with specific gravity and percentage of salt are shown in the following table, and, as will be seen, do not differ so very much from the degrees of the salometer scale : Percentage of Salt by Weight. Specific Gravity. Degrees on Beaume's scale, 60 F. Degrees on Beck's scale, 600 F. 1 5 10 15 20 25 1.0000 1.00?2 1.0362 1.0733 1.1114 1.1511 1.1923 1 5 10 8 23 1 J if 23 28 CHLORIDE OF CALCIUM. Some engineers prefer to use chloride of calcium for the preparation of brine in preference to common salt. It is higher in price than the latter, but is said to keep the pipes cleaner, causing less wear and a better conduc- tion of heat. The physical properties of the chloride of calcium solution, as appears from the subjoined table, are quite similar to those of common salt. The freezing point, however, can be depressed several degrees lower by the use of the former, and for this reason the use of chloride of calcium may be advisable in such extreme cases. Other- wise the preparation of the solution of chloride of cal- cium is the same as that of ordinary brine. PROPERTIES OF SOLUTION OF CHLORIDE OF CALCIUM. Percentage by Weight. Specific Heat. Spec. Grav. at 60 F. Freezg. Pt. degrees F. Freezg. Pt. degs. Cels. 1 5 10 15 20 25 0.996 0.964 0.896 0.860 0.834 0.790 1.009 1.043 1.087 1.134 1.182 1.234 31 27.5 22 15 5 8 0.5 2.5 5.6 9.6 14.8 22.1 BRINE CIRCULATION VS. DIRECT EXPANSION. The principal reason why brine circulation is still preferred by many to direct expansion, is to be sought in fear entertained with regard to the escaping ammonia in THE AMMONIA COMPRESSION SYSTEM. 143 case the pipes should leak. The danger from this source, however, seems to have been greatly exaggerated, as but few accidents of this kind have been known, the pressure in the ammonia pipe being generally not much higher tnan in the brine coils. Another advantage frequently quoted in favor of brine circulation is the fact that comparatively great quantities of refrigerated brine are made and stored ahead, a supply which can be drawn on in case the ma- chinery should have to be stopped for one reason or another. In case of a prolonged stoppage, refrigerating brine made by dissolving ice and salt together can be circulated through the brine pipes, which is also impracticable in case of direct expansion. It is also claimed that in small plants, in case of brine circulation, the general machinery might be stopped and only the brine pump be kept going to dispense the sur- plus refrigeration which had been accumulated in the brine during the day. THE DRYER. The dryer is an attachment of more recent coinage with which many compression plants are provided, its purpose being the drying of ammonia gas. It is a kind of trap on the suction pipe connected in such a manner (by means of a by-pass) that the gas can be passed through it when necessary. This trap is provided with removable heads for the introduction of some moisture absorbing substance (freshly burnt unslaked lime, as a rule) and for the with- drawal of the spent absorbent. LIQUID TRAP. It is also recommended to have an additional trap between the expansion valve and the expanding coils. The vaporization then takes place within the chamber or trap, and oil and other undesirable foreign matter will be deposited in this trap, and will not be carried over into the expansion coils. The trap is provided with a by -pass, so that it can be cleaned without stoppage. If such a trap can be placed within the rooms to be refrigerated it may be of some advantage ; but if it has to be placed outside, as in the case of brine circulation, much refrigeration is wasted. 144 MECHANICAL. REFRIGERATION. CHAPTER V. ICE MAKING AND STORING. SYSTEMS OF ICE MAKING. One of the principal uses of mechanical refrigeration is the production of artificial ice, which is carried out after different methods or systems. The two methods which are most generally used are the so-called can sys- tem and the plate system. ICE MAKING CAPACITY OF PLANT. . From the temperature of brine tank respectively, the temperature in expansion coils (which will be from 5 to 10 lower), the temperature in condenser coil from the size of compressor, etc., the theoretical refrigerating capacity of the plant can be calculated as above shown, making allowance for clearance, etc., as mentioned. The ice making capacity of the plant is, of course, much below this theoretical refrigerating capacity. An allowance from 6 to 12 per cent loss due to radiation in brine tank, pipes, etc., must be made in the start, and in addition to that a further allowance for the refrigeration of the water from the ordinary temperature to that of freezing, and for the refrigeration of the ice from 32 to the temperature of the brine. For that and other reasons it may be assumed that the ice making capacity of a ma- chine is from 40 to 60 per cent of its theoretical refriger- ating capacity. CAN SYSTEM. In making ice by what is called the can system, the water is placed in cans or molds made of galvanized iron of convenient shape, which are inserted in a tank filled with brine, the latter being kept cool by coils of pipe in which the expanding ammonia circulates. Temperature of brine varies from 10 to 25 F., 15 F. being considered favorable. SIZE OF CANS. The cans or molds for freezing vary in size and shape. The sizes of cans in most common use are shown in the following table: No. lean, 8^X15X32, weight of cake, 100 Ibs., No. 18 Iron. " 2 " 8^X16X44, " " 150 " " 18 " " 3 " 11 X11X32, " " 100 " " 18 " " 4 " 11 X22X32, " " 200 " " 16 " " 5 " 11 X22X44, " " 300 " " 15 " The weightis net. Allowance is made for about 5 per cent more to allow for loss in thawing, etc. ICE MAKING AND STORING. 145 =3^ 'IP " ^S ^ 8 g 8 8 S 8 3 ,,-. Tons Ice Making Capacity. 3 row to - *+ *-..-.,- No. of Tanks. S& 8 SJ 8 StjS 1 II 1 I i i 1 IlJ OOO O O O O OOO 'Length of Tank FeetCi Inches. 09 gj 5; CO Width of S 8 f ?? r f r r r m 000 O O O <00t Tank M Feet & Inches. o 9 IB" -vJk.^CO CO CO CO COCOCOCO 000000 CO CO CO CO CO BOOM Depth of hj' Tank > in Inches. A 7? co co co Thickness X)f Plates, laches'. 3 ssss 8 s s sss. No. of Coils. ' IP --- - - Size of Pipe, Inches. a> ;/> 0000000 00 00 00 00 05OO Na of Pipes High. 2,0 (t> 1 1 1 1 1 1 1 1 1 1 1 000 *0 00*. Length of Coils. T O O O K> O W OO O O O 4^ Total Feet: of Pipe in Tank. 2. a gMMCO CO CO CO CO WtOW Feet of Pipe per Ton- Ice Making Capacity. | Number of Ice Molds in Tank. 3> Qj? 2 XXXXXXXXXXXXXXXX Size of Molds 3 XxXX XXXXXXXXX XXX ia Inches. 5 ea 3* Sli888l8is88888 Net Weight of Ice from Each. 1 Mold. . 5>K3> S o o 2 o co ^ co '* '* * * g * Number of Molds per Ton Ice Mak- ing Capacity. P ^***S* 88 ->-* tfi. 10 co to w i?o to tar 01 CO CO. tO.tO tO to1 ' 'OS ^ #>.* CO tO 10 tO tO tO v-i t-i O * *. rfx CO tO tO tO tO tO i-i >-* I-A 81.88888888888! %\ to to 1-1 1- -H* >- pi OjSSjfs*. j O-CDjXjX)_CS * tO tO J- toccwto rf- CO 10 W *+ M.-H* ** Oilers $1.25 per day. ; remen $1.25 per day. Tankmen and Laborers $1.00 per day. Genera lpers $ per day 15 cts. per Cw $3.00 per ton. Oil Waste, Lights and Sundries. Da Oper Expe oS " 3 CD nS" OQ 03 CD tyj ^ , Lw :lSif *4) illiU. APICAL SKATING RINKS. Artificial ice is also used for skating rinks to be operated all the year round. The amount of refrigera- tion, piping, etc., required for such installations depends largely on local conditions and other circumstances. A skating rink in Paris 7,700 square feet has 15,000 feet 1-inch pipe, and the refrigerating machine requires a 100-horse power engine. A skating rink in San Francisco, 10,000 square feet, is operated by machine of sixty tons refrigerating capacity. The skating floor at the Shenley Park Casino in Pittsburg is constructed as follows: It consists of a 3-inch plank floor covered with two thicknesses of impervious paper; the second floor likewise covered, leaving an air space below. About 80,000 pounds of coke breeze, or about ten inches in thickness, was placed on the last named floor, the whole surmounted by 3 x 6-inch yellow pine decking, carefully spiked down and joints calked, the whole finished with a heavy coat of brewer's pitch, this preventing any dampness from reaching the insulation. Nearly 300,000 feet of lumber were used for this structure, the rink being 70 x 225 feet, or about 16,000 square feet. On the top of the floor, with the ends extending through the two ends of tank, which are rendered water tight, are 72,000 feet of 1-inch extra heavy pipe, and they are simply straight pipes 228 feet long, connected at each end by a manifold. They are operated by direct expansion. This rink will, in case of a rush, accommodate 1,100 people, and one having one-quarter of its surface would probably suffice for a patronage of 200 people. The refrigerating ma- chine used to operate this plant has a refrigerating capacity of about 160 tons. QUALITY OF ICE. The keen competition between manufactured and natural ice has brought up a number of questions touch- ing the relative merits of these articles. Although it is quite generally conceded that ice made from distilled water is in every respect purer and'more healthful than natural ice, still there are claims to the contrary, some claiming that natural ice will last longer, others that distillation takes the life out of the water and ice, etc. As far as the keeping is concerned, there is no difference if the blocks are wholly frozen without holes or cracks ICE MAKING AND STORING. 157 in them; and as to the life in manufactured ice, it is cer- tainly one of its advantages that all bacterial life is killed in the same. WATER FOR ICE MAKING. Expressed broadly, water that is fit for drinking pur- poses is fit for ice making, but while for drinking pur- poses a moderate amount of air and mineral matter in the water is more or less desirable, for ice making the absence of both is necessary if the ice is to be clear But even if a natural ice from a certain source is apparently or temporarily free from pathogenic (disease) bacteria, it may nevertheless be suspected of possible or future contamination if its analysis indicates contamin- ation with sewage or other waste matter. This is to be suspected when the ice or the water melted from the same contains an excess of ammonia, especially album- inoid ammonia, of nitrates and of chlorides. In order to give expression to this condition of things, many municipalities have special laws defining the purity re- quired for marketable ice. The corresponding ordinance in the city of Chicago demands that : " All ice to be de- livered within the city of Chicago for domestic use shall be pure and healthful ice, and is hereby defined to be ice which, upon chemical and bacteriological examination, shall be found to be free from nitrates. and pathogenic bacteria, and to contain no more than nine-thousandths of one part of free ammonia and nine-thousandths of one part of albuminoid ammonia in 100,000 parts of water." CLEAR ICE. Although ice that is impure may be clear, and ice which is practically pure may be cloudy or milky, clear ice is nevertheless desirable, and generally called for, While many natural waters will furnish clear ice after the plate system, the can system always requires boiling, and generally previous distillation and reboiling of the water in order to furnish clear ice. ( It sometimes happens that the ice of some cans is white and milky, while that of others is clear. This is generally due to a leak in the cans yielding the milky ice, whereby brine enters the same. It may be readily detected by the taste of the ice. ) BOILING OF WATER. In case a natural water is almost free from mineral matter (or if the same consists chiefly of carbonates of 158 MECHANICAL REFRIGERATION. lime and magnesia), and contains only suspended matter and air in solution, it may be rendered fit for clear ice making by vigorous boiling, either with or without the assistance of a vacuum, and with or without subsequent filtration, as the case may require. DISTILLED WATER. In order to save a vast amount of fuel, 40 per cent and upward, the exhaust steam from the engine is gen- erally used to supply the distilled water as far as it goes, and a deficiency is supplied directly from steam boiler. The impurities, such as grease, etc., carried by the exhaust steam, are removed by a so-called steam filter, and then the vapors are passed through a condenser con- structed on the same principles as the ammonia con- denser. The condenser may be submerged in water or be an atmospherical or open air condenser. For cooling, the overflow water from the ammonia condenser is used in all cases. AMOUNT OF COOLING WATER. If 960 B. T. U. is the latent heat of steam, and the temperature of the cooling water when it reaches the condenser is 1 t , and when it leaves the condenser is t, the theoretical amount of cooling water, P, in pounds required per ton of distilled water is p __ 2000 X 960 t-t, To this from 2 to 20 per cent should be added for loss, etc., according to size of plant. SIZE OF CONDENSER. If t is the mean temperature of the cooling water, that is, the average between the temperature of the water entering and leaving the condenser, and if t t is the average temperature in the condenser (presumably about 210 F.)t then the number of square feet condenser surface, inches. 170 MECHANICAL REFRIGERATION. The cold storage chambers built at the St. Kather- ine dock, London, are constructed as follows: On the concrete floor of the vault, as it stood origi- nally, a covering of rough boards l 1 ^ inches in thickness was laid longitudinally. On this layer of boards were then placed transversely, bearers formed of joist 4% inches in depth by 3 inches in width, and spaced 21 inches apart. These bearers supported the floor of the storage chamber, which consisted of 2%-inch battens tongued and grooved. The 4^-inch wide space or clearance between this floor and the layer or covering of rough boards upon the lower concrete floor was filled with well dried wood charcoal. The walls and roof were formed of uprights 5^x3 inches fixed upon the floor joists or bearers, and having an outer and inner skin attached thereto; the former consisting of 2-inch boards, and the latter of two thicknesses or layers of 13^-inch boards with an intermediate layer of especially prepared brown paper. The 5^-inch clearance or space between the said inner and outer skeins of the walls and roof was likewise filled with wood charcoal, carefully dried. CONSTRUCTION OF SMALL ROOMS. Small storage rooms, down to ice boxes, are always built of wood, paper, cork, etc., on lines similar to those given for wooden walls, but with endless variations. COKSTBUCTIONS AND THEIR HEAT LEAKAGE. The following construction of walls for cold storage buildings, taken from the catalogue of the Fred W. Wolf Co., have also been practically tested, and the ap- proximate heat leakage through them per square foot and per degree of difference in temperature between in- side and outside of the room, is also given in British thermal units in twenty-four hours. FIREPROOF WALL AND CEILING. Brick wall of thickness to suit height of building, 3-inch scratched hollow tiles against brick wall, 4-inch space filled with mineral wool, 3-inch- scratched hollow tiles, cement plaster. Heat leakage 0.70 B. T. U. The ceiling to match this wall consists of the follow- ing layers : Concrete floor, 3-inch book tiles, 6-inch dry underfilling, double space hollow tile arches, cemeni plaster. Heat leakage 0.80 B, T. U. COLD STORAGE. 171 WOOD INSULATION AGAINST BRICK WALL. The following wood insulation against a brick wall has a leakage of 1.74 B. T. U., and consists of the fol- lowing layers : Brick wall, against which are nailed wooden strips 1X2 inches. On these are nailed two layers of 1-inch sheathing with two layers of paper ibetween ; next we have 2 x 4-inch studs sixteen inches apart, filled in be- tween with mineral wool, 1-inch matched sheathing, two Ifyers of paper; 1 X 2-inch strips, sixteen inches apart from centers ; double 1-inch flooring with two layers of paper between. CONSTRUCTIONS OF WOOD. The following constructions of wall, ceiling and floor may be followed for cold storage rooms when built of wood : The wall is constructed as follows : Outside siding, two layers of paper, 1-inch matched sheathing, 2x6- inch studs, sixteen inches apart from centers, two layers of 1-inch sheathing, with two layers of paper between, 2 X 4-inch studs, sixteen inches apart from centers, filled M between with mineral wool, 1-inch sheathing, two layers of paper, 2 x 2-inch strips, sixteen inches from center to center, two layers 1-inch flooring, with two layers of paper between. The heat leakage through this wall is 2.90 B. T. U. The ceiling has the following details : A double 1-inch floor with two layers~of paper be- tween, 2 x 2-inch strips, sixteen inches apart from cen- ter, filled in between with mineral wool, two layers of paper, 1-inch matched sheathing, 2 X 2-inch strips, sixteen inches apart, filled between with mineral wool, two layers of paper, 1 inch matched sheathing, joists, double 1-inch flooring, with two layers of paper between.. The heat leakage through this ceiling amounts to 2.17 B. T. U. The details of the floor are as follows : Two-inch matched flooring, two layers of paper, 1-inch matched sheathing, 4 X 4-inch sleepers, sixteen inches apart from centers, filled between with mineral wool, double 1-inch matched sheathing, with twelve lay- ers of paper between, 4 x 4-inch sleepers sixteen inches aprxt from centers imbedded in 12-inch dry under- filling. 172 MECHANICAL REFRIGERATION. The heat leakage through this floor is given at 1.92 B. T. U. PIPING. All ammonia brine and heating pipes, headers and mains ought to be in the corridors, well insulated. CONSTRUCTIONS WITH AIR INSULATIONS. In the following constructions, taken from the cata- logue of. the De La Yergne Refrigerating Machine Co., the insulating spaces are made by confined bodies of air, it being claimed by some that any filling of these spaces with loose non-conducting material will settle in places. The penetration of air and moisture is specially guarded against by the use of pitch in connection with brick or stone, or by paper where wood is used. Joints between boards should be laid in white lead and corners should be protected by triangular pieces of wood with paper placed carefully behind. CONSTRUCTIONS OF WOOD. The main walls of buildings (for refrigerators of hotels, restaurants and cold storage in general) built on the foregoing principles, have the following details, commencing inside: ,% -inch, spruce, insulating paper, %-inch spruce, 1-inch air space, twelve inches square, %-inch spruce, insulating paper, %-inch spruce, 1-inch air space, ,%-inch spruce, insulating paper, %-inch hard wood. The ceiling or floor, when the room above or below is not cooled, has the following details, commencing be- low the joists : ,%-inch board, insulating paper, %-inch board, floor beams, ^-inch board, insulating paper, ,%-inch board (two inches air space, %-inch board, insul- ating paper, % inch board). If room above is cooled, the parts in parenthesis may be omitted. Partitions between two cooled rooms, where differ- ence of temperature does not exceed 20, may be constructed as follows : ,%-inch board, insulating paper, ^-inch board, 1^-inch air space, ,%-inch board, insu- lating paper, %-inch board. For main inside walls between two rooms, of which one is not cooled, the following construction may be followed : %-ineh board, insulating paper, %-inch board, two inches air space, %-inch board, insulating paper, ^6-inch board, two inches air space, ,%-inch board, in- sulating paper, Ji-mch board. C6LD STORAGE. 173 CONSTRUCTION IN BRICK. The outer walls in buildings of brick may be con- structed as follows, commencing outside : Brick wall of proper strength, two coats of pitch, two inches air space, %-inch board, insulating paper, Jg-inch board, two inches air space, ^-inch board, insulating paper, %-inch board. The ceiling may be constructed as follows, when room above is not cooled (commencing at the top layer): One inch asphalt, two inches concrete, brick, wooden stiips, ,%-inch board, insulating paper, ^-inch board, two inches air space, %-inch board, insulating paper, ^-inch board. If the difference in temperature between the lower and upper room does not exceed 20 F. the following construction for ceiling may|be used : One inch asphalt, two inches concrete, brick. SURFACE OF INTERIOR WALLS. It is claimed that the porosity of the surfaces of walls in cold storage rooms is in a measure responsible for the spoiling of provisions. Such walls, if made of cement, plaster and similar semi-porous material, pos- sess sufficient moisture to give rise to all sorts of putrefactive and bacterial growths, allowing them to thrive under favorable conditions. A further objection to this kind of walls is the quicker radiation of heat through them. For these reasons it has been urged that the walls in cold storage houses for cold and espe- cially meat storage, should be made from porcelain, and that they should be cleaned several times during the year. REFRIGERATION REQUIRED. The amount of refrigeration required in a given case depends on a number of circumstances and conditions, the size of the room, the frequency with which the arti- cles are brought in and removed, their temperature, spe- cific heat of produce, etc. For these reasons it is impos- sible to give a simple general rule, and the following figures, which are frequently used in rough calculations, must be considered as approximations only: For storage rooms of 1,000,000 cubic feet and over, 20 to 40 B. T. U. per cubic foot per twenty- four hours. For storage rooms 50,000 cubic feet and over, 40 to 70 B. T. U. per cubic foot per twenty-four hours. 174 MECHANICAL KEFRlGEKAflOK. For boxes or rooms 1,000 cubic feet and over, 50 to 100 B. T. U. per cubic foot per twenty-four hours. For boxes less than 100 cubic feet, 100 to 300 B. T. U. per twenty-four hours. For rooms in which provisions are to be chilled, about 50 percent additional refrigeration may be allowed in approximate estimations. For actual freezing the amount should be doubled (see also Meat Storage). PIPING AND REFRIGERATION. The foregoing rules on refrigerating capacity, aa well as those given elsewhere, and including also the rules for piping given on pages 134 to 138, and elsewhere, have in common one vital defect, in that they fit only one given temperature or rooms of one certain size. This condition of things necessarily gives rise to numer- ous misunderstandings and many errors, and for this reason I have endeavored to outline some tables which would do equal justice to all the elements involved, or at least indicate how this could be done. The desire of the author to supply such much needed tables without further delay must be an excuse for their imperfections,as so far only comparatively few of the values given therein could be verified by data taken from actual experience. TABULATED REFRIGERATING CAPACITY. The amount of refrigeration required for cold storage buildings for provisions, beer, meat, ice, etc., depends, as has been mentioned repeatedly, principally on the size of the rooms, their insulation, the maximal outside tempera- ture and the minimal inside temperature (leaving open- ings, opening of doors and refrigeration of contents, etc., out of the question). The chief variants among these quantities are the degree of insulation, the size of rooms or houses and the minimal temperature within (the latter depending on the objects of storage) ; while for the maximal outside temperature we may agree upon a certain fixed quantity, which for approximate calculations will apply for a large territory of the United States, at least. We may safely take this maximal temperature for most of the United States at 80 to 90 F., so it will amply cover 8 F. Doing this, we can readily outline a table which will show the amount of refrigeration required for rooms of different sizes and of different insulation for any given COLD STORAGE. 175 temperature, as, for instance, the following table, which gives the number of cubic feet in cold storage buildings which can be covered by one ton of refrigerating capac- ity for rooms of different sizes, for different temperatureg and for different (excellent and poor) insulation during a period of twenty-four hours : NUMBER OF CUBIC FEET COVERED BY ONE TON REFRIG- ERATING CAPACITY FOR TWENTY- FOUR HOURS. Size of building- Temperature F. in cub. ft. Insulation. more or less. 10 20 30 40 50 excellent 150 600 800 1,000 1,600 3,000 100 poor 70 300 400 600 900 2,000 1 OOO excellent 500 2,500 3,000 4,000 6,000 12,000 poor 250 1,500 1,800 2,500 5,000 10,000 10,000 excellent poor 700 300 3,000 1,800 4,000 2,500 6,000 3,500 9,000 7,000 18,000 14,000 30,000 excellent poor 1,000 500 5,000 3,000 6,000 3,500 8,000 5,000 13,000 11,000 25,000 20,000 100,000 excellent poor 1,500 800 7,500 4,500 9,000 5,000 14,000 8,000 20,000 16,000 40,000 35,000 The next table is constructed on the same basis, giving the amount of refrigeration required per cubic foot of space for storage rooms of different sizes for dif- ferent temperatures, expressed in British thermal units, and for a period .of twenty-four hours. REFRIGERATING CAPACITY IN B. T. U. REQUIRED PER CUBIC FOOT OF STORAGE ROOM IN TWENTY-FOUR HOURS. Size of building 1 Temperature P. in cub. ft. Insulation. more or less. 10 20" 30 40 50 10O excellent 1,800 480 360 284 180 95 AVW poor 4,000 960 480 470 330 140 1 000 excellent 550 110 95 70 47 24 J., \J\J\J poor 1,100 190 165 110 55 28 10,000 excellent poor 400 900 95 160 70 110 47 81 30 40 16 20 30,000 excellent 280 55 47 35 22 11 poor 550 95 81 55 26 14 100,000 excellent poor 190 350 38 63 30 55 20 35 14 18 7 4 176 MECHANICAL REFRIGERATION. The expression " excellent insulation" in the above and following tables may be taken to refer to wallu, ceilings, etc., the heat leakage of which does not exceed two B. T. U. for each degree F. difference in tempera- ture per square foot in twenty-four hours ; and the ex- pression "poor insulation" may be taken to refer to walls, etc., the heat leakage in which amountn to four B. T. U. and more. The average of the amounts of refrigeration, space and pipes given in the tables may be taken for average good insulation, other circum- stances being equal. TABULATED AMOUNTS OF PIPING. The amount of piping required for cold storage buildings depends, in the first place, on the amount of re- frigeration to be distributed thereby, and therefore indirectly on the same conditions as does the amount of refrigeration required. In addition thereto the amount of piping also depends on the difference between the temperature within the refrigerating or direct expan- sion pipes, and without. As this difference may be varied arbitrarily by the operator, and necessarily differi for different storage temperatures, it would be veiy difficult to arrange a table fitting all possible conditions. However, it stands to reason that for each storage temperature there is one preferable brine or expansion temperature, and the accompanying tables on piping are expected to fit these temperatures for practical calcula- tions. LINEAL FEET OF 1-INCH PIPE REQUIRED PER CUBIC FOOT OF COLD STORAGE SPACE. Size of building Temperature F. in cub. ft. Insulation. more or less. 10 20 30 40 50 100 excellent 3.0 0.78 0.48 0.36 0.24 0.15 JL\J\J poor 6.0 1.50 0.90 0.66 0.48 0.30 1,000 excellent 1.0 0.26 0.16 0.12 0.08 0.05 poor 2.0 0.50 0.30 0.22 0.16 0.10 10,000 excellent 0.61 0.16 0.10 0.075 0.055 0.035 poor 1.2 0.33 0.20 1.15 0.11 0.07 30 000 excellent 0.5 0.13 0.08 0.06 0.040 0.025 poor 1. 0.25 0.15 0.11 0.03 0.05 100,000 excellent 0.38 0.10 0.06 0.045 0.03 0.009 poor 0.75 0.20 0.12 0.09 0.06 0.018 COLD STORAGE. 177 The quantities of pipe given in the foregoing table refer to direct expansion, and should be made one and one-half times to twice that long for brine circulation. They also refer to 1-inch pipe, and by dividing the lengths given by 1.25, or multiplying them by 0.8, the corresponding amount of 1^-inch pipe is found. To find the corresponding amount of 2-inch pipe, the length given in the table must be divided by 1.08, or multiplied by 0.55. The next table is for the same purpose as the one preceding, but it shows the number of cubic feet of storage building which will be covered by one foot of 1-inch pipe during a period of twenty-four hours for different sized rooms and different storage temperatures. NUMBER OF CUBIC FEET COVERED BY ONE FOOT OF ONE-INCH IRON PIPE. Size of building- Temperature F. in cub. ft. Insulation. more or less. 10 20 30 40 50 100 excellent 0.3 1.3 2.1 2.8 4.2 7.0 A.\J\J poor 0.15 0.7 1.1 1.5 2.1 3.5 1 000 excellent 1.0 4. 6.0 8.4 12.4 20. .L, \J\J\J poor 0.5 2. 3.2 4.5 6.2 1.0. 10,000 excellent poor 1.7 0.85 6. 3. 10. 5. 13. 6.5 18. 9. 28. 14. 30,000 excellent 2.0 8. 14. 18. 25. 40. poor 1.0 4. 7. 9. 13. 20. 100,000 excellent poor 2.6 1.3 10. 5. 17. 8.5 22. 11. 33. 17. 110. 55. The number of cubic feet of space given in the last table as being covered by one lineal foot of pipe refers to direct expansion, and only one-half to two-thirds of that space would be covered by the same amount of pipe in. case of brine circulation. The figures in this table also refer to 1-inch pipe ; and to find the corresponding amounts of cubic feet of space which would be covered by one lineal foot of 1^- inch pipe, the numbers given in the table have to be multiplied by 1.25 or be divided by 0.8. To find the corresponding amount of space which will be covered by one lineal foot of 2-inch pipe, the numbers given in the, table must be multiplied by 1.8 or divided by 0.55, 178 MECHANICAL REFRIGERATION. The foregoing tables are calculated for a maximum outside temperature of 80 to 90 F. If the same is ma- terially more or less about 10 per cent of refrigeration and piping should be added or deducted for every 5 F. more or less, as the case may be. TABLES FOR REFRIGERATING CAPACITY. The accompanying table designed by Criswell is cal- culated on the lines laid out in the foregoing paragraphs, on the assumption that the walls, ceiling and floor ol the cold storage building have an average heat leak- age of three B. T. U. per square foot in each twenty-four hours for each degree Fahrenheit difference in tempera 4 ture outside and inside of building. The maximum temperature is taken at 82 F. Accordingly the total refrigeration for such .a building is found by multiplying its total surface in square feet (.third column of table) by 3, and the difference between the temperature in de- grees Fahrenheit within the storage building and 82 F. It is then divided by 284,000 to reduce the refrigerating capacity to tons of refrigeration. We will take for an example the building, 25x40x10. Its surface is 3,300 square feet, and the total refrigera- tion required for a temperature of 32 within the cold 495 000 storage house is therefore 3,300x3x(82-32)=2g^- Q ^ 1.53 tons, or, in round numbers, 1.5 tons. The building here referred to contains 10,000 feet, i n nno consequently one ton of refrigeration would cover * 1.51 =6,600 cubic feet of such a building. Tnis figure should agree with the corresponding figure, given in the accom- panying table (at least, approximately so), some of the figures in the table being obtained by interpolation or averaging. If we compare this table with the table given on page 175 we will note several apparent discrep- ancies. They are explained by the desire to give a very liberal estimate in the tables on page 175, and to make allowance not only for the refrigerating of the contents, but also for the opening of doors. These are doubtless the reasons why the refrigerating capacity for smaller rooms in table on page 175 appears so large, especially at lower temperatures, as in these cases the opening of cjoors, etc., acts most wastefully. COLD STORAGE. 179 TABLE FOR REFRIGERATING CAPACITY. x x Sl gggggggggggM S 1 Contents, iubic feet. Surface in square feet. Ratio cubic feet to square feet. ?2 5 fc C S o> 0= JlfggflHf s ii 3 DOORS IN COLD STORAGE. \t may not be amiss on this occasion to state that the doors of cold storage buildings and rooms and ice boxes play a most important r6le in the economy of a plant; and therefore their construction, which is frequently left to the discretion of an ordinary carpenter, is a mat- ter of the greatest importance. Not only should they be constructed on the basis of the least heat transmission, but so framed and hung as to be tight and remain so for the longest possible time, as well as open freely at all times. Readjustments long neglected involve financial 180 MECHANICAL REFRIGERATION. losses in many directions, often expensive repairs, when a proper construction would avoid both by rendering the first needless. Facility for easily and quickly opening and closing, fastening and unfastening is most import- ant. Workmen persistently leave doors open while going in and out if these points be neglected, with a consequent great ingress of heat and moisture. For this reason it is but fair to recognize the laudable exertion of those firms who make the rational construction of doors used in cold storage buildings, rooms, etc., a special feature. CALCULATED REFRIGERATION. For more exact estimates the refrigeration required in a given case may be calculated by allowing first for the refrigeration required to keep the storage at a cer- tain given temperature in consequence of the radiation through walls; and second for the refrigeration re- quired to cool the articles or provisions from the tem- perature at which they enter the storage room down to the temperature of the latter. RADIATION THROUGH WALLS. If the number of square feet contained in a wall, ceiling, floor or window be /, the number of units of re- frigeration, jR, that must be supplied in twenty-four hours to offset the radiation of such wall, ceiling or floor, may be found after the formula: B=fn(t t l )'B. T. units, or expressed in tons of refrigeration In these formulae t and t t are the temperatures on each side of the wall, and n the number of B. T. units of heat transmitted per square foot of such surface for a differ- ence of 1 F. between temperature on each side of wall in twenty-four hours. The factor n varies with the con- struction of the wall, ceiling or flooring, from 1 to 5. For single windows the factor n may be taken at 12, and for double windows at 7 ( Box). For different materials one foot thick we find the following values for n: For pine wood ....... 2.0 B. T. U. For sawdust ......... 1.1 B. T. U. " mineral wool ... 1.6 " - " charcoal, pow'd 1.3 " " granulated cork 1.3 " " cotton .......... 0.7 " " Tyood ashes ..... l.Q " " * " soft paper felt . P- " " " COLD STORAGE. 181 For brick walls of different thicknesses the factor n may be taken as follows after Box : l / 2 brick 1 i* 3 4 4*4 inches thick n = 5.5 B. T. Units. = 4.5 14 " ' = 3.6 18 " ' = 3.0 = 2.6 For walls of masonry of different thicknesses the factor n may be taken as follows after Box: Stn ne walls B inches thick, n = 8.2 B. T. u. " 18 24 80 aa M ;; - r>.o 4.5 4.:} 4.1 = : \ German authorities give values for n which are less than one-half of the values here quoted. For air tight double floors of wood properly filled un- derneath so that the atmosphere is excluded, and for ceilings of like construction, n is equal to about 2 B. T. U. An air space sealed off hermetically between two walls has the average temperature of the outside and in- side air, hence its great additional insulating capacity. If the air space is hermetically sealed inside and outside, it appears that its thickness is immaterial; half an inch is as good as three inches. If a wall is constructed of different materials having different known values for n, viz., w lt n 2 , ^ 3 , etc., and the respective thicknesses in feet d^d 2 , d 3 , the value, n, for such a compound wall may be found after the form- ula of Wolpert, viz. : In case of an air space perfectly sealed off the factor n may be determined for that portion of the wall between the air space and the outside, which value is then in- serted into the formula But in this case while 1 1 stands for the maximum out- side temperature t stands for the temperature of the air space, which may be averaged from the inside and outside temperature, taking into consideration the conductibility and thickness of the component parts of the wall. In the selection of insulating substances, their power to withstand moisture plays an important part in most cases. In this respect cork is a very desirable material, 182 MECHANICAL REFRIGERATION. likewise pitch and mixtures of asphalt; lamp black and a mixture of lamp black with mica scales is also used with great success, especially in portable refrigerating chambers, refrigerator cars and the like, as it will not pack from jolting, owing to its lightness and elasticity, and it also withstands moisture very well. REFRIGERATING CONTENTS. If the amount of refrigeration required to replace the cold lost by the transmission of walls, windows, ceil- ings, etc., has been determined upon, the refrigeration required to reduce the temperature of the goods placed in storage to that of the storage room is next to be ascertained. If p, Pi, P 2 , etc., be the number of pounds of differ- ent produce introduced daily into the storage room and s, s t , s 2 , etc., their respective specific heat, t their tem- perature and t l the temperature of the storage room, we find the amount of refrigeration, .R, in B.T. units required daily to cool the ingoing product after the formula: R = (p s + p s, + p 2 s,) (t t t ) B. T. units, or, expressed in tons of refrigeration : R (V s +Pi s i + P2 s z ) (t t ) t 284000 The specific heat of some of the articles frequently placed in cold storage may be found in the following table: SPECIFIC HEAT AND COMPOSITION OF VICTUALS. *8 14 S* W>^ &M JS a K N Water. Solids. S3 *& 43 5J 'c3 |* Z OQ c3 2u> o O a ir o 3o Lean beef 72 00 28 00 0.77 0.41 102 Fat beef 51.00 49.00 0.60 0.34 72 Veal 63 00 37.00 0.70 0.39 90 Fat pork 39 00 61 00 51 30 55 Eggs 70 00 30 00 0.76 0.40 100 Potato T4 00 26 00 80 42 105 91.00 9.00 .0.93 0.48 129 Carrots .............. 83 00 17.00 0.87 0.45 118 69 25 30 75 68 38 84 Milk 87 50 12.60 0.90 0.47 124 Oyster .... 80 38 19 62 84 0.44 114 Whitefisn 78.00 22.00 0.82 0.43 111 Eels 62 07 37.93 0.69 0.38 88 76.62 23.38 0.81 0.42 108 72 40 27.60 0.78 0.41 Chicken . 73 10 26 30 0-80 0.42 COLD STOKAGE. 183 CALCULATION OF SPECIFIC HEATS OF VICTUALS. The specific heats in the fifth column of the forego- ing table is calculated after the formula s= __ 0.2^=0.008 a + 0.20 1UU in which formula s signifies the specific heat of a sub- stance containing " a" per cent of water and "6" per cent of solid matter; 0.2 is the value which has been uni- formly assumed to represent the specific heat of the solid constituents of the different articles in question. If the articles are cooled below freezing, which takes place be- low 32 F., the specific heat changes, owing to the fact that the specific heat of frozen water is only a^out half of that of liquid water. In conformity with this fact, and considering that the specific heat of the solid mat- ter is not apt to change under these circumstances, we find the specific heat, s', of the same articles in a frozen condition after the following formula : and in this way I have obtained the figures in the sixth column of the above table. The figures in the last column, showing the latent heat of freezing, have been obtained by multiplying the latent heat of freezing. water, which is 142 B. T. U. by the percentage of water contained in the different ma- terials considered. In this manner the specific heat for other articles may be readily calculated. For still more approximate determination we may assume that the specific heat of all kinds of produce is about 0.8. On this basis the amount of refrigeration, .R, required to reduce the temperature of the produce to that of the refrigerating room is B=P(tt 1 ) 0.8 units. And expressed in tons= E = 35500Q tons of refrigeration. P being the total weight of the produce introduced daily. FREEZING GOODS IN COLD STORAGE. If, in addition to the refrigeration of the goods to be stored the same have to be actually frozen and cooled clown to a certain temperature below freezing, the re- frigeration as calculated in the foregoing paragraph 184 MECHANICAL REFRIGERATION. must be corrected, for the water contained in the goods must be frozen, which requires an additional amount of refrigeration. On the other hand, the specific heat of the frozen water being one-half of that of water, this circumstance lessens somewhat the amount of refrigera- tion required below freezing point. Therefore if p rep- resents the. number of pounds of water contained in a daily charge for cold storage to be chilled and reduced to a temperature, t t , the amount, R, found by the foregoing rules must be corrected by adding to it an amount of refrigeration equivalent to p (126 + 0.5^) units. CONDITIONS FOR COLD STORAGE. For the preservation of perishable goods by cold storage the teipperature is the main factor, although other conditions, such as clean, dry, well ventilated rooms and pure air, are of paramount importance. Humidity is almost as important as temperature. Extreme cold tem- perature will react on certain goods like eggs, fruits, etc , so that when taken out the change of temperature will deteriorate their quality quickly. Hence the conditions under which articles must pass from cold storage to con- sumption are often of as vital importance as the cold storage itself, for which reason special rules must be followed in special cases. MOISTURE IN COLD STORAGE. Besides the temperature in a cold storage room the degree of moisture is of considerable importance. It is neither necessary nor desirable that the storage room should be absolutely dry; on the contrary, it may ba too dry as well as it may too damp. If the room is tow dry it will favor the shrinkage and drying out ot certain goods. If the room is too damp goods are liable to spoil and become moldy, etc. For this reason the moisture should always be kept below the saturation point. This condition can be ascertained by the hygrometic methods described in the chapter treating on water and steam. There is little danger that the rooms will ever be too dry; on the other hand, they are not required to be abso- lutely dry, and as to chemical dryers, such as chloride of calcium, oatmeal, etc., they are probably superflu* ous, with proper ventilation and refrigerating machinery properly applied. STORAGE. 185 Generally the artificial drying of air is considered superfluous in coM storage, as the air is kept sufficiently dry by the condensation that forms on the refrigerating pipes. In this way the moisture exhaled by fruits, etc., is also deposited. Special care, however, is to be taken to remove the ice from the coils from day to day as it forms, in which case it is readily removable. Chemical dryers are seldom used in storage houses refrigerated by artificial refrigeration. Freshly burnt lime is sometimes used in egg rooms. In cold storage houses operated by natural ice, chem- ical or physical absorbents, such as oatmeal, burned lime, chloride of calcium and chloride of magnesium are fre- quently used. The latter substance is the principal con- stituent of the waste bittern of salt works, which is sometimes used for drying air in the cold storage of fruit. The waste bittern is spread out on the entire sur- face of the floor, and, if needed, on additional surfaces above it. One square foot of well exposed bittern, either in the dry state or state of inspissated brine, will be enough to take up the moisture arising from two to six bushels of fruit, varying according to its condition of greenness or ripeness. The floors of the preserving room should be level, so that the thick brine running from the dry chloride may not collect in basins, but spread over the largest surface. The moisture from the fruit taken up by the absorbent varies from about three to ten gal- lons for every 1,000 bushels of fruit weekly. The spent chlorides or the spent waste bittern may be revived by evaporation, by which they are boiled down to a solid mass again. The waste bittern is also used as a crude hydrometer by dissolving one ounce of the same in two ounces of water and by balancing the shallow tin dish containing this mixture on a scale placed in the cold storage room. If the scale keeps balanced, it indicates the proper state of dryness, but if the weight of the mixture increases, the moisture in the room is increasing and the means for keeping the air dry should be put in operation. DRY AIR FOR REFRIGERATING PURPOSES. To produce a dry air by mechanical means St. Clair considers the entire absence of any condensing or refrig- erating surface in the space to be refrigerated absolutely 186 MECHANICAL REFRIGERATION- necessary. The rapid circulation of the air in the room is also of vital importance; and in such circulation no con- tact of the incoming cold air with the outgoing warm air to cause condensation is the result aimed at. To insure these conditions he places the refrigerator at the highest point, and has communicating air shafts from the bottom of the same to the rooms to be cooled. Like shafts ascend from the top of the rooms cooled to top of the refrigerator. The refrigerating coils in the refrigerator are kept at a temperature of zero to 15 below, and a small stream of strong brine is allowed to drip over the coils to a pan underneath, being pumped back to the upper drips as fast as deposited. This brine will have a temperature rang- ing from zero to 4 below. The action is said to be simple and effective; all moisture is either condensed or frozen instantly as it comes in contact with such low temperature, and an absolutely dry air descends in the air shafts to the rooms to be cooled. VENTILATION OF COLD STORAGE ROOMS. The foul air in storage rooms is removed by ventila- tion, which is effected in various ways. Frequently the change of air brought about by opening doors, etc., is considered sufficient; in some cases windows are opened from time to time. Ventilating shafts located in the ceil- ing of storage rooms are also often used as means to effect a change of air. A small rotary fan, located in the engine room and connected with the storage rooms by galvanized iron pipes, provided with gates or valves, is a very effi- cient device to remove foul air. Where fans cannot be applied for want of motive power or other reasons a ventilating shaft, if properly constructed, will answer every purpose, and is much less expensive to operate. The air ducts, or pipes, should be located in the hallways, and connection made thence to each room through the side wall near the ceiling, and some suitable device should be arranged on the end of the pipe extending into the cooling room to regulate the amount of ventilation. The several air ducts leading from the various hallways should have a common ending, and connection made thence to the smoke stack. The strong up draft from the furnace insures ample ventila- tion from rooms at all times, provided that the pipes are made air tight and large enough for the purpose. COLD STORAGE. 187 The simple expedient of a ventilating shaft extend- ing just outside of the building without being raised to a considerable height, or some provision made to artifi- cially produce a draft, often proves inoperative as a means of ventilating refrigerating rooms, because the air in the rooms, becoming cold, settles to the floor and escapes through crevices about the doors or when the doors are opened, causing a down draft, and in many cases over- balancing the uptake of the ventilating pipe. FOBCBD CIRCULATION. Of the various recent devices for forced circulation and the drying of air in cold storage, most are based on the principle of St. Clair delineated in the foregoing paragraph. It may also be combined with any system of artificial ventilation which may be brought about by fans, ventilators, etc. The introduction of air cooled a few degrees below the temperature of the storage room (by drawing the air over refrigerated surface, as is done in the St. Clair and similar systems) insures dry ventila- tion. VELOCITY OF AIB. If, as in the St. Clair system of forced circulation, the air after having been cooled (and dried) by being passed over the refrigerating coils located in the top part of the storage rooms, falls down from the bottom of the coil through a shaft or shafts to the bottom of the room, while the hot air from the top of the room ascends to the top of the coil by shafts or a shaft, the velocity of the air current thus produced by a difference in temperature, or rather by a difference in gravity due thereto, may be expressed by the following formula: V= 1346 ~ (1X0.0021 V ^o In this formula T and degrees absolute Fahrenheit) of the air in the hot and cold air shafts respectively, which are supposed to have the same sectional area, and Fis the velocity with which the air moves through the shafts in feet per second. NUMERICAL RULES FOR MOISTURE. The proper degree of humidity in cold storage rooms, especially also for the storage of eggs (to avoid mold and shrinkage at the same time) is of the utmost impor- tance, and Cooper finds that the relative humidity should 188 MECHANICAL REFRIGERATION. differ with the temperature at which the rooms are kept. Thus a room kept at 28 F. should have a relative hu- midity of 80 per cent, while a room kept at 40 F. should have a humidity of only 53 per cent, and intermediate degrees of humidity for intermediate temperatures. At least one correct normal thermometer (to correct the others by) should be kept in each cold storage plant. DISINFECTING COLD STORAGE ROOMS. Meat rooms and other cold storage rooms may be dis^ infected if necessary by formaldehyde vapors, which are produced by burning wood spirit in an ordinary spirit lamp, the wick of which is covered by a platinum wire screen, in the form and size of a thimble, to make it only glow, and not burn with a flame. Special lamps are made also for this purpose. COLD STORAGE TEMPERATURES. Generally speaking, the temperature of cold storage rooms is about 34 F. For chilling the temperature of the room it is generally brought down to 30 F., and in the case of freezing goods from 10 F. to F. The temperatures and other conditions considered best adapted for the cold storage of different articles of food, provisions, etc., have been compiled in the follow- ing paragraphs, which reflect the views of practical and successful cold storage men as expressed by them in Ice and Refrigeration: STORING FRUITS. The temperatures for storing fruits are given in the following table: FRUIT. REMARKS. F Apples 30-40 Bananas 34-36 Berries, fresh For three or four days 34-36 Canteloupes Carry only about three weeks 32 Cranberries 33-34 Dates, figs, etc 34 Fruits, dried 35-40 Grapes 32-40 Lemons 36-45 Oranges 36 Peaches 35-45 Pears 33-36 W atermelons Carry only about three weeks 32 In general, green fruits and vegetables should not be allowed to wither. Citrus fruits sheuld be kept dry until the skin yields its moisture, then the drying process should be immediately checked. For bananas no rule can be made ; the exigencies of the market must govern the ripening process, which can be manipulated almost at will- COLE STORAGE!. 189 Fruits, especially tender fruits, should be placed in cold storage, just when they are ripe. They will keep better than if put in when they are not fully ripe. Pears will stand as low a temperature as 33. Sour fruit will not bear as much cold as sweet fruit. Catawba grapes will suffer no harm at 26, while 36 will be as cold as is safe for a lemon. The spoiling of fruit at temperatures below 40 P. is due to moisture. ONIONS. Onions, if sound when placed in cold storage, can be carried several months and come out in good condition. It is important that the onions be as dry as possible when put into cold storage. If they can be exposed to a cool, dry wind, they will lose much of their moisture. They are usually packed in ventilated packages or crates. It is claimed, however, that they will keep all right in sacks, if the sacking is not too closely woven, and stored in a special way, being arranged in tiers so the air has free access. Authorities differ as to the best tempera- ture at which to keep the onions, the range being from 30 to 35 P. But 32 to 33 seems to be generally pre- ferred. The rooms should be ventilated and have a free circulation of dry air. Onions should not, of course, be stored in rooms with other goods. When the onions are removed the rooms should be well aired, thoroughly scrubbed and, after the walls, ceiling and floor are free from moisture, should be further purified and sweetened by the free use of lime or whitewash; and a good coat of paint or enamel paint would be advantageous, after which the rooms can be used for the storage of other goods, though some practical cold storage men are of the opinion that such rooms should not afterward be used for the storage of eggs, butter or other articles so sensitive and susceptible to odors, but should be set aside for the storage of such goods as would not be injured by foreign odors. Attempts have been made to kiln dry onions, but this was found impracticable, owing to the fact that the extreme heat required to penetrate the tough outer skin of the onion caused it to soon decay. Experiments have also been made with evaporating onions after removing the outer skin, but this was also unsuccessful. There is GO difficulty, however, in keeping onions in cold storage 190 MECHANICAL REFRIGERATION. for six or seven months and having them come out in perfect condition, if the above suggestions are followed. PEARS. Pears, like other tender fruit, should be placed in cold storage when still firm, and before the chemical changes which cause the ripening have set in ; and they must be handled very carefully. The temperature at which to store them is from 33 to 40 F. The pears after having been kept in cold storage will spoil very rapidly after coming out, and should be consumed as short a time thereafter as may be. Pears should be picked as soon as the stem will readily part from the twig, and before any indications of ripeness appear ; and, as in the case of apples, should immediately be placed in storage, but the temperature should not be as low as for apples. Few kinds of pears can be kept as late as April and May; even after January there is considerable risk. The temperature should be between 33 and 40, but, as for all winter storage goods, must be constant and uniform, for which reason the rooms should have heating as well as chilling pipe. The paper wrapper will best protect them from touching each other in storage. LEMONS. The best storage temperature for lemons is allowed to be 45 and below, but below 36 F. they are liable to be injured, if kept at that temperature for any length of time. The acid, which is the principal ingredient ot lemons, is decomposed, and those containing the least acid will stand the least cold. Lemons should not be ex- pected to keep good in cold storage over four months. Lemons stored during the first three months of the year are said to hold good for at least five months, but if stored later it is more difficult to preserve them. GRAPES. Grapes for cold storage must be well selected and very carefully packed. No crushed or bruised or partly decayed berries are allowable; a whole lot may be tainted by a single berry. Grapes lose much in flavor and taste in cold storage. Malagas hold their flavor best, and will last till Christmas and even longer, but the Concord and other softer grapes will not hold out after Thanksgiving day, as a rule. The best temperature is from 33 to 40. COLD STORAGE. 191 At the latter temperature the flavor appears to suffer less, especially with the Concord, and the lower tem- perature has more effect on the Concord than on the Malaga, it appears, generally speaking. APPLES. Apples may be kept either in barrels or boxes or in bulk, it is said, with equally good results. The barrels, etc., if kept in storage for any length of time, must be refilled to make up for shrinkage, before being put on the market. Opinions as to best temperature for apples vary all the way from 30 to 40. The latter temperature should not be exceeded in any case. If the air in cold storage is too dry it wilts the apples, and if it is too damp it bursts and scalds apples, especially if the temperature is not low enough. The so called " Rhode Island Green- ing" seems to be most susceptible to scalds. Apples should be picked early and put in cold storage with the least possible delay. Apples when stored in barrels should not be stored on ends, but preferably on their sides. A temperature of 33 is considered most favor- able by some. In storing apples eight to ten cubic feet storage room space is allowed per barrel, and twenty to twenty-five tons daily refrigerating capacity per 10,000 barrels. STORING VEGETABLES. ARTICLES. F. Asparagus 84 Cabbage 32-34 Carrots 33-34 Celery 83-35 Driedbeans 33-40 Dried corn 35 Dried peas 40 Onions 82-34 Parsnips 33-34 Potatoes 34-36 Sauerkraut 35-38 Sweet corn 35 Tomatoes 34-35 Asparagus, cabbage, carrots, celery, are carried with little humidity; parsnips and salsify, same as onions and potates, except that they may be frozen without detri- FERMENTED LIQUORS. ARTICLES. F, Beer, ale, porter, etc 83-42 Beer, bottled 46 Cider 30-40 Ginger ale 36 Wines 40-45 Clarets., ..,,* 45-50 192 MECHANICAL REFRIGERATION. The temperatures at which these articles are to be kept in storage is of course not the temperature at which they should be dealt out for consumption. Beer, ale and porter should not be offered for consumption at a temper- ature below 52 F., and temperatures between 57 and 61 are even preferable on sanitary grounds, which, however, are often disregarded to insure a temporarily refreshing palate sensation. STORING FISH AND OYSTERS. Fish if previously frozen should be kept at 25 after being frozen. Oysters should not be frozen. The follow- ing temperatures are given: ARTICLES. F. Driedfish 35 Freshfish. 25-30 Oysters 33-40 Oysters in shell 40 Oysters in tubs 35 A successful firm describes the freezing of fish as follows: When the fish are unloaded from the boats they are first sorted and graded as to size and quality. These are placed in galvanized iron pans twenty- two inches long, eight inches wide and two and a half inches deep, covered with loosely fitting lids, each pan containing about twelve pounds. The pans are then taken to the freezers. These are solidly built vaults with heavy iron doors, resembling strong rooms, and filled with coils of pipes so arranged as to form shelves. On these shelves the pans are placed, and as one feature of the fixtures is economy of space, not an inch is lost. The pans are kept here for twenty- four hours in a temperature at times as low as 16 below zero. Each vault or chamber has a capacity of two and a half tons, and there are sixteen of them, giving a total capacity of forty tons, which is the amount of fish that can be frozen daily if required. On being taken out of the sharp freezers the pans are sent through a bath of cold water, and when the flsb are removed they are frozen in a solid cake. These cakes are then taken to the cold storage warehouse, which is divided into chambers built in two stories, almost the same as the sharp freezers. The cakes of fish, as hard as stone, are packed in tiers and remain in good condition ready for sale. It is possible to preserve them for an indefi- nite time, but as a rule frozen fish are only kept for a sea- son of from six to eight months. They are frozen in the spring and fall when there is a surplus of fish, and sold COLD STORAGE. 19'j generally in the winter or in the close season when fresh fish cannot be obtained. For shipment, flsh may be packed in barrels after the following directions: Put in a Shovelful of ice at the bottom of the barrel, and be always careful to see that auger holes are bored into the bottom of the barrels, to let the water leak out as fast as it is produced by the melting ice. After putting in a shovelful of fine ice, crushed by an ice mill, put in about fifty pounds of fish; then another shovelful of ice on top of the fish, etc., until the barrel is full, always leaving space enough on the top of the barrel to hold about three shovelsf ul of ice. By shovels, scoop shovels are meant. Oysters are said to keep six weeks safe at 40. In one instance they have been kept ten weeks at this tempera- ture for an experiment. STORING BUTTER. Butter is preserved both ways : by keeping the same at the ordinary cold storage temperatures, and also by freezing. Both processes have given satisfactory results, but it appears that those obtained by actual freezing are quite superior, the flavor and other qualities of the butter being perfectly preserved by the freezing. To obtain the best results butter should be frozen at a tem- perature of 20 and the variation should not be over 2 C to 3. For long storage, however, butter, like fish, should be frozen quickly at a temperature of from 5 to 10, and subsequently it should be kept at about 20- F. Ash and spruce tubs make the best packages for butter. As regards thawing it, it is simply taken from the freezer, as in the case of ordinary cold storage goods, with- out paying any attention to the thawing out process. The thawing comes naturally, and the effect that it has upon the butter is to give it a higher and quicker flavor when thawed out than when frozen. When selling frozen goods it is sometimes necessary to let them stand out a little time in order to get the frost out of the butter; particu- larly so in the case of high grade goods, for the thawing develops the flavor. June butter is considered the best for packing and storage. It is essential to exclude the air from butter while being held in cold storage, hence cooperage must be the best, and soaked in brine for twenty -four hours. If the top of the butter is well cov- ered with brine, a temperature of 33 to 35 will answer, 134 MECHANICAL REFRIGERATION. For ordinary cold storage of butter and similar articles, the following temperatures are given: ARTICLES. P. Butter 32-35 Butterine 35 Oleomargarine 35 STORING CHEESE. The best temperature for the storage of cheese is generally considered 32 to 33, and should not vary more than 1. Cheese should not have been subjected to any high temperature before being placed in cold storage. Cheese should be well advanced in ripening before it is placed in cold storage, to avoid bad smell in the house. It generally enters the cold storage room in June and July, and leaves by the end of January, sooner or later when needed. It will keep much longer, however, over a year when needed. It must be kept frem freezing. If frozen, it must be thawed gradually, and consumed thereafter as soon as possible, or otherwise it will spoil internally. The humidity of the room must keep the cheese from shrinking and cracking, but the room must not be damp either, otherwise mold will set in. MILK. Milk is not as a rule kept in cold storage except for a short period. It has been proposed, however, to con- centrate milk by a freezing process, by which part of the water in the ice is converted into ice. The ice is allowed to form on the surface of the pans, which are placed in cold rooms, and the surface of the ice is broken fre- quently, to present a fresh surface for freezing. EGGS. Eggs should be carefully selected before being placed in cold storage, and every bad one picked out by can- dling. The best temperature for storing eggs is between 32 and 33 F. As eggs are very sensitive and will absorb bad odors, etc., it is not advisable to store them together with cheese or other products exhaling odors. For some purposes the contents of eggs may be stored in bulk. In this case the eggs are emptied into tin cans containing about fifty pounds and stored for any length of time at 30 F. They must be used quickly after thawing. Eggs are generally placed in cold storage in April and early May; later arrivals will not keep as well. They are seldom kept longer than February. The tern- COLD STORAGE. 195 perature best suited for eggs is supposed to be between 31 and 34 by American packers, but English dealers claim that 40 to 45 is equally good. The humidity of the air in the cold storage room has doubtless a great bearing on this question. Eggs which have been stored at 30 must be used soon after leaving storage, while eggs kept at 35 to 40 will keep nice for a longer time, as the germ has not been killed in the latter, and consequently they taste fresh. Eggs for the market, especially those to go in cold stor- age, must not have been washed. Washed eggs have a dead and lusterless looking shell, looking like burned bone through a magnifying glass. It is also recommended that eggs in cold storage should be reversed at least twice weekly. The age of eggs may be approximately determined by the following method," based upon the decrease in the density (through loss of moisture) of the eggs as they grow old: Dissolve two ounces of salt in a pint of water, and when a fresh egg is placed in the solution it will im- mediately sink to the bottom of the vessel. An egg twenty-four hours old will sink below the surface of the water, but not to the bottom of the vessel. An egg three days old will swim in the liquid, and when more than three days old will float on the surface. The older the egg the more it projects above the surface, an egg two weeks old floating on the surface with but very little of the shell beneath the water. Experiments have been made for the preservation of eggs by dipping them in chemicals, but with no notable success. It is reported that when preserved in lime water, or in a solution of waterglass or by coating with vaseline they will keep for eight months, but doubtless not with- out some detrimental alteration in taste and flavor. DRYING OF EGG ROOMS, ETC. For the drying of egg rooms, etc., Mr. Cooper recom- mends supporting a quantity of chloride of calcium above the cooling coils, over which the air is circulated by mechanical means. The brine formed by the absorp- tion of moisture by the chloride of calcium will then trickle down over the pipes and thereby effectually pre- vent any formation of frost on the pipes, and therefore keep them at their maximum efficiency at all times, The air, in passing over the brine moistened surface of 196 MECHANICAL REFRIGERATION. the coils, is purified, and the briiie, after falling to the floor of the cooling room, goes to the sewer, and no fur- ther contamination takes place. The re-use of the salt after redrying is objected to by some on account of these contaminations; but it seems to us that they will be ren- dered entirely harmless if the salt is dried at a sufliciently high temperature, and this can hardly be avoided if the water is all driven off, to do which requires calcination at a tolerably high temperature, a temperature which ?e far above that at which all germs are destroyed. STORAGE OF MISCELLANEOUS GOODS. ARTICLES. REMARKS. Canned Goods: F. Fruits 35 Meats 35 Sardines 35 Flour and Meal: Buckwheat flour 40 Corn meal 40 Oat meal 40 Wheatflour 40 Miscellaneous: Apple and peach butter 40 Chestnuts 33 Cigars 35 Furs, woolens, etc 25-32 Furs, undressed 35 Game to freeze Long storage 0-5 Game, after frozen Short storage 25-28 Hops 33-36 Honey 36-40 Nuts in shell 35-38 Maple syrup, sugar, etc 40-45 Oil 35 Poultry, after frozen .... Short storage 28-30 Poultry, to freeze Long storage 5-10 Syrup 35 Tobacco 35 LOWEST COLD STORAGE TEMPERATURES. Temperatures below zero Fahrenheit are hardly of any utility in cold storage, although in some instances even lower temperatures are produced. A room piped about four cubic feet of space to one lineal foot 1-inch pipe, direct ammonia expansion, could be brought to 8 F. below zero. Theoretically a temperature of 28 F. can be produced with ammonia refrigeration at a back pressure equal to that of the atmosphere (and even lower at lower pressures), but practically it is not likely that temperatures lower than 20 F. can be obtained with ammonia, although it may be done by carbonic acid; but as stated before, it is to no purpose as far as cold stor- age is concerned. BREWERY REFRIGERATION. 10" CHAPTER VII. BREWERY REFRIGERATION. PRINCIPAL OBJECTS OF BREWERY REFRIGERATION. The principal uses for refrigeration in a brewery are as follows: First. Cooling of the wort from the temperature of the water as it can be obtained at the brewery to the temperature of the fermenting tuns (about 40 F. ). Second. Withdrawal of the heat developed by the fermentation of the wort. Third. Keeping cellars and store rooms at a uniform low temperature of about 32 to 38 F. Fourth. Cooling brine or water to supply attemper- ators in fermenting tubs. Fifth. For the storage of hops and prospectively in the malting process. ROUGH ESTIMATE OF REFRIGERATION. Frequently the amount of refrigeration required for breweries is roughly estimated (in tons) by dividing the capacity of the brewery in barrels made per day by the figure (4). As a matter of course, this can answer only for very crude estimates. For closer estimates the dif- ferent purposes for which refrigeration is required must be considered separately. SPECIFIC HEAT OF WORT. The wort by the fermentation of which the beer is produced consists chiefly of saccharine and dextrinous matter dissolved in water. Its specific heat, which is the chief quality that concerns us now, varies with the Strength of Wort in Per Cent after Balling. Corresponding Specific Gravity. Corresponding Specific Heat. 8 1.0330 .944 9 1.0363 .937 10 1.0404 .930 11 1.0446 .923 12 .0488 .916 13 .0530 .909 14 .0572 .902 15 .0614 .895 16 .0657 .888 17 .0700 .881 18 .0744 .874 19 .0788 .867 20 1.0832 .861 amount of solid matter which it contains; this may be ascertained by finding its specific gravity by means of a odccharometer or other hydrometer. The specific heat MECHANICAL REFRIGERATION. of wort of different strength or specific gravity may be found from the accompanying table. These figures are calculated for a temperature of 60 F. For every degree Fahrenheit that th temperature of the wort is below 60, the number 0.00015 must be added to the specific gravity given in above table, and for every degree above the number 0.00015 must be subtracted. Thus the specific gravity of a wort of 13 per cent being acccording to the table 1.0530 at 60, at 50 it would be 60 50=10x0.00015 = 0.0015 more, or 1.0545. PROCESS OF COOLING WORT. The wort as prepared in the brewery is boiling hot, and has to be cooled to the temperature of the ferment- ing tuns. It is first cooled at least, generally so by ex- posing it to the atmosphere in the cooling vat, in which, however, it should not remain over two to three hours, nor at a temperature below 110 F. After this the wort is allowed to trickle over a system of coils through which ordinary cold water circulates by which the temperature of the wort is reduced to that of the water, about 60 F. or thereabouts. A system of coils, generally placed be- low the one mentioned already, finishes the cooling process by reducing the temperature of the wort to about 40 F. or below in ale breweries to about 55 F. This is done by circulating either cooled (sweet) water or refrig- erated brine or refrigerated ammonia through the latter coils while the wort trickles over the same. REFRIGERATION REQUIRED FOR COOLING WORT. The amount of cooling required in this latter opera- tion must be furnished by artificial refrigeration, and its amount expressed in B. T. units, U, may be calculated exactly if we know the number of barrels, B, of wort to be cooled, its specific heat, s, and its specific gravity, g, after the following formula: TJ=*B x 259 X g X s (t 40) units, in which t stands for the temperature to which the wort can be cooled by the water to be had at the brewery. To reduce this amount of ^refrigeration to tons of re- frigeration it must be divided by 284,000. SIMPLE RULE FOR CALCULATION. Assuming that the average temperature of the wort after it has been cooled b* 7 the water as it is obtainable BREWERY REFRIGERATION. 199 at the brewery, is about 70 F., and that the average strength of wort in breweries is between 13 and 15 per cent of extract, corresponding to a specific weight of about 1.05, and to a specidcheatof 0.9. the above formula may be simplified and the refrigeration required daily for the cooling of the wort of a brewery j)f a daily capacity of B barrels, expressed as follows: U=Bx 7400 units. Or, expressed in tons of refrigeration, U t ' In other words, about one ton of refrigeration is re- quired for about thirty-eight barrels of wort under the conditions mentioned. If the water of tke brewery cools the wort to 60, one ton of refrigeration would an- swer for about fifty-two barrels of wort. The former figure on one ton of refrigeration for forty barrels of wort is generally adapted for preliminary es- timates. SIZE OF MACHINE FOR WORT COOLING. The capacity of an ice machine is generally expressed in tons of refrigeration produced in twenty-four hours. However, the wort in a brewery must be cooled in a few hours; therefore, in order to find the capacity of the ice machine required to do the above duty the number of tons of refrigeration found to be required to do the cool- ing of the wort must be multiplied by the quotient -V- in fi which h means the time expressed in hours in which the cooling of the wort must be accomplished. This of course applies to cases in which a separate machine is used for wort cooling, as is done in large breweries. Frequently the cooling of the wort is accomplished by employing nearly the whole refrigerating capacity of the brewery for this purpose for a comparatively short time. INCREASED EFFICIENCY IN WORT COOLING. In these cases, therefore, the total refrigerating ca- pacity of a brewery must never be less than that required to do the wort cooling in the desired time when all other refrigerating activity is suspended during that time. In this connection it should, however, be mentioned that the brine system, as well as the direct expansion system, 200 MECHANICAL REFRIGERATION. may be made to work with increased efficiency when ap- plied to wort cooling. In the former case this may be accomplished by storing up cooled brine ahead, and in the latter case by allowing the ammonia to re-enter the com- pressor at a much higher temperature after having been used for wort cooling than in other cases. HEAT PRODUCED BY FERMENTATION. The cooled wort is now pitched with yeast and allowed to ferment, by which process the saccharine constituents of the wort are decomposed into alcohol and carbonic acid with the generation of heat after the following formula: C 1Z H 22 1 , H 2 0=4 C z H B OH+ 4 CO 2 + 66,000 units. Maltose. Alcohol. Carbonic Acid. Heat. In other words, this means that 360 pounds of malt- ose during fermentation will generate 66,000 pounds Cel- sius units of heat, or that one pound of maltose while decomposed by fermentation will generate about 330 B.T. units of heat. CALCULATING HEAT OF FERMENTATION IN BREWERIES. If the weights of the wort and that of the ready beer are determined by means of a Balling saccharometer, and are b and b t respectively, the heat, H, in B. T. units gen- erated during the fermentation of B barrels of such wort, may be determined after the formula E== B X 0.91 (b-bj (259+ 6) 330 unita> 100 And the refrigeration required to withdraw this heat from the fermenting rooms, expressed in tons, U, of refrigerating capacity is SIMPLE RULE FOR SAME PURPOSE. Again, if we assume that the wort on an average shows 14 per cent on the saccharometer, and after fer- mentation it shows 4 per cent, the above formula, giving the refrigeration in tons, U^, in tons required in twenty- four hours to withdraw the heat generated by the fer- mentation of B barrels of wort turned in on an average daily, may be simplified as follows: fiREWERY REFRIGERATION. 201 In other words, one ton of refrigerating capacity is re- quired for every thirty-four barrels of beer produced on an average per day of above strength. This rule will apply to pretty strong beers ; for weaker beer it may be- come much less, so that one ton of refrigeration will answer for fifty barrels, and even more. This shows the importance of this branch of the calculation, which is frequently passed over in a " rule of thumb " way. For preliminary estimates one ton of net refrigerat- ing capacity is allowed to neutralize the heat generated by the fermentation of twenty-five barrels of beer. DIFFERENT SACCHAROMETERS. If in the above determinations of the strength of wort of beer any other kind of saccharometer has been used its readings can be readily transformed into read- ings of the Balling scale, by using the table on the fol- lowing page, which may also be used in connection with the other tables on hydrometer scales in this book. In this way any hydrometer may be made available for the purpose contemplated in the above formula. REFRIGERATION FOR STORAGE ROOMS. Besides the heat generated by fermentation, the heat entering the fermenting and storage rooms from with- out must be carried away by artificial refrigeration, so as to keep them at a uniform temperature of 32 to 38P F. The amount of refrigeration required on this account is also frequently estimated by a "rule of thumb," allow- ing all the way from twenty to seventy units of refrigera- tion for every cubic foot of room to be kept cool during twenty-four hours. The difference in refrigeration is due to the size of the buildings and to the manner in which the walls and roofs are built. Generally thirty units are allowed per cubic foot of space, in rough preliminary estimates, for capacities over 100,000 cubic feet. For capacities between 5,000 and 100,000 cubic feet from forty to seventy units are allowed, and above 100,- 000 from twenty to forty units per cubic foot of space. Sometimes, after another way of approximate figuring, about 20 to 100 units of refrigeration (generally 50) are allowed per square foot of surrounding masonry ceiling and flooring. 202 MECHANICAL REFRIGERATION. TABLES FOB THE COMPARISON OF DIFFERENT SACCHAR- OMETERS AMONG THEMSELVES AND WITH SPECIFIC GRAVITY. S *? 1 1 IT! L fe s' t" -. CO 4, * S 3! if 3| !! B o o ll ajl II il 11 J! * O ||| |s* CO Ow 1 |i j s & 1 80 Sf 0.00 0.00 0.00 1.000 262.41 12.00 17.45 14.fr 1.0488 275.21 .25 .36 .30 1.001 262.66 .25 .83 1.0498 275.49 ..50 .72 ,.60 1.002 262.92 .50 18.21 15^2 1.0509 275.76 .75 1.08 .90 1.003 263.18 .76 .60 .60 1.0520 276.04 1.00 .44 1.20 1.004 263.45 13 00 .99 92 1.0530 276.32 .25 .80 ..60 1.005 263.71 .25 19.38 16.24 1 0540 276.60 ,.50 2 16 .80 1.006 263.97 .50 .77 .65 1.0551 276.88 .76 .62 2.10 1.007 264.23 .75 20 16 .86 1.0662 277.15 2.00 .88 .40 1.008 264 50 14.00 .55 17.17 1 0572 277.42 .25 3:24 .70 1.009 264.76 .25 .94 .48 1.0582 277.68 .60 .60 3.00 1.010 265.02 .50 21.33 .80 1.0593 277.96 .75 .96 .30 1.011 265.28 .75 .72 18.12 1.0604 278.25 3.00 4.32 .60 1.012 265.55 15.00 22.11 .43 1.0614 278. 52 .25 .68 .90 1 013 265.81 .25 .60 .75 1.0625 278.80 .60 5.04 4.20 1.014 266.07 .50 .89 19 07 1.0636 279.09 .75 .40 .50 1.015 266.33 .75 23.27 .39 1.0646 279.86 4.00 .76 .80 1.016 266.60 16.00 .66 .71 1.0657 279.63 .25 6.12 5.10 1.017 266.86 .25 24 05 20.03 1.0668 279.92 .50 -.48 .40 1.018 267.12 .50 .44 .35 1.0679 280.21 .75 .84 .70 1.019 267.38 .75 83 .67 1.0690 280.60 6.00 7.20 6.00 1 020 267.65 17.00 25.22 21.00 1.0700 280.77 .25 .56 .30 1.021 267 91 .25 .61 .33 1.07U 281.06 ( .50 .92 .60 1.022 268 17 .50 26 00 .66 1.0722 281.34 .75 8 28 .90 1*023 268.43 .75 .39 .99 1.0733 28163 6.00 .64 7.20 1*024 268.69 18.00 .78 22.32 1-0744 281.92 .25 9 00 .50 1J.025 268.96 .25 27.17 .65 1.0755 282.21 .50 .36 80 1?026 269 2. .50 .56 .98 1.0766 282.60 .75 -72 8.10 1.027 269 48 .75 .96 23.31 1.0777 282.78 7.00 10.08 .40 1 028 269 74 19 00 28.36 .64 1.0788 283.08 .25 .44 .70 1.029 270.00 .25 .76 97 1.0799 283 37 .50 .80 9.00 1 .030 270.27 .50 29.16 24.30 1 0810 283.65 .75 11.16 .30 1.031 270.53 .75 .56 .63 1.0821 283.93 8.00 .62 .60 1.032 270.79 20.00 .95 .96 1.0832 284.21 .25 .96 .96 1.0332 271.11 .25 30.34 25.29 1.0843 284 49 .60 12.32 10.26 1 0342 271.37 60 .73 .62 1.0854 284.77 .75 .68 .57 1 0352 271 64 .75 31.12 .95 1.0865 285.05 9 00 13 04 .88 1.0363 271 91 21.00 .50 26.27 1 0876 285.33 .25 .40 11.19 1 0374 272.19 25 .87 .60 1.0887 286 62 .50 .76 .50 1 0384 272.47 !50 32 25 93 1.0898 285.91 .75 14.12 .81 1.0394 272.74 75 .64 27.26 1.0909 286 19 10.00 .48 12.11 1.0404 273.00 22 00 33.04 .69 1.0920 286.47 .25 .84 .42 1.0415 273.28 .25 .44 .92 1.0931 286.77 .50 15.21 .73 1 0425 273.56 .50 .84 28.25 1.0942 287 06 -75 .58 13 06 1.0436 273.84 .75 34.23 .68 1.0953 287.36 11.00 .95 .37 1.0446 274 11 23.00 .63 .91 1.0964 287.66 .26 16.32 .68 1.0457 274 39 .25 35.03 29 24 1 0976 288.96 .50 .69 14.00 1.0467 274 66 .50 .43 .67 1.0986 288 20 76 17.07 .32 1.0478 274.94 .75 83 .90 1.0997 288.60 24.00 36.23 30.23 1.1008 98880 CLOSER CALCULATION. For calculations required to be more exact the power for transmission of heat by the walls and windows, as well as the difference of temperature within and without, must be taken into consideration. BREWERY REFRIGERATION. 203 For calculations of this kind the same rules apply which have been given under the head of cold storage, pages 153, etc. The number of units of refrigeration found to be required must be divided by 284,000 to express tons of refrigeration. COOLING BRINE AND SWEET WATER. The amount of refrigeration required to cool brine or sweet water to supply the attemperators in the fer- menting tubs is included in the estimate for the refriger- ation required to neutralize the heat of fermentation. TOTAL REFRIGERATION. Therefore the total amount of refrigeration required is composed of the first three items mentioned in the second paragraph of this chapter, and by adding them we find the actual capacity of the machine or machines required in a given case. It may be verified in accordance with the considerations mentioned in the paragraph on " Increased Efficiency for Wort Cooling." DISTRIBUTION OF REFRIGERATION. The practical distribution of the refrigeration in the brewery is carried out on different principles, and should follow the figures obtained in the above calculations. Formerly the cooling of rooms in breweries was fre- quently effected by the circulation of air, which was furnished direct by compressed air refrigerating ma- chines. Later on the air to be used for this purpose was refrigerated in separate chambers with the aid of am- monia compression machines. At present, however, the chief means for cooling brewery premises are coils of pipe mto which the ammonia is allowed to expand di- rectiy as it leaves the liquid receiver. These coils are generally placed overhead, in which position they assist greatly in keeping the air dry. DIMENSIONS OF WORT COOLER. The amount of refrigeration destined to do the cool- ing of the wort takes care of itself, provided the cooler, which, as already described, is generally constructed after the Baudelot pattern, is large enough to do the cooling in the proper time. The proportions frequently employed for the ammonia portion of the wort cooler are 204 MECHANICAL REFRIGERATION. about ter lengths of 2-inch pipe, each length sixteen feet long, for fifty barrels of wort to be cooled from about 70 to 40 F. within three to four hours. For 100 barrels of wort to be cooled the ammonia por- tion of the cooler consists of fourteen lengths of pipe six- teen feet long; for 180 barrels,of fifteen lengths twenty feet long; and for 360 barrels, twenty lengths twenty feet long, all pipes to be 2-inch. These are practical figures, and given with a view to afford ample cooling surface. The amount of refrigeration which must circulate through the wort cooler within that time has been deter- mined by the above calculation. In the case of brine circulation, salt brine being used in the wort cooler, the surface of pipe should be made 20 percent more than given above; in other words, a cooler of the above dimensions will answer for forty barrels of wort, instead of fifty, in case brine circulation is used. DIRECT EXPANSION WORT COOLER. In case of brine circulation, to which the foregoing dimensions apply, the pipes of the wort cooler may be of copper, but in case of direct expansion being used, the inside of the pipes cannot be copper, but must be iron or steel, and, therefore, copper plated steel pipe or polished steel pipe is used in this case, the latter being given the preference by most manufacturers on account of cheap- ness and relative efficiency. The ammonia portion of the wort cooler should be made in two or more sections, having separate and direct connections for inlet of liquid ammonia and outlet of ex- panded vapor. PIPING OF ROOMS. The balance of refrigeration, that is, the whole amount, less that used for wort cooling, must be dis- tributed over the store and fermenting rooms in due pro- portion. In doing so the time within which the refrigera- tion is to be dispensed must be considered foremost. The subsequent figures are based on the assumption that dur- ing every day the machine or brine pump is active for twenty-four hours to circulate refrigeration; if less time is to be used for that purpose more distributing pipe must be used in proportion. As a general thing too much piping cannot be em- ployed, for the nearer the temperature of the room to be cooled is to that within the pipe, the more economical will be the working of the ice machine. In case of direct expansion it is frequently assumed that in order to properly distribute one ton of refrigera- tion about storage and fermenting rooms, it will require a pipe surface of 80 square feet, which is equivalent to 130 feet of 2-inch pipe, and to about 190 feet of 1^-inch pipe. Smaller pipe than that it is not advisable to use. If radiating disks are employed less pipe may be used. For brine circulation much more piping, even as much as 200 square feet of surface, are allowed per ton of refrigeration to be distributed. In very close calculations allowance should be made for the difference in temperature in the different vaults, which for fermenting rooms is about 42 F., for storage rooms about 33- F., and for final storage or chip cask about 37 F. HEAT OF FERMENTATION AGAIN. In addition to the piping allowing for the transmis- sion of heat through the walls, the balance of piping, i. e., that which is to convey the refrigeration required to neutralize the heat during fermentation, must be appor- tioned according to the amount of heat which is de- veloped in the different rooms. This can also be calcu- lated very closely after the above rules, if the method of fermentation to be carried on is known. But as a rule this is not the case, and to supply this deficiency it may be assumed that from the heat gener- ated during fermentation about four-fifths is generated in the fermenting room, and about one-fifth in the ruh and chip cask cellar together. In this proportion the ad- ditional piping in these rooms may be arranged after due allowance has been made for the refrigeration conveyed by the attemperators. EMPIRICAL RULE FOR PIPING ROOMS. More frequently than the foregoing method empirical rules are followed in piping rooms in breweries, it being assumed that nearly all of the heat generated in the fermenting room proper (during primary fermentation) is carried off by the attemperators. On this basis it is fre- quently assumed that one square foot of pipe surface will cool about 40 cubic feet of space in fermenting room, and about 60 to 80 cubic feet of space in ruh and chip cask cellar (direct expansion). 206 MECHANICAL REFRIGERATION. These figures then apply to direct expansion; for brine circulation, about one-half of the above named spaces will be supplied by one square foot of refrigerating surface. This figure appears to contemplate a range of about 9 F. difference between the temperature of rooms and that of refrigerating medium within pipe. Much more and much less pipe is frequently used fcr the same pur- pose, which is to be accounted for by reasons given on pages 135 and 136. Here we allow more space per square foot of refriger- ating pipe surface than is done in the rule at the bottom of page 135 for storage rooms in general to keep the same temperature. This is partially explained by the fact that brewery vaults are less frequently entered from without, and that their contents are less frequently changed than is the case with general storage vaults. Furthermore it is evident that the size of vaults is also a matter for consideration in this respect. ATTEMPERATORS. The attemperators are coils of iron pipe, one to two inches thick, the coil having a diameter of about two- thirds of the diameter of the fermenting tub, in which it is suspended, and a sufficient number of turns to allow about twelve square feet pipe surface per 100 barrels of wort, corresponding to about nineteen feet of 2-inch pipe. The refrigeration is produced by means of cooled water or brine circulating through the attemperators. The attemperators are suspended with swivel joints so that they can be readily removed from the fermenting tub. There is a great variety in the form of attemperators, box or pocket coolers being also frequently used. On the whole the pipe attemperator as described seems to be the simplest and most popular. It has also been proposed (Galland) to cool the fer- menting wort by the injection of air, purified by filtration through cotton and refrigerated artificially. This plan, however, does not seem to be followed practically to any great extent. REFRIGERATION FOR ALE BREWERIES. While the general calculations relating to heat of fermentation, cooling of the wort and cooling of rooms are the same for ale as for lager beer, the specific data relating to piping, etc., in above paragraph, are given BREWERY REFRIGERATION. 207 with special reference to lager beer, and must be modified when applied to ale. This is due to the fact that the ale wort is cooled to a temperature of about 55 F. only, and that the storage rooms are to be kept at a temperature of 50 F., or there- abouts. Accordingly, for ale wort cooling one ton of refriger- ation will be required for every seventy-five barrels. For keeping the rooms at the temperature of 60 about twenty B. T. units and less of refrigeration for every cubic foot in twenty-four hours will be sufficient. The refrigeration necessary to remove the heat of fermentation is calculated in the same manner as above. The piping of store rooms in ale breweries is fre- quently done at the rate of one running foot of 2-inch pipe per sixty cubic feet of space. The tables on refrigeration and piping discussed in the chapter on cold storage may also be consulted in this connection. SWEET WATER FOR ATTEMPERATORS. The circulation of refrigerated brine in the attem- perators is not considered a safe practice by brewers in general, as a possible leak of brine would be liable to cause great damage to the beer. For this reason cooled or ice water (it is also termed sweet water to distinguish it from salt water or brine) is circulated in the attem- perators, generally by means of an automatic pump which regulates the proper supply of sweet water to the attemperators, no matter how many or how few of them are in operation at the time. The ice or sweet water is cooled in a suitable cistern or tank which contains a cooling pipe in which ammonia is allowed to expand di- rectly, or through which refrigerated brine is allowed to circulate. In some breweries the wort is also cooled by refrigerated sweet water made in the above way. This method absolutely precludes the possibility of contami- nation of ammonia or brine, but at the same time it is very wasteful in regard to the very indirect mode of ap- plying the refrigeration*, and for this reason brine in cir- culation is now mostly used for this purpose, experience having shown that the danger of contamination is prac- tically excluded. 208 MECHANICAL REFRIGERATION. CHILLING OF BEER. Recently it has been found desirable to subject the ready beer to a sort of chilling process immediately before racking it off into shipping packages. This pro- cess, however, is of no practical utility if the beer is not filtered after it has been chilled and before it goes into the barrels. In this case much objectionable albuminous matter, still contained in the ready beer, is precipitated by chilling and separated from the beer by filtration, while without filtration- this matter would redissolve in the beer and cause subsequent turbidities, especially if the beer is used for bottled goods. BEER CHILLING DEVICES. The chilling was first effected by passing the beer through a copper worm placed in a wooden tub which was filled with ice. But by this the desired object was attained only partially. Therefore, the ice was mixed with salt to obtain a still lower temperature in the beer passing through the worm. Still more recently, and of course in all breweries where mechanical refrigeration is employed, the pipes through which the beer passes are cooled by brine or by direct expansion. Special apparatus are also made for this purpose, and generally consist of a series of straight pipes provided with manifold inlet and outlet, and placed in a cylindrical drum, through which refrigerated brine or ammonia is allowed to pass in a direction opposite to the beer. COOLING OF WORT. Coolers of the same construction are now also fre- quently used for wort cooling instead of the Baudelot coolers. For both purposes, i. e., the chilling of the ready beer and the cooling of the wort, the refrigerated brine appears to act as the best cooling medium, at least so with some makes of this kind of coolers as they are constructed and operated at present. If direct expansion is used it has been found impracticable (at least in the cases reported to the author) to effect a thorough chilling in the desired time. If used for wort cooling, direct expansion has also caused some trouble when used witli some kinds of these new coolers, but it has been overcome in a measure by allowing the ammonia to enter the cooler almost on- half to one hour before the wort is passed through the same. BREWERY REFRIGERATION. 209 SAFEGUARDS TO BE EMPLOYED. It has also been experienced that the expanded ammonia, especially if the expansion valve (one of which must be provided for each of these coolers) is not mani- pulated very carefully, enters the compressor in an over- saturated condition if allowed to pass directly to the same. Under such conditions the compressor will oper- ate in an irregular manner, and even the cylinder head may be blown out in extreme cases. To guard against such calamities it is necessary to carry the expanded ammonia to the compressor in proper condition by allow- ing the same to mix with the expanded ammonia coming from the expansion pipes in other parts of the brewery, before reaching the compressor. To do this the ex- panded ammonia from the wort cooler and that from the cellar may enter a common conduit pipe at a sufficient distance from the compressor to insure a thorough mix- ture of the gases. CAUSES OF TROUBLE. The foregoing contains, we believe, the principal safeguards known at present to be of service to over- come the troubles with these coolers; troubles which, while they are not gainsaid by their makers, are never- theless, we understand, declared by some of them so paradoxical in their action that they upset the entire theory of transmission of heat as given by the scientists at present. On the other hand, and to partly offset a statement so derogatory to the engineering profession, it may be permissible to suggest that the chief of the apparatus makers, while being expert practical copper- smiths, are perhaps not sufficiently versed in the intricate details offered by problems of heat transmission to give the construction of apparatus of a novel tendency the proper consideration. It is not unlikely that the relative sizes of direct expansion pipes and brine pipes in the refrigeration of rooms have been taken as cases parallel to these coolers, while in fact the transmission of heat proceeds at a rate entirely different in both cases. DIRECT REFRIGERATION. Instead of refrigerating the fermenting and storage rooms of the brewery it has also been proposed to refrig- erate the contents of the tubs and casks separately and in a more direct manner, just as the surplus heat of fer- 210 MECHANICAL REFRIGERATION. meriting tubs is now withdrawn, by means of attempera- tors or similar devices. At first sight there would seem to be a source of considerable saving in this proposition, but it would be at the expense of cleanliness, dryness and reliable supervision of the brewery. Therefore it must be considered a change of very doubtful expediency. BREWERY SITE. In former times it was generally considered that the best location for a brewery site was on a hill side, to enable the fermenting and storage rooms to be built into the hill into natural rock, in order to profit by the natural low underground temperature in the summer and the higher underground temperature in the winter time; in other words, by the even temperature all the year around. This position was certainly well taken when the beer was made exclusively by top fermenta- tion, and the position still holds good in a measure for ale breweries. As the great majority of breweries, how- ever, are operated for the production of lager beers which have to ferment, and are stored at temperatures much lower than those obtaining in natural vaults (at least, in the moderate zones), artificial refrigeration or ice has to be resorted to. In either case the natural vaults offer very little advantage to overground structures, well insulated, especially if the larger cost of construction of natural vaults, their inconvenience as to room, and generally also as to accessibility, is considered. For these reasons the site for a brewery nowadays is generally selected with sole reference to convenience as to ship- ment of produce, reception of material and quality and accessibility of water supply. ICE MAKING AND BREWERY REFRIGERATION. Very frequently it happens that a brewery is to be operated in connection with an ice plant, and, generally speaking, it is doubtless not only more convenient, but also good economy to have more than one refrigerating machine in such cases on account of different expansion or back pressures that we have to work with. STORAGE OF HOPS. To keep hops from degeneration their storage at 32 34 F, in a dry, dark, insulated room has been found the only successful way. The hops should be well dried, sulphurized and well packed before being placed in cold storage. Artificial refrigeration, as well as ice, may be BREWERY REFRIGERATION. 211 used, but special precaution has to be used to keep the room dry in the latter case. REFRIGERATION IN MALT HOUSES The cold air which is required in malting, especially in the so called pneumatic methods of malting, it has also been proposed to furnish by means of refrigerating machinery, but it does not appear that it can be done successfully from a financial point of view, except, perhaps, under very exceptional circumstances. ACTUAL INSTALLATIONS. The following figures are taken from actual meas- urements of an existing installation in a brewery having a daily capacity of 375 barrels lager beer, which has the following appointments : One ammonia compression machine of fifty tons, chiefly for wort 'cooling, direct expansion, reduces tem- perature of whole output, 375 barrels, from 70 to 40 F. in four hours (the ammonia portion of Baudelot cooler consisting of twenty pieces of 2-inch pipe, each twenty feet long). One ammonia compression machine, 50 tons capacity, for storage . attemperators, etc. (direct expansion). Fermenting room, 90x75 feet, fourteen feet high, is piped at the rate of one foot 2-inch pipe for every twenty- seven cubic feet space. Each one of the sixty- five fermenting tubs contains an attemperator coil of twenty-one feet 2-inch pipe. Ruh cellar, 90X74 feet, and twenty feet high, is piped at the rate of one foot 2-inch pipe for every forty cubic feet of space. Chip cask cellar, 90x73 feet, and sixteen feet high, is piped at the rate of one foot 2-inch pipe for every fifty- two cubic feet of space. A fifty-barrel lager beer brewery was equipped with machinery to furnish refrigeration in accordance with the following estimates : 3,200,000 B. T. units for storage. 416,000 B. T. units for cooling wort. 300,000 B. T. units for attemperators. Total, 3,916,000 B.-T. units=13.8 tons, or in round figures equal to fifteen tons refrigerating capacity. The whole capacity is calculated to cool the wort in four hours. 212 MECHANICAL REFRIGERATION. CHAPTER VIII. REFRIGERATION FOR PACKING HOUSES, ETC. AMOUNT OF REFRIGERATION REQUIRED. The application of refrigeration in slaughtering and packing houses is quite similar to its application to cold storage in general, and the amount of refrigeration re- quired in a -special case may be estimated on the same principles. THEORETICAL CALCULATION OF SAME. The refrigeration required to keep the rooms at the required temperature is found after the rules given on page 151, etc. The additional refrigeration to chill or freeze the meat can be calculated after the rules given on page 157, etc. PRACTICAL RULES FOR SAME. The temperature of the chilling rooms is below 32 F. and the fresh slaughtered meats are stored in them until they have acquired the storage temperature in storage rooms, to which they are then removed. For practical estimates it is frequently assumed that a refrigeration equivalent to about 80 B. T. units is re- quired for every cubic foot of chilling room capacity in twenty-four hours. The refrigeration for meat storage rooms is the same as that required for ordinary storage, i. e. , from 20 to 50 units (40 units being calculated on an average) for every cubic foot of space in twenty-four hours. For crude estimates calculations are frequently made on the basis of allowing 3,000 to 5,000 cubic feet space per ton of refrigeration in twenty-four hours in chilling rooms, and 5,000 to 8,000 cubic feet space per ton of refrig- eration in twenty-four hours in storage rooms, accord- ing to insulation, size of rooms and other conditions. FREEZING ROOMS. The freezing of meat is performed in rooms kept at a temperature of 10 F. and below. Considerable additional refrigeration is required for freezing, not only on account of the latent heat of freezing, which has to be withdrawn, but also on account of the low temperature at which the rooms have to be kept. For rough estimates at least 200 REFRIGERATION FOR PACKING HOUSES 213 B. T. units of refrigeration should be allowed for every cubic foot of freezing room capacity. CALCULATION PER NUMBER OF ANIMALS. If the average number and kind of animals to be dis- posed of daily in slaughtering house is known, calcula- tions are also made on a basis similar to the following: From 6,000 to 12,000 cubic feet of space are allowed per ton of refrigerating capacity to offset the loss of refrig- eration by radiation through walls and otherwise, and in addition to that, the extra refrigeration to be allowed in the chilling room for the chilling proper is arrived at in accordance with the assumption that one ton of refriger- ation will take care of the chilling of 15-24 hogs (average weight, 250 pounds). 5- 7 beeves (average weight, 700 pounds). 45-55 calves (average weight, 90 pounds). 55-70 sheep (average weight, 75 pounds). In actual freezing one ton of refrigeration will take care of one ton of meat (in twenty-four hours). PIPING OF ROOMS. The piping of rooms in packing houses may be ar- ranged after rules referred to already. Not infrequently, however, other empirical rules are followed, viz.: For chilling rooms, for instance, one running foot of 2-inch pipe (or its equivalent) is allowed for thirteen to fourteen cubic feet of space ; that is, in case of direct expansion, and for seven to eight cubic feet of space for brine circulation. For storage rooms, one running foot of 2-inch pipe is allowed for forty-five to fifty cubic feet in case of di- rect expansion, and for fifteen to eighteen cubic feet in case of brine circulation. For freezing: rooms, one running foot of 2-inch pipe is allowed for six to ten cubic feet of space for direct expansion, and for three cubic feet of space in case of brine circulation. Others proportion the piping by the number of ani- mals slaughtered, allowing thirteen feet of 2-inch pipe per ox, and six feet 2-inch pipe per hog in case of direct expansion in chilling room. In case of brine expansion thirteen feet 1^-inch pipe are allowed per hog, and twenty-seven feet 1^-iuch are al- lowed per ox in chilling room. (Large installations.) 214 MECHANICAL REFRIGERATION, STORAGE TEMPERATURES FOB- MEATS. The temperatures considered best adapted for the storage of various kinds of meats are given in the follow- ing table: ARTICLES. F. Brined meats 35-40 Beef, fresh 37-39 Beef, dried 36-45 Hams, ribs, shoulders (not brined) 30-35 Hogs 30-33 Lard , 34-45 Livers.-. 30 Mutton 32-36 Oxtails 32 Sausage casings 30-35 Tenderloins, butts, ribs 30-35 Veal 32-36 OFFICIAL VIEWS ON MEAT STORAGE. The report of an official commission created by the French government to investigate the cold storage of meats, etc , closes with the following conclusions : First. Whenever meat is to be preserved for a com- paratively short time, for market purposes, the animals being slaughtered close to the cold storage or not having to be transported, after slaughtering, for a distance in- volving more than a few hours (as much as twelve), in transit, congelation is not required to insure the con- servation. It should be avoided, as by such a practice, that is, the temperature being kept in the storage above the freezing point, the meats are sure to retain all 'jheir palatable and merchantable qualities. Second. In special circumstances, such as for a pro- tracted conservation, in case of a transportation of the slaughtered animals from very long distances, involving days or weeks in transit, congelation appears to be pref- erable and safer It does not necessarily render the meats less merchantable, wholesome or palatable, if they are frozen and thawed out, very slowly, gradually and carefully; and only after they have been deprived partially of the excess of moisture of their tissues. Third. Cold, dry air should be the vehicle of cold; it should circulate freely around the meats. FREEZING MEAT. The same commission recommends that in case the meat must be frozen it should be done in such a way that the fiber is not altered; it should preserve its elasticity as long as possible, up to the very moment when the liquid elements of the meat begin to solidify, so that, at the REFRIGERATION FOR PACKING HOUSES. 215 point of congelation, the dilatation of the water, in changing state, should not cause the bursting of the or- ganic cells, leaving a uniform mass of disagreeable ap- pearance at the thawing out. The congelation must proceed very slowly from the start, progressing gradually and very regularly through the mass, as soon as the freezing point has been reached; the temperature should be carefully watched, very evenly lowered without any sudden depression. Once congealed, the temperature of the meats can be carried very low without detriment. CIRCULATION OF AIR IN MEAT ROOMS. The required circulation of air in the meat rooms is either produced by natural draft or (especially in Europe) by means of blowers or fans, which circulate air, cooled artificially. The cooling of air used for the latter purpose is generally done in a separate room in which the air is brought in contact with the surfaces of pipes which are refrigerated by direct ammonia expansion. The warmer air is continuously exhausted from the meat rooms by means of a blower, which forces it through the cooling apparatus and thence back to the meat rooms in a cold and dry condition. See also what has been said on ventilation, etc., in the chapter on cold storage. BONE STINK. As already stated, the freezing of meat must be done very carefully, in order to avoid any injury to the meat. Moro particularly the chilling and freezing must be done very gradually, for when the meat is plunged at once in a chamber below the freezing point, the external parts are frozen more quickly than the internal parts, and the latter are cut off by this external frozen and poorly con- ducting zone from receiving the same intensity of cold. The external frozen zone contracting on the internal portion causes many of the cells to be ruptured and the contents to escape, and on cutting into meat so frozen a pulpy consistency of the meat is found near the bones. This is particularly the case when whole carcasses are treated, but also parts of the animal show similar defects when frozen carelessly. The so called "bone stink," which shows itself as decaying marrow in the interior of the bones of many frozen meats, is also gen- erally due to the too hasty freezing. However, the con- dition of animal at the time of killing (exhaustion by a 216 MECHANICAL REFRIGERATION. long journey, injudicious feeding, excitement, delay in skinning, etc.) appears to favor the liability to bone stink. Hanging the animals too closely together after they are slaughtered and dressed is said to be a fruitful source of bone taint, for when they are throwing off the animal heat and gases contained in the bodies, if hung too closely together they will steam one another and prevent this animal heat and gas from getting away. The ab- sence of proper ventilation and an insufficient circulation of fresh air is also a likely cause, bearing in mind that what has to be aimed at is the driving away of this ani- mal heat and gas as it passes out of the carcass. While the temperature of the cooling chamber should be kept moderately low, it should not be too low; a free circula- tion being of far more importance than lowness of tem- perature during this early cooling or chilling process. Bone taint can be detected without actually cutting up a carcass, in the following way: A long wooden skewer is inserted at the point of the aitch bone; this passes the cup bone and enters the veins that divide the silver side from the top side, where, if any taint exists, it is sure to be found, the wooden skewer bringing out the taint upon it. For testing while in a frozen state a carpenter's brace and bit should be used. This must be inserted as above described. FREEZING MEAT FROM WITHIN. It has also been proposed to prevent the bone stink, etc., by freezing meat from the center by introducing into the same a pipe shaped like a hollow sword divided by a partition around which refrigerated brine or am- monia is permitted to circulate. DEFROSTING OF MEAT. The importance of doing the defrosting of meat with the same care as the freezing is well illustrated by a number of patents taken out for this operation. One of these processes subjects the meat to a continuous circu- lation of dry air formed by mixing cold air at a tempera- ture of 19 and dry air heated to 70, the combined cur- rent at about 26, increased to about 60, being forced through the thawing chamber by a fan. Time required for thawing, two to five days. This process is in use at Malta and Port Said. Another patent provides for the circulation ol air, REFRIGERATION FOR TACKING HOUSES. 217 dried by arrangement of pipes containing cooling me- dium, and suitably heated by steam pipes, passing over the meat by natural means, and, by gradually increasing temperature, abstracting the frost without depositing moisture. Time required for defrosting: Beef, four days; sheep, two days. Process has been in continuous use in London for two and one-half years; it is also used in Paris and in Malta for meat supplied to troops. MOLDY SPOTS ON MEAT. The white mold spots which sometimes form on meat in cold storage are due to the growth of a fungus (Oidium albicans) the germs of which are quite common in the air. For this reason the formation of this mold may be prevented by providing a circulation of air which has passed over the cooling pipes (St. Clair's system, described under "Cold Storage") , by which the moisture and mold germs are withdrawn from the air. KEEPING OF MEAT. Meat, if kept constantly at 31 in a properly venti- lated room from the time it has been slaughtered can be kept fresh at least six months, '~>ut if the temperature goes up at times as high as even only 33 the meat might not keep over a month; however, if the ventilation and humidity are properly regulated it should keep about two months in good condition in the latter case. Beef should be placed in cold storage within ten hours after killing. SHIPPING MEAT. Meat properly prepared may be kept at a tempera- ture between 32 and 35 F. for any length of time, but to insure against a break down of the refrigerating ma- chinery aboard the vessel, the meat is generally frozen be- fore it is loaded, thus providing. for a deposit of cold (100 tons of frozen meat being equivalent for refrigerating purposes to seventy tons of ice) that can be drawn on in case the machinery fails temporarily. REFRIGERATION FOR OTHER PURPOSES. From the data, rules and examples given under the heads of cold storage, packing house and brewery re- frigeration, and on refrigeration in general, it will be practicable to make the required approximate estimates for most of the other numerous applications of refrig- erating machinery. 218 MECHANICAL REFRIGERATION. REFRIGERATION IN OIL WORKS. In oil refineries artificial refrigeration has become indispensable for the purpose of separating the parafflne wax and refining the oil. Stearline, India rubber works, eto., can no longer be without artificial refrigeration. DAIRY REFRIGERATION. In the dairy practice, the cooling and freezing of milk, in butter making, etc., there is a great future for artificial refrigeration. Eefrigeration has also been patented for the special purpose of freezing the water out of milk in order to concentrate the same without heat. REFRIGERATION IN GLUE WORKS. Some glue manufacturers have found it to their in- terest to improve their product by drying their gelatine in rooms artificially refrigerated, thus permitting them to use glue solutions less concentrated. VARIOUS USES OF REFRIGERATION. Manufacturers of oleomargarine, of butterine, soap, chocolate, etc., derive great benefit from artificial refrig- eration. For seasoning lumber it is also employed to some extent already. Skating rinks, ice railways, etc., are kept in working order all the year now by artificial refrigeration. Young trees are kept in cold storage to hold back unseasonable and premature growth. The preservation of the eggs of the silkworm, so as to make the eclosion of the eggs coincide with the ma- turity of leaves of the mulberry tree has also become a subject of artificial refrigeration. Many transatlantic vessels are equipped with gigantic refrigerating apparatus to enable them to transport per- ishable goods, chiefly meat, but also fruits, beer, etc. In dynamite factories for maintaining the dynamite at a low temperature during the process of nitrating. In manufactories of photographic accessories, for cooling gelatine dry plates. In the establishments of wine growers and merchants for reducing the temperature of the must or un fer- mented wine, and for the obtainment of an equable tem- perature in the cellars, etc. Wool and woolen garments, as likewise furs and peltry, are preserved from the attacks of moths by artifi- cial refrigeration. BEFRICKERATION FOR PACKING HOtfSES. 2lO Beds in summer time may be cooled by pans filled with ice in the same way as they are warmed by warm icg pans in winter. This cooling of beds is said to pro- duce immediate sleep and rest, and is especially recom- mended in cases of insomnia and other afflictions. Decorative effects, quite novel and artistic, to adorn the dining table, etc., may be produced by freezing flow- ers, fishes, etc., tastefully grouped in clear crystal ice blocks of convenient shapes. For refrigeration of dwellings, hospitals, hotels, pub- lic institutions, etc.: This subject has been much written about, but in the practice of refrigerating dwellings and hotels during the hot season little progress has been made so far, many being of the opinion that it would be too expensive for general use. While this may be so, there is doubtless a great field open in this direction for the application of refrigeration in those cases in which expense is a second- ary consideration. The value of ice in therapeutics is generally recog- nized. From among the more recent applications in this direction may be mentioned the following : Ice is used for the induction of failing respiration by rubbing slowly the mucous membrane of the lips and mouth with a piece of ice to the rhythm of normal respiration. Ice is said to moderate inflammation of the brain or its membranes, and also the severe headache of the early stages of acute fevers, also to relieve the pain and vomit- ing in cases of ulcer or cancer of the stomach. It is also excellent for the sore throat of fevers, and in cases of diphtheria. Sucked in small pieces, it checks secretions of the throat. Ice also arrests hemorrhage in a measure. Artificial refrigeration is also very extensively used m the shipping of all sorts of produce, especially meat, eggs, etc., and the refrigerating installations in vessels crossing the ocean, and in railroad cars crossing the plains, are subjects of special study and detail which it would be beyond the scope of this book to enter into here. We may add, though, that the refrigeration during transit is not confined to railroad cars and steamboats, but that small delivery wagons for meat, eggs, etc., are now constructed with special reference to the keeping of their refrigerated contents until delivered to the con- sumer or retailer. 220 MECHANICAL REFRIGERATION-. In distilleries for keeping the spirits in the store tanks cool during hot weather, and thereby obviating the very serious loss that is otherwise experienced through evaporation. In chocolate and cocoa manufactories to enable the cooling room to be maintained at a low temperature in summer, and the process to be worked continuously all the year around. A great saving is likewise effected by the rapid solidification which is rendered possible, and the waste thus avoided; and furthermore, as the choco- late leaves the molds readily and intact, a considerably fewer number of the latter are required to do the same amount of work. In sugar factories and refineries for the concentra- tion of saccharine juices and solutions by freezing or congealing the water particles, which are then removed, leaving the residuum of a greater strength. In India rubber works for the curing and hardening of India rubber blocks, thereby facilitating the cutting of same into sheets for manufacture of various elastic articles. The material in that state admitting of its be- ing worked up in a much superior manner, and, more- over, at a far lower cost REFRIGERATION IN CHEMICAL WORKS. Some of the chemical industries in which artificial refrigeration is extensively used have been mentioned al- ready, and to these may be added ash works, asphalt and tar distilleries, nitroglycerine works, etc. In fact, all chemical operations which depend largely on differences in temperature, notably all those involving crystalliza- tion processes, can in most cases be greatly assisted by the use of artificial refrigeration. This is particularly true of substances which it is difficult to obtain in a pure state, and which do not pass into the solid state, except at very low temperature. To successfully purify such sub- stances and there are a great many of them artificial refrigeration is the most valuable auxiliary, and very re- markable results have been obtained already in this direc- tion. The most successful purification of glycerine is an instance of this kind. Chloroform is another still more re- markable example. This substance, although considered pure, was nevertheless of a very unstable character. Time, action of light, heat and other unavoidable conditions, REFRIGERATION FOR PACKING HOUSES. 221 caused its degeneration, until it was shown by Pictet that an absolutely pure article of chloroform could be obtained by crystallizing the same at a temperature of about 90. This is a very low temperature, considering practical possibilities of the present day, but it accomplishes the object; and there are many more equally useful applica- tions not yet thought of, or beyond the reach of practical refrigeration at present. CONCENTRATION OF SULPHURIC ACID. The concentration of sulphuric acid, which is accom- plished in expensive platinum vessels, can be accom- plished, according to Stahl, in leaden vessels, if artificial refrigeration is used to crystallize the strong acid, which can then be separated from the weak mother acid. Another interesting chemical change brought about by artificial refrigeration is the decomposition of the acid sulphate of soda into neutral salt and free sulphuric acid. DECOMPOSITION OF SALT CAKE. Another interesting application of refrigeration in chemical manufacturing is the decomposition of the so- called salt cake (acid sulphate of soda) into sulphuric acid and neutral sulphate of soda, which takes place when a watery solution of the said salt is subjected to a low temperature. PIPE LINE REFRIGERATION. In many cities refrigeration is furnished to hotels, butchers, restaurants, private houses, etc., by a pipe line which carries liquid ammonia; another pipe line return- ing the expanded ammonia to the central factory, at which a large supply of liquid ammonia is kept in store to regulate inequalities in the demand for refrigeration. REFRIGERATION AND ENGINEERING. When making excavations in loose soil, it has been found expedient to freeze the ground by artificial refrig- eration, and this artifice is now extensively applied in mining operations, in the sinking of bridge piers, in tun- neling through loose or wet soil, etc. One of the greatest pieces of engineering with the aid of refrigerating machinery was accomplished about two years ago in the opening of a coal mine in Anzin, France. The coal was over 1,500 feet below the surface, and below strata strongly saturated with water, and im- passable without artificial solidification. 222 MECHANICAL REFRIGERATION. CHAPTER IX. THE ABSORPTION SYSTEM. THE CYCLE OF OPERATIONS. As in the compression system of ammonia refrigera- tion, the operations performed in the absorption system constitute what has been termed a cycle of operations, the working medium, ammonia liquor, returning period- ically to its initial condition, at least theoretically so. A COMPOUND CYCLE. It is, however, not a reversible cycle, but rather two cycles merged into one, or a compound cycle. The anhy- drous ammonia after leaving the still at the top, passes through the analyzer, condenser, receiver and refrigera- tor to the absorber, where it meets the weak liquor com- ing through the heater and exchanger from the still, and t"ien after having been absorbed by the latter, passes as rich liquor from the absorber through the ammonia pump to the exchanger, and through the heater to the still, entering the latter by first passing through the analyzer, generally located at the top of the still. APPLICATION OF FIRST LAW TO CYCLE. Owing to the complexity of the operations of the double or compound cycle, its theoretical working condi- tions cannot be expressed by so simple a formula as in the case of a reversible cycle. Nevertheless, the tenets of the first law of thermodynamics apply in this case also, and therefore the heat and work which is imparted to the working substance while performing the operations of one period of the cycle must be equal or equivalent to the heat and work which are withdrawn during the same period all quantities to be expressed by the same kind of units. EQUATION OF ABSORPTION CYCLE. Hence, if W t is the heat imparted to the liquid in the still, and W 2 the heat imparted to the anhydrous ammonia in the refrigerator, and W 3 the heat equivalent of the work of ammonia pump, we find H t being the heat withdrawn from the anhydrous ammonia in the condenser, and H 2 being the heat with- drawn from the working substance in the absorber. THE ABSORPTION SYSTEM. 223 As all the quantities in the above equation (besides Wi) can be readily determined, it enables us to find, if not a simple at least an artless expression for W l (i. e., the heat which must be imparted to the liquid in the still). WORKING CONDITIONS OF SYSTEM. For the purpose of determining the theoretical values of the quantities which determine the efficiency of an absorption machine, we make the following stipulations which, we hold, are such as to be within the theoretical possibility of realization, although practically they have not as yet been fully realized, viz.: That the apparatus is provided with efficient analyzer and rectifier, so that the ammonia when entering the condenser is practically in an anhydrous condition. That the poor liquor when entering the absorber is only 5 warmer than the rich liquor when leaving the absorber. That all the heat of the poor liquor, except that brought into the absorber, is imparted to the rich liquor on its way to the still in the exchanger. That the uncompensated heat transfers from the at- mosphere to the colder portions of the plant, and from the warmer portions of the plant to the atmosphere, are so well guarded against that they may be neglected in this connection. HEAT ADDED IN REFRIGERATION. The above premises being granted, the different items of the above equation are readily expressed. The heat, W 2 , added to the working fluid in the expansion or re- frigerating coils, is theoretically equal to tbe amount of refrigeration which is produced by its evaporation. The refrigeration, r, in B. T. units which may be pro- duced by the vaporization of one pound of anhydrous ammonia in an absorption machine is the same as in a compression machine, and is therefore expressible by the same formula: r = h l (t t t }s units, hi being the heat of volatilization of one pound of am- monia at the temperature t n of the refrigerator; t is the temperature of the liquid anhydrous ammonia, i. e., the temperature of the condenser, and s the specific heat of ammonia. 224 MECHANICAL REFRIGERATION. For the purpose of this calculation the temperature of the outgoing condenser water may be taken for , but in order to find the maximum theoretical refrigerating effect, the temperature of the incoming condenser water, or rather, about 5 C added to that, should be taken for t, as the liquid anhydrous ammonia can be cooled to that degree by the condenser water. This also applies to the same calculation for compression system. HEAT INTRODUCED BY PUMP. The heat, W 3 , imparted to the working medium by the operation of the ammonia pump is equivalent to the work required to lift the rich liquor from the pressure of the absorber to that of the still. It is not a very im- portant quantity in this connection, and may be neglected in approximate calculations. However, it may be de- termined by the formula: for each pound of anhydrous ammonia which is volatil- ized in the expander. In this formula P 2 stands for the number of pounds of rich liquor which must be moved for every pound of ammonia volatilized in the expander; and z and z^ being in feet the heights of columns of water corresponding to the pressure in the still and pressure in absorber, respectively. S represents the specific grav- ity of the rich liquor, and 772 the equivalent of the heat unit in foot-pounds. In exact calculations the heat due to friction of pumps should be added. RICH LIQUOR TO BE CIRCULATED. The number of pounds of rich liquor, P 2 , which must pass the ammonia pumps in order that one pound of liquid anhydrous ammonia may be disposable in the ex- pander or refrigerator coils, depends on the concentra- tion or strength of the poor and rich ammonia liquor, and if the percentage strength of the former be a, and that of the latter be c, we find P 100 _ (100-a) 100 ]b (100 c) a (100 a) c (100 c) a c ~~ (100 a) THE ABSORPTION SYSTEM. 225 STRENGTH OF AMMONIA LIQUOR. The percentage strength of the rich liquor depends largely on the construction of the absorber. Theoretically it is determined by the temperature at which it leaves the absorber and the pressure in the latter as shown in the tables on solutions of ammonia given by Starr, pages 96 and 97. The lowest possible percentage strength of the poor liquor depends in a similar manner on the temperature and pressure in the still, but is also greatly affected by the constructive detail and operation of this appliance. HEAT REMOVED IN CONDENSER. The amount of heat, H^ which is taken away from the working substance in the condenser, while one pound of vapor is condensed into liquid ammonia, is equal to the latent heat of volatilization of that amount of ammonia at the temperature of the condenser (temperature of out- going condenser water), and may be readily obtained from the table on saturated ammonia, page 92. HEAT REMOVED IN ABSORBER. The amount of H 2 which must be withdrawn from the working liquid in the absorber is composed of differ- ent parts, viz.: The heat developed by the absorption of one pound of ammonia in the poor liquor, H n . The heat brought into the absorber by a correspond- ing quantity of poor liquor, H g . The negative heat brought into the absorber by one pound of the refrigerated ammonia vapor, H y . Hence we find H 2 = H n -^-H g ~ Hv units. HEAT OF ABSORPTION. The heat developed by the absorption of ammonia vapor in the poor liquor may be obtained after the form- ula given, pages 99 and 100, viz.: = - - ~ pounds. OF THE **A UNIVERSITY } 228 MECHANICAL REFRIGERATION. HORSE POWER OF AMMONIA PUMP. The power, F tt to run the ammonia pump while pro- ducing a refrigerating effect of m tons in twenty-four hours, is, therefore and expressed in horse power F 2 , S being taken equal to 1: F - -PXmX 384000 X(g- gi * 2 ~ rx 33000X24X60 33,000 being the equivalent of a horse power in foot- pounds per minute. The formula for F 2 may be simplified to _ P 2 X m(z z l ) 0.006, F 2 = - - horse power. This is the horse power required theoretically, to which must be added the friction, clearance and other losses of the pump, as well as of the engine which ope- rates the pump, to find the actual power and the equiva- lent amount of steam required for this purpose. AMOUNT OF CONDENSING WATER. The water required in the condenser expressed in gallons, Gr, for a refrigerating capacity of m tons in twenty -four hours is /H X m X 284000 or approximately per minute in gallons, G t in which formula h t is the latent heat of volatilization of ammonia at the temperature of the outgoing con- denser water, t, and t t the temperature of the outgoing condenser water; r is the refrigerating effect of one pound of ammonia. WATER REQUIRED IN ABSORBER. The amount of heat to be removed in absorber for each pound of ammonia vaporized in refrigerator being Ifj, as found in the foregoing, the amount of water re- THE ABSORPTION SYSTEM. 229 quired iii absorber for a refrigerating capacity of m tons in twenty-four hours, expressed in gallons, G 2 , is . H 2 X m X 284000 or expressed per minute in gallons, Gr 8 ^ _H 2 XWX24 r(t-t t ) ECONOMIZING WATER. When water is scarce or expensive, the same water after it has been used in condenser is used in the absorber, which, of course, raises the temperature of the ingoing and outgoing absorber water correspondingly. The water may also be economized by using open air con- densers or by re- cooling the same by gradation, etc. ECONOMIZING STEAM. As the poor liquor is less in volume and weight than the rich liquor, it cannot possibly heat the latter to the temperature of still, other reasons notwithstanding. For this reason the waste steam of the ammonia pump may be used to still further heat the rich liquor on its way to the generator after it has left the exchanger. This is done in the heater, and the heat so imparted to the work- ing fluid should be deducted from the heat to be fur- nished to the generator direct in theoretical estimates. The condensed steam from generator may be returned to boiler if it is not used for ice making. AMOUNT OF STEAM REQUIRED. The theoretical amount of steam required in gener- ator expressed in pounds P 5 per hour for a refrigerating capacity of m tons in twenty-four hours is approximately found after the formula Wi X m X 284000 24 X r X h a h 8 being the latent heat of steam at the pressure of the boiler, or, closer still, at the temperature of the generator. As stated in the beginning, these calculations are based on ideal conditions, which are never met with in practical working, and therefore the quantities found must be modified accordingly, and the theoretical amount of steam as found must be increased by from 20 to 40 per cent, and even more, to arrive at the facts jp most practical cases, 230 MECHANICAL REFRIGERATION. The amount of steam used by the ammonia pump must be added to the above: It is generally about to | of the steam used in the generator. ACTUAL AND THEORETICAL CAPACITY. In order to compare the actual refrigerating capacity of an absorption plant with the theoretical capacity, the amount of steam used in the still, as well as the amount of rich liquor circulated by the ammonia pump, may be taken as a basis. The first case is practically disposed of in the foregoing. In the latter case the amount of liquid moved by the ammonia pump is equal to its capacity per minute, which is found by calculation, as in the case of a compressor, and reduced to pounds per minute. If this quantity is called O, and if P 2 is the number of pounds of rich liquor which must be circulated for each pound of active anhydrous ammonia, as found from the strength of the poor and rich liquor (see foregoing table), the refrig- erating capacity of the machine, -K, should be R= -73 units per minute. * z The theoretical and actual heat balances can also be compared by determining the heat removed in the con- denser and absorber, as well as the heat brought into the refrigerator and to the generator by actual measurement. SIMPLER EXPRESSION FOR W x . If we neglect the work of the liquor pump and assume that the poor liquor arrives at the absorber at the absorber temperature, we can express the amount of heat W^ theoretically required in the generator for each pound of anhydrous ammonia circulated by the formula W t = Hn (h z h) units, h 2 being the latent heat of volatilization of ammonia at the temperature of the absorber, and h t the latent heat of volatilization of ammonia at the. temperature of the condenser. It is frequently argued that an equivalent of the whole heat of absorption must be furnished to the gen- erator, but this is only the case (theoretically speaking) when the temperature of the absorber is equal to Unit of the condenser, THE ABSORPTION SYSTEM. 231 EXPRESSION FOR EFFICIENCY. The maximum theoretical efficiency J5?, of an absorp- tion machine may be expressed in accordance with the above. r fr t -(t-*t)* * and if we include the work of the ammonia pumps, etc., we have also COMPARABLE EFFICIENCY OF COMPRESSOR. In order to compare the maximum theoretical effi- ciency of an absorption plant with that of a compression plant the foregoing formula: may be used, when in the case of compression W t stands for the amount of heat theoretically necessary to produce the work required from the engine for the circulation of one pound of ammonia. If the absolute temperature of steam entering the engine is T, and that of the steam leaving the engine is T 1 , and if the work of the engine which operates the com- pressor is expressed by Q t (in heat units), we find for W^ the expression If we omit friction of compressor and engine and in- sert for Qi the theoretical work of the compressor (page 111) we find Qi (r-rjhi r and r t being the absolute temperatures of condenser and refrigeration respectively. It is then u , hi(r rJT and for the maximum theoretical efficiency of the com- pression machine, leaving out friction, etc., we find 232 MECHANICAL REFRIGERATION. CONSTRUCTION OF MACHINE. The construction details of the absorption plants vary so much that in this place we can only give the general outlines touching the appliances and contriv- ances which by a concert of action make up the refrig- erating effect. The dimensions of parts vary also very greatly, and those given in the following paragraphs and tables are based on data reported from machines in actual operation where not otherwise stated. THE GENERATOR. The generator, retort or still is generally an upright cylinder heated with a steam coil in which the concen- trated or rich liquor is heated. The rich liquor passes in at the top and leaves at the bottom. The retort and dome is made of steel plate, sometimes of cast iron; and this vessel, the same as other parts containing ammonia gas, should be capable of withstanding a liquid pressure of 400 pounds per square inch. SIZE OF GENERATOR. The size of the still or generator depends on the size of the machine, and for a 10-ton machine (actual ice making capacity) is about two to two and one-half feet wide and fifteen to eighteen feet high, and a little over half of this height is generally occupied by the steam coil. An English author gives the following table of di- mensions for generators or stills of absorption machines, but they appear rather small compared with American structures for the same object : Ice Made in Gallons of .880 SIZE OF GENERATOR. 24 Hours. Ammonia. Diameter. Length. 1 27 13. 5 inches. 5 feet 6 inches. . 2 54 17.0 6 " 3 80 21.5 6 " 4 108 22.5 6 " 6 6 162 22.5 10 " 6 8 216 25.0 12 " 10 252 26.0 12 " 12 270 28.0 13 " 15 405 29.5 14 " 24 540 35.0 14 " BATTERY GENERATOR. Generators have also been constructed on the battery plan, three or more cylinders being connected td form one generator, the rich liquor passing gradually from the first cylinder to the last, which it leaves as poor liquor. In this manner it is possible to attain a wider THE ABSORPTION SYSTEM. 233 difference between the strength of the rich and poor liquor, it is claimed. COILS IN RETORT. The heating coils in retort or still are placed in the lower part ,of the retort, and consist of one or more spiral coils of pipe placed concentrically. According to Coppet, their connections should be at both the bottom entrance and exit, and should be made right and left handed, the object being to prevent the steam (when rushing down in the coils) from imparting a gyrating motion to the liquor, thus shaking the retort. The coils should be made of purest charcoal iron, free from defects or spots, as the hot ammonia liquor is very apt to pene- trate such bad places and cause leaks. The space in still occupied by steam coil should always contain ammonia liquor, so that the coil is never exposed to the vapors. For this reason a gauge is provided, which shows the height of the liquor in the generator. As a further pre- caution there is placed above the steam coils an in- verted cone, with a large central opening, placed so that the liquor will be deflected to the center of still, and not fall upon the coils, if ever the liquor should stand below them. A valve is provided at the bottom of the retort to empty same, if necessary, and also one at the poor liquor pipe leading to exchanger. The heating surface of the coil in retort varies considerably, and for aJLO-ton ma- chine it covers from eighty to 100 feet. THE ANALYZER. In the upper part of the still the so called analyzer is located. In it the rich liquor is made to pass over numerous shelves or disks into corresponding basins, over which it runs in a trickling shower from one disk through the next basin over the following disk, and so on, until it reaches the top of the boiling liquid in retort. While the rich liquor runs downward over these devices, the vapor from the retort passes them in its upward course and constantly meeting the rich liquid over an extended area, is enriched in ammonia, and deprived of water. Thus the ammonia vapor is rendered almost free of water when it reaches the top of the analyzer. At the same time the temperature of the rich ammonia liquor is increased from about 150 to 170, at which it reaches the analyzer, to about 20CP, more or less, when it reaches the body of liquor in the retort. 234 MECHANICAL REFRIGERATION". The passages in the analyzer must be amply large for the passage of water and ammonia vapor in opposite directions In order to avoid foaming, overloading, etc. The best iron or steel plate must be used in the construc- tion of the analyzer. As also stated elsewhere, galvan- ized iron pipes and zinc surfaces in general must be avoided wherever they come in contact with ammonia. The surface in the analyzer runs from fifty to seventy square feet in a 10-ton machine. THE RECTIFIER. Frequently the vapor on its way from analyzer to condenser passes the so called rectifier, which is a small coil partly surrounded by cooling water, the lower end of which is connected with the condenser coil, but has also a liquid outlet to a separate liquor receiver which receives all watery condensation which may have formed in the rectifier. In this manner the vapors, when they enter the condenser proper, are as nearly anhydrous as they can practically be made. About twenty-five square feet of cooling surface is allowed in the rectifier for a machine of ten tons ice making capacity. The liquid separated from the vapor in the rectifier, after passing through a separate cooler, is returned to the ammonia pump, whence it passes back to the generator or still. The following table, giving the heating surfaces of generator coils and surface in analyzer and rectifier for machines of different ^sizes, is also given on English authority, and these figures also fall short of the sizes employed in the United States : Size In Tons of Ice Made in 24 Hours. Surface in Gene- rator Coils. Surface in An- alyzer Disks. Surface in Rectifier Coil. Tons Square Feet. Square Feet. Square Feet. 2 6 12 15 30 50 16 43 81 160 214 304 14 34 68 133 169 262 4 11 20 40 50 74 THE CONDENSER. The vapor after leaving the still or rectifier enters the condenser which is constructed on the same principles as the condenser in a compression machine. Besides the submerged condenser and the open air or atmospheric condenser (the latter, on account of accessibility, simplic- THE ABSORPTION SYSTEM. 235 ity and cleansability, now most generally adopted) it has also been proposed to use condensers exposed to the at- mosphere alone, thus to save the cooling water. Such condenser requires a considerable surface, at least over eight times that of the submerged condenser, and over five times that of the atmospheric condenser. The ma- terial for condenser coils, as well as for all other coils in the absorption machine, should be the very best iron. Still another form of condenser consists of one pipe within another, in which the water surrounds the out- side pipe and also runs through the internal pipe, while the gas passes through the annular space between the two pipes. This is a very effective form of condenser, but the difficulty of keeping it clean is very great, and it is almost impossible when the water is liable to leave a deposit. For sizes of condenser coils the same subject under compression machines should be referred to, also the subsequent table on general dimensions. LIQUID RECEIVER, ETC. The vapors after having passed the condenser, reach the receiver in a liquid form and thence pass through the expansion valve to the coils in freezing or brine tank. These parts of the plant, their construction and the mode of operating them are quite the same as in case of the com- pression plant. The liquid receiver for an absorption ma- chine should be at least large enough for the storage of sufficient liquid ammonia to bring the poor liquor at the bottom of the retort to between 18 and 20 Reaumur when the machine is in operation. THE ABSORBER. In the absorber the vapor of ammonia, after having done its duty in the freezing tank or expansion coils, meets the poor liquor coming from the generator, and is reab- sorbed by the latter. The absorber should be constructed in such a manner as to allow the ammonia solution as it gets stronger to meet the cooling water flowing in an opposite direction, so that the warmer water cools the weaker solution and the colder water cools the stronger solution . In compliance with this condition the vapors of ammonia should be in constant contact with the liquor, and the surface of contact ought to be of reasonable area. This may be accomplished by passing the ammonia and weak liquor over traps or disks, similar to those 236 MECHANICAL REFRIGERATION. in the analyzer, or through a series of pipes or coils, where they are in constant contact with each other, the pipes being efficiently cooled from the outside by water (spent water from condenser generally), in order to remove the heat of solution of the ammonia as fast as it is formed. Generally the ammonia gas and the poor liquor are mixed together into a manifold at the lower end of the coils. The surface of these pipes exposed to the cooling water in a tank in which they are submerged (atmospheric cooling, as in the case of atmospheric con- densers, may also be used), is variously estimated at 300 to 500 square feet for a machine of ten tons ice making capacity. THE EXCHANGER. In the exchanger the heat which the poor liquor carries away from the still should be imparted to the rich liquor on its way to the still. As a matter of course the two liquids should flow in opposite directions, so that the hottest rich liquid meets the poor liquid when it is hottest, and the cold poor liquid meets the rich liquid when it is coldest. The exchanger is also to be made of the best sheet steel, and the coils within should be extra heavy, and the whole apparatus must be able to sustain the same pressure as the retort. It should stand upright, and the liquor pump should force the rich liquor through these coils to the top of the retort or to the heater, and the poor liquor should pass in the opposite direction. In causing the liquors to take this course the pressure in the body of the exchanger can be regulated by the valve on the poor liquor pipe coming from the retort. The amount of surface between the poor and rich liquor in exchanger varies according to its construction, all the way from twenty-five to fifty square feet for a 10- ton plant (ice making capacity). This statement covers those plants of which we have knowledge. According to Starr, who assumes the heat transfer to amount to 40 B. T. units per square foot surface per hour, for each degree Fahrenheit difference in temperature, about 120 square feet of exchanging surface would be required for an ice making plant of ten tons daily capacity. THE HEATER. The heater is another contrivance frequently used to further the objects of the exchanger. It consists of a coil THE ABSORPTION SYSTEM. 237 of pipe through which the rich liquor passes from the exchanger before it reaches the retort. This pipe is located in a drum in which steam (generally spent steam from liquor pump) is circulated. It is constructed on the same principles as the other receptacles and coils. The surface of the heater coil is about thirty to fifty square feet in a 10-ton ice making plant. THE COOLER. The cooler is an arrangement frequently used to do for the poor liquor what the heater does for the rich liquor, i. e., to promote the objects of the exchanger by withdrawing all the heat possible from the poor liquor before it reaches the absorber. This contrivance is built on the same principles as a condenser, and consists of a coil or series of coils, submerged in a tank through which cooling water circulates, or placed over a vat to allow the cooling water to trickle over them, similar to an atmospheric condenser. The surface of the cooler may be from sixty to eighty feet for a 10- ton ice making ma- chine, and larger or smaller for different capacities, as the case may be. THE AMMONIA PUMP. The ammonia pump, which takes up the rich liquor from absorber to force it through the exchanger and heater to the generator, is generally a steam pump, the en- gine and pump cylinder being mounted on a common base. A pump driven by belt may also be used. The size and number of strokes of pump depend on the size of plant, but also largely on the strength of poor and rich liquor. (See table, page 139.) For a 10-ton plant (ice making capacity) the pump has generally a diameter of three inches, the stroke being from six to ten inches and the number of strokes from twenty-five to fifty per minute. The ammonia pump is generally single-acting, in order to relieve the pressure on stuffing box, which latter fixture requires particular care in order to secure proper working of the pump. MISCELLANEOUS ATTACHMENTS. Like the condenser, the refrigerator, expansion coils, as also the brine tank (and brine pump) or the freez- ing tank, are constructed on the same lines in an absorp- tion as in a compression plant, and therefore need no fur- ther mention here. The same may be said of the expan- 238 MECHANICAL REFRIGERATION. sion valve, and of other valves required when desirable to shut off certain portions of the machine, of the required pressure gauges, thermometers and other attachments. In the use of the absorption plant for various purposes the same rules apply as in the use of a compression ma- chine. As the spent steam from the generator is used for distilled water, and as the same cannot be contam- inated with lubricating oil, the steam filter or oil sepa- rator is superfluous if the boiler feed water is of ordinary purity. OVERHAULING PLANT. In order to keep an absorption plant in the best possible order for the longest possible time it is neces- sary that the different parts be opened and overhauled from time to time (according to the water used and as other conditions may indicate) every alternate season or so in order to thoroughly clean and inspect the interior part, and to repair them in order to anticipate any pos- sible breakdowns, etc. In all cases, before starting up to open a new season, the coils and traps should be tested. COMPRESSION VERSUS ABSORPTION. The question is frequently asked as to which kind of refrigerating plant a compression or absorption plant- is the most profitable and the most economical; and many different answers are given to these questions. Dif- ferent as the two kinds of machines look at first sight, the theoretical principles as well as defects are the same, as has been already explained, although the natural facilities, as relative price of coal and cooling water, etc., may be more favorable in certain localities for one class of machines than for another. Taking this into due con- sideration, . the principal difference between the two machines in a given case must be sought in the more or less greater care and perfection with which they are built and operated, more particularly also in the quality, quantity and proper distribution of material, the work- manship and the life of the plant, considering also the kind of water and ammonia to be used. When it is considered how difficult it is to give due regard to all these circumstances in the valuation or planning of an individual plant, the apparently conflict- ing results of different kinds of plants working in differ- ent localities and conditions, and the different opinions on them are explained in a great measure. THE ABSORPTION SYSTEM. TABULATED DIMENSIONS, ETC. 239 The great variations in the dimensions of the various parts of absorption machines of different makes find expression in the following table, which purports to give the dimensions, capacity, etc., of different machines. For the correctness of these figures we are unable to vouch, as the manner in which we obtained them does not exclude clerical errors, hence we must -submit them for what they are worth: TABLE SHOWING DIMENSIONS, ETC., OF ABSORPTION MACHINES. Actual Ice making capacity in tons of ice 3 8 12 15 25 10 Number and size of steam boiler horse power or dimen- sions Pounds of coal used 15 65 30 140 40"x20' 135 50 220 J2 42" 1 x21 l / 2 ' 504 12 42" fxlO' 168-180 Number and size of 30"xlO' 30"xl6' 24"xl8' 44"xl4' J2 30" 28"xl5' Size of coil in gener- ator in square feet Surf ace of disks, etc., in analyzer in 24 10 48 20 91 64 96 34 1 xll l A' 400 125 80 24 Cooling surface in exchanger in square feet Cooling surface of traps in absorber in 34 130 51 260 22* 191 68 470 65 1900 25 673 Cooling surface in condenser in square f eet 345 690 220 1380 1220 544 Surface in expander or refrigerator in square feet Cooling surface in rectifier in square f QQ^i 410 1200 726 25 2100 4000 1600 Cooling surface in 41 Temperature of water in degrees F. Temperature of brine in degrees F. 70 10-20 70 10-20 80 10-12 70 10-20 76 7 80-94 10-14 From the foregoing table it appears that in absorp- tion machine one pound of coal will make from four to seven pounds of ice. On the continent it is assumed that one pound of coal will make about ten pounds of ice in an absorption machine ; the evaporative power of the coal being taken at eight pounds of water per pound of 240 MECHANICAL REFRIGERATION. CHAPTER X. THE CARBONIC ACID MACHINE. GENERAL CONSIDERATIONS. Among the refrigerating machines which use other refrigerating media than ammonia, those compression machines using carbonic acid have found favor for many specific purposes, especially so for the refrigeration of storage rooms in hotels and restaurants, where the im- peccability of the gas to victuals is prominently valued. The non-corroding action of carbonic acid on any of the metals, and the fact that it cannot be decomposed dur- ing compression, etc., speak principally in favor of its use. The fact that a leak of carbonic acid is not demon- strated by its smell might be overcome by the addition of some odoriferous substance. The capacity of the compressor may be very small as compared with other refrigerating plants (see page 89), but the parts of the machine must also be made correspondingly stronger on account of the high pressure of the gas. The cheapness of liquefied carbonic acid is also quoted in its favor as a refrigerating agent, as also its lesser dan- ger to respiration in case of leaks. It is claimed that air containing 8 per cent of carbonic acid gas can be inhaled without danger, while an atmosphere containing only K per cent of ammonia is said to be decidedly dangerous. On the other hand, the presence of the least amount of ammonia in the air demonstrates itself by the smell, while this is not the case with carbonic acid. Not only the neutrality of carbonic acid toward metals and packings, but also toward water, meat, beer and other products subjected to cold storage, should be mentioned in this connection. The use of carbonic acid in refrigerating machines of the compression type has been somewhat stimulated by the cheap manufacture of liquid carbonic acid as a by-product of the brewing industry, especially in Ger- many, where over 400 such machines (1894) are said to be working satisfactorily. PROPERTIES OF CARBONIC ACID. The carbonic acid, which is a gas of 1.529 specific gravity (air = 1) at the atmospheric pressure, becomes liquid at a temperature of 124 F. at that pressure. At 32 F. it is liquid under a pressure of 36 atmospheres, and then has a specific weight of 0.93 (water= 1). The specific weight of the liquid at different temperatures, according THE CAT5BONIC ACID MACHINE. 241 to Mitchel, is at 32 F. = 0.93, at 42 F. = 0.8825, at 47.30 F.,= o.853, at 65.3 F.= 0.7385, and at 86 F.=0.60. The specific heat of carbonic acid gas by weight = 0.2167 (air = 0.2375). Of the liquid it is 1 . . The author's attention has been called to the appar- ent inconsistency existing between the specific gravity of liquid carbonic acid, as given in the foregoing para- graph (0.6 at 86 F.), and the amount of carbonic acid contained in the cylinders in which the same is shipped. The cylinders have a capacity of 805 cubic inches (29.11 pounds of water) and are made to contain 20 pounds of liquid carbonic acid, and some manufacturers are said to crowd in 21 and 22 pounds, although this is doubtless a very risky proceeding. But even at 20 pounds the cyl- inders contain over 2> pounds more (at 86 F.) than what is consistent with the above specific gravity. The fact that the drums do not burst with such a charge tends to show that the foregoing specific gravity is not correct (too low) or that different densities exist for different pressures at or near the temperatures charac- terizing the critical condition of carbonic acid (88 F.)- PROPERTIES OF SATURATED CARBONIC ACID GAS. Transformed to English units from a metric table computed by Prof. Schroter, by Denton and Jacobus. Tem- pera- ture of ebulli- tion in deg. F. Abso- lute press- ure in Ibs. per sq. in. Total heat reck'n'd from 32 Fahr. Heat of liquid reck'n'd from 32 Fahr. Latent heat of evapo- ration. Heat equiv- alent of ex- ternal work. Incr'se of vol- ume during evapo- ration. Dens' y of va- por or weight of one cu. ft. t P-M44 y q r APit u 22 210 98.35 37.80 136.15 16.20 .4138 2.321 -13 249 99.14 32.51 131.65 16.04 .3459 2.759 - 4 292 99.88 26.91 126.79 15.80 .2901 3.265 5 342 100.58 -20.92 121.50 15.50 2438 3.853 14 396 101.21 14.49 115.70 15.08 .2042 4.535 23 457 101.81 7.56 109.37 14.58 .1711 5.331 32 525 102.35 0.00 102.35 13.93 .1426 6.265 41 599 102.84 8.32 94.52 13.14 .1177 7.374 50 680 103.24 17.60 85.64 12.15 .0960 8.708 59 768 103.59 28.22 75.37 10.91 .0763 10.356 68 864 103.84 40.86 62.98 9.29 .0577 12.480 77 968 103.95 57.06 46.89 7.06 .0391 15.475 86 1,080 103.72 84.44 19.28 2.95 .0147 21.519 A, in the column heading, stands for the reciprocal of the mech- anical equivalent of heat. The preceding table, showing the properties of satur- ated carbonic acid, may be used in connection with the formulae given in the chapter on the ammonia compres- 242 MECHANICAL REFRIGERATION. sion system. However, the results obtained in this man- ner are only approximations, since the carbonic acid is in a superheated condition during several stages of the cycle constituting the refrigerating process, as a reference to the practical data, given hereafter, will amply show. CONSTRUCTION OF PLANT. The refrigerating plants operated with carbonic acid are built on the same general plan as the ammonia com- pression plants, compressor, condenser and refrigerator being the identical important parts, specified as follows by a leading manufacturer: THE COMPRESSOR. The compressor is either of the horizontal or the ver- tical type (for smaller machines generally the latter). It should be made of the best material, steel or semi-steel, and it is provided with a jacket through which the return gas passes, which arrangement gives additional strength to the cylinder and tends to keep it cool. The piston rods, connecting rods, crank pins and valves should be made of forged steel, and so as to be interchangeable at any time. STUFFING BOX. The stuffing box is made gas tight by means of cupped leathers on the compressor rod. Glycerine is forced into the spaces between these leathers at a pressure superior to the suction pressure in the compressor, so that what- ever leakage takes place at the stuffing box is a leakage of glycerine either into the compressor or out into the atmosphere, and not a leakage of gas. What little leakage of glycerine takes place into the compressor is advantageous, inasmuch as it in the first place lubricates the compressor, and in the second place fills up all clearances, thereby increasing the efficiency of the compressor. In order to replace the glycerine which leaks out of the stuffing box of the horizontal machine, there is a belt driven pump which operates continuously. The smaller machines are fitted with a hand pump, a few strokes of which are required to be made every four or five hours. GLYCERINE TRAP. Any glycerine which passes into the compressor be- yond what is necessary to fill the clearance spaces is dis- charged with the gas through the delivery valves. In order to prevent this going into the system, all the liquid THE CAHBONIC ACID MACHINE. 243 passes through a trap in which the glycerine drains to the bottom, whence it is drawn off from time to time. It may be remarked here that the glycerine has no affinity for carbonic anhydride, hence it undergoes no change in the machine, and therefore there is no chance of the condenser coils becoming clogged. CONDENSER. The condenser consists of coils of wrought iron extra heavy pipes, which are either placed in a tank and sur- rounded by water, or are so arranged that water trickles over them, forming the well known atmospheric con- denser. The coils are welded together into such length as to avoid any joints inside the tank, where they would be inaccessible. In connection with the condensers, where sea water only is available for condensing purposes, one very im- portant advantage of carbonic anhydride machines is claimed: As carbonic anhydride has no chemical action on copper, this metal is used in the construction of the coils, giving same longer life. EVAPORATOR. The evaporator consists of coils of wrought iron extra heavy pipe, welded into long lengths, inside which the carbonic anhydride evaporates. The heat required for evaporation is usually obtained either from brine sur- rounding the pipes, as in cases where brine is used as the cooling medium, or else from air surrounding the pipes, as in cases where air is required to be cooled direct. Between the condenser and evaporator there is a regulating or so called expansion valve for adjusting the quantity of the liquid carbonic anhydride passing from the condenser. SAFETY VALVE. In order to enable the compressor to be opened up for examination of valves and piston without loss of carbonic anhydride, it is necessary to fit a stop valve on the suction and delivery sides so as to confine the carbonic anhydride to the condenser and evaporator. It is, of course, pos- sible for a careless attendant to start the machine again without opening the delivery valve, and in such cases an excessive pressure would be created in the delivery pipe, from which there would be no outlet. To provide aga inst this danger a safety device is adopted, consisting of a housing, at the base of which is a thin disk, which is 244 MECHANICAL REFRIGERATION. designed to blow off at a pressure considerably below that to which the machines are tested. JOINTS. All joints should be made with special flange unions and brass bushings. They should be made absolutely tight with packing rings of vulcanized fiber, which with- stand the heat and still have the necessary elasticity to insure the joint being perfectly tight when either hot or cold. STRENGTH AND SAFETY. The working pressure varies from about fifty to seventy atmospheres. Owing to the very small diameter of all parts, even in large machines, there is no difficulty in securing a very ample margin of strength. All parts of the machine subject to the pressure of the carbonic anhydride should be tested at three times the working pressure. APPLICATION OF MACHINE. Both the direct expansion and the brine system are used in connection^ with a carbonic acid refrigerating machine, but for most purposes the former is deemed preferable, as is also the case with ammonia compression. For ice making the can or plate system may be used, and also for other refrigerating purposes the application of the carbonic acid refrigerating plant is quite similar to that of any other compression or absorption plant. A plant quite similar, or rather identical in its main feature with a carbonic acid refrigerating plant is also used for the manufacture of liquefied carbonic acid, as it may be obtained from breweries, distilleries, calcination of lime and other sources. EFFICIENCY OF SYSTEM. The efficiency of the carbonic acid machine is some- what lessened by the high specific heat of the liquid, and therefore decreases with greater divergence of tem- perature. It has been proposed to reduce this loss in efficiency by introducing a motor between the condenser and refrigerator, which would perfect the cycle of opera- tions. After another method, the loss of efficiency due to the specific heat of liquid is reduced by allowing the liquid during its flow to expand from the condenser pressure to an intermediate pressure, and to return the vapors so produced after having cooled the remaining liquid to tie condenser by an auxiliary compressor, THE CARBONIC ACID MACHINE. 245 It has frequently been argued that carbonic acid compression machines could not be operated successfully when the temperature of the condenser water exceeds 88 F., the critical temperature of carbonic acid. Accord- ing to the present conception of the critical condition, above the said temperature carbonic acid can only exist in the gaseous form, and cannot be converted into a liquid by means of the withdrawal of the latent heat of volatilization. This being the case, the refriger- ating effect of a carbonic acid machine working with condenser water above 88 F. would only be that of a compressed gas while expanding against resistance, which would be comparatively small when compared with refrigerating effect produced by the volatilization of the liquefied medium. These considerations and argu- ments are, however, in direct conflict with the statements of Windhausen, according to which carbonic acid ma- chines operated with condensing water of 90 to 94 F. and in tropical countries produce refrigerating effects ten times larger than what they would be if the carbonic acid acted simply as a compressed gas at such tempera- tures. Experiments cited by Linde show that a carbonic acid machine working with a temperature of 92 F. at the expansion valve gives a refrigerating effect about 50 per cent less than when the temperature at the expan- sion valve was 53 F. CAUSE OF APPARENT INCONSISTENCIES. The foregoing and other apparent inconsistencies be- tween the theory and practice of the working of the car- bonic acid refrigerating plant have recently been fully ex- plained on the basis that the carbonic acid is in the state of a superheated gas in the compression stage; in fact, it must be so if the condensing gas reaches a tempera- ture over 80, in order to produce refrigerating effects at all. The loss due to the absence of an expansion cylinder (completing a perfect reversible cycle) to reduce the tem- perature of the liquefied carbonic anhydride from the temperature of the condenser to that of the refrigerator, which constitutes the chief difference in the economy between ammonia and carbonic acid refrigerating ma- chines, has ajso been somewhat overestimated in dero- gation of the carbonic acid machine as shown by Mollier 246 MECHANICAL REFRIGERATION. COMPARISONS OF EFFICIENCY. The calculation on the former basis (specific heat times weight of ciirbonic acid circulated is unit of time) gave this loss as about 0.80 per cent of the whole theoretical refrigerating effect for every degree difference between the temperature of the condenser and that of the refrig- erator, as compared with 0.18 per cent loss in the case of ammonia. The accompanying table was calculated and published by Ewing several months ago, showing the relation between the ammonia and carbonic acid refrig- erating plant with reference to the loss due to cooling of the liquid. In this table the upper limit of temperature in the condenser, or rather immediately before the ex- pansion valve, is taken at 68 F., while the temperature in the refrigerator varies from 50 to 4 F. THEORETICAL CO-EFFICIENT OF PERFORMANCE IN VA- POR COMPRESSION MACHINES, UNDER WET COMPRES- SION, UPPER LIMIT OF TEMPERATURE BEING 68 F. Lower Limit of Temperature, Deg. F. Theoretical Co-efficient of Performance. Co-efficient of Performance in Oarnot Cycle. Ammonia. Carbonic Acid. 50 40 32 33 14 4 27.8 18.1 13.2 10.2 8.3 6.9 25.7 20. 11.4 8.5 6.8 4.5 28.3 18.5 13.6 10.7 8.8 6.3 It will be noticed that with ammonia the theoretical performance namely, that of a compression machine without an expansion cylinder is only a little less than the ideal performance which would be obtained by fol- lowing Carnot's cycle. Hence with this substance al- most nothing would be gained by adding an expansion cylinder to the machine nothing, certainly, that would in any way compensate for the increase of complexity and friction and cost which an expansion cylinder would involve. With carbonic acid there is considerably more falling away from the ideal of Carnot, for the reason that the specific neat of the liquid bears a greater proportion to the latent heat of the. vapor. But even then the saving in work which an expansion cylinder would bring about is not great, and in practice the expansion cylinder, even in carbonic acid machines, is never used so far. THE CARBONIC ACID MACHINE. 24" PRACTICAL COMPARATIVE TESTS. Quite a number of practical tests published by Linde several years ago led him to the compilation of the fol- lowing table, which shows the excess of efficiency in per cents of ammonia refrigerating machine over and above that of a carbonic acid machine, both working 'at differ- ent temperatures before the expansion valve, the temper- ature in the brine surrounding expansion coil being the same (about 23 F.) in all cases. Temperature before expan- sion valve F 54 63 72 81 90 Excess of efficiency of am- monia plant 17 '% 2356 3156 47J6 101J6 The tests referred to by Linde, on which the fore- going table is based, were made in the Experimental Refrigerating Station in Munich, Germany, by Schroeter, and in the following little table are compiled some of the actual results of these experiments obtained in the case of an ammonia and of a carbonic acid refrigerating ma- chine: AMMONIA MACHINE. CARBONIC ACID MACHINE. No. OF TEST. 1 2 3 4 5 6 7 8 Temp, in brine tank, degrees Celsius. .. 6.1 -6.4 6.4 -4.8 4. 4.8 4.8 6.7 Temp, in condenser, degrees Celsius . . . 21.4 21.4 21.4 34.9 20.9 21.2 22.2 30 Temp, before expan- sion valve, degrees Celsius 6.5 11.6 18.4 28.3 7.9 10 16.8 28.8 Refrigeration per hour per horse power of steam en gine in calories . . . 3,897 3,636 3,508 2,237 3,832 3,178 2,867 1,477 The correctness of these figures has never been doubted, and in view of these facts the efficiency of a carbonic acid machine now in the market, which is given at 4,300 and 3,700 calories for temperatures of 10 and 20 Celsius before the expansion valve per indicated horse power, must be considered as something phenomenal indeed. This machine has no expansion cylinder, and therefore its efficiency is comparable to the efficiencies given under tests 6 and 7 in the above table, which are nearly 25 per cent less. 243 MECHANICAL REFRIGERATION'. CHAPTEK XI.-OTHER COMPRESSION SYSTEMS. AVAILABLE REFRIGERATING FLUIDS. Besides ammonia other liquids are used, and still others have been proposed as working fluids in refriger- ating machines. Most of these liquids are used on the same plan as ammonia in the compression system, and the machines, barring certain details, are constructed on the same principles as the ammonia compression ma- chine, and the same rules and calculations apply to all of them. The following table shows the pressure and boiling point of some liquids available for use in refriger- ating machines as given by Ledoux. (Denton and Jacobus' edition.) Tension of Vapor, in pounds per square inch, above Zero. Deg. Fahr. Sul- phuric ether. Sul- phur di- oxide. Am- monia Methy- lic ether. Car- bonic acid. Pictet fluid. (1) (2) (3) (4) (5) (6) (7) 40 10.22 31 13.23 22 5 56 16 95 11 15 13 7 23 21.51 13 85 251 6 4 1.30 9.27 27.04 17.06 292.9 J3.5 5 1.70 11.76 33.67 20.84 340.1 16.2 14 2.19 14.75 41.58 25.27 393.4 19.3 23 2.79 18.31 50.91 30.41 453.4 22.9 32 3.55 22.63 61.86 3(5.34 520.4 26.9 41 4.45 27.48 74.55 43.13 694.8 31.2 50 5.54 33.26 89.21 50.84 676.9 36.2 59 6.84 39.93 105.99 59.56 766.9 41.7 68 8.38* 47,62 125.08 69.35 864.9 48.1 77 10.19 56.39 146.64 80.28 971.1 55.6 86 12.31 66.37 170.83 92.41 1,085.6 64.1 95 14 76 77 64 197. 83 1,207.9 73 2 104 17 59 90 32 227.76 1,338.2 82.9 MACHINES IN ACTUAL OPERATION. Of those compression machines which are in actual usfe besides the ammonia and carbonic acid machine, which have been described already, those operated with sulphur dioxide, Pictet liquid, ethylic ether (sulphuric ether), ethyl chloride and methyl chloride may be men- tioned especially. The latter machine is comparatively new, and not so far in practical use to any extent, and therefore no special account can be given of the same in the following short remarks. OTHER COMPRESSION SYSTEMS. 240 Recently we have found some accounts given of a machine operated with chloride of methyl in an ice fac- tory at Algiers. We are informed that the size of the engine is 30 horse power, that about eighty pounds of the chemical at about fifty cents per pound were needed to operate the plant during 5,000 hours without the least disturbance, and we are informed of a number of other details, but as to the actual amount of ice produced we are left in the dark entirely. The temperature of the brine is 4F. The pressure in the expander appears to be very low THE ETHYL CHLORIDE MACHINE. A refrigerating machine using ethyl chloride as a refrigerant has been in use to some extent lately. The ethyl chloride evaporates at a quite high temperature; the machine works under a vacuum, and condensing pressures are very low, about fifteen pounds (gauge pressure) as a maximum. The refrigerating coils are made of sheet copper, flat, several inches broad, and about an inch thick in an experimental plant in opera- tion in Chicago. The machine appears to be designed for small work only, fruit rooms, creameries, small butcher shops, etc., and is operated by any sort of a small motor. REFRIGERATION BY SULPHUR DIOXIDE. The sulphurous acid refrigerating machines are also in practical operation to some extent. They require, how- ever, a much greater compressor capacity than the am- monia compressors (nearly three times as much), and give a low efficiency at very low refrigerator temperatures. PROPERTIES OF SULPHURIC DIOXIDE. The specific heat^of liquid sulphurous acid is 0.41; the critical pressure 79 atmospheres, and the critical temperature 312 F. The specific gravity of the gaseous acid is 2.211 (air = l), and the specific gravity of the liquid at- 4^ F = 1.491. The relation of the specific gravity, s, of the liquid to the temperature, t, is expressed by the following for- mula given by Andreef: s = 1.4333 0.00277 t 0.000000 271 1* The specific heat of liquid sulphurous acid is 0.4J (water 1). 250 MECHANICAL REFRIGERATION. LEDOUX'S TABLE FOR SATURATED SULPHUR DIOXIDE GA3 1 p! ha 3g f|| 2o3 . :2.s otal Heat Rec k o n e d from 32 F. 1 atent Heat of Evapora- tion. !eat Equiva- lent of Ex- ternal Work a crease of Volume dur- ing Evapor ation. _ J;| H * 68.6 11.8 22.8 16.1 29.4 i fl 24 84.2 15.0 27.4 24.2 11. T d e3 i > * o 2 3 II fit* J 1302 T3 p 1 > 1 3-S 03 O 1*11 1P & +J43_a)^ of S I W S . 1 ^ ffi " W E~ W~ . 00 B. T. B. T. B. T. B. T. B. T. Units. Units. Units. Units. U nits. 32 3.54 0.00 376 00 376.00 345.80 30.20 1.278 .048 60 5.51 21.28 393.76 372.48 341.48 31.00 0.844 .073 68 8.31 42.80 411.12 368.32 336.52 31.80 0.574 .107 86 12.20 64.56 428.00 363.44 330.88 32.u6 0.401 .154 104 17.46 86.42 444.44 357.92 324.60 33.32 0.287 .232 122 24.32 88.76 460.44 351.68 317 64 34.04 0.210 .294 140 33 17 131.20 476.00 344.80 310.12 34.68 0.158 .392 158 44.32 153.92 491.12 337.20 301.96 35.24 0.120 .515 176 58.13 176. 84 505.76 328.92 293.28 35.64 0.093 .705 194 74.96 200.00 520.00 320.00 284 12 35.68 0.073 .848 212 95.25 223 44 532.76 310.32 274.48 35.84 0.057 1.074 230 119.51 247,08 547.12 300.04 264.52 35.32 0.005 1.350 248 148.44 270.96 560.00 289.04 254.28 34.76 0.036 1.703 EFFICIENCY OF ETHER MACHINES. The following data relating to the working of an ether machine are not the result of a careful test, but repre- sent practical working, it is claimed. 252 MECHANICAL REFRIGERATION. For a production of fifteen tons of ice in twenty-four hours 245,000 B. T. units were abstracted per hour, and the indicated horse power of the engine was eighty-three, of which forty-six indicated horse power was used for the ether compressor and the balance for friction in compressor, pumping water, working cranes, etc. The temperature of the cooling water entering the condenser was 52 F. in this case. REFRIGERATION BY PICTET'S LIQUID. This liquid, which is also used in compression ma- chines, is a mixture of carbonic acid and sulphurous acid, which, according to Pictet,who introduced the same, cor- responds to the formula CO 4 S. According to Pictet, the pressure of this mixture or compound at higher tempera- ture is less than the law of pressure relating to ordinary mixtures would indicate. The following table shows the relations of pressures and temperatures of this substance: Pressure Pressure Temperature, Degrees F. (Absolute) in Atmospheres. Temperature, Degrees F. (Absolute) in Atmospheres. 22 0.77 50 2.55 13 0.89 59 2.98 4 0.98 68 3.40 2.2 1.00 77 3.92 5 1.18 86 4.45 14 1.34 95 5.05 23 1.60 104 5.72 32 1.83 113 6.30 41 2.20 122 6.86 If the Pictet liquid were an ordinary mixture its pressure would gradually rise from 0.77 to 13.98 atmos- pheres from the temperature 22 to +112 degrees Fahren- heit. Instead of that the pressure increases from 0.77 to 6.86 atmospheres only, and at 77 F. is less than that of the sulphurous " acid " or sulphur dioxide alone. ANOMALOUS BEHAVIOR OF PICTET'S LIQUID. It is claimed that a compression plant, if operated with Pictet's liquid, will produce a greater effect than what is compatible with the familiar thermodynamic formula given on page 71 of this compend. This anoma- lous behavior is sought to be explained by the physical or chemical work done by the liquids while combining into one substance in the condenser, which work it is argued replaces part of the work which would have to be done if OTHER COMPRESSION SYSTEMS. 2oJ a simple working fluid were used. If this explanation were correct we would have to assume that while a cer- tain amount of work (i. e. heat) is given off in the con- denser, an equivalent amount of heat must be absorbed in the refrigerator, thus increasing the efficiency of the machine in two directions, a most happy coincidence, but one which is in no wise corroborated by the second law of thermodynamics. OTHER EXPLANATIONS FOR THE ANOMALY. In accordance with thermo-chemical tenets, the combination of carbonic and sulphuric dioxide should ab- sorb heat while being formed in the condenser, and should generate heat while being decomposed in the re- frigerator. Such a behavior would bring the working of a machine with Pictet's liquid within the scope of the second law, but it would hardly account for the alleged anomalous efficiency of such a machine. Generally it is supposed that the influence of heat on chemical combinations is such that they become less permanent with increase of temperature, and that at a very high temperature they are dissolved in their elements. This is quite correct for such combinations which are formed by the development of heat, and which absorb heat while being decomposed. But the contrary takes place in the case of combinations which are formed under absorption of heat. These latter com- binations become more permanent with the increase of temperature. BLUEMCKE ON PICTET'S LIQUID. According to experiments made by Bluemcke the pressure of Pictet's liquid is always higher than that of sulphurous acid at all temperatures. Furthermore he claims that the commercial "Pictet's liquid" is not compounded after the formula CO 4 >$, but that it contains only 3 percent of CO 2 by volume. The mixture CO, 6 S 7 , for which Pictet has established 76 as the boiling point has a tension of four atmospheres at a temperature, of 17 C C. Such conflicting statements as these are hardly calculated to remove the doubts connected with the use of Pictet's liquid, and more authentic experi- ments by disinterested parties and with liquids of well known composition will be required to definitely settle this matter. l>r,4 MECHANICAL REFRIGERATION. MOTAY AND ROSSI'S SYSTEM. Previous to Pictet's invention Motay and Rossi had operated a refrigerating machine on a similar plan with a compound of two liquids, one of which liquefies at a comparatively low pressure and then takes the other in solution by absorption. Their mixture consisted of or- dinary ether and sulphur dioxide and has been termed ethylo-sulphurous dioxide. It is stated that the liquid ether absorbs 300 times its volume of sulphur dioxide at ordinary temperature and at 60 F. the tension of the vapor of the mixture is below that of the atmosphere. The compressing pump has less capacity than would be required for ether alone, but more than for pure sulphur dioxide. Before exact formulsB can be given for the dimen- sions and efficiency of machines working with compound liquids their chemical and physical, and especially their thermo-chemical behavior, must be more definitely settled by experiments. CRYOGENE REFRIGERATING AGENTS. Cryogene is another name for refrigerating medium, and literally translated means ice generator. Certain hydrocarbons, naphtha, gasoline, rhigoline or chimo- gene have also been recommended and used to some ex- tent as refrigerating media. These liquids are used in much the same way as ether, in common with which they have a great inflammability; but they are much cheaper to start with. Van der Weyde's refrigerating machine consists of an air pump and a force pump, a condenser and two refrigerator coils, one of which also serves as a reservoir for the condensed liquid. The water to be frozen is placed in molds which are surrounded by a glycerine bath. The glycerine bath in turn is surrounded on the outside by the refrigerating medium, naphtha, gasoline, chimogene, etc., which is evaporated by means of the air pump, thereby abstract- ing sufficient heat to cause the formation of ice. ACETYLENE. Acetylene, which has lately been so prominently mentioned as the illuminating agent of the future, has also been talked of as a refrigerating agent. Jt is a com- bination of hydrogen and oxygen after the formula (7 2 H 2 . It is highly inflammable and said to require a pressure of 48 atmospheres to be liquefied at freezing point of water. AIR AND VACUUM MACHINES. 255 CHAPTER XII. AIR AND VACUUM MACHINES. COMPRESSED AIR MACHINE. Air is used in various ways as a working fluid in re- frigerating plants, but on the whole to a limited extent only. The compressed air machine is based on the utiliza- tion of the reduction of temperature which takes place when compressed air expands while doing work in an air engine. The air is compressed by a compressor and the heat which is generated by compression is withdrawn by cooling water. The cold air leaving the expansion en- gine is used for cooling purposes. CYCLE OF OPERATIONS. This may be done in such a way that the air having served for refrigerating purposes is periodically returned to the compressor in the same condition. In this case the operations of the refrigerating system constitute what is termed a perfect cycle, and the thermodynamic laws applicable to such a cycle obtain also in the case of the compressed air machine. Practically it is far more convenient to reject the working fluid (air) along with the refrigeration, but for the purposes of the following calculations, which are rendered after Ledoux, we will assume that the opera- tions of a cycle are fully performed. WORK OF COMPRESSION. For the work, TP r , of compression of the air, which is supposed to be done adiabatically (without losing or gain- ing heat), Ledoux gives the following formula: W r = k^p (P t V t - P F ) foot-pounds; and also Wr = -^| (T L - TO ) foot-pounds. A. In these equations P and T are the initial press- ure and temperature of the air, counted from absolute zero. F is the volume described by the piston of the com- pressor cylinder. F t is the volume described by the same piston during the outflow of the compressed air. P, and 2\ are the temperature and pressure of the compressed air when leaving the compressor, 256 MECHANICAL REFRIGERATION. A is the reciprocal of the mechanical equivalent of heat = yf ? . k is the ratio of specific heat of constant pressure to the specific heat of constant volume. 0.23751 "0.16844 ~ In the following equations: m stands for the weight of air (in pounds) whose volume passes from V to F t . c stands for the specific heat of air of constant volume. P 2 and T 2 are the pressure and temperature of the air after expansion. F 2 is the volume of the expansion cylinder. TEMPERATURE AFTER COMPRESSION. The temperature, T A , of the air after adiabatic com- pression may be found after the following formulae : 1. 1 (~p 1 1 P ^O rp 71 / V" *! ^0 I -I-. COOLING OF THE AIR. The air after having been compressed is cooled down from the temperature T t to the temperature T 3 , and volume F 3 , and the quantity of heat, # , which must be withdrawn from the air to accomplish this is Q t m k c (T T 3 ) units. AMOUNT OF WATER REQUIRED. The amount of cooling water, P , required is 8.8 (-t. t and t being the respective temperatures of incoming and outgoing condenser water. WORK DONE BY EXPANSION. The work, W m , which may be obtained theoretically Jt>y allowing the air, after being cooled, to expand against Alii AND VACUUM MACHINES. ^>< a piston adiabatically until the temperature 2\ is reached is : W m = ^- l {P l V 3 P 2 F 2 ) foot-pounds. or W m y^- (T 3 T 2 ) foot-pounds. A. TEMPERATURE AFTER EXPANSION. The temperature, T 2 , of the air after expansion is found after the formula : T 8 and P t being the temperature and pressure of the air when entering the expansion cylinder. REFRIGERATION PRODUCED. The refrigeration, H, which is produced by the air during adiabatic expansion is expressed by H= m1cc(T T 2 ) units, T being the temperature of the air after it leaves the refrigerator. WORK FOR LIFTING HEAT. The net work, W, therefore which is theoretically required to lift the amount of refrigeration, H t is ex- pressed by the formula W= W r W m foot-pounds, or also- ^ _ TQ} _ (TS _ 7>) J foot .poundB. EQUATION OF CYCLE. If the quantities, Q lt H and W r and W m are ex- pressed in the same (thermal) units, the equation of the cycle of operations may be expressed by \f W r and Wm are expressed in foot-pounds 258 MECHANICAL, REFRIGERATION. EFFICIENCY OF CYCLE. The theoretical efficiency, E, of this refrigerating cycle may be expressed by the formula: w T T and ~- being equal 7,, , we also find This expression is the same as that found for the maximum theoretical efficiency of a reversible refriger- ating machine, page 71. The above formulae apply also in case any other per- manent gas is employed in place of air. SIZE OF CYLINDERS. From the above equations the relative sizes Fand V 2 of compression and expansion cylinders, for a given amount of refrigeration in a given time, can be readihr ascertained for theoretical conditions. The ratio which should exist between the volumes of the two cylinders in order that the air is expelled at atmospheric pressure is expressed by the following equations : V* - V, T 3 V 3 standing for the volume of air after compression and after subsequent cooling, when it has the tempera- ture T 3 . ACTUAL EFFICIENCY. Owing to the bulkiness of air, the compression and expansion cylinders have to be very large, a, fact which tends to increase the friction considerably. Besides this there is considerable clearance, and the moisture con- tained in the air also decreases the efficiency, all of which circumstances, combined with others of minor importance, reduce the actual performance of the air machine muclj below the theoretical efficiency. AIR AND VACUUM: MACHINES. RESULTS OF EXPERIMENTS. 250 The foregoing remarks are forcibly illustrated by the following tests of compression machines, which were published by Linde some time ago. The figures in this table show that in the most favorable experiment (Light- foot) the actual efficiency is scarcely 33 per cent of the theoretical efficiency. (After Ledoux the friction alone reduces the theoretical refrigerating for about 25 per cent.) ACTUAL PERFORMANCE OF COLD AIR MACHINES. SYSTEM Bell- Lightfoot Haslam Colem'n. TE^T No 1 2 3 Diameter of compression cylin- der 28" j 27" | s'gle act'gr j 25H" 1 2-cylinder Diameter of expansion cylinder Diameter of steam cylinder 21" 21" 22" j 19K" I 2-cylinder l 20" H. P. Stroke of all cylinders Revolutions per minute Air pressure in receiver, pounds 24" 63.2 61 18" 62 65 ( 31" L. P. 36" 72 64 Temperature of air entering the compression cylinder 65H F 52 F. Temperature of air after ex- pansion. 52.6 F. 82 F. 85 F. I. H. P. in compression cylinder I. H. P. in expansion cylinder.. I. H. P. in steam cylinder B. T. U. abstracted per hour and I. H. P. of steam cylinder at 20 F 124.5 58.5 84.4 668 43.1 28.0 24.6 1,554 346.4 176.2 332.7 954 The figures for test No. 1 have been observed and published by Professor Schroeter( Untersuchungen an Kcelte- maschinen verschiedener Systeme, Munich (1887); those for No. 2 are published in minutes Proc. Inst. Mecfi. Eng., London, 1881. The data for trial No. 3 are taken from a paper read last year before the Manchester Society of Engineers. WORK REQUIRED FOR ISOTHERMAL COMPRESSION. If the compression of air takes place isothermically, in which case the air is kept at constant temperature during compression by injection of cold water and a cold water jacket, the work of compression is lessened. The work W 2 in foot-pounds required in theory to compress isothermically V cubic feet of air under a pressure of 2GO MECHANICAL REFRIGERATION. P pounds (per square foot) to the volume of V t cubic feet is W= P VX 2.3026 log ^- foot-pounds. " WORK DONE IN ISOTHERMAL EXPANSION. The work, W lt in foot-pounds which can be done theoretically by the isothermal expansion of F x cubic feet of air to the volume of V cubic feet, and the press- ure P is W, = P VX 2.3026 log OTHER USES OF COMPRESSED AIR. The isothermal expansion of air is employed in cases where compressed air is used, not for refrigeration, but for the production of power, as in tunneling, drilling in mines, transmission of power by compressed air, etc. These are purposes for which the compressed air has been extensively used. TABLE SHOWING LOSS OF PRESSURE BY FRICTION OF COMPRESSED AIR IN PIPES. (F. A. Halsey.) Diameter of Pipe. Cubic Feet of Free Air compressed to a Gauge Pressure of 60 Ibs. per Square Inch, and passing through the Pipe per Minute. 50 75 100 125 150 200 250 300 400 600 Loss of Pressure in Pounds per Square Inch for each 1,000 Feet of Straight Pipe. Ins. 1 1& $ 2/2 3 31/2 5 6 Lbs. 10.40 2.63 1.22 .35 .14 Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. 5 90 2.75 .79 .32 .11 4.89 1 41 .57 .20 7.65 2.20 .90 .31 .15 11.00 3.17 1.29 .44 .21 5.64 2.30 .78 .38 .20 8.78 3.58 1.23 .59 .31 .10 '5.18 1.77 .85 .45 .15 '9]20' 3.14 1.51 .80 .26 'i'.05 3.40 1.81 .69 .23 CALCULATED EFFICIENCY. The best working pressure for a compression air ma- chine appears to be at 4> atmospheres, and the calcula- tions for this pressure give, according to Denton, a theo- retical efficiency of 17. 5 pounds ice melting capacity per pound of coal (assuming three pounds of coal per horse power). Allowing for friction, one pound of coal should AIR AND VACUUM MACHINES. 261 give a refrigerating effect equivalent to eleven pounds ice melting capacity with a consumption of nine gallons of water. ( T = 59 F. and T 3 = 64.4 F. weight of one cubic foot of air with 0.0357 pounds of moisture =0.07524 pounds.) LIMITED USEFULNESS. In consequence of the low practical efficiency the air compression system is impracticable for indirect refrigera- tion, and can best be used where cold, dry air is the ultimate object, and even in this case its economical adaptability seems to depend on circumstances. One of the chief difficulties in cold air machines, says Gale, is the presence of moisture held in suspension by the atmosphere. Moisture in the air occasions loss of efficiency in two ways. If the air enters the expansion cylinder in a saturated condition, when the air is cooled by expansion while performing work, a certain amount of vapor is condensed and thrown down the point of saturation being dependent on the temperature. The vapor in changing to a liquid state gives its latent heat of vaporization to the air ; and as the expansion of the air continues and the temperature is still further dimin- ished, the liquid freezes and accumulates in the form of snow or ice in the valves and passages, giving up its heat of liquefaction to the air. Thus does not only the pres- ence of moisture in the air produce mechanical difficul- ties, choking the air passages and impeding the action of the valves, but, for the same expenditure of energy, the cold air leaves the machine at a higher temperature than would have been the case if there had not been a superabundance of moisture in the air during expansion, VACUUM MACHINES. With the name of vacuum machines is designated a class of refrigerating apparatus in which water is used as a refrigerating agent. In their most simple form they work on the same principle as a compression ma- chine. The vaporization of the water at a temperature low enough to cause the freezing of the water must take place under vacuum. The vacuum is formed by a vacuuifi pump which acts exactly like a compressor, withdrawing the vapors or vapor from the refrigerator where the pressure is about 0.1 pound per square inch, and com- 262 MECHANICAL REFRIGERATION . pressing the same into a condenser against a pressure of about 1.5 pounds per square inch. REFRIGERATION PRODUCED. The refrigeration produced by the evaporation of a part of the water in the refrigerator causes a correspond- ing portion of the water to turn into ice. As the latent heat of ice is about 142 and that of the watery vapor about 940, theoretically the evaporation of one pound of water would be able to produce from six to seven pounds of ice. EFFICIENCY AND SIZE. The efficiency, dimensions, etc., of a vacuum machine if worked on the plan of reversible cycle may be calculated by the same rules given for the ammonia compressor. As the latent heat of watery vapor is very great in com- parison to the specific heat of the liquid (see page 87) the theoretical efficiency of a vacuum machine will be found considerably greater than that of the other compression machines. This seeming advantage, however, is more than counterbalanced by the enormous size of the compressor required on account of the low tension of the water vapor at the temperature of the refrigerator. It is found that the compressor or vacuum pump of a vacuum ma- chine of a certain capacity will have to be about 200 times as large as that of an ammonia compression ma- chine of the same capacity. If the temperatures to be produced by a vacuum ma- chine are to be lower than that of freezing water, a solution of salt has to be placed in the refrigerator in- stead of pure water, to prevent the freezing of the re- frigerating agent. COMPOUND VACUUM MACHINE. In order to avoid compressors of such an enormous size the foregoing form of a vacuum machine has been complicated by the addition of an absorbent, preferably concentrated sulphuric acid, which, by means of its ab- sorbent power for watery vapor, releases the work of the compressor or air pumps. A machine of this construc- tion works on nearly the same principle as an absorption machine, and its efficiency, etc., may be discussed on the same basis. AIR AND VACUUM MACHINES. 263 In the machines constructed on the latter principle, which vary considerably in detail, the fuel used to recon- centrate the sulphuric acid (which has become diluted from 60 to 52 Beaume) represents one of the principal expenses. The vacuum pump is small, but in continuous operations there must also be a pump for the exchange of the diluted and concentrated acid. This exchange is performed in such a way that the cold, weak acid leaving the absorber withdraws the heat from the strong acid coming from the evaporator. EXPENSE OF OPERATING. The larger part of the heat withdrawn from the water or salt brine in the refrigerator appears again in the absorber as heat of combination between the sul- phuric acid and the vapor. It is removed by cooling water. It is stated that for the production of 100 pounds of ice it will take about eight pounds of coal in the evapo- rator and about twelve gallons of cooling water. Besides this we must allow for the power required to operate the vacuum and acid pumps. OBJECTIONS TO SULPHURIC ACID. The vessels and pipes containing or carrying the sul- phuric acid must be of lead or lead lined, and on the whole the handling of this liquid is considerable of an in- convenience. For this and other reasons the use of the vacuum machine will probably be confined to special cases. The making of ice in connection with some other industry requiring the production of diluted sulphuric acid on a large scale, and at a great distance from the sulphuric acid factory, would be such a case. SOUTHBY'S VACUUM MACHINE. The apparent simplicity and directness of action of a vacuum machine for the direct production of ice has produced several inventions in this direction. In a ma- chine designed by Southby & Blyth, the freezing can, or cans, containing the water to be frozen is placed in a box, which can be closed air tight, and from this box the air, and eventually the watery vapor, is exhausted by means of two pumps of peculiar construction.' One is an air pump which is designed to draw all the air from the in- terior of the machine, and the vacuum so formed fills 264 MECHANICAL REFRIGERATION. itself with watery vapor from the water in the freezing can. A second larger pump then compresses the vapor and forces the same into the condenser. But in order to do this effectually the condensation of vapor in the com- pressor has to be prevented, as otherwise the tension of the compressed vapor to be ejected would be so small in quantity that it would not be forced through the exit valve. To accomplish this the cylinder of the large pump is heated to a temperature above that at which the vapor will condense, and in this way the compressed vapor is almost entirely forced into the condenser. The water forming in the condenser, together with the air drawn over from the water, etc., is ejected by the small air pump. The small air pump, in connection with the large compressor, and the heating of the latter, are the two principal new features which are claimed to insure the success of this machine. Owing to the low pressures (from 0.15 to 2 inches, average pressure on piston 1-6 pound per square inch) the frictureof the compressor can be made very small. OPERATING SOUTHBY'S MACHINE. When starting the machine air at a comparatively high pressure has to be dealt with, occasioning an ad- verse pressure on the piston of say seven pounds, or over thirty times that of the working pressure; and the air being non-condensible will not disappear on com- pression, as is the case with watery vapor. For this reason, provision has been made that both ends of the vapor pump cylinder can be kept open for any neces- sary length of time during the first portion of the deliv- ery stroke, so as to permit the air to return to the under side of the piston and thereby lessen and regulate the expenditure of power to be expended in obtaining a vacuum. This is accomplished by means of a by-pass and valve, which can be opened at starting, and kept open for about nine-tenths of the piston stroke, being closed gradually as soon as the vacuum becomes more perfect, and altogether as soon as all the air has been got rid of. According to British writers the manufact- urers of this machine intend the same to be used in confined places, on board ship, or where the escape of injurious gases would be dangerous, also for making ice by hand power. The quantity of cooling water for the condenser is said to be very small indeed. LIQUEFACTION OF GASES. 265 CHAPTER XIIL-LIQUEFACTIOtf OF GASES. HISTORICAL POINTS. The liquefaction of the formerly so called permanent gases has always attracted considerable attention on the part of physicists and chemists as a means of studying matter in different states of aggregation, and also as means of producing extremely low temperatures. The names of Faraday, Thilorier, Natterer, De La Tour, and, more recently Pictet, Cailletet, Wroblewski, Olszewski, Dewar and others have become famous in connection with this subject. The former methods used for liquefaction of gases on a larger scale than the bent tubes used by Faraday, etc., and which until recently were also employed by Dewar in the production of larger quantities of liquid oxygen, etc., were practically identical with those originated by Pictet and Cailletet, who in addition to pressure used a suc- cession of various cooling agents (liquefied gases), one cooling the next, and so on, until at last a temperature was reached low enough to liquefy the gas in hand. Although large quantities of liquid gases could be prepared in this manner, and could be experimented upon, still their production was extremely expensive, and therefore the whole subject was confined to scientific studies and experiments. These costly methods, however, have been replaced within recent years by more practical operations, which render the liquefaction of the most permanent gases an easy and comparatively inexpensive task, and have made the subject one of general and perhaps practical interest. SELF-INTENSIFYING REERIGERATION. This surprising result was consummated by Prof. Linde, the originator of the ammonia compression sys- tem of refrigeration, who inaugurated and perfected a self - intensifying refrigerating method, by which the lique- faction of gases, notably air, oxygen, nitrogen, can be carried out on a large scale and at moderate cost. The first large apparatus working on Linde's new plan was exhibited before a body of physicists, chemists and engi- neers in Munich in the month of May, 1895, and then and there large quantities of liquid air were produced at the rate of several quarts per hour. The principles upon which Linde's apparatus works are very ingeniously conceived, and the ingenuity dis- 266 MECHANICAL REFRIGERATION. played in this direction are only equaled by the simplicity in the construction of the apparatus itself. Linde dispenses entirely with the use of auxiliary refrigerants, but makes the gases themselves supply the refrigeration required for their liquefaction, by means exclusively mechanical; i. e., by the use of an ordinary compressor, exchanger, water cooler, expansion valve and liquid receiver. LINDE'S SIMPLE METHOD. The gas to be liquefied, atmospheric air for example, is taken in by a compressor, and after compression is forced through an ordinary water cooler to dispose of the heat of compression; thence it is forced through a coil several hundred feet long, the end of which is provided with an expansion valve, which dips into a liquid receiver or collection vessel; from this vessel issues another pipe, which forms a coil surrounding (forming an annular concentric space) the coil previously mentioned, and which returns the air (after having expanded into the liquid receiver) to the compressor. The compressed air while expanding into the liquid receiver, against pressure, as it were, does a certain amount of (interior) work, and generates a corresponding amount of refrigeration; i. e., it lowers its own temperature correspondingly. In this condition the air flows back to the compressor, and on the way, while passing around the coil through which the compressed air passes, cools the latter before it enters the liquid receiver. The air when it again reaches and passes the compressor and water cooler leaves the same with a higher pressure, and again enters the liquid receiver at lower temperature than it did before, and in this manner pressure and refrigeration gradually increase in the liquid receiver by what may be termed an accumula- tive effect, produced by constant repetitions of the cycle of operations just described, until finally the critical temperature is reached, at which the air liquefies and collects at the bottom of the liquid receiver, whence it may be withdrawn by means of a faucet. AS fast as the air becomes more compressed and is finally withdrawn from the cycle in its liquid form, other air must be supplied to the compressor, and as the effi- ciency of the cycle is at its best at very high pressure, the original air is already supplied to the same in a com- pressed state by an auxiliary compressor. The system of LIQUEFACTION OF GASES. 267 concentric coils forming the exchanger and the liquid receiver must be inclosed in a chamber especially well insulated in order to render the apparatus operative. THE RATIONALE OF LINDE'S DEVICE. Several schemes of "regenerative," accumulative or self-intensifying systems of refrigeration and liquefac- tion have been proposed before, but none succeeded in producing liquid air before Linde, who also was the first who clearly understood and pointed out the physical prin- ciples underlying the operation, and who gave numerical data regarding the efficiency of the cycle of operation in- volved therein. Accordingly, the performance of interior work by the very gas to be compressed is the source of the refrigera- tion, which causes its temperature to fall below the crit- ical point, at which it is readily liquefied by pressure. It was known long ago, and it had been experiment- ally elaborated some thirty years by Joule and Thompson that the law of Gay Lussac did not strictly apply to air and some other gases, and that a certain amount of in- terior work (to overcome the mutual attraction of their molecules) was done on expanding; still, this amount of interior work (and corresponding refrigeration) was deemed so insignificant that expansion, while doing actual mechanical work (moving a piston in an expansion cylinder), was considered indispensable in an air refriger- ating machine. Linde, however, pointed out that this refrigeration, due to the free expansion of a gas from a higher to a lower pressure, although small at low press- ure, would increase very rapidly with the pressure in an apparatus working on the accumulative principle. The increase of the heat elimination with the press- ure, and the economic principle of Linde's method, be- come readily apparent when we analyze the formula which expresses the relation between the lowering of temperature d and the pressure p before and the pressure p t after expansion. In this formula T is the temperature at which the compressed gas ex- pands in degrees absolute Fahrenheit; the pressures are expressed in atmospheres. The fall of temperature of a gas during free expan- sion from a higher to a lower pressure is frequently 268 MECHANICAL REFRIGERATION. referred to as the "Joule effect," or as the "Joule- Thompson effect." VARIABLE EFFICIENCY. This formula readily shows that the refrigeration of the gases increases with the increase of the difference PPit tnat is, the difference of pressure on both sides of the expansion valve; and also with the decrease of T,that is, with the expanding temperature. As the latter is .constantly lowered in accordance with the accumulative principle on which the apparatus works, the efficiency of the system evidently increases the nearer the tempera- ture of the gas reaches its critical point. While the degree of refrigeration depends on the difference, pp^ the amount of work or power required to operate the apparatus or to force the air round and round the circuit depends on the quotient JL or the ratio Pi of pressure in front and back of the compressor piston. By making JL. small and p p t great, which can be done by working at very high pressures, the efficiency of the system may be brought near a maximum figure. To accomplish this, in a measure, the air or gas to be liquefied is already brought to a pressure of some fifty atmospheres by an auxiliary compression before it is fur- nished to the compressor, which operates the liquefying circuit proper. HAMPSON'S DEVICE. In keeping with the foregoing consideration, Hamp- son has constructed a similar apparatus, which may be operated with compressed air or gases contained in cyl- inders alone, and without a compressor and water cooler. In this case, only that portion of the gas or air which is actually liquefied remains in the system; the other por- tion is exhausted or wasted, so to speak. This appa- ratus is specially adapted for lecture purposes, and is only a modification of Linde's, well foreshadowed in the latter's original observations on the subject. ' OTHER METHODS. Regarding the history of Linde's method of liquefac- tion, it may be mentioned that Siemens, as early as 1857, applied for a patent in Germany on a self-intensifying or regenerative process of refrigeration, in accordance with which the air is first compressed with an ordinary LIQUEFACTION OF GASES. 269 compressor, and then expanded in a motor cylinder, whereby the temperature is reduced; the air is then passed through an exchanger, in which it is cooled by the compressed air which enters the exchanger from the opposite side. Siemens did not attempt to carry out his invention, it appears, but in 1885 Solvay patented a similar device and put the same in operation, but did not succeed in obtaining temperatures lower than 140 F., and did not succeed in liquefying air. In 1893 Tripler obtained an English patent for a gas liquefying apparatus, and for several years has been pro- ducing liquid air and experimenting with the same. On this fact it appears that some people try to establish the priority of Tripler for the production of liquid air by the self-intensifying process over Linde. TRIPLER'S INVENTION. In this connection, however, it must not be over- looked that Tripler, no more than Solvay or Siemens, made no mention in his specification of the effect due to the air expanding against pressure through a narrow orifice or expansion valve, nor is there any evidence on record that Tripler made any liquid air until a con- siderable time after Linde and even Mr. Hampson had made the same in large quantities. The latter, in writing to the Engineer (London, England), makes the following and apparently not unjust reference to Tripler's dis- coveries: "So far as is known to the public, Mr. Tripler can only be credited with three attainments of any magni- tude. In 1893 he patented in this country an invention for liquefying gases by cold, which involved an obvious fallacy so gross and so important to the invention that, instead of producing cold, it would actually produce heat. That is attainment No. 1. In 1897, having imitated on a larger scale my invention for a self-intensive liquefier, which had been made and illustrated in detail nearly two years before, he showed it as an oiiginal in- vention; and having performed, with but slight variations except their larger scale, experiments with which the scientific world on this side of the Atlantic had long been familiar, he omitted all reference to that fact. Thirdly, in 1899, in connection with the working of a liquid air engine, he overlooked the vital point in the liquefaction of air that the latent heat given out in liquefaction must 270 MECHANICAL REFRIGERATION. be removed by some other substance than the liquefied portion." USES OF LIQUID AIR. Much has been written about the utilization of liquid air in various ways, especially as a motive power. It is entirely superfluous here to assert the ^practicability of the use of liquid air as a vehicle for motive power under ordinary circumstances. A medium in which the motive power has to be stored up at such a low tempera ture, entailing the loss of considerable mechanical energy, could not be considered economical for the trans- fer of power, for this reason alone. As a means for the storage of power, liquid air has also been prominently mentioned by the lay press, but the very fact that it is impracticable to store or main- tain it for any length of time under ordinary conditions with any degree of safety or without losing the larger portion of the liquid precludes this idea altogether. Another reason, moreover, for the unavailability of liquid air as motive power is to be sought in the fact that not only mechanical power, but also considerable refrig- erative capacity, is stored up in this medium, for which no adequate return would be obtained if it were used as a motive power for ordinary purposes. The circumstance may not exclude the possibility of the use of liquid air for motive power in cases where ex- pense is of little consideration, and in which certain con- veniences are aimed at, as for instance for the throwing of projectiles, for the preparation of high explosives, for the propelling of torpedoes, for aerial navigation and in other cases of emergency. With regard to the use of liquid air as a refrigerating medium, similar considerations do obtain. The expense of its production is too high to render it available for or- dinary refrigeration; but where very low temperature is required for specific purposes, as for the preparation and purification of certain chemicals, for medical uses, for physical experiments, etc., liquid air and doubtless other liquefied gases have certainly many advantages, and therefore this subject cannot be ignored by the pro- gressive engineer. SPECIFIC USES OF LIQUID AIR. From among the specific uses of liquid air, which al- ready have taken a more practical form, we may men- LIQUEFACTION OF GASES. 271 tion the production of liquid oxygen for which Linde also constructed a special apparatus which is based on the observation that when liquid air is allowed to evap- orate under certain precautions, the nitrogen evaporates first, leaving a liquid containing 50 per cent and more of oxygen. The apparatus used by Linde for this purpose is quite similar to his liquefaction apparatus, the principal novel feature of it being an arrangement whereby the nitrogen as well as the oxygen is enabled to leave the machine at ordinary temperature. Thus the whole refrigeration bestowed on the gases during liquefaction is returned to or retained in the system. This liquid, consisting chiefly of oxygen, has already been put to practical uses in the production of very high temperatures. Inasmuch as in combustions with ordi- nary air the nitrogen, which has to be heated also, carries away much of the heat of combustion, the " Linde air" will work a great change in this direction. Not only in ordinary combustion, but also in other chemical oxidizing processes in which the presence of nitrogen lessens the affinity, the Linde product will be of great service, and is already utilized in the manu- facture of chloride after the " Deacon" process. For illuminating purposes the "Linde liquid " (liquid air containing over 50 per cent oxygen) will doubtless also be made available, and it is possible that the electric furnace may soon have a rival in a furnace operated with "Linde air," for it has been reported already that cal- cium carbide has been prepared by such a furnace without the use of electricity. Another interesting use of liquid air is the rapid production of high vacuum. For this purpose the vessel to be exhausted is filled with a gas more easily condens- able than air, say with carbonic acid gas. The vessel is provided with an extension which can be sealed off very readily. The open end of the extension is then immersed into liquid air, when the carbonic acid is withdrawn from the vessel and deposited in the extension, which is then sealed off, leaving a high vacuum in the vessel. TABULATED PROPERTIES. The accompanying table shows the physical constants of a number of gases, which have also been studied in the liquid states, as compiled by Peckham. 272 MECHANICAL REFRIGERATION. rt flC5 sis 3 s| I mi 0) l-i SIS 2 J! fl fe S <3 o S3 M * r4 Tf * 0\ C4 rH T-l <-l i-H 8 ' I^O^O, O c |> O\ ] Mi 000 O O VOVOOOONON } if) lOOO^OiHTj- I rO f*5 u^ CO U3 t* lO U50O 00X000 ftR9S9S- 77771 I ola ^%* a ^ ^^ :&9|j B - ^.b~rt =5 a 2 lo ^ ^ aj o3 01 > gt N N'OJ Q OOOG MANAGEMENT OF COMPRESSION PLANT. 273 CHAPTER XIV. MANAGEMENT OF COMPRESS- ION PLANT. INSTALLATION OF PLANT. The installation of a refrigerating plant comprises the proper mounting of all its parts, the proving of the pumps, piping, etc., and the charging of the plant with ammonia. A working test is also frequently made. For the mounting the same rules apply as in the case of other motive machinery. PROVING OF THE MACHINE. In order to prove a new plant, before it is charged with ammonia it should be filled with compressed air to a pressure of about 300 pounds. This is done by working the compressor, while the suction valves pro- vided for' this purpose are opened. Thick soap lather, which is spread over the pipes, etc. , shows leaks by the formation of bubbles under the above pressure. The condenser and brine tanks, filled with water, show leaks by the bubbles of air escaping through the water. The air pressure thus obtained on the system may be used to blow out the pipes, valves, etc. After a pressure is pumped on the system, and after the temperature is equalized throughout the whole system, the pressure gauge ought to remain stationary if the plant is abso- ,lutely air tight. PUMPING A VACUUM. If the machinery is found to be perfectly air tight, all the air is discharged from the system by opening the proper valves and working the pumps. After a vacuum has been obtained all outlets are closed, and the con- stancy of the vacuum is observed on the vacuum gauge to see if the plant will withstand external pressure. CHARGING THE PLANT. After the vacuum is shown to be perfect, the drum with ammonia is connected to the charging valve. Before opening the valve on ammonia flask, the expansion valve between ammonia receiver and expander is closed. Now the liquid ammonia is exhausted into the system, while the compressor is kept running at a very slow speed with suction and discharge valves opened and water running on the condenser. 274 MECHANICAL REFRIGERATION. CHARGING THE PLANT BY DEGREES. If the air is not completely exhausted from the plant, i. e., if the vacuum is not perfect, it is advisable to charge the plant with ammonia by degrees. First about one-half of the total amount of ammonia is charged, and after this has thoroughly circulated in the system, most of the remaining air will have collected in the top of condenser, whence it can be blown off by a cock. After this has been done the balance of the ammonia is charged in a similar way in one or two additional installments. OPERATION OF PLANT. The proper working of a compression machine is chiefly regulated by the amount of ammonia passing through the same, which is done by the expansion valve, which must be manipulated very carefully. The pipe conveying the compressed ammonia to the condenser should not get warm, and the temperature of the brine should be about 5 to 10 F. higher than the temperature corresponding to the indication of pressure gauge on refrigerator. The temperature of the cooling water should be about 10 to 15 F. (sometimes as much as 20) below the temperature corresponding to the pressure in condenser coils. The sound of the liquid ammonia passing the regu- lating valve should be continuous and sonorous, this in- dicating the absence of a mixture of gas and liquid. DETECTION OF LEAKS. If any ammoniacal smell is discovered while charging the plant, it is probably due to leaks, and they should be instantly located and mended. It is of importance to discover the existence of a leak at the first inception. When in a machine in operation, the liquid in the tanks begins to smell, it shows either a very considerable leak or one of long standing, and in order to detect a leak readily under those circumstances it is best to test those liquors regularly from time 'to time with Nessler's solu- tion, of which a few drops are added to some of the sus- pected liquid in a test tube or other small glass vessel, as described on page 103. MENDING LEAKS. It is a very efficient and simple method to close small leaks by soldering them up with tin solder, which is fre- MANAGEMENT OF COMPRESSION PLANT. 275 quently employed and gives general satisfaction. The soldering fluid, in order to properly clean the iron, should contain some chloride of ammonia, and it is best and proper that its quantity should be such as to form a con- siderable proportion of a double chloride of zinc and am- monia. A soldering liquid of this kind can be made by dissolving in a given amount of muriatic acid as much zinc as it will dissolve, and to do this in such a manner as to be able to ascertain the weight of zinc that has been thus dissolved. An amount of chloride of ammonia or sal ammoniac approximately equal in weight to that of the zinc dissolved is then added to the solution of zinc in muriatic acid. If the leaks are too large to be mended in this way, new coils or new lengths of pipe must be put in. In some cases, where conditions are favorable, electric welding may be resorted to. A cement made by mixing litharge with glycerine to a stiff paste is also recommended for closing leaks. In this case the cement must be fortified by the application of sheet rubber and sheet iron sleeves kept in position by iron clasps. Generally the amount of ammonia is determined after a rule of thumb fashion, allowing one-third pound of ammonia for every running foot of 2-inch pipe (or its equiv- alent) in expansion coils. Thus a plant of twenty-five tons ice making capacity having about 5,000 feet of 2- inch pipe would require about 5 - s - = 1.666 pounds of am- monia, while a direct expansion plant of twenty-five tons refrigerating capacity having at the rate of 2,000 feet of 2- inch pipe would require about 2 - 5 QO = 700 pounds of am- monia. A machine of the same capacity (twenty-five tons refrigeration) with brine circulation would require only about 275 pounds of ammonia. Calculated for capacity, this would correspond to about forty-five pounds of ammonia per ton of ice mak- ing capacity, twenty-five pounds of ammonia per ton of direct expansion refrigerating capacity and twelve pounds of ammonia per ton of refrigerating capacity, brine cir- culation. These rules are arbitrary, some allowing much less ammonia, according to the location of pipes. WASTE OF AMMONIA. Another question of considerable interest to the practical operators of ice plants is in regard to the waste 276 MECHANICAL REFRIGERATION. of ammonia that may be expected to be incurred. Theoretically speaking, no waste ought to take place, as the same quantity of ammonia is used over and over again, but in practice the anhydrous ammonia gives way in the course of time. This is due to leakage in a great measure, and partly also to decomposition of ammonia. The amount of wastage depends, of course, largely on the care with which the plant is operated, and in the absence of any actual leakage is altogether due to decomposition of ammonia, which can be obviated in a great measure by keeping down the temperature around the compressor as much as possible. The amount of ammonia wasted while a machine is running depends almost entirely on the care and watchfulness, and may run all the way up to 200 pounds per year on a plant of twenty-five tons capacity. In some cases it amounts to very little, but about fifty to 100 pounds is generally considered as an un- avoidable waste for a 25-ton machine. Where there is a liquid receiver provided with a gauge glass, the attend- ant can readily tell when the ammonia is running low in the machine. Otherwise the insufficiency of ammonia is shown by a fluctuating pressure, variation in the tem- perature of the discharge pipe, and by the running of the valves in the compressor, which sometimes run smooth and easy, and at other times hard, showing that the sup- ply of ammonia and the consequent resistance varies. A rattling noise of the liquid while passing the ex- pansion valve shows the passage of vapor along with the liquid ammonia, and proves that the ammonia in the system is deficient. AMMONIA IN CASE OF FIRE. It appears that the dangers of ammonia in case of fire have been greatly over-rated, and at least in the begin- ning of a fire it acts as an extinguisher rather than other- wise. For this reason it seems more advisable in case of fire to allow the ammonia to escape whenever it is deemed good policy to stand the loss of the" ammonia rather than run the risk of fire. If the latter happened the am- monia would be lost anyhow, and that, too, most likely, at a temperature high enough to make it share in the conflagration, while when allowed to escape, as long as the fire is low it may help to stifle the same or extin- guish it altogether. MANAGEMENT OF COMPRESSION PLANT. 277 Before resorting to such an expedient the pros and cons should, of course, be duly considered, and the at- tendant should properly protect himself by a mask or similar contrivance against the suffocating effect of the ammonia vapors to which he may be exposed while pro- viding means for their escape in the free atmosphere. In order to further provide for such an emergency, the out- let valve at the lower end of the condenser should be conveniently located, as the liquid ammonia should be permitted to escape first. While countenancing such heroic measures, I will not dispute that under certain conditions decomposing ammonia may, through ignition, also become the cause of fire. When, for instance, the head of a compressor running very hot should be blown off , the escaping hot ammonia,especially if saturated with lubricating oil, may be in a condition prone to decompose, and in case these vapors should come in contact with the flame of a light, the fire under the boiler, or a lighted match, a flash of fire might take place, which amid the con- fusion generally attending an accident of this kind might give rise to a destructive conflagration. In view of this possibility, it has been recommended that the lamps in the engine room of a refrigerating plant should be pro- tected by a fine wire screen, that the doors leading to the boiler door should be likewise made of fine wire cloth and be provided with a reliable self-closing contrivance. The lighting of matches, etc., should be avoided in the engine room for the same reason. CONDENSER AND BACK PRESSURE. The lower the pressure and temperature in condenser coil, and the higher the pressure and temperature in ex- panding coil (back pressure), the more economical will be the working of the plant. This is readily apparent from the formulae given for the estimation of the compressor capacity; it is even more readily apparent from the sub- joined tables, showing the actual result obtained by Schroeter in working an anhydrous ammonia compressor under different conditions. For these reasons the cooling water on the condenser should be used as cold as it can be had and in as ample profusion as possible. Likewise the expansion or back pressure should be held as high as possible. In brewery refrigeration, cold storage and other es- tablishments in which the temperature is to be kept at 278 MECHANICAL REFRIGERATION. 32 F., or thereabouts, by direct expansion, a back press- ure of about 33 pounds gauge pressure, corresponding to about 20 P., is generally maintained. In case brine circulation is used for above purposes, the brine returns with a temperature of 24 to 26 F. and enters the room with a temperature of about 20. The back pressure in ammonia coils in this case is 25 to 28 pounds, corresponding to a temperature of 10 to 15 F. During the chilling stage in meat or other cold stor- age, the temperature in the room rises in the beginning to 5(P, and a higher back pressure about 60 pounds, corresponding to a temperature of about 40 in ammonia coil is maintained. Gradually, as the temperature falls in the room, the back pressure also decreases until it reaches the point corresponding to the temperature 'of the room for cold storage, viz., about 30 pounds. In freezing meat, for which purpose temperatures of F. and below in rooms are required, the back press- ure gets as low as 4 pounds, corresponding to a temperature of 20 F. For ice making a temperature of 10 to 20 is main- tained in the brine, and the back pressure in ammonia coils in this case is from 20 to 28 pounds, corresponding to a temperature of 5 to 15 F. TABLE SHOWING EFFICIENCY OF PLANT UNDER DIFFER- ENT CONDITIONS. N o. of test 1 2 3 1 Temperature of ) ?]+ ^ otr refrigerated |8S8S8jr Specific heat of brine (per unit of volume), 43.194 37.054 0.8608 28.344 22.885 0.8508 13.952 8.771 0.8427 -0.279 -5.879 0.8374 Quantity of brine circulated per hour cu ft 1,039.38 908.84 633.89 414.98 Cold produced;B. T. U. per hour Temperature 1 r } t d F W^JS^S 342.909 48.832 66.724 263.950 49.476 68.013 172.776 48.931 67.282 121.474 49.098 67.267 condenser, j Quantity of cooling water per hour in cu. ft 338 . 76 260.83 187.506 139.99 Heat eliminated by condenser, B. T U per hour 378.358 301.404 214.796 158.926 I. H. P. in compressor cylinder. I. H. P. in steam engine cylinder Consumption of steam per hour in Ibs... 13.82 15.80 311 51 14.29 16.47 335 98 13.53 15.28 i05.S7 11.98 14.24 278.79 1 Per I. H. P. in Cold produced comp. cyl $er hour, B. Per I. H. P. in . U. steam cyl Per Ib. of steam 24.813 21.703 1,100.8 18.471 16.026 "85.6 12.770 11.307 564.9 10.140 8.530 435.82 MANAGEMENT OF COMPRESSION PLANT. 279 PERMANENT GASES IN PLANT. As long as their amount is small and as long as there is sufficient liquid in the condenser coil to act as a seal preventing the free circulation of the permanent gases in the system, their presence will only decrease the capacity of the condenser coil, as it were, requiring either a little more cooling water or increase the pressure in the condenser. If these gases are present in larger quantity, and especially when there is no excess of liquid ammonia in condenser coils, they will disseminate themselves through the whole plant and interfere both with the economical working of the plant and the correct indications of the gauges, etc. For these reasons the engineers ought to be watchful to prevent any accumulation of such gases. Sometimes they consist chiefly of atmospheric air, but sometimes also of hydrogen and nitrogen, due to the decomposition of ammonia. The best way to remove these gases from the system is by drawing them off at the top of the condenser coil. It is advisable when drawing off the permanent gases to make the condenser as cold as possible by using an excess of cooling water and by stop- ping the inflow of ammonia gas to the condenser for the time being. A small hose, or, better still, a permanent small pipe, may be attached to the top of the condenser or provided with a valve near the condenser, the other end dipping in cold water. If on opening the valve bubbles are seen to escape through the water the valve should be kept open as long as such bubbles appear in the water. If, however, the bubbles cease to appear in noticeable quantity, while a crackling noise in the water indicates that most of the gas escaping through the pipe is ammonia, which is absorbed by the water, then the valve should be closed, as all the permanent gases that can be removed at the time without undue loss of am- monia have been disposed of, at least for the time being. FREEZING BACK. The tendency of freezing back shown by certain ma- chines and not by others, is explained by their mode of working. The former machines work by what is called the method of wet compression, and the others by the method of dry compression. The tendency to freeze back itself involves no loss, for a > machine intended for wet compression may also be worked with dry gas, by 280 MECHANICAL REFRIGERATION. opening the expansion valve very little, but in doing so the capacity of the machine is reduced and the power required to work the compressor is increased. PRACTICE IN WET COMPRESSION. In working with wet expansion the object is to deliver the gas from the compressor in a saturated con- dition, but if this were actually done we would never be sure that certain amounts of liquid were not mixed with the gas, which would constitute a severe loss. For this reason it is indicated to allow the temperature of the vapor leaving the compressor to be about 20 above that of the liquid leaving the condenser. Inattention to this point probably accounts for many differences of opinion in regard to dry and wet compression. Any liquid present under such conditions would fill the clear- ance space, and by expanding would destroy a corre- sponding percentage of compressor capacity (^-inch clearance filled with liquid ammonia would reduce the capacity over one-third). ORIGIN OF PERMANENT GASES. In the operation of a compression plant the undue heating of the gas during compression must be consid- ered as the chief cause for the decomposition of am- monia and the origination of permanent gases. How- ever, it also frequently happens that air is drawn into the system through leaks, in case a vacuum has been pumped, which some engineers are unnecessarily in the habit of doing whenever they stop the plant for a length of time. CLEARANCE MARKS. The clearance in the compressor is not a fixed quan- tity, but changes with the natural wear of cranks and cross-head. For this reason clearance marks should be provided for on the guides and cross-heads of compressors as well as engine. These will indicate if the clearance is equalized at the end of cylinders, and guide us in the matter of keying up the bearings. The clearance should not exceed & part of an inch. VALVE LIFT. The lift of compressor valves must be carefully ad- justed to the speed of piston (to get full discharge), sup- ply of condenser water, etc. MANAGEMENT OF COMPRESSION PLANT. 281 If valves are not properly set and cushioned they pound, which may even cause the texture of the metal to change in such a way as to cause their breaking to pieces. PACKING OF COMPRESSOR PISTON. If the piston rod is of uniform diameter and well polished, the packing will last several months, other- wise it may have to be renewed every month. If the compressor valves or pistons should leak, the refrigerator pressure will rise and the condenser pressure will fall. When it becomes necessary to open any part of the plant the ammonia should be transferred to another part, or if this is impracticable it should be removed by absorption in water. POUNDING PUMPS AND ENGINES. Sounds that appear to proceed from first one place and then another about the engine and pumps can gener- ally be located by the use of a piece of rubber tubing, one end of which is held to the ear while the other end is brought close to the suspected place. The opposite ear should be closed to shut out the sound. An old yet very effective way to locate any noise in- side of an engine or pump cylinder is to place one end of a wrench or other piece of metal between the teeth, and resting the other end on the cylinder head, close both ears. Every sound within the cylinder can thus be readily heard. CLEANING CONDENSER. If the condenser coils have a tendency to become incrusted by deposit from the water, they should be cleaned from time to time. On such occasions they may also be tested with a water pressure of some 400 pounds per square inch to discover corrosion, perforation and other bad places. CLEANING COILS, ETC., FROM OIL. If there is oil in parts of the system whence it cannot be removed by the oil traps, those parts may be blown out, and if consisting of pipe they can be blown out by sections, if practicable. Another way more strongly recommended, and more simple, to clean am- monia pipes from oil, consists in allowing high pressure ammonia gas to enter them; this warms and liquefies the 282 MECHANICAL REFRIGERATION. oil sufficiently to permit of its being drawn (mixed with the ammonia) into the compressor, whence it passes to the oil traps, where it is separated from the ammonia. This method of cleaning the coils is said to be very effective if repeated from time to time, say once a week, or better still, every other day. INSULATION. The most important point in the economical running of a plant is insulation, and especially does this refer to the ammonia on its way from the refrigerator to the compressor, and from the condenser to the refrigerator through the liquid receiver, etc. For these reasons these conduits cannot be insulated too well. The same applies to brine tank, freezing tank, etc. PAINTING BRINE TANKS, ETC. Light colored surfaces radiate and absorb less heat than dark surfaces under the same conditions. Also smooth and bright surfaces will radiate and absorb less heat than rough and dead looking surfaces of the same color. That the differences in radiation brought about in this way are great enough to be quite observable about a refrigeration plant, for instance, on the efficiency of a brine tank or other vats, we make no ttoubt. For this reason light colors, possibly white, and smoothly varnished at that, are, doubtless, best adapted to all sur- faces. Preferably a white earthy paint, like barytes, etc., but no white lead, should be used for this purpose, LUBRICATION. The oil used for lubricating the compressor differs from ordinary lubricating oil in that it must not congeal at low temperature, and must be free from vegetable or animal oils. For this reason only mineral oils can be used, and of these only such as will stand a low tempera- ture without freezing, such as the best paraffine oil, will do. Regular cylinder oil, however, should be used for the steam cylinder, and a free flowing oil of sufficient body for all bearings and other wearing surfaces. For heavy bearings on ice machines a heavy oil should be used, while small bearings, such as shafts of dynamos, should be lubricated by a very light oil, to avoid undue heating in either case. Graphite or black lead is also an efficient lubricant. MANAGEMENT OF ABSORPTION PLANT. 283 CHAPTER XV. MANAGEMENT OF ABSORP- TION PLANT. MANAGEMENT OF ABSORPTION MACHINE. The management of an ammonia absorption plant has many points in common with that of a compression plant. The detection and mending of leaks, lubrication, the management of ammonia, withdrawal of permanent gas, etc., are the same in both, and they have been en- larged upon in the foregoing. There are, however, many precautions and troubles peculiar to the absorption sys- tem, and the most important of them will be shortly mentioned hereafter, and some of these in turn will also apply to the operation of the compression plant. INSTALLATION OF ABSORPTION PLANT. The installation and testing of an ammonia absorp tion plant is generally attended to by the manufacturers. The plant before being put in operation should be tested to a pressure of about 300 pounds per square inch. CHARGING ABSORPTION PLANT. Before the ammonia is charged into the machine, it is necessary to expel from the entire apparatus the air which it naturally contains. There are two methods of doing this, one of which consists in opening all the connecting valves in the machine; leave one open to the atmosphere, introduce direct steam in the retort until all the air is forced out, and then shut the outlet valve and let the apparatus cool off. When it becomes cold, there will be found to be a vacuum in the whole apparatus. It is then ready to receive the ammonia. This method, however, is not to be recommended, as the heat of the steam will soften the joints, especially if rubber is used. The best way is to pump a vacuum by means of a good pump. The boiler feed pump or the ammonia pump may be used for this purpose, and when a vacuum of twenty-five inches is obtained, close all the valves. Then connect the charge pipe with the drum of aqua ammonia, taking care not to let any air enter the pipe after the drum is empty. Close the charge valve and repeat the operation with another drum, until the vacuum in the machine is gone, and then pump in the balance with the ammonia pump until nearly the requisite charge is put in; then heat the ammonia slowly by turning steam through the heater coils. When the pressure gauge 284 MECHANICAL REFRIGERATION. indicates 100 pounds, more or less, open the purge cock and lead the discharge into a pail of cold water through a rubber tube until no air bubbles come out*, then turn on the condensing water into the condenser cooler and absorber, and apply the steam until the liquefied gas shows in glass gauge. Then open distributing valve to freezing tank, and turn the poor liquor into absorber, and in a few minutes the ammonia pump may be started to pump the enriched liquor through the coils of ex- changer and into the retort. Let the condensed steam into the deaerator and let cooling water run over the distilled water cooler coils. Let it run out until the water becomes clear and tasteless. Proceed in this way, carefully watching for ammonia leaks wherever there are joints. If none exist, keep on until all the pipes in the freezing tank become coated with frost, and the remaining air has consequently been driven out through the coils and out of the absorber purger. Then close down and proceed and make the brine solution, when the machine is ready to start again and the balance of the ammonia may be put into the machine and operated in the regular manner. OVERCHARGE OF PLANT. In charging an absorption machine with, ammonia liquor, which is generally done when it is cold, it should be borne in mind that the liquid expands when heat is applied, and that if the machine is charged to its work- ing point when cold, it will invariably be overcharged under working conditions. In such a case the liquor may go out of sight in the gauge and great variations of pressure take place, which are apt to damage the recti- fying pans, and the proportionate strengths of poor and rich liquor are disturbed. AMMONIA REQUIRED. When the regular automatic operation of the absorp- tion cycle has been inaugurated, a surplus of liquid am- monia should show itself in the liquid receiver. If there is a deficiency in this respect it can be supplied by the ad- dition of anhydrous ammonia, or by the addition of strong ammonia liquor, and the withdrawal of a corresponding amount of weak liquor. The sound of the liquor passing the expansion valve should be continuous and sonorous, as in the case of the compression machine, indicating the absence of a mixture of gas and liquid. MANAGEMENT OF ABSORPTION PLANT. 285 RECHARGING ABSORPTION PLANT. For the purpose of recharging an absorption plant De Coppet gives the following rational directions: When the gas has leaked out or the liquor has become impov- erished, and knowing the original charge by weight and density, as for instance, say the original charge was 4,000 pounds at 26 B., there would be 1,040 pounds of am- monia in 2,960 of water; if the density through leakage or purging came down to say 23, there would be a loss of 120 pounds in the original charge, which can be easily sup- plied by placing a drum of anhydrous ammonia on a scale, taking a long and small flexible pipe, say a half inch, connected between the drum and same part of the machine, say the feed pipe to freezing tank, weigh the drum accurately before opening the valve, let the liquid gas run in the machine until there are within a few pounds of the quantity missing; run out of the cylinder into the machine, say ten or fifteen pounds, then close the cylinder valve and try the machine by running it in the usual way for an hour or two. Then add the ten or fifteen pounds extra, and if all the air has been blown out of the tube, and if the ammonia is pure, his machine will work all right again. When the liquor is lacking it is best to recharge the machine with strong aqua at 26 to 28 until the original level is reached, which can easily be ascertained if a glass level or test cock has been placed on the generator or still. He has adopted this method for fifteen years, and finds it far preferable to that of concentrating the liquid and recharging it with rich ammonia afterward, securing the same amount of poor liquor, besides saving time and money. When the question presents itself as to how much anhydrous ammonia, as, in pounds must be added to m pounds of ammonia liquor of the percentage strength a in order to convert it into ammonia liquor of the per- centage strength 6, it may be readily answered after the following formula: 100-6 CHARGING WITH RICH LIQUOR. When the absorption system is charged with strong aqua ammonia it happens sometimes that the pump will not readily take the strong liquor. This is due to the great tension of the ammonia in the strong solution, which 286 MECHAKiOAL REFRIGERATION. fills the pump up with ammonia vapor in such a way that the liquid cannot be drawn in. The same thing fre- quently happens with boiler feed pumps, when- the feed water becomes nearly boiling hot. Generally it is found that in such cases the pump stands too high; if it stands below the liquid to be pumped the latter will fill the pump in preference to the vapor, and the pump will gen- erally work all right. It should be noticed, however, that this artifice of elevating the receptacle containing the rich liquor above the pump will only be efficient if it is done in such a manner that the liquid will run into and fill the pump by its own gravity. If the liquid has to be syphoned over by the pump, it will make little difference whether the pump stands a little above or below the liquor, as in either case the vapor of the rich liquor will fill the syphon and pump in preference to the liquid if the pump is not in first-class working order. This tendency is increased when the pump is allowed to run dry and hot on starting, and for this reason the cooling of the pump with water frequently remedies the trouble. This, the cooling of the pump, so it will take the rich liquor, may be accomplished according to a practical operator by stopping the pump, while the machine otherwise is running as usual. In this way the absorber is cooled down in a short time ; mean- while the drum containing the rich liquor has also been connected with the pump which is now started first to pump cold liquor from the absorber for a few seconds when the absorber valve is closed and the pump started on the rich liquor, which will then be taken readily. If not the procedure may be repeated once or twice. PERMANENT GASES IN ABSORPTION PLANT. The permanent gases in the absorption plant may be due to decomposition of ammonia and also air which has found its way into the system. It appears, however, that the decomposition of water vapor in the presence of iron (and probably iron containing carbon in a greater quantity or in a more dissolvable form than other iron) is largely responsible for their presence. The carbon which is pres- ent in all iron may also combine with hydrogen, forming carburetted hydrogen. That the nature of the iron of still and condenser worms has some influence in this direction is proven by the fact that some plants are MANAGEMENT OF ABSORPTION PLANT. 287 much more damaged by these corroding influences than others. This difference in behavior must be attributed to the iron rather than to the ammonia. CORROSION OF COILS. As may be inferred from the foregoing paragraph, it will not only be the permanent gases, thus found, which annoy the manufacturer, but also the corrosion and con- sequent destruction of the coils and tanks. This is, in- deed, the case especially in the upper regions of ammonia still and in the condenser. As a precautionary measure it is well to have the coil in the still always covered with liquid. ECONOMIZING CONDENSER COILS. As has been stated, the iron of the coil or worm in condenser and in the ammonia still suffers much from pitting and corrosion, especially if the liquid does not al- ways stand above the coil in the still. Coddington finds that the pitting takes place first at the top of the coils, and therefore he has found it a good practice to turn the condenser coil over after a certain period, say after it has been used about four years. KINDS OF AQUA AMMONIA. The difference between the different kinds of aqua ammonia in the market is only in strength and price, the latter differing like that of other commodities, according to the law of demand and supply. _ At present we find in the market (according to Beaume hydrometer scale for liquids lighter than water, the latter showing 10): 1. 16 aqua ammonia, often called by druggists F. F. F., containing a little more than 10 per cent of pure anhydrous ammonia. 2. 18 aqua ammonia, called by druggists F. F. F.F., containing nearly 14 per cent of anhydrous ammonia. 3. 26 aqua ammonia, called by druggists stronger aqua ammonia, and containing 29^ per cent of pure anhydrous ammonia. This is the aqua ammonia gener- ally used in absorption plants for the start. At last quoting the prices (in carboys) were about two and one- half cents per pound for the 16, three and one-half cents per pound for the 18 and four and three-quarters cents per pound for the 26, the latter not in carboys, but in iron drums. 288 MECHANICAL REFRIGERATION. It is also frequently supposed that a difference in the nature of ammonia is due to the different sources from which it is derived, viz., from gas liquor direct, or from intermediate sulphate of soda, but manufacturers claim, and with apparent reason, that this is not the case if both kinds are equally well purified. LEAKS IN ABSORPTION PLANT. If, while the pump and generator appear to work regularly, there is a great disproportion in the strength of the poor and the rich liquor, so that the strength of the former to the latter is 22 to 25, where it should be 17 to 28, or thereabouts, it is likely due to some leaks, more particularly in the. exchanger or equalizer or in the recti- fying pans. LEAK IN EXCHANGER. If there is a leak in the equalizer coil large enough to seriously affect the working of the machine, the pipe connecting the equalizer and the coil in the weak liquor tank will become cool when the pump is running fast, and the equalizer will be cool back to a short distance from the leak, where the cold ammonia from the absorber mingles with the weak liquor from the generator. And at times, when the pump is running very fast, the whole weak liquor line may cool back to within a few inches of the generator, showing that strong ammonia is being pumped into the bottom and top of generator, as well as into absorber. There will also be a ringing or hissing noise in the neighborhood of the leak. First locate the trouble in the equalizer by noticing the cooling of the pipes, and then find the place in the equalizer by feeling the different sections with the pump running slower, having also the assistance of an ear tube. Another way to try an exchanger coil while the machine is running is as follows: Close poor liquor valve between the generator and exchanger; close absorber poor liquor feed, and run pump as slow as possible; open the poor liquor feed wide; if there is a leak, the pump will start faster. When the poor liquor feed is closed at the absorber and between retort and exchanger, the pump is working against the generator's pressure, while when the absorber feed is wide open the pump is work- ing against a lower pressure (ten pounds per square inch) through the leaky coil of the exchanger, then to the absorber, thus forcing a by-pass circulation of rich or MANAGEMENT OF ABSORPTION PLANT. 289 enriched poor liquor from the absorber through the exchanger, through the leak of the coil of the exchanger, back through the poor liquid cooler and to the absorber again. If the leak in the coil is of a large size, the machine will come to a standstill, and will stay that way until the leaky coil is not removed. LEAK IN RECTIFYING PANS. If under existing regularities in the relative strength of the poor and rich liquor the exchanger has not been found leaking, but perfect in its working, it is almost beyond doubt that the rectifying pans are out of order. In order to make sure on this point a certain small quantity of the liquefied ammonia may be withdrawn from the liquid receiver, and then be allowed to evapo- rate (the vessel containing the ammonia being placed in ice water). If under these conditions a remnant (water) amounting to 20 per cent and more is shown, then there is doubtless a leak in the rectifying pans, which should be repaired. STRONG LIQUOR SYPHONED OVER. When the ammonia is short in a machine the same may be absorbed so quickly in the absorber as to cause the contents of the still to be syphoned or drawn over in the absorber and (if not guarded against by check valve) into the refrigerator. Defective action of the am- monia pump may cause the same trouble. For this rea- son the gauge at still must be closely watched, so that the liquor always covers the steam coil, by which an un- due decomposition of the ammonia and formation of per- manent gases is also avoided. This siphoning over of the ammonia from one part of the system, and absorption into another where it does not belong, is frequently called a "boil-over "; and besides the siphoning over of the liquid to the absorber, etc., it sometimes happens, also, that the liquid runs over from the generator into the condenser coils. If the liquified or condensed ammonia collects promptly in the liquid receiver, which shows on the gauge glass of same, there is always pressure enough behind the expansion valve to hold the ammonia in the generator, and there will be no danger of a boil-over unless the am- monia pump receives the liquid from the absorber too fast. To avoid this the absorber is always supplied with 290 MECHANICAL REFRIGERATION. a gauge glass, so the ammonia can be kept at a certain height by means of a valve commonly called the poor liquor valve. But if the engineer does not watch it very closely, the ammonia will get out of his sight, and some- times even into the expansion coils. This is sometimes made worse by not having a governor on the ammonia pump, which is sure to vary with the variation in steam pressure, causing the pump to run faster or slower. REMEDY FOR BOIL-OVER. If, however, through carelessness on these points or otherwise, a boil-over into the expansion coils has taken place it may become necessary to nearly close the expan- sion valve long enough to pump a vacuum on the absorber, and then blow what gas is on hand through the coils. This generally cleans them and takes the ammonia back to the absorber. This is rather troublesome work, but the work will have to be done before the machine will work satisfactorily. If the expansion coils are divided in sections sup- plied by manifolds, so that all the sections except one can be shut off, and all the ammonia gas be made to pass through one section at a time, each of the sections can be cleaned without pumping a vacuum on the absorber. CORRECTION OF AMMONIA IN SYSTEM. To avoid the boil-over or siphoning over, the gen- erator gauge must be closely watched, as has already been mentioned, and if the liquid line is not visible in the gen- erator the weak liquor should be cut off from the absorber, and the generator glass watched to see if the liquid rises; and if it does, and no part of thechargehas goneioverinto condenser or brine tank coil, and the absorber has been pumped down below where it is usually carried, it is a plain case of shortage of aqua ammonia. If there is no frost on the pipes, aud the receiver glass is full of liquid, the weak liquor valve should be left closed and the expansion valve opened wider; and if the absorber fills without much of the rumbling noise, it is filling with liquid from the brine tank coil. If the machine is found to contain enough ammonia, and there is no leak in the pans or the equal- izer, and the head pressure is too low and the back press- ure too high, the trouble is to be found in the pump. But if the high pressure is too low and the low pressure not too high, with everything else all right, the machine should have an addition of anhydrous ammonia. MANAGEMENT OF ABSORPTION PLANT. 291 CLEANING THE ABSORBER. Most cooling waters used in the operation of absorb- ers in connection with absorption machines contain carbonates of lime, magnesia and iron in sufficient quan- tity to form a scale inside of the absorber. This scale consists of the carbonate of lime, etc., mentioned before, which becomes insoluble at the temperature of the ab- sorber, owing to the volatilization of the free carbonic acid in the water which held them in solution. It is a matter of considerable trouble, but also of necessity, to remove this scale from time to time, which depends on the nature of the water. This is generally done by taking the coils out and suspending them over a fire to be heated considerably above the boiling point of water (not red hot, however). While still hot, or better still, after cooling, the scale may be removed by hammering and rolling the coil about. As a much simpler device Coddington recommends the use of crude hydrochloric acid (price two and a half cents per pound) diluted with six times its weight of water. With this mixture he fills up the coils and lets them stand until it ceases to digest the scale, which usually requires two hours. If one dose of acid does not clean the pipe thoroughly he repeats the same. In this case it is not required to remove the coils at all, but only the bottom and top of the absorber have to be dis- connected. Some care, however, must doubtless be ex- ercised, so as not to have the acid act for^too long a time, as in that case the iron of the coil itself might be affected. HIGH PRESSURE IN ABSORBER. Too high pressure in the absorber, and, incidentally thereto, too high temperature in the refrigerator, may be due to too much liquid in the system, or to too little cool- ing water. Too high pressure in the absorber may also be due to air or permanent gases in the system. These must be withdrawn through the purge cock at the top of the absorber, through a pipe or hose leading into a bucket of water, as described under the head of compression plant. OPERATING THE ABSORBER. It is often claimed that the absorber runs too hot, which may be due to the presence of permanent gases, due to decomposition of ammonia or to the presence of air, or to incrustation of the pipes, all of which prevent 292 MECHANICAL REFRIGERATION. the full utilization of the cooling surface of the con- denser. It may also be that in such a case the ex- changer does not do its full duty or that ammonia pump is not in good working order and that it does not displace a sufficient amount of liquid. Another point of great importance in this respect is the proper regulation of the expansion valve, so as to prevent any excess of ammonia entering the refrigerator and the absorber. Any ammonia which enters the ab- sorber in a non-volatilized or wet condition, means so much additional heat in the absorber, more cooling water and more waste all around. For this reason we are advised to so regulate our expansion valve that the pressure on absorber gauge is about three pounds, and not much over. If, on the other hand, there is too little or no press- ure on the absorber, the ammonia pump will not do its duty, and this will be prevented by the foregoing press- ure on absorber also. In order to correct too low a press- ure in the absorber the decrease of the water supply to the latter is generally the most convenient remedy. PACKING AMMONIA PUMP. The packing of the liquor or ammonia pump is done the same way as in case of any other pump, but owing to the pressure and the smell in case of leaks it ought to be attended to with special precaution. The packing used should be of the best kind, as it will wear least on the rods, and does not require to be pulled up so tight, which increases the work and the wear and tear. The pump rod should be turned true if unevenly worn, as it is next to impossible to pack a bad rod well. Any good hemp packing is excellent for most pumps. It should be well packed into the stuffing box, but not too hard. If, after screwing down the nut in place, the box is not full, remove the nut again and put in more pack- ing. Replace the nut and screw well down, not too tight. If properly done, thumb and finger will screw the nut tight enough. The piston rod should be kept properly oiled. The packing nuts should be. tightened up from time to time, and the packing should be renewed occasion- ally without waiting till it is burned out. Some operators use pure gum rings that will slip into the stuffing box with light pressure. Square or rectangular gums will answer if the rings are not convenient to get. This packing must not be screwed down too tight, as the ammonia MANAGEMENT OF ABSORPTION PLANT. 293 will swell the rubber, and in that case it may bind the rod so tightly that it will roll it out of the stuffing box. Use mineral oil for lubricating. ECONOMIZING WATER. The economizing of water is a question of even more importance with the absorption system than with the compression system, as it is used not only in the condenser and boiler, but also for the absorber. In this case also it can be recooled and re-used by gradation, and in locali- ties where the water is warm, it may be good policy to cool it by gradation in the first place. The water after hav- ing passed the absorber is better for boiler feeding than the natural water, not only because it is heated to some extent already, but also because it has already deposited some or most of its mineral matter which would tend to form scale in the boiler. The cooling water after hav- ing left the absorber might be used to condense the moist steam from ammonia pump, in case this is also needed for ice making before it enters the boiler. Some absorption machines use the cooling water for the double purpose of cooling the absorber first, and then the condenser, or vice versa. OPERATING BRINE TANK. The principal information relating to brine and freezing tanks is given elsewhere. The following may be added relative to their operation: In order to be able to fully utilize the coils in brine tanks, they should be made in short runs, and kept free from ice. Sometimes when the brine is not strong enough, the formation of ice around the expansion coil may take place, and this greatly reduces the capacity of the freezing tank, and in some measure accounts for the great variation in pipe lengths required in different plants. No galvanized iron pipe should be used for direct expansion, and con- nections, etc., should be made with extra strong unions, flanged joints, etc. No right and left coupling, nor ordi- nary couplings should be used, and the element of un- certainty should be entirely avoided. LEAKS IN BRINE TANKS. Small leaks in brine tanks may sometimes be stopped by the application of bran or corn meal near the place where the leak is. The meal or bran should be carried (in small portions at the time) to the place where the leak is, by means of a short piece of open pipe. 294 MECHANICAL REFRIGERATION. In making repairs to coils while immersed in brine the workmen should besmear their arms and hands with cylinder oil, lard or tallow, as that will enable them to keep them in the cold brine without much inconven- ience for some time. TOP AND BOTTOM FEED BRINE COILS. The expansion coils in brine tanks are fed from bot- tom or top according to the system of refrigeration, as mentioned elsewhere, but it is claimed that the disad- vantages of both ways of feeding can be avoided by using what is called TOP FEED AND BOTTOM EXPANSION. This system is a combination of the best elements of the two systems above described. Each alternate coil in a tank is connected to a liquid manifold (provided with regulating valves) at the top of the tank, and the ammonia is evaporated downward through one-half of the coils in the tank. All of the coils in the tank are connected to a large bottom manifold (which might be called an equalizing expansion manifold), and the gas is returned up through the second half of the coils to a gas suction manifold at the top of the tank, located be- hind and a little above the liquid manifold. The suction manifold is provided with a tee for connecting the suction pipe leading to the compressors. CLEANING BRINK COILS. When the pipes in the brine tank are to be blown out by steam, the brine must be removed and the head- ers of the coils must be disconnected and each coil must be steamed out separately with dry steam, care being taken to let the steam blow through the coils long enough to heat them thoroughly, so that when the steam is shut off the coils are left hot enough to absorb all moisture inside. DRIPPING CEILING. Dripping ceiling is an awkward trouble liable to oc- cur where rooms are to be refrigerated. There seems to be no universal cure for a dripping ceiling; even as to the causes of such occurrence the most experienced en- gineers seem to have only conjectures. In some cases it seems that in storage rooms located one above the other the ceiling of the lower drips on account of the cold iloor above. In other cases it appears that the space between the ceiling and refrigerating coils is too small, MANAGEMENT OF ABSORPTION PLANT. 205 allowing condensation to form on the ceiling which oth- erwise would have settled on the pipes again. It is asserted that porous ceilings, formed with brick arches laid in ordinary mortar, will prevent condensation over- head, while ceilings formed of sheet metal, wood painted, and varnish air tight and ditto cement ceilings are prone to condense moisture. The dripping from re- frigerating coils should be caught in drip pans placed or hung below them, and, generally speaking, the drippings ought to be prevented from entering the fermenting tubs, dripping over meat, vegetables and cold storage goods in general. REMOVING ICE FROM COILS. The removal of ice from ammonia expansion coils can be best effected by allowing hot ammonia vapor to enter them, and a connection to permit this should be provided for. The ice can be thawed off in this way or loosened so that it can be knocked off. If the ice is re- moved soon after it has formed, say daily, it is sufficiently loose in itself, so that it can be cleaned off without any special artifices. MANAGEMENT OF OTHER PLANTS. The management of other refrigeration plants, notably of those which work on the compression plan, such as the sulphurous acid, the carbonic acid and" Pictet liquid " machines, is in most principal points like that of the ammonia compression machines. In the case of carbonic acid it is somewhat difficult to detect and locate leaks on account of its being free from odor. The best avail- able means in this connection are soapsuds, smeared over the pipes, joints, etc., when leaks will demonstrate themselves by the formation of bubbles. COST OF REFRIGERATION. The principal expense in the production of artificial refrigeration and artificial ice IB coal and labor. And as it takes much less labor in proportion to run a large plant than a small one, it is evident that larger plants, especially for ice making, are more profitable. Also less coal is required for larger than for smaller plants. While four men are required to operate ice plants of one to five tons capacity, it will take only five men to operate a 10- ton plant, and only eight men to operate a 35-ton plant, 206 MECHANICAL REFRIGERATION. CHAPTER XVI. TESTING OF PLANT. TESTING OF PLANT. The testing of a plant is executed in different ways in accordance with what the test is intended to prove. When the question is simply as to what a plant can be made to do, independent of the use of coal, the use of condensing water and the wear and tear of machinery, the test is simply a matter of shoveling coal and, pumping condenser water. However, the time of such tests has gone by, and the question nowadays is, as to what a ma- chine will do under normal comparable conditions and as to how the refrigeration produced compares with the amount of work expended and the amount of coal con- sumed. FITTING UP FOR TEST. To make a test of this kind a number of preparations have to be made. The compressor as well as the steam en- gine has to be provided with indicators; the condensing water supply has to be connected with a meter, and the amount of brine circulated must be ascertained in a similar manner. The temperature of incoming and out- going brine, of the incoming and outgoing condenser water, must be measured as exactly as possible, as also the actual temperature of the gas when entering and leaving the compressor, for which purpose mercury wells should be placed in the suction and discharge pipe near the compressor. , MERCURY WELLS. A mercury well is simply a short piece of pipe, closed at one end and fitted tightly into a pipe or vessel, the temperature of which is to be ascertained. The pipe is filled with mercury, and an exact thermometer is placed in the latter. THE INDICATOR DIAGRAM. An indicator diagram shows the outline of a surface, limited on one side by a horizontal line, the length of which represents the length of the stroke of a piston (of a pump, engine, compressor, etc.), in reduced scale. A line connecting the two ends of the straight line overhead is formed by connecting the points, which by their vertical distance from the said horizontal line indicate the press- ure working on the piston when passing their respective points on the horizontal line on a certain scale. TESTING OF PLANT. 207 These diagrams are obtained by instruments called indicators, which are applied in accordance with instruc- tions accompanying each instrument when bought. The area of such a diagram limited by a straight line on one side and by a curve on the other sides, repre- sents the work done by the compressor during one stroke in foot-pounds. The area of the diagram may be found by calculation in dividing the same into convenient sections, measuring them and adding them up. The area may also be measured by a machine con- structed for this purpose, called a planimeter. With proper precaution and an accurate scale, the area of these diagrams can also be ascertained by cutting them out carefully and weighing them. The weight so obtained can then be compared with that of a rectangu- lar piece of paper of the same thickness and known sur- face. In addition to the actual work done by or applied to a piston during each stroke, these diagrams show at a glance the conditions of pressure at the different posi- tions of the piston, give also a ready idea of the regular- ity of its working, the working of the valves and the changes of temperature. CALCULATION OF DIAGRAM. Usually, and in the absence of a planimeter, the indi- cator diagram of the compressor is divided into ten ver- tical stripes, the median heights of which are added and divided by 10. whereby the median height of the dia- gram is found in inches or millimeters. As it is known for every indicator spring what pressure corresponds to one millimeter or to one inch or fraction of an inch, we can readily find the mean pressure of the compressor from the average height of the diagram. The average pressure in pounds per square inch multiplied by the area of the piston in square inches and by the number of feet trav- eled by the same per minute gives the work of the com- pressor in foot-pounds per minute, which may be divided by 33,000 to find the horse power of the compressor. In close calculations allowance must be made for the thick- ness of the piston rod in double-acting compressors, as the area of the piston is lessened on one side to that ex- tent. It is also well to obtain a number of indicator dia- grams at intervals of from ten to thirty minutes. MECHANICAL REFRIGERATION. MEAN PRESSURE OF COMPRESSOR. In the absence of an indicator diagram the mean pressure in the compressor, and indirectly the work of the compressor, may be found approximately in the accompanying table (De La Vergne's catalogue) from the refrigerator and condenser pressure and temperature. 0500OS OOr^rH lr- OO rH O5 OS Oi Cq CO OO rH CO -* O-^OO CO CO O IQ^ rHO OCOCO ooooo oi--os - ^OO IOIOU3 -CD CO l~- O ^T^IO r5 rH 00 00 O CD CO O t- O T* i 1 CO CO COtC^ OS CO CO rHLQr- -^ CO Oi O rH C- A INTERPRETATION OF DIAGRAM. In order to interpret the compressor diagram with regard to the working of the compressor, its valves, defects, etc., Lorenz gives the following outlines: If all parts of the machine are in proper condition, the general appearance of the diagram will be that repre- sented in Fig. 1. The suction line, I W 05 * O ' 61 O CO D O CO OS W 5O 81 Mill CO < L-* OD HIS 91 fl T-l CO CM O CO 81 CO OO CO O M Ol CO CO O !> SliiB co e oo co 1113 01 5O t- OS O rs t- oo os >-i 'O CO O t-- S 3 O t- CO O t- O t- CO O 88 SS t CO O t- CO S SS 3 88 85 CO t 00 05 O 326 MECHANICAL REFRIGERATION. TABLE FOB CONVERTING FEET HEAD OF WATER INTO PRESSURE PER SQUARE INCH. Feet. Head. Pounds per square inch. Feet. Head. Pounds per square inch. Feet. Head. Pounds per square inch. 1 .43 55 23.82 190 82.29 2 .87 60 25.99 200 86.62 3 1.30 65 2&15 225 97.45 4 1.73 70 30.32 250 108.27 5 2.17 75 32.48 275 119.10 6 2.60 80 34.65 300 129.93 7 8.03 85 36.81 325 140.75 8 3.40 90 38.98 350 151.58 9 3.90 95 41.14 375 162.41 10 4.33 100 43.31 400 173.24 15 6.50 110 47.64 500 216.55 20 8.66 120 51.97 600 259.85 25 10.83 130 56.30- 700 303.16 30 12.99 140 60.63 800 346.47 35 15.16 150 64.96 900 389.78 40 17.32 160 69.29 1000 433.09 46 19.49 170 73.63 60 21.65 180 77.96 .....V 1 14.7 14.7 0.4X lb. pressure lb. - Ibs. or 1 atmosphere, i Iper square inch is equivalent to a head of water of... 2.3093 feet. 27.71 inches, 33.947 feet. 10.347 meters. 1 foot. 43.3 Ibs. J 100 feet. TABLE OP THEORETICAL HORSE POWER REQUIRED TO RAISE WATER TO DIFFERENT HEIGHTS. Feet. 5 10 15 20 25 30 35 40 45 50 60 Gals, per Minute. 5 .006 .012 .019 .025 .031 .037 .044 .05 .06 .06 .07 JO .012 .025 .037 .050 .062 .075 .087 .10 .11 .12 .15 15 .019 .037 .056 .075 .094 .112 .131 .15 .17 .19 .22 20 .025 .050 .075 .100 .125 .150 .175 .20 .22 .25 .30 25 .031 .062 .093 .125 .156 .187 .219 .25 .28 .31 .37 30 .037 .075 .112 .150 .187 .225 .262 .30 .34 .37 .45 35 .043 .087 .131 .175 .219 .262 .306 .35 .39 .44 .52 40 .050 .100 .150 .200 .250 .300 .350 .40 .45 .50 .60 45 .056 .112 .168 .225 .281 .337 .394 .45 .51 .56 .67 50 .062 .125 .187 .250 .312 .375 .437 .50 .56 .62 .75 60 .075 .150 .225 .300 .375 .450 .525 .60 .67 .75 .90 75 .093 .187 .281 .375 .469 .562 .656 .75 .84 .94 1.12 90 .112 .225 .337 .450 .562 .675 .787 .90 1.01 1.12 1.35 100 .125 .250 .375 .500 .625 .750 .875 1.001.12 1.25 1.50 125 .156 .312 .469 .625 .781 .937- 1.094 1.251.41 1.56 1.87 150 .187 .375 .562 .750 .937 1.125 1.312 1.501.69 1.87 2.25 175 .219 .437 .656 .875 1.093 1.312 1.531 1 75 1.97 2.19 2.63 200 .250 .500 .750 1.000 1.250 1.500 1.750 2:00|2.25 2.50 3.00 250 .312 .625 .937 1.250 1.562 1.875 2.187 2 5012.81 3.12 3.75 300 .375 .750 1.125 1.500 1.875 2.250 2.625 d. 003. 37 3.75 4.50 350 .437 .875 1.312 1.750 2.187 2.625 3.062 o Js.94 4.37 5.25 400 .500 1.000 1.500 2.000 3.500 3.000 3.500 lS3460 5.00 6.00 500 .625 1.250 1.875 2.500 a. 125 3.750 4.375 I.-88I 8 -" 6.25 7.50 APPENDIX I. 327 jad spuno -i uj M RHOrTTIOnmJJ ; ; ; ' ' ; ; ; * * <=> ; O OOOOOOO:<=> : -Hp-cjw^tot- g " " ^ ^ ^ ^ ^~^ ^ ^55 HO TCO i i o '*o M< puooggjad :::::::: : : : r^ M .* C4 ;CO USWt-QOOrHN I . . . .0 U5'* spunoj . . G 1 o M -puooagaad I :: ::"::: ;^SS33jo< i : I'"?'^ 00 . 00 .^** 1H ;C4 'CO ;* 'U3t-OMU5^0 M -spunoj ut O SSO'T UOl^OW^ I OOOTHWCOIO^OOOO fe ' _ puoo9g aad O iH N CO * O D t- 00 O> CO 03 (j? -sputio j n| I o puooagjad I 8dlJUl'OOT8A I HCOCOt*0>QT7|COg> . -spunoj ui w BSOT; ^H ^^ puooagaad I R"^1 c< ! eo . ce . f0 . 9dl UI 'OO19A I W-*CoMj50 spuno^ nt ot-*o g ssoi M pnooag aad 9dii ui -ooia spuno jui ssoi puooagaad ^? : : : : ; : : 000 jod 328 MECHANICAL REFRIGERATION. FLOW OF STEAM THROUGH PIPES. 23 Diameter of Pipe in inches. Length of each Pipe, z a 240 Diameters. 0) 02 | * 1 1*6 2 f* 3 4 1! a 1-4 ft Weight of Steam per Minute in Pounds, with One Pound Fall of Pressure. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. 1 1.16 2.07 5.7 10.27 15.45 25.38 46.86 10 1.44 2.57 7.1 12.72 19.15 31.45 48.05 20 1.70 3.02 8.3 14.94 22.49 36.94 68.20 30 1.91 3.40 9.4 16.84 25.35 41.63 76.84 40 2.10 3.74 10.3 18.51 27.87 45.77 84.49 50 2.27 4.04 11.2 20.01 30.13 49.48 91.34 60 2.48 4.32 11.9 21.38 32.19 52.87 97.60 70 2.57 4.58 12.6 22.65 34.10 56.00 103.37 80 2.71 4.82 13.3 23.82 35.87 58.91 108.74 90 2.83 5.04 13.9 24.92 37.52 61.62 113.74 100 2.95 5.25 14.5 25.96 39.07 64.18 118.47 130 3.16 5.63 15.5 27.85 41.93 68.87 127.12 150 3.45 6.14 17.0 30.37 45.72 75.09 138.61 For any other given length of pipe divide 240 by the given length in diameters and multiply the tubular values by the square root of the quotient, to give the flow for one pound fall of pressure. For any other given fall of pressure multiply the tubular weight by the square root of the given fall of pressure. HORSE POWER OF BOILERS. Thirty pounds of water evaporated at seventy pounds steam pressure per hour from feed water at 100=1 horse power. In calculating horse power of steam boilers consider for Tubular boilers, fifteen square feet of heating surface equivalent to one horse power. Flue boilers, twelve square feet of heating surface =1 horse power. Cylinder boilers, ten square feet of heating surface =1 horse power. Doubling the diameter of a pipe increases its capac- ity four times; friction of liquids increases as the square of velocity. To find the pressure, in square inches, of a column of water: Multiply the height of the column in feet by .434 approximately. Every foot elevation is equal to half pound pressure per square inch; this allows for ordinary friction. APPENDIX I. 329 WOOD'S TABLE OF SATURATED AMMONIA.* Recalculated by GEORGE DAVIDSON, M. E. Tempera- ture. Pressure, Absolute. & ** y 2s I!* P ig W (4 1 ^ -?s 2* * c3 -* 5 h 6 jju N || s!^ o 5"S "o^ Sl| O 3*^ tL en -P O ai 3 'C *H ** rr> a>(v <% 43 O } +3 o QQ Q) rHtl 3 3*3 fP fl f4 O G 4-j S fc f] F^l JPMS ^2 ^ H **"* 15" a . a ^ to ^ o +3 O** ^ a> * 3f 3 S bo A- 1 |A O |SP "3 P.P "^ fl p 40 420.66 1539.90 10.69 4.01 579.67 24.388 .02348 .0410 42.589 40 39 1 1584.43 11.00 3.70 579.07 23.735 .02351 .0421 42.535 39 38 2 1630.03 11.32 3.38 578.42 23.102 .02354 .0433 42.483 38 37 3 1676.71 11.64 3.06 577.88 22.488 .02357 .0444 42.427 37 36 4 1724.51 11.98 2.72 577.27 21.895 .02359 .0457 42.391 36 35 425.66 1773.43 12.31 -2.39 576.68 21.321 .02362 .0469 42.337 35 34 6 1823.50 12.66 2.04 576.08 20.763 .02364 .0482 42.301 34 33 7 1874.73 13.02 1.68 575.48 20.221 .02366 .0495 42.265 33 32 8 1927.17 13.38 1.32 574.89 19.708 .02368 .0507 42.213 32 31 9 1980.78 13.75 0.95 574.39 19.204 .02371 .0521 42.176 31 30 430.66 2035.69 14.13 0.57 573.69 18.693 .02374 .0535 42.123 30 29 1 2091.83 14.53 0.17 573.08 18.225 .02378 .0549 42. 052 29 28 2 2149.23 14.92 +0.22 572.48 17.759 .02381 .0563 42.000 28 27 3 2207.94 15.33 +0.63 571.89 17.307 .02384 .0577 41.946 27 26 4 2267.97 15.76 +1.05 571.28 16.869 .02387 .0693 41.893 26 25 435.66 2329.34 16.17 +1.47 570.68 16.446 .02389 .0608 41.858 -25 24 6 2392.09 16.61 1.91 570.08 16.034 .02392 .0624 41.806 24 23 7 2456.23 17.05 2.35 569.48 15.633 .02395 .0640 41.754 23 22 8 2520.45 17.50 2.8 568.88 15.252 .02398 .0656 41.701 22 21 9 2588.77 17.97 3.27 568.27 14.876 .02401 .0672 41.649 21 20 440.66 2657.23 18.45 +3.75 567.67 14.507 .02403 .0689 41.615 -20 19 1 2727.17 18.94 ^.24 567.06 14.153 .02406 .0706 41.563 19 18 2 2798.62 19.43 4.73 566.43 13.807 .02409 .0725 41.511 18 17 3 2871.61 19.94 5.24 565.85 13.475 .02411 .0742 41.480 17 16 4 2946.17 20.46 5.76 565.25 13.150 .02414 .0760 41.425 16 15 445.66 3022.31 20.99 +6.29 564.64 12.834 .02417 .0779 41.374 -15 14 6 3100.07 21.53 6.83 564.04 12.527 .02420 .0798 41.322 14 13 7 3179.45 22.08 7.38 563.43 12.230 .02423 .0818 41.271 13 12 8 3260.52 22.64 7.94 562.82 11.939 .02425 .0838 41.237 12 11 9 3343.29 23.22 8.52 562.21 11.659 .02428 .0858 41.186 11 10 450.66 3427.75 23.80 +9.10 561.61 11.385 .02431 .0878 41.135 10 9 1 3513.97 24.40 9.70 560.99 11.117 .02434 .0899 41.084 9 8 2 3601.97 25.01 10.31 560.39 10.860 .02437 .0921 41.034 8 7 3 3691.75 25.64 10.94 559.78 10.604 .02439 .0943 41.000 7 6 4 3783.37 26.27 11.57 559.17 10.362 .02442 .0965 40.950 6 5 455.66 3876.85 26.92 +12.22 558.56 10.125 .02445 .0988 40.900 5 4 6 3972.62 27.59 12.89 557.94 9.894 .02448 .1011 40.845 4 3 7 4069.48 28.26 13.56 557.33 9.669 .02451 .1034 40.799 3 2 8 4168.70 28.95 14.25 556.73 9.449 02454 .1058 40.749 2 1 9 4269.90 29.65 14.95 556.11 9.234 .02457 .1083 40.700 1 +0 460.66 4373.10 30.37 +15.67 555.50 9.028 .02461 .1107 40.650 +0 1 1 4478.32 31.10 16.40 554.88 8.825 .02463 .1133 40.601 1 2 2 4486.60 31.84 17.14 554.27 8.630 .02466 .1159 40.551 2 a 3 4694.96 32.60 17.90 553.65 8.436 .02469 .1186 40.502 3 4 4 4806.46 33.38 18.68 553.04 8.250 .02472 . 1212 40.453 4 * For values at temperatures higher than 100 F. see Wood's table on page 92. 330 MECHANICAL REFRIGERATION. WOOD'S TABLE OF SATURATED AMMONIA Continued. Tempera- ture. Pressure, Absolute. Si !! - !=>_ P* flff || ri i II *J K I^U !|l O Q 0} IS O <% a o Ogfe 7j ^ ^ ~ sH 3^" 13 t3 , -po^ In* IK^O WJ^ fi^lS S g noaftn OQQ ft esPMM 8SP "o a2 13 p-2 '55 .So '.So te Q ^ > Q ~+5 466.66 4920.11 34.16 +19.46 552.43 8.070 .02475 .1240 40.404 +5 6 6 5035.95 34.97 20.27 551.81 7.892 .02478 .1267 40.355 6 7 7 5153.99 35.79 21.09 551.19 7.717 .02480 .1296 40.322 7 8 8 5274.28 36.63 21.93 550.58 7.553 .02483 .1324 40.274 8 9 9 6396.83 37.48 22.78 549.96 7.388 .02486 .1353 40.225 9 +10 470.66 5521.71 38.34 +23.64 549.35 7.229 .02490 .1383 40.160 +10 11 1 6649.48 39.23 24.53 548.73 7.075 .02493 .1413 40.112 11 12 2 5778.50 40.13 25.43 548.11 6.924 .02496 .1444 40.064 12 13 3 5910.52 41.04 26.34 547.49 6.786 .02499 .1474 40.016 13 14 4 6044.96 41.98 27.28 546.88 6.632 .02502 .1507 39.968 14 +15 475.66 6182.00 42.94 +28.24 546.26 6.491 .02505 .1541 39.920 +15 16 6 6321.24 43 90 29.20 545.63 6.355 .02508 .1573 39.872 16 17 7 6463.24 44.88 30.18 545.01 6.222 .02511 .1607 39.872 17 18 8 6607.77 45.89 31.19 544.39 6.093 .02514 .1641 39.777 18 19 9 6754.90 46.91 32.21 543.74 5.966 .02517 .1676 39.729 19 +20 480.66 6904.68 47.95 33.25 543.15 5.843 .02520 .1711 39.682 +20 21 1 7057.15 49.01 34.31 642.53 5.722 .02523 .1748 39.635 21 22 2 7211.33 50.09 35.39 541.90 5.605 .02527 .1784 39.572 22 23 3 7370.27 51.18 36.48 641.28 5.488 .0^529 .1822 39.541 23 24 4 7530.96 52.30 37.60 540.66 5.378 .02533 .1860 39.479 24 +25 485.66 7694.52 53.43 +38.73 540.03 5.270 .02536 .1897 39.432 +25 26 6 7860.89 54.59 39.89 539.41 5.163 .02539 .1937 39.386 26 27 28 7 8 8030.16 8202.38 55.76 66.96 41.06 42.26 538.78 538.16 5.058 4.960 .02542 .02545 .1977 .2016 39.339 39.292 27 28 29 9 8377.56 58.17 43.47 537.53 4.858 .02548 .2059 39.246 29 +30 490.66 8555.74 59.42 +44.72 536.91 4.763 .02551 .2099 39.200 +30 31 1 8736.96 60.67 45.97 536.28 4.668 .02554 .2142 39.115 31 32 2 8921.26 61.95 47.25 535.66 4.577 .02557 .2185 39.108 32 33 3 9108.71 63.25 48.55 535.03 4.486 .02561 .2229 39.047 33 34 4 9299.32 64.58 49.88 534.40 4.400 .02564 .2273 39.001 34 +35 495.66 9493.07 65.92 +51.22 533.78 4.314 .02568 .2318 38.940 +35 36 6 9690.04 67.29 52.59533.13 4.234 . 02571 .236238.894 36 37 7 9890. 75 68.68 53.98532.52 4.157 .02574 .241338.850 37 38 8 10093.91 70.09 55. 39J531.89 4.068 .02578 .245838.789 38 39 9 10300.88 71.53 56.83 531.26 3.989 .02582 .2507 38.729 39 +40 600.66 10511.16 72.99 +58.29 530.63 3.915 .02585 .2554 38.684 +40 41 1 10724.95 74.48 59.78529.99 3.839 .02588 .260538.639 41 42 2 10942.18 75.99 61.29529.36 3.766 .02591 .265538.595 42 43 3 11162.93 77.52 62.82528.73 3.695 .02594 .2706 '38. 550 43 44 4 11387.21 79.08 64.38 528.10 3.627 .02597 .2757 38.499 44 +45 505.66 11615.12 80.66 +65.96 527.47 3. "559 .02600 .2809 38.461 +45 46 6 11846.64 82.27 67.57 526.83 3.493 .02603 .2863 38.417 46 47 7 12081.80 83.90 69.20 526.20 3.428 .02606 .2917 38.373 47 48 8 12320.71 85.56 70.86 525.57 3.362 .02609 .2974 38.328 48 49 9 12563.36 87.25 72.55 524.93 3.303 .02612 .3027 38.284 49 +50 510.66 12809.91 88.96 +74.26 524.30 3.242 .02616 .3084 38.226 -1-50 51 1 13080.21 90.70 76.00523.66 3.182 .02620 .3143 38.167 51 52 2 13314.43 92.46 77.76523.03 3.124 .02623 .3201 88.124 52 63 3 13572.52 94.25 79.55 522.39 3.069 .02626 .3258 38.080 53 54 4 13834.64 96.07 81. 371521. 76 3.012 .02629 .3320 38.037 54 APPENDIX I. 331 WOOD'S TABLE OF SATURATED AMMONIA Continued. Tempera- ture. Pressure, Absolute. i$ *i i 8= 8* 5 a !*' 2 S3 " emper-|| iture. j| . SM h . eSt 5,4 fel ^a cw 'Ho ^"1? H w S 1 1 p,g si- *i$ |*I J*| 43 fl^2 pO o S*s tn 1- 1 fjffii ao-^ ill & lls "o P.3 Sfg a SlsS Sj cu o H * > J 5j Q +55 515.66 14100.74 97.92 +83.22 521 12 2.958 .02632 .3380 37.994 +55 66 6 14370.92 99.80 85.10 520.48 2.905 .02636 .3442 37.936 56 57 7 14645.18 101.70 87.00 519.84 2.853 .02639 .3505 37.893 57 58 8 14923.98 103.64 88.94 519.20 2.802 .02643 .3568 37.835 58 59 9 15206.28 105.60 90.90 618.57 2.753 .02646 .3632 37.793 59 +60 520.66 15493.09 107.59 +92.89 517.93 2.705 .02651 .3697 37.736 +60 61 1 15784.23 109.61 94.91 517.29 2.658 .02654 .3762 37.678 61 62 2 16079.67 111.66 96.96 516.65 2.610 .02658 .3831 37.622 62 63 3 16379.51 113.75 99.05 516.01 2.565 .02661 .3898 37.579 63 64 4 16683.75 115.86 101.16 515.37 2.520 .02665 .3968 37.523 64 +65 66 525.66 6 16992.50 17305.70 118.09 120.18 +103.33 105.48 514.73 514.09 2.476 2.433 .02668 .02671 .4039 .4110 37.481 37.439 +65 66 67 7 17623.45 122.38 107.68 513.45 2.389 .02675 .4189 37.383 67 68 8 17945.89 124.62 109.92 512.81 2.351 .02678 .4254 37.341 68 69 9 18272.81 126.89 112.19 512.16 3.310 .02682 .4329 37.285 69 + 71 530.66 1 18604.53 18941.00 129.19 131.54 +114.49 116.84 511.52 510.87 2.272 2.233 .02686 .02689 .4401 .4479 37.230 37.188 +70 71 72 2 19282.21 133.90 119.20 510.22 2.194 .02693 .4558 37.133 72 73 3 19628.32 136.31 121.61 509.58 2.153 .02697 .4645 37.079 73 74 4 19979.22 138.74 124.04 508.93 2.122 .02700 .4712 37.037 74 +75 535.66 20335.16 141.22 +126.52 508.29 2.087 .02703 .4791 36.995 +75 6 20696.00 143. 72 129.02 507.64 2.052 .02706 .4873|36.954 76 77 7 21061.85 146.26 131.56 506.99 2.017 .02710 .4957 36.900 77 78 8 21432.82 148.84 134.14 506.34 1.995 .02714 .501236.845 78 79 9 21808.85 151.45 136.75 505.69 1.952 .02717 .512336.805 79 +80 540.66 22190.15 154.10 +139.40 505.05 1.921 .02721 .520536.751 +80 81 1 22576.51 156.78 142.08 504.40 1.889 .02725 .529436.696 81 82 2 22968.88 159.50 144.80 503.75 1.858 .02728 .538236.657 82 83 3 23365.38 162.26 147.56 603.10 1.827 .02732 .547336.603 83 84 4 23767.81 166.05 150.35 502.45 1.799 .02736 .5558 36.549 84 +85 545.66 24175.61 167.88 +153.18 501.81 1.770 .02739 .5649 36.509 +85 8b 6 24588.92 170.75 156.05 501.15 1.741 .02743 .574436.456 86 87 7 25007.80 173.66 158.96 500.50 1.714 .02747 .583436.407 87 88 8 25432.16 176.61 161.91 499.85 1.687 .02751 .592736.350 88 89 9 25862.14 179.59 164.89 499.20 1.660 .02754 .6024 36.311 89 *1 550.66 1 26297.88 26739.88 182.62 185.69 +167.92 170.99 498.55 497.89 1.634 1.608 .02758 .02761 .6120 .6219 36.258 36.219 +90 91 92 2 27186.56 188.79 174.09 497.24 1.583 .02765 .6317 36.166 92 93 3 27639.43 191.94 177.24 496.59 1.558 .02769 .6418 36.114 93 94 4 28098.26 195.13 180.43 495.94 1.534 .02772 .6518 36.075 94 +95 555.66 28563.00 198.35 +183.65 495.29 1.510 .02776 .6622 36.023 +95 96 6 29033.86 201.62 186.92 494.63 1.486 .02780 .6729 35.971 96 97 7 29510.69 204.94 190.24 493.97 1.463 .02784 .6835 35.919 97 .98 8 29993.52 208.29 193.59493.32 1.442 .02787 .6934 35.8K1 98 99 9 30482.52 211.68 196.98 492.66 1.419 .02791 .7047 35.829 99 +100 560.66 30977.78 215.12 +200.42 492.01 1.398 .02795 .7153 35.778 +100 332 MECHANICAL REFRIGERATION. TABLE OF HUMIDITY IN AIR. 2 g ri 0> p 2 g ^ PO !|8| 1^5*1 g"w^S "S py^^o a c'"^^ | 8.?^O 5 > H ffo 10 2.1 2.3 +13 11.2 11 4 9 2.3 2.5 +14 11.9 12.1 8 2.5 2.7 +15 12.7 12.9 7 2.7 2.9 +16 13.5 13.6 6 2.9 3.2 +17 14.4 14.6 6 3.1 3.4 +18 15.4 15.4 4 3.4 3.7 +19 16.3 16.3 3 3.7 4.0 +20 17.4 17.3 2 4.0 4.3 +21 18.5 18.4 1 4.3 4.6 +22 19.7 19.4 4.6 4.9 --23 20.9 20.6 + 1 6.0 5.3 --24 22.2 21.8 + 2 5.3 5.6 --25 23.6 23.1 + 3 5.7 6.0 --26 25.0 24.4 T 4 6.1 6.4 +27 26.6 25.8 T 5 6.5 6.8 +28 28.1 27.2 T 6 7.0 7.3 +29 29.8 28.8 *4~ 7 7.5 7.8 +30 31.5 30.4 + 8 8.0 8.3 +31 33.4 32.1 + 9 8.6 8.9 +32 35.4 33.8 +10 9.2 9.4 +33 37.4 35.7 +11 9.8 10.1 +34 39.3 37.6 +12 10.5 10.7 +35 41.5 39.3 TABLE SHOWING AMOUNT OF MOISTURE TO 100 LBS. OF DRY AIR WHEN SATURATED AT DIFFERENT TEMPERATURES. Temper- ature. Fahr. Degrees. Weight of Vapor in Ibs. Temper- ature. Fahr. Degrees. Weight of Vapor in Ibs. Temper- ature. Fahr. Degrees. Weight of Vapor in Ibs. 20 10 +10 20 32 42 52 0.0350 0.0574 0.0918 0.1418 0.2265 0.379 0.561 0.819 62 72 89 92 102 112 122 132 1.179 1.680 2.361 3.289 4.547 6.253 8.584 11.771 142 152 162 172 182 192 202 212 16.170 22.465 31.713 46.338 71.300 122. (543 280.230 Infinite. LATENT UNITS OI TION I " HEAT OF FUSION AND VOLATILIZA- ER POUND OF SUBSTANCE. Solids Melted to Liquids. -f, Latent Heat B. T. Units Liquids Converted to Vapor. Latent Heat B. T. Units Ice to water .... 142 25.6 50.6 17.0 9.72 5.00 175 550 233 46.4 Water to steam Ammonia 966 495 372 298 212 174 137 184 167 175 Tin Zinc Alcohol, pure Carbonic acid Bisulphite of carbon. Ether, sulphuric Essence of turpentine Oil of turpentine Mercury Lead Mercury Beeswax ...... .... Bismuth Cast iron Spermaceti Chimogene APPENDIX I. 333 COLD STORAGE RATES. The charges for cold storage and rates for freezing must depend greatly upon various conditions, such as capacity of house, demand and supply, competition to be met and other local conditions. For general use and as a basis for figuring, the following rates, which are those now in force in the principal cold storage points and which are generally adhered to, will be found useful: COLD STORAGE BATES PER MONTH. GOODS AND QUANTITY. 11 E l Each Succeeding Month. In Large Quantities, per Month. Season Rate per Bbl. orlOOLbs. 1 II 4 Ibs. = 7H gallons. 1 Ib. water = 27.8 cubic inches = 1 pint. The friction of water in pipes is as the square of its velocity. Doubling the diameter of a pipe increases its capacity four times. In tubular boilers, 15 square feet of heating surface are equiv- alent to one horse power; in flue boilers, 12 square feet of heating surface are equivalent to one horse power; in cylinder boilers, 10 square feet of heating surface are equivalent to one horse power. One square foot of grate will consume, on an average, 12 Ibs. of coal per hour. Consumption of coal averages 7^ Ibs. of coal, or 15 Ibs. of dry pine wood, for every cubic foot of water evaporated. The ordinary speed to run steam pumps is at the rate of 100 feet piston travel per minute. APPENDIX I. 339 r C, ^, mooooo nternal q. Inch. External Sq. Inch rn he Externa Inches. gss Act nte Inc Actual Externa Inches. Nomina Internal Inches. O CO OS C SSss * lls? SS3S icgao SS85 5fl 05 00 00 >0 lls igjO i! 340 MECHANICAL REFRIGERATION. UN? gSSsssSSIs'ssi^ 3 g jojiaureig M^^^'oogtofc-fc-^QOQeQOQoaotaggsjggg EH j ni'Ba^g rj XfL, .__ tvj> ' -FH ^lOOt-OSOrt rH TJH US O CO ^ 01 CO CO * CO 00 rH 91 *H Oi JO JIOBR Sd OD M S5 O -" """- Jb i- t-tioOOOOSOJOSOS OS gOrH^^^ON^M MM M^h H TH iH r-( r-l i-l ri r-i i-liHi-l i-H T-I T-I fH rH i-H iH ^^i pt g CO CO 05 Q ^i rt jj w s 8 SI .'r-SS^^tHSSSfe Q -- ^^ - te 8 3 o S f 1 ? 5!Sg:^rtlS5gr:ggS8SS^g^ W PM o ^0^-5 ^^^^^s^ssss^ss^^fli^lSlliliii o 3 a -ow APPENDIX I. 341 TABLE OF MEAN TEMPERATURE OF DIFFERENT LOCALI- TIES, DEGREES FAHR. LOCATION. i >H b| a I CO Summer. Autumn. Winter. Algiers . 63 63 74 5 70 5 50 4 Berlin 47 B 46 4 63 1 47 8 30 6 Berne 46.0 45.8 60 4 47.3 30.4 Boston 49 48 66 53 28 Baltimore 64 9 60 83 64 6 43 5 Buenos Ayres 62 5 59 4 73 64 H 52 6 Cairo 72 3 71 6 84 6 74 3 58 5 Calcutta. . 78 4 82 6 83 3 80 67 8 69 8 69 8 82 72 9 54 8 Christiania. ... 41 7 39 2 59 5 42 4 25 2 Cape of Good Hope 66 4 63 5 74 1 66 9 58 6 Constantinople .... 56 7 51 8 73 4 60 4 40 5 46 8 43 7 63 48 7 31 3 Chicago 45 9 52 8 74 6 61 2 38 4 Cincinnati 54 7 63.2 81.8 6t5.4 46 6 Edinburgh 47 5 45 7 57 9 48 38 5 62 2 60 6 72 6 66 3 49 6 Jamaica (Kingston) Lima (Peru) 79 66 2 78.3 63 81.3 73 2 80 69 6 76.3 59 Lisbon. . 61 5 59 9 71 1 62 6 52 3 50 7 49 1 62 8 51 3 39 6 Madeira (Funchal) 65 7 6H 5 70 67 6 61 3 Madrid 57 g 57 6 74 1 56 7 42 1 Mexico City 60 5 53 6 63 4 65 2 60 1 Montreal 43 7 44 2 69 1 47 1 17 5 Moscow 38 5 43 3 62 6 34 9 13 5 Naples 61 5 59 4 74. g 62 2 49 6 New Orleans 72 73 84 72 58 New York 53 50 72 56 33 New Zealand 59 6 60 1 66 7 58 53 5 Nice 60 1 65 9 72 5 63 48 7 Nicolaief (Russia) 48 7 49 3 71 2 50 25 9 Paramatto (Australia)... . 64 6 66 6 73 9 64 8 54 5 Palermo 63 59 74 3 66 2 62 5 Pekin (China) 52 6 56 6 77 8 54 9 29 Paris 51 4 50 5 61 6 52 2 '37 9 Philadelphia 55 52 76 67 34 Quito (Equador) Quebec 60.1 40 3 60.3 60.1 62.5 59.7 Rio Janeiro 73 6 72 5 79 74 5 68 5 Rome 59.7 57 4 73 a 61 7 46 6 San Francisco 57 5 58 59 60 53 St. Louis 55 84 6 67 8 44.6 4H St Petersburg 38 3 35 1 60 3 40 5 16 6 Stockholm 42.1 38 3 61 43 7 25 5 Trieste. ... 55 8 53 8 71 5 56 7 39 4 Turin 53 1 53 1 71 6 53 8 33 4 Vienna. . ... ... 50 7 49 1 62 8 51 3 39 6 Warsaw 45 5 44 6 63 5 46 4 97 5 Washington 59 69 79 58 38 USEFUL DATA ABOUT LIQUIDS. A gallon of water contains 231 cubic inches, and weighs 8i pounds (U. S. standard). A cubic foot of water contains 7^ gallons, and weighs pounds. One U. S. gallon=.133 cubic feet; .83 imperial gal- Ion; 3.8 liters. 342 MECHANICAL REFRIGERATION. An imperial gallon contains 277.274 cubic inches. .16 cubic feet; 10.00 pounds; 1.2 U. S. gallons; 4.537 liters. A cubic inch of water=.03607 pound; .003607 impe- rial gallons; .004329 U. S. gallon. A cubic foot of water =6.23 imperial gallons; 7.48 U. S. gallons; 28.375 liters; .0283 cubic meters; 62.35 pounds; 557 cwt.; .028 ton. A pound of water = 27.72 cubic inches; .10 imperial gallon; .083 U. S. gallon; .4537 kilos. One cwt. of water = 11.2 imperial gallons; 13.44 U. S. gallons; 1.8 cubic foot. A ton of water = 35.9 cubic feet; 224 imperial gallons; 298.8 gallons; 1,000 liters (about); 1 cubic meter (about). A liter of water = .220 imperial gallon: .264 U. S. gallon; 61 cubic inches; .0353 cubic foot. A cubic meter of water = 220 imperial gallons; 264 U. S. gallons; 1.308 cubic yards; 61,028 cubic inches; 35.31 cubic feet; 1,000 kilos; 1 ton (nearly); 1,000 liters. A kilo of water = 2.204 pounds. A vedros of water = 2.7 imperial gallons. An eimer of water = 2.7 imperial gallons. A pood of water = 3.6 imperial gallons. A Russian fathom = 7 feet. One atmosphere = 1.054 kilos per square inch. One ton of petroleum = 275 imperial gallons (nearly). One ton of petroleum = 360 U. S. gallons (nearly). A column of water 1 foot in height = .434 pound pressure per square inch. A column of water 1 meter in height = 1.43 pounds pressure per square inch. One pound pressure per square inch = 2.31 feet of water in height. One U. S. gallon of crude petroleum = 6.5 pounds (nearly). One wine gallon, or U. S. gallon, Is equal to 8.331 pounds=3,785 cubic centimeters=58,318 grains. One imperial gallon (English gallon) is equal to about ten pounds=4.543 cubic centimeters =70,000 grains. One grain=0.0649 grams one gram= 15.36 grains. One barrel=1.192 hectoliters one hectoliter=0.843 barrels. One English quarter=eight bushels =290.78 liters. One English bushel=36.35 liters=0.3635 hectoliters. One English barrel =36 gallons. One American barrel =31 gals. One bushel malt (English), 40 pounds; American, 34 pounds (32 pounds cleaned); one bushel barley (American), 38 pounds. One kilogram square centimeter equal to 14.2 pounds inch pressure (equal to about one atmosphere). Four B. T. units equal to about one calorie. APPENDIX I. 343 TEMPERATURES FAHRENHEIT AND CENTIGRADE. jr. -c. F. G "F. C. "F. "C. op "C. F.| C. ; 330 165.6 267 130.6 206 96.7 143 61.7 80 26 7 19 - 7.2 329 165. 266 130. 205 96.1 142 61.1 79 26.1 18 78 328 164.4 265 Ii9.4 204 95.6 141 60.6 78 25.6 17 8.3- 327 163.9 264 128.9 203 95 140 60 77 25. 16 8.9 326 163.3 2*i:; 128.3 202 94.4 139 59 4 76 24 4 15 9.4 325 162.8 2(12 127.8 201 93.9 138 58.9 75 23.9 14 10. 324 162.2 261 127.2 200 93 3 137 58.3 74 23.3 13 10-6 323 161.7 2<;o 126.7 19!) 92.8 136 57.8 73 22.8 12 11.1 322 161.1 25!) 126.1 198 92.2 135 57.2 72 22.2 n -11.7 321 160.6 25S 125.6 197 91 7 134 56 7 71 21.7 10 -12.2 320 160. 257 125. 190 91 1 133 56.1 70 21 1 9 12.8 319 159.4 256 124.4 195 90.6 132 55.6 69 20.6 8 13.3 318 158.9 255 123.9 194 90. 131 55. 68 20. 7 -13.9 317 158.3 123.3 L93 89.4 1HO 54.4 67 19 4 6 -14.4 316 157.8 253 122.8 192 .88.9 12!) 53.9 66 18.9 5 -15. 315 157.2 252 122.2 191 88.3 12X 53.3 65 18.3 4 15.6 314 156.7 251 121.7 190 87.8 127 52.8 64 17'. 8 3 16.1 313 156.1 250 121.1 1X9 87.2 126 52.2 63 17.2 2 -16 7 312 155.6 24!) 120.6 1XX 86.7 125 51 7 62 16.7 1 -1-7.2 311 155. 24S 120. 1X7 86.1 124 51.1 61 16.1 17.8 310 154,4 247 119.4 1X6 85.6 123 50 6 60 15 6 1 -18.3 30!) 133*9 24i ; 118.9 1X5 85. 122 50. 59 15 2 -18.9 308 153.3 245 118.3 1*1 84.4 121 49.4 58 14 4 - 3 -19 4 307 152.8 244 117.8 1X3 83 9 120 48.9 57 13.9 4 -20 306 152.2 243 117.2 1S 83.3 11!) 48'. 3 56 13 3 5 -20.6 305 151.7 242 116.7 181 82.8 118 47.8 55 12.8 - 6 -21.1 304 151.1 241 116.1 180 82.2 117 47.2 54 12.2 7 -21.7 303 150.6 240 115.6 179 81.7 11(1 46.7 53 11.7 - 8 -22.2 302 150. 239 115. 178 81.1 115 46 1 52 11.1 9 -22.8 301 149.4 114.4 177 80,6 114 45.6 51 10.6 -10 -23.3 300 148.9 237 113.9 17'i 80. 113 45. 50 10. 11 23 9 299 148.3 236 113.3 175 79.4 112 44.4 49 9 4 12 -24 4 298 147.8 285 112.8 174 78.9 111 43.9 48 8.9 -13 -25. 297 147.2 234 112.2 173 78.3 110 43.3 47 8.3 -14 -25 6 296 146.7 233 111.7 172 77.8 109 42.8 46 7.8 15 --26 1 295 146.1 232 111.1 171 77.2 108 42 2 45 7.2 -16 -26.7 294 145.6 231 110.6 170 76.7 107 41.7 44 a. 7 -17 -27.2 293 145. 230 110. 16!) 76.1 10(1 41.1 43 6.1 -18 -27.8 292 144.4 22!) 109.4 1(18 75.& 105 40.6 42 5.6 -19 8.3 J291 143.9 228 108.9 167 75. 104 40. 41 5 -20 -28.9 290 143.3 227 108.3 ]M 74.4 103 39 4 40 4.4 -21 -29.4 289 142.8 "26 107.8 1(>5 73.9 102 38.9 39 3.9 -22 288 142.2 225 107.2 1(14 73.3 101 38 3 38 3.3 -23 js&Iot'O 287 141.7 224 106.7 1(13 72.8 100 37.8 37 2.8 -24 Sl l a% 286 141.1 223 106.1 1(12 72.2 99 37.2 36 2 2 -25 31 7 285 140.6 222 105.6 161 71.7 98 36 7 35 1.7 -26 -32 2 284 140. 221 105 160 71.1 97 36 1 34 1.1 2T -32.8 283 139.4 220 104.4 159 70.6 96 35.6 33 0.6 -28 -33.3 282 138.9 219 103.9 158 70. 95 35. Water freezes 29 33.9 281 138.3 218 103.3 157 69.4 94 34.4 0> f\ -30 -34.4 280 279 137r8 137,2 217 216 102.8 102.2 156 155 68.9 68.3 93 92 33.9 33.3 oJ U. =1 i-35. -35/6 31 0.6 278 136.7 215 101.7, 154 67.8 91 32.8 30 1.1 -33 36.1 277 136.1 214 101.1 153 67.2 90 32.2 29 17 34 36 7 276 )*7C 135.6 11C 213J 100.6 152 i i 66-.7 C 1 X!) 31.7 M 1 28 2.2 2Q 35 -37.2 410 274 1J5. 134.4 Water boils 151 150 bo. 1 65.6 87 dl.l 30. 6. 26 - 3.3 36 37 37. H 38.3 273 133.9 212 100. 149 65. 86 30. 25 3.9 38 9 272 133.3 211 99.4 148 64.4 85 29.4 24 4.4 39 39.4 271 132.8 210 98.9 147 63.9 84 28.9 23 - 5 270 269 132.2 131.7 209 98.3 208 97.8 14(i 145 63.3 62.8 83 82 28.3 27.8 22 21 5.6 6.1 Mercury freezes 26b 131,1 207 97.2 144 62.2 81 27.2 20 -8.3 40 40. j 344 MECHANICAL REFRIGERATION. SPECIFIC GRAVITY TABLE (BEAUME). The meaning of the degrees of the Beaume scale for liquids heavier than water has been defined somewhat differently by the manufacturing chemists of the United States. Accordingly the specific gravity for any given degree Beauine" is found after the formula: 145 Specific gravity= 145 _ deg Beaum< . The following table is calculated after this formula by Clapp: Degrees. Specific Gravity. Degrees. Specific Gravity. Degrees. Specific Gravity. 1.000 18 1.142 45 1.450 1 1.007 19 1.151 50 1.526 2 1.014 20 1.160 55 1.611 3 1-.021 21 1.169 60 1.706 4 1.028 22 1.179 65 1.812 5 1.036 23 1.188 70 1.933 6 1.043 24 1.198 7 8 9 1.051 1.058 1.066 25 26 27 1.208 1.218 1.229 66 Used by sulphuric acid man- u f a ctur- ers. 1.835 10 1.074 28 1.239 11 1.082 29 1.250 12 1.090 30 1.261 13 1.098 32 1.283 14 1.107 34 1.295 ' 15 1.115 36 1.306 16 1.124 38 1.318 17 1.133 40 1.381 APPENDIX I. 345 TABLE ON SOLUTIONS OF CHLORIDE OF CALCIUM. Specific Gravity at 84 F. Degree Beaum6 at 64 F. Degree Salometer at 64 F. Per Cent of Chloride of Calcium. Freezing Point. Deg. F. Ammonia Gauge. Pounds per Square Inch at Freezing Point. 1.007 1 4 0.943 +31.20 46 1.014 2 8 1.886 +30.40 45 1.021 3 12 2.829 +29.60 44 1.028 4 16 3.772 +28.80 43 1.035 5 20 4.715 +28.00 42 1.043 6 24 5.658 -26.89 41 1.050 7 28 6.601 -25.78 40 1.058 8 32 7.544 -24.67 38 1.065 9 34 8.487 -23.56 37 1.073 10 40 9.430 -22.09 35.5 1.081 11 44 10.373 h20.62 34 1.089 12 48 11.316 -19.14 32.5 1.097 13 52 12.259 -17.67 30.5 1.105 14 56 13.202 -15.75 29 1.114 15 60 14.145 -13.82 27 1.112 16 64 15.088 [-11.89 25 1.131 17 68 16.031 - 9.96 23.5 1.140 18 72 16.974 - 7.68 21.5 1.149 19 76 17.917 - 5.40 20 1.158 20 80 18.860 - 3.12 18 1.167 21 84 19.803 0.84 15 1.176 22 88 20.746 - 4.44 12.5 1.186 23 92 21.689 8.03 10.5 1.196 24 96 22.632 11.63 8 1.205 25 100 23.575 15.23 6 1.215 26 104 24.518 19.56 4 1.225 27 108 25.461 24.43 1.5 1.236 28 112 26.404 29.29 L " Vacuum 1.246 29 116 27.347 35.30 5 " 1.257 30 120 28.290 41.32 8.5 " 1.268 31 29.233 47.66 12 " 1.279 32 30.176 54 . 00 15 " 1.290 33 31.119 44.32 10 " 1.302 34 32.062 34 66 4 " 1.313 35 33 25.00 1.5 Ibs. This table, which has been published by a manu- facturer of chloride of calcium, gives the freezing points much lower in some cases than the small table on page 142. 346 MECHANICAL REFRIGERATION. FRICTION OF WATER IN PIPES. Frictional loss in pounds pressure for each 100 feet in length of cast iron pipe discharging the stated quanti- ties per minute: <33* 37$ 830 k37. 1867 P75 0490 95 K SUBS OP PJPES, INSIDE DIAMETER. %, j| 9.oo aj.5 H.OS 438 . ". i 47 3.62 3 75 82^.40 iL \i.a6 a;oi 2-44 .W M-9 281 37-5 47-7 .- '?' S3 28.06 33- 4^ 42.96 :35 74 1.31 3-85 7.76 11.20 15.20 19.50 25.00 30,80 :* 3-65 4-73 6.01 7 '43 III .910 365 38 .& The frictional loss is greatly increased by bends or irregularities in the pipes. COMPARISON OF Acceleration of gravity Acceleration of gravity 1 dyne . 1 dyne 1 grain . 1 gram . 1 pound avdp. 1 foot pound 1 foot pound 1 foot pound 1 metric horsepower hour 1 metric horsepower hour 1 metric horsepower hour 3 metric horsepower hour 1 metric horsepower hour 1 horsepower hour 1 horsepower hour 1 horsepower hour 1 horsepower hour 1 horsepower hour UNITS OF ENERGY (BERING.) = 981.000 centimeters per second. = 32.186 feet per second. .015731 grain. .0010194 gram. = 63.668 dynes. = 981. dynes. = 444976. dynes. .0012953 pound Fah., heat unit. .007196 pound C., heat unit. .0003264 kilogr.-C., heat unit. = 1952940. = 270000. = 2529.7 = 1405.4 .98634 = 2685400. -1980000. = 2564.8 = 1424.9 = 646.31 foot pounds, kilogram meters, pound Fah., heat units, pound C., heat units, horsepower hour, joules. foot pounds, pound Fah., heat units, pound C., heat units. kilogr.-C., heat units. APPENDIX I. 347 COMPARISON OF UNITS OF BNBBGY (BERING). 1 pound Fahrenheit . 1 pound Fahrenheit . 1 pound Fahrenheit . 1 pound Fahrenheit . 1 pound Fahrenheit . 1 pound Fahrenheit . 1 pound Fahrenheit . 1 pound Centigrade 1 pound Centigrade 1 pound Centigrade 1 pound Centigrade 1 pound Centigrade 1 pound Centigrade 1 kilogram Centigrade 1 kilogram Centigrade 1 kilogram Centigrade = 1 kilogram Centigrade =" 1 kilogram Centigrade = 1 watt-hour 1 watt-hour 1 watt-hour 1 erg 1 erg 1 gram centimeter 1 Joule 1 volt-coulomb 1 watt during every second 1 volt ampere dur- ing every second 1 volt ampere dur- ing every second 1 foot-pound 1 foot-pound 1 foot-pound = 1047.03 joules. = 772. foot pounds. = 106.731 kilogram meter. .56556 = .25300 pound Centigrade, kilogram Centigrade. .29084 watt-hour. 1 Brit, therm, unit (B.T.TJJ = 1884.66 1389.6 foot pounds. !l 192.116 kilogram meters. __ 1.8 pound Fahrenheit. = .62352 watt-hour. Z .0007018 3063.5 horsepower hour, foot pounds. =. 423.54 kilogram meters. = 3.9683 pound Fahrenheit. = 1.1542 watt-hours. _ .0015472 horsepower hour. _ 3600. joules. = 2654.4 3.4383 foot pounds. 1. dyne-centimeter. a .0000001 joules. = 981.00 ergs. B 10000000. ergs. = .737324 foot pound. .101937 Kilogram meter. .0013406 horsepower for one sec. .0009551 - 13562600. 1.35626 = 13825. 1 foot-pountk 1 horsepower 1 horsepower 1 horsepower 1 horsepower . 1 Ib. F. heat unit per min = 1 Ib.F. heat unit per min _ 1 Ib.F. heat unit per min = 1 Ib. Ct. heat unit per min = 1 k. Ct. heat unit per min = 1 Pferdekraft = 1 erg per second = 1 watt = 1 volt ampere = 1 volt coulomb per sec. =- 1 volt coulomb per sec. = 1 foot pound per min. = 1 foot pound per min. 1 foot pound per min. - 1 metric horsepower 1 French horsepower 1 chevalvapeur 1 force de cheval _ 1 horsepower 1 horsepower 1 horsepower = 1 horsepower = 1 ton of ref rig. capacity = .0018434 745.941 42.746 1.01385 17.4505 .033718 .023394 .043109 pound F. heat unit. ergs. joules. kilogram meter. metric horsepower for one second, watts. foot pounds per minute. Ib. P., heat unit per min. metric horsepowers, watts. metric horsepower, horsepower, horsepower, horsepower, klg. cent, watt. ergs per second, foot pounds per min. Ib. F. heat unit per min. horse power,, watt. metric horsepower. .000030303 horsepower. 735.75x107 ergs per second. foot pounds per minute. Ib. F. heat units per min. Ib. Ct. heat unit per min. foot pounds per minute, foot pounds per hour. H. units per kour (B.T. units). B. T. units per minute. B. T. units. 10.625 .0000001 10000000. 412394. .0573048 .0013400 .0326043 .00003072 82549.0 42.162 33000. 1980000. 2565. 43.75 284000. 1 ton of refrig. capacity = to about H-ton ice 1 ton of ref. cap. per day = to about 12000 B. T. units per hour. 1 ton of ref. cap. per day => to about 200 B. T. units per minute. In these tables the mechanical equivalent of heat is taken at 772. Many engineers prefer the more recent figure, 778. 348 MECHANICAL REFRIGERATION. TABLE OF MEAN EFFECTIVE PRESSURES. The above graphical table will be found of assistance to the engineer by affording a ready, and, at the same time, comprehensive means of ascertaining the mean effective pressure of steam in an engine cylinder, when the initial steam pressure and the point of cut-off or the number of expansions of the steam are known. AMMONIA COMPRESSION UNDER DIFFERENT CONDITIONS. WetQas. Dry Gas. Condenser pressure 113.3 15.6 69.2' .5' 16.8 13.3 50.3 .792 116.7 27.2 70.5' 14.3' 18. 19.5 53.4 1.088 36.7$ 147.3 13. 82.7' 8.2' 73.6 46.5 59.9 .632 161.8 27.5 87.7' 14.5' 88.6 74.4 70.5 .840 32.9$ Suction pressure . Condenser temperature Suction temperature Horse power (indicated of steam cylinder) Kef rigeration (tons per 24 hours) M: E. P in compressor Refrigerating capacity per horse power (tons per 24 hours) Economy of high over low evaporat- APPENDIX I. 349 MEAN EFFECTIVE PRESSURE OF DIAGRAM OF STEAM CYLINDER. The M. E. P. for any initial pressure not given in the table can be found by multiplying the (absolute) given pressure by the M.E.P. per pound of initial, as given in the third horizontal line of the table. NOTE. This table is reprinted from " Indicating the Refriger- ating Machine," publisha by H, S. Rich & Co., Chicago. 350 MECHANICAL REFRIGERATION. RELATIVE EFFICIENCY OF FUELS. One cord of air dried hickory or hard maple weighs about 4,500 pounds and is equal to about 2,000 pounds of coal. One cord of air dried white oak weighs about 3,850 pounds and is equal to about 1,715 pounds of coal. One cord of air dried beech, red oak or black oak weighs about 3,250 pounds and is equal to about 1,450 pounds of coal. One cord of air dried poplar (white wood), chestnut or elm weighs about 2,350 pounds, and is equal to about 1,050 pounds of coal. One cord of air dried average pine w< and is equal to about 625 pounds of coal. From the above it is safe to assume that two and one-quarter pounds of dry wood is equal to one pound average quality of soft coal, and that the full value of the same weight of different wood is very nearly the same. That is, a pound of hickory is worth no more for fuel than a pound of pine, assuming both to be dry. It is important that the wood be dry, as each 10 per cent of water or moisture in wood will detract about 12 per cent from its value as TABLE SHOWING TENSION OF WATER VAPOR AT DIFFERENT TEMPERATURES IN ABSOLUTE PRESSURE, AND CORRESPOND- ING VACUUM IN INCHES OF MERCURY. jhs about 2,000 pounds, Temperature. Deg; F. Absolute Pressure. Vacuum, Inches. Atmospheres. Inch of Mercury. 212 1. 30. o. 158 0,307 9.270 20.730 140 0.196 5.880 24.120 122 0.121 3.630 26.370 113 0,094 2.820 27.180 104 0.0722 2.166 27.834 95 0.0550 1.650 28.350 86 0.0415 1.245 28.755 77 0.0310 0.930 29.070 68 0.0229 0.687 29.313 59 0.0167 0.501 29.499 50 0.0121 0.363 29.637 41 0.0086 0.258 29.742 32 0.0061 0.183 29.817 14 0.0026 0.078 29.922 4 0.0012 0.036 29. 964 BOILING POINTS UNDER ATMOSPHERIC PRESSURE. Liquids. Fahr. deg. Cent, deg. Liquids. Fahr. deg. Cent, deg. Wrought iron (?) 5000 2760 Alcohol 173 78 Cast iron (?) .... 3300 1815 Ether 96 35 Mercury 675 352 Carbon, bi-sulphurated. . 116 47 Whale oil 630 332 Water, 'distilled.. 212 100 Oil of linseed .... Oil of turpentine Sulphuric acid. . . 600 357 593 570 316 180 312 300 Salt, sea water.... Water, 20% salt... Water, 30# salt... Water, 40$ saturated 213 218 222 227 101 103 105 108 Phosphorus Sweet oil 557 412 292 211 Ammonia, liquid. Water, in vacuo . 140 98 60 36 Naphtha 320 160 Chimogene +38 33 Nitric acid 220 104 Carbonic acid. . . . -112 -80 Milk of cows 213 101 Ammonia 30 34 Petroleum, rectified 316 158 Benzine 187 86 APPENDIX I. 351 COMPOSITION OF COMMON WATER Chloride of sodium contains Na Chloride of magnesium contains... Mg Chloride of calcium contains Ca Chloride of potassium contains K Carbonate of soda contains Na O Carbonate of magnesia contains. ..Mg O Carbonate of lime contains Ca O Carbonate of potassa contains K O Sulphate of soda contains Na O Sulphate of magnesia contains ....MgO Sulphate of lime contains Ca O Sulphate of potassa contains K O CONSTITUENTS. 39.3 and Cl 60.6 26.28 and Cl 74.73 36.06 and Cl 63.94 52.45 and Cl 47.55 58.5 and CO 2 41.5 47.62 and C O a 52.38 56.0 and C O, 44.0 68.17 and C O 2 31.83 43.66 and SO 3 56.34 33.33 and SO 3 66.67 41.18andSO 3 58.82 54.08 and S O 3 45.92 Carbonate of lime multiplied by 0.56=lime. Sulphate of baryta multiplied by 0.343=sulphuric acid. Phosphate of magnesia multiplied by 0.036=magnesia. Magnesia multiplied by 0.6=magnesium. Magnesium multiplied by 1.66=magnesia. Cubic centimeter carbonic acid multiplied by 0.003=carbonic acid C. 0. mtrate of silver solution multiplied by 0.0035=chlorlne in grams. Chloride of sodium multiplied by 0.39=sodium. Carbonate of soda multiplied by 0.58=soda. Chloride of potassium and platinum multiplied by 0.16=potasium. In the construction of water analysis from constituents it Is advisable, as most consistent with practical requirements to com- bine chlorine with magnesium (balance of chlorine with sodium or balance of magnesia with sulphuric acid). Carbonic acid combines with lime, balance of lime with sul- phuric acid, balance of sulphuric acid with soda (or balance of carbonic acid with magnesia). When alkaline carbonates are present all the chlorine is to be combined with sodium, Magnesium carbonate and calcium sul- phate are supposed not to coexist. MILLIGRAMS PER LITER TO GRAINS PER U. 6. GALLON. GRAINS PER U. S. GALLON TO MILLIGRAMS PER LITER. Milligrams per Liter. Grains per D. S. Gal. Milligrams per Liter. Grains per D. S. Gal. Grains per U. S. Gal. lilligrams per Liter. Grains per U.S. Gal. Milligrams per Liter. 1 0.058 26 1.519 1 17.1 16 444.9 2 0.117 27 1.578 2 34.2 27 462.0 3 0.175 28 1.636 3 51.3 28 479.1 4 0.234 29 1.695 4 68.4 29 496.2 5 0.292 30 1.753 5 85.6 30 513.4 6 0.351 31 1.S12 6 102.7 31 630.5 7 0.409 32 1.870 7 119.8 32 547.6 8 0.468 S3 1.929 8 136.9 83 664.7 9 0.626 34 1.987 9 154.0 84 581.8 10 0.584 35 2.045 10 171.1 85 598.9 11 0.643 36 2.104 11 168.2 36 616.0 12 0.701 37 2.162 12 205.3 87 633.1 13 0.760 38 2.221 13 222.5 38 650.3 14 0.818 39 2.279 14 239.6 89 667.4 15 0.877 40 2.338 15 256.7 40 684.5 16 0.935 41 2.396 16 273.8 41 701.6 17 0.993 42 2.454 17 290.9 42 718.7 18 1.052 43 2.513 18 308.0 43 735.8 19 1.110 44 2.571 19 325.1 44 762.9 20 1.169 45 2.630 20 343.2 45 770.0 21 1.227 46 2.688 21 359.4 46 787.8 22 1.286 47 2.747 22 376.5 47 604.S 23 1.344 48 2.805 23 393.6 48 8S1.4 24 1.403 49 2.864 24 410.7 49 838.5 25 1.461 50 2.928 25 427.8 50 856.0 352 MECHANICAL REFRIGERATION. EXPERIMENTS IN WORT COOLING. The following tabulated experiments of the per- formance of a tubular refrigerator for wort cooling are gleaned from Engineering. The water and wort are moved in opposite directions, the former through thin metallic tubes, which are surrounded by the wort to be cooled: WORT. WATER. bo >> o> ed cj , w s i rJ i|| g O If? ** & BO; &$ Is s a ^ s, gi; & eg & o E E^BJ Q. What will be the volume of one cubic foot of air if heated at constant pressure from 32 to 45 F., its press- ure at the former temperature being one atmosphere? According to the same equation we find T 45 -4- 461 p V = 493 = 493 or P remaining unit. KAf> v== |^==1.03 cubic feet. Q. If the volume of a confined body of a permanent gas be one cubic foot at the temperature of 32 and at a pressure of one atmosphere, what will have to be its tem- perature T in order that it may occupy a volume of one- half cubic foot at a pressure of four atmospheres? The same equation answers the question, viz. : p v = ^ or T=493p v = 493X4XM = 986 F. absolute. 01986 461 = 525 F. WORK REQUIRED TO LIFT HEAT. Q. What amount of work must be expended theo- retically by a perfect refrigerating machine to withdraw 284,000 units of heat (one ton refrigeration) from a refrig- 356 MECHANICAL REFRIGERATION. erator at temperature of 10 if the temperature in the condenser is 90 ? Prom the equation, page 71, 5 = m T we find W T t -T The work is aere expressed in heat units, which are equivalent to: 49,000 X 772 = 37,830,000 foot-pounds (page 346) or to = ' 8 - horse Pr*-**(pa g e 346). REFRIGERATING EFFECT OF SULPHUROUS AGED. Q. What is the theoretical refrigerating effect r of one pound and of one cubic foot of sulphurous acid if used in a compression machine, the temperature in re- frigerator coils being 5 and in condenser coils 95 F.? The equation r = h^ (t t t )s t on page 115, applies also for sulphurous acid, for which we find fi t = 171 units (page 250) and s = 0.41 (page 250) ; hence r = 161 (95 5) 0.41 16137 = 124 units. From same table we find the weight of one cubic foot of sulphurous acid at 5 equal to 0.153 pounds; hence the refrigeration of one cubic foot is 124X0.153 = 18.97 units. REFRIGERATING CAPACITY OF A COMPRESSOR. Q. What is the refrigerating capacity of a double- acting compressor, 70 revolutions per minute, diameter 9^ inches and stroke 16^ inches, temperature in re- frigerator coil 5 and in condenser coil 85 F.? The compressor volume C per minute after formula on page 303 is C=d z X I X m X 0.785 = 9^ 2 X 16^ X 0.785 X 70. From table on page 250 we find 9^ 2 X 0.785 = 76.58. Hence G = 76.58 X 16.5 X 70 = 88410 cubic inches. The compressor being double-acting, this is equal to From table on page 125 we find that 3.34 cubic feet of ammonia must be pumped per minute, at above named condenser and compressor temperature to produce a refrigerating effect of one ton in twenty-four hours, hence APPENDIX II. 357 the above compressor represents a theoretical refrigerat- ing efficiency of 15i= 30.5 tons. 3.34 SECOND METHOD OF CALCULATION. The actual refrigeration will be from 15 to 20 pei cent less, or equivalent to about 25 tons (commercial capacity ?); see table page 302, according to which the nominal daily refrigerating capacity is _= 25.5 tons. 4 4 The agreement between this amount and the amount found by the first calculation holds good only for the temperature selected; otherwise the last rule affords only a crude approximation. THIRD METHOD OF CALCULATION. The theoretical refrigerating effect E of this com- pressor can also be calculated after the formula on page 118 E = C X 60 X r We find, according to formula on page 115 and table on page 94,r = h, (t t t ) s = 552.43 ( 85 5) 1 = 552-80 = 472 units, and v =8.06 (page 94) 109 V fiO V 4.79 E = ofi - units or in tons p er dav - _ 102X60X472X24 8 X 284.000. ' 0nS< Or, again, the actual refrigerating capacity will be about 15 to 20 per cent less, or equivalent to about twenty- five tons, and the actual ice making capacity will be about thirteen tons per twenty-four hours. The last method of calculation will answer also for other refrigerating media if r and v are found and inserted accordingly. COOLING WORT. Q. A direct expansion ammonia refrigerating ma- chine is applied to the cooling of beer wort, and reduces the temperature of 300 barrels of wort from 70 to 40 F. in four hours. What is the refrigerating capacity U of the machine if the weight of the wort is 14 Balling? From table on page 202 we find the specific gravity corresponding to 14 equal to 1.0572 (1.06), and from table 358 MECHANICAL REFRIGERATION. on page 197 we find the specific heat 0.895 (0.9), hence in accordance with formula on page 198 U B X 259 X g X s (70 40) 300 X 259 X 1.06 X 0.9 X 30 222300 units. This is the refrigeration in three hours; expressed for twenty-four hours, and in tons of refrigeration, it is equal to about 60 ton, The actual refrigeration required to cool the wort is only one-eighth of that (for three hours), i. e., 1% tons, which is about one ton for every forty barrels. The rule on page 199 allows one ton for every thirty-eight barrels. HEAT BY ABSORPTION OF AMMONIA. Q. What is the heat H n developed when one pound of ammonia vapor is absorbed by enough of a 20 per cent solution of ammonia in order to produce a 33 per cent solution of ammonia ? On page 226 we find a 925 _ 248X1426 =unlta- n In accordance with the definitions given on page 226 we find n, that is the number of pounds of water present to one pound of ammonia in a 20 per cent solution, = 80 yz = 4, and the number of pounds of ammonia (6 + 1 pounds) which are present for every four pounds of water 4 X 33 in a 33 per cent solution -^ 2 pounds. 6 + 1 being = 2, it follows 6 = 1. We now insert these values in the above equation for a-WS-^i^i 819 units. RICH LIQUOR TO BE CIRCULATED. Q. How many pounds P 2 of rich liquor of 33 per cent strength must /be circulated in an ammonia absorption plant if the poor liquor enters the absorber at 20 per cent strength ? We find this in accordance with equation on page 224: _ (100 a) 100 (100 20)100 ** ~~ (100 a) c ( 100 c) a = (100 20) 33 (100 33) 20 8000 = Poo = 6.1 pounds. APPENDIX II. 359 CAPACITY OF ABSORPTION MACHINE. Q._\Vhat should be the theoretical refrigerating capacity R of an ammonia absorption machine if the rich liquor is 33 per cent and the poor liquor 20 per cent strong, and if the ammonia pump makes fifty revolutions per minute and each stroke is seven inches and the diameter of pump piston three inches? From page 139 we find the capacity C of this pump to be 2.14 gallons at ten strokes per minute, hence at fifty strokes it is expressed in pounds C = 2.14 x 5 X 8.3 = 90 pounds in round figures. By calculating as before from table on page 226 we find P 2 = 6.1, and according to formula on page 230 we find X 90X453 -*2 O.-L The value for r is found after the rule on page 185, which,assuming the temperature in refrigerator coils to be 4 and the pressure in condenser to 210 pounds, equiva- lent to an absolute pressure of 225 pounds and to a tem- perature of 104 F. (see table on page 94), reads r = /i x (tt t ) s = 553 (104 4) 1 = 453 units. hj = 553 units from table on page 94. One ton of refrigerating capacity per day being equal to 284000 units, one ton per hour is equal to about 12000 units, and one ton of refrigerating capacity per minute is equivalent to 200 units per minute, and therefore the above refrigeration is equivalent to = 33.5 tons per day (theoretical capacity). If we allow 25 per cent for losses all around slips of pumps, radiation, etc., we find the actual refrigerating capacity 33.5 8.4 = 25.1 tons, and the actual ice making capacity being about half of that = twelve tons per day. HEAT AND STEAM REQUIRED. What is the theoretical amount of heat TFi and of steam P 5 required in still of above plant ? From page 192 we find Wi = Hn (h 2 fi) = 819 (495489) = 813 units, h 2 at a temperature of 90 in absorber being 495 units, h and at a temperature of 104 in condenser being 489 360 MECHANICAL REFRIGERATION. units, after table on page 92. H 819, from table on page 226. The amount of steam P 5 in pounds required per hour to run this plant would be (see page 229): p TV* X m X 28400 813 X 25 X 284000 77Q 24 X r X h B 24 X 453 X 686 pounds of steam per hour. h B = 886 (at pressure in boiler 100 absolute or 85 pounds gauge pressure). To this should be added about to allow for steam to run the ammonia pump, so that the whole would amount to about 900 pounds per hour. COLD STORAGE EXAMPLES. Q. What is the refrigeration E required for a local storage room 40X50X10 if each day about 30,000 pounds of fresh meat (about 120 hogs) are placed in the same at a temperature of 95 to be envied to a temperature of 35, if the temperature of atmosphere is to be 85 P.? METHOD OF CALCULATION. The side walls of room 2x50x10+2x40X10=1,800 sq.ft. The ceiling and floors 2 X 40 X 50 =4,000 " Total ............................ 5,800 sq.ft. If we take n as 3 all around (assuming an average de- gree of insulation (see page 181), we have frigeration per day to keep the room at the desired temperature. The additional refrigeration to chill the meat, assum- ing its specific heat to be 0.8, we find (page 183) P( t ) 30000(95 35) = ^~ 355000 "" 355000 tons which makes a total refrigeration of 8.1 tons required. For closer estimates the rules on pages 181 and 182 may be used. APPROXIMATE ESTIMATE. The cubic contents of the room are equal to 20,000 cubic feet, and in accordance with the rules on page 173 from fifty to 100 units (say seventy-five units in this case) are allowed per cubic foot, and in addition to that about 50 per cent more for chilling, which amounts to about 110 units in all per cubic feet, or a daily refrigeration of r Und APPENDIX II. 361 For opening doors, for windows, etc., about 10 to 15 per cent extra refrigeration may be allowed, making the total about nine tons refrigerating capacity per day. See also rules on page 212 and 213. PIPING REQUIRED. Q. What will be the amount of 2-inch pipe direct circulation required for the above room and purpose? In accordance with rule on page 128 we assume that one square foot of pipe will convey about 2,500 units of refrigeration; this is equal to 1.6 foot of 2-inch pipe (table on page 129), hence to distribute nine tons in twenty-four hours the pipe required will be 9 X 284000 X 1.6 =160Q ^ Qf ^^ pjpe _ According to another rule, given on page 212, one running foot of 2-inch pipe is allowed for thirteen cubic feet chilling room capacity, in accordance with which 9Q QQQ ^ \ = 1,540 feet or thereabouts of 2-inch pipe would lo be required. After still another rule, given on page 212, we find that six feet 2-inch pipe are allowed per hog slaughtered in chilling room; according to this rule we would only re- quire 720 feet of 2-inch pipe for above room, but the rule from which this result is obtained applies to large instal- lations having over a hundred times the capacity contem- plated in the example as given and calculated above. EXAMPLES ON NATURAL GAS. Q. What amount of refrigeration and work can be produced by natural gas expanding adiabatically from a pressure of 255 pounds (seventeen atmospheres) to a pressure of fifteen pounds (one atmosphere) absolute pressure, and to a volume of 1,000,000 cubic feet at the ordinary temperature and pressure? TEMPERATURE AFTER EXPANSION. If we assume the initial temperature of the gas to be 70 == 70 + 461 = 531 absolute we find the temperature jP 2 of the gas after expansion after the rule on page 257, viz: fc 1 .1.41 1 0.291 or 362 MECHANICAL REFRIGERATION. log. T t = log. 531 X 0.291 (log. 1- log. 17) 2.7251-0.6432 = 2.0819. r z = num. log. 2.0819 = 121 absolute = 461 121 = 34(PF. REFRIGERATING CAPACITY. ^The theoretical refrigeration H produced by 1,000,000 cubic feet expanded in this manner if the gas leaves the refrigerator at the temperature T of 5 = 466 absolute is found after the formula on page 257. H mkc (T T 2 ] = mfcc(466 121) c=- 0.468 (page 47) w= 0.0316 pounds (page 233 coal gas) hence H= 0.0316X0.468X1.41X345 = 7.0 units per cubic foot or 7,000,000 units per 1,000,000 cubic feet, which is equivalent to a theoretical refrigerating capacity of about twenty-five tons. The actual ice making capacity would probably be less than ten tons per day. WORK DONE BY EXPANSION. The amount of work, Wm, that can be obtained theoretically by the adiabatic expansion to 1,000,000 cubic feet of the gas is expressed by the formula Wm = (T T 2 ] = 0.0316 X 0.468 X 1.41 (531 - 121) X 772 about 6600 foot-pounds per cubic foot, or for 1,000,000 cubic feet per day ab Ut 147 h rse P0wers per da y- According to this calculation the power to be gained would be of considerably more consequence than the ice, but it must not be forgotten that these are theoretical calculations which are naturally greatly reduced in prac- tical working, not to speak of possible difficulties con- nected with the same. SIZE OF EXPANDING ENGINE. As the expanded gas leaves the expanding engine at the temperature of 121 absolute, its volume x is less in the following proportion 1000000 : x = 531 : 121 (page 55) 228000 cubic feet. APPENDIX tt. 363 This is the volume over which the piston of expand- ing engine must sweep in one day. If it is double-acting and makes fifty revolutions a minute the size of the cylinder must be 6oirS3<60=m = 1 - 6cublcfeet - If the stroke be two feet the area of piston must be 0.8 square feet. EXPANSION WITHOUT DOING WORK. Q. What amount of refrigeration can be produced by natural gas expanding from a pressure of 255 pounds, absolute, to a volume of 1,000,000 cubic feet at the atmospheric pressure without doing work? REFRIGERATION OBTAINABLE BY EXPANSION ALONE. For the sake of simplicity we neglect the contraction of the gas due to reduction of temperature, and allow the theoretical refrigeration to be equivalent to the external work, JE?, done by the expanding gas, which can be found by the formula for steam on page 106 P(V-V^) v representing the final volume and v t the original volume of the expanding gas, and calculated for one cubic foot; hence E = 2 "~ ** = 0.31 units per cubic foot. or 310,000 units for 1,000,000 cubic feet of gas, of which only a fraction could be utilized for ice production, which would probably be less than one-third ton per day. CALCULATION OF REFRIGERATING DUTY. Q. A machine is required to cool water from 55 F. to 40 F. during part of the day, and to keep a cold storage at 15 F. at other part of the day. What indicated horse power steam engine will be required to work compressors to extract 3,000,000 B. T. U. per hour from the water at above temperatures, and what size compressors, with number of revolutions per minute ? What B. T. U. per hour would same machine extract at same speed when working on the cold storage, and what would then be its indicated horse power ? Condensing water at 60 and leav- ing condenser at 70 F. 364 MECHANICAL REFRIGEKATION. If we assume that you work by direct expansion, the temperature of the expanding ammonia would have to be about 10 lower than the water after it is cooled, i. e., 30; consequently by using the latent heat of vaporiza- tion at that temperature, as we find it in table on page 94, viz., 536, and formula on page 115 of Compend we mid r = 536 (7030) 1 = 496 units, which is the refrigerating effect of one pound of ammonia, when the temperature of the refrigerator is 30 and that of the condenser 70, the specific heat of the ammonia being 1. The amount of ammonia to be evaporated per minute is, therefore From same table on page 94, we find volume of one pound of ammonia vapor at 30 =< 4.75 cubic feet, con- sequently the compressor capacity per minute will have to be 101 X 4.75 480 cubic feet in round numbers. If we add to this 20 per cent for clearance losses by radiation, etc., we require an actual compressor capac- ity of 576 cubic feet per minute. If we assume that the work is to be done by one double-acting compressor, making, say, seventy revolutions per minute, we require a compressor having the cubic capacity of 576 72 X 2 4.2 cubic feet. If we distribute this capacity over two compressor cylinders each one has to have a volume of 2.1 cubic feet. Taking the diameter of each of them at fifteen inches the area is (1.25 2 X 0.785) 1.227 cubic feet, and the stroke will have to be -== 17.12 inches. If we start from a different given stroke and num- ber of revolutions, as we probably shall, the diameter changes accordingly, after the foregoing simple rule. If a single double-acting compressor making fifty revolutions were to do the work, its dimensions, calcu- lated on the same basis as above, would be twenty inches diameter by 31^ -inch stroke. APPENDIX II. 365 The work of the compressor is found after the for- mula on page 119 : W= 0.0234 WK horse power; X 536X101=104 horse power. And the horse power of engine, after rule on page 121 of Compend, is found to be 104X1.4= 145.6 horse power. The same two compressors, if required to do duty in a cold storage plant, would probably have to run with a temperature of 5 F. in refrigerator. In this case (their cubic capacity being 576 cubic feet per minute) their re- frigerating capacity in tons per day is found by the for- mula on page 303 of Compend, viz.: B _fc-H 1 ) = :^t5)_ 212 ^ ln round figures (hj^ and v being found from table on page 94). Or in thermal units per hour 212 ^-^^ 2500000 units. This is the theoretical capacity; to bring it on a prac- tical basis, we have to subtract 20 per cent, as we did in the case of water cooling before this yields 2500000500000 = 2000000 units per hour actual refrigerating capacity for cold storage. To find the horse power of the compressor in this case we find the amount of ammonia to be circulated in a minute, as before, viz.: r = 546 (70 15) = 491, and .~ 2000000 49TX60 Placing this value in the equation from page 119, as before, we find TF4= 0.0234 X 7 ^~ 5 X 546 X 68118.7 horse power; and the horse power of engine- US. 7 X 1.4 = 166 horse power. These horse power are calculated from the amount of ammonia theoretically required, and about 15 to 25 per cent should be added to bring them within practical range. We have also assumed that the temperature in condenser is that of outflowing condenser water, when in fact it should be taken 5 higher. 366 MECHANICAL REFRIGERATION". CALCULATING ICE MAKING CAPACITY. Q. What is the ice making capacity of two single- acting compressors 7x12 inches, 100 revolutions per minute? The capacity in cubic feet, (7, for each compressor per minute, according to formula on page 117 of Com- pend, is C=r 2 X 3.145 X6xm 7* X 3.145 X 12 X 100 9ft , .. f - - = =26.7 cubic feet, or for both compressors, 26.7 x 2 = 53.4 cubic feet, which under general conditions, when no back pressure, etc., is mentioned, has been calculated to be equivalent to ~ 13.35 tons of refrigerating capacity in twenty- four hours (see page 118 of Compend), and of this from iS to !% is available actual ice making capacity, which accordingly is about seven tons per day (more or less; see page 144 of Compend). VOLUME OF CARBONIC ACID GAS. Q. What is the volume of one pound of carbonic acid gas at a pressure of thirty pounds and at a tem- perature of 50? The formula that applies here is given on page 48 of the Compend, viz.: Fp^ + 461) If in this formula we insert for V the volume of one pound of carbonic acid gas at the atmospheric pressure, viz., 8.5 cubic feet, and forp the pressure of the atmos- phere, viz., 14.7 pounds, and for t the temperature of 32 F. this formula becomes: V1 _ 8.5(461 + ^)14.7 115 + 0.25 < t 493 p l p Hence the volume F 1 of one pound of carbonic acid gas at any given temperature and pressure, say at an ab- solute pressure of thirty pounds, and a temperature of 50, is found by inserting these quantities in the fore- going formula: Trf 115 + 0.25X50 127.5 . oe ,. F 1 -- ^~~w --- = go = 4. 25 cubic feet. For apparent reasons the numerical results of above examples have been rounded off in most cases. APPENDIX II. 367 HORSE POWER OP STEAM ENGINE. Q. What is the horse power of a steam engine the piston of which has a diameter of 12 inches, a stroke of 30 inches at 90 revolutions a minute if the gauge pressure of the steam is 80 pounds, cut-off ? To calculate the horse power in this case we have to find the mean effective pressure by means of an indi- cator diagram, as shown on page 297. If it is imprac- ticable to obtain a diagram we take the mean average pressure as we find it in table on page 349, which is 49.4 pounds, or 50 pounds in round numbers, in this case. Multiply the same by the area of the piston in square inches and the speed of the piston in feet per minute, and divide the product by 33,000 (foot-pounds of horse power per minute. See table on page 347). The area of piston in square inches we find, accord- ing to rule given on page 309, equal to 12* X0.7854=144X 0.785=113.0, which is also given direct in table on page 314. The piston speed is 30X , 9 X2 =450 feet per minute. us Hence the horse power 113X450X50 , 33^0 =77 horse power. This is the indicated horse power, the net effective horse power being the indicated horse power less the friction of the engine. The table on Corliss engine, on page 340, gives the indicated horse power of an engine of above description at 54, this difference being probably due to a difference in the mean effective pressure and to an allowance for piston space having been made in the latter case. WORK OF COMPRESSOR. Q. What is the work of compression done by a double-acting ammonia compressor 9 inches in diameter, 15 inches stroke at 70 revolutions per minute? The back pressure is 28 pounds and the condenser pressure 115 pounds. This problem is calculated on the same principles as the foregoing example; but, as in that case, the proper way is to obtain the mean effective pressure from an indicator diagram. If we use the table on page 298 instead we find the mean pressure in this case at 52.6 368 MECHANICAL REFRIGERATION. pounds. The area of piston, by table on page 314, is G3.6 square inches, and its travel per minute equal to 2X70X15 1t . j2 =116 feet; hence the work done by the compressor is equal to This is the indicated horse power of the work done by the compressor. In order to find the indicated horse power (of an engine) required to do this work we must add to the above the work required to overcome the fric- tion in the compressor as well as in the engine itself. CALCULATION OF PUMP. Q. How many revolutions must be made by a single- acting pump having a piston of 4 inches in diameter and 12 inches stroke in order to force 400 gallons of water 60 feet above the level of pump per hour, and what will be the power required to do this work ? According to table on page 322 the displacement by this pump for each stroke is 0.653 gallons ; hence 4.00 -|jg-= 605 strokes; or, in round numbers, 600 strokes must be made per hour; and as the pump is single-acting this corresponds to 600 revolutions per hour, or ten per minute. The work done by this pump in lifting the water may be calculated the same way as the work done by a compressor, by simply inserting, instead of the mean average pressure, the pressure corresponding to a water column of 60 feet in height, viz. : 26 pounds in round numbers, as per table on page 326. WATER POWER. Q. 1. What is the power of a water fall twenty feet high and 300,000 cubic feet of water per minute? 2. What amount of coal and steam respectively would give the same power during twenty-four hours ? In accordance with page 108 one cubic foot of water weighs 62.5 pounds; hence by using rule on water power given on page 43, we find the theoretical power of the water fall in question equal to Of this theoretical effect may be utilized 30 to 75 per cent by water motors, according to construction, etc.; 50 to APPENDIX II. 369 75 per cent by turbines ; 70 to 80 per cent by water press- ure engines (generally not used for falls less than fifty feet in height). Taking 50 per cent as a safe basis, the actual work that can be expected from the fall would be equal to 12,400 = 6 ^ 200 horge power This power would of course still be correspondingly reduced if the mechanical power of the water motor had to be converted into electricity, to be transmitted to a distant locality, there to be converted into mechanical power again. Leaving this out of the question, and assuming that electricity was the form of energy wanted, we find, from page 108 of the Compend, that from fifteen to thirteen pounds of steam will produce a horse power per hour, and that a pound of average coal will make about eight pounds of steam; hence a horse power will require not over two pounds of coal per hour with a good engine, and therefore 6,200 horse power may be estimated equivalent to 6,200x24x2=297,600 pounds of coal in twenty-four hours. Allowing fifteen pounds of steam per horse power, the actual power of the water fall would be represented by 6,200x15=93,000 pounds of steam per hour. With first-class machinery it would take less steam and coal. MOTIVE POWER OF LIQUID AIR. Q. What is the amount of work expressed in foot- pounds and in horse power that can be done by one pound of liquid air while expanding or volatilizing at the con- stant temperature of 70, this being the average atmos- pheric temperature V According to page 260, we find the work, Wi, in foot- pounds, which can be done theoretically by the isothermal expansion of Fj, cubic feet of liquid air to the volume of V cubic feet and the pressure P (in pounds per square foot) after the formula W t = P V X 2.3026 by y In the problem on hand we have P = 2,117 pounds. F" lf the volume of one pound of liquid air, is not exactly TT known but 1 , the ratio of the volume after and before 370 MECHANICAL REFRIGERATION. expansion, is about 800, and V t the final volume of one pound of air in cubic feet at 70 F. and at atmospheric pressure is equal to about 13.34 cubic feet. Hence the formula developes into ^=2,117X13.34X2.3020 log. 800=188,800 foot-pounds. (Log. 800 being equal to 2.9031. See table on page 316.) In order to express this effect in horse power, the time in which the pound of air is to expand should be stated also. Assuming that it takes place at the rate of one pound of liquid air expanding per minute, the horse power would be 188,800 33 000 = horse power. This is the theoretical figure; practically, a reduction would have to be made for friction, etc. MOISTURE IN COLD STORAGE. Q. Assuming that 34 is the proper temperature for an egg storage room, what is the proper percentage of moisture which it should contain, and how should the wet bulb thermometer of a hygrometer or sling psychrometer stand in order to indicate that percentage of moisture ? According to Cooper the percentage of moisture for cold storage rooms, especially for eggs, should vary with the temperature as follows : Temperature in Degrees F. Relative Humid- ity, Per Cent. Temperature in Degrees F. Rel'tive Humid- ity, Per Cent. 28 29 30 31 32 33 34 80 78 76 74 71 69 67 35 36 37 38 39 40 65 62 60 58 56 53 Therefore for a storage temperature of 34 the moisture, or relative humidity, should be 67 per cent (100 per cent corresponding to air saturated with moisture), and by referring to table on page 112 we find that this corresponds to a difference between the dry and the wet bulb of 3.5. Hence the wet bulb thermometer should show 343.5=30.5. CARBONIC ACID VS. AMMONIA. Q. We would like to ask you for some information pn ice machines, as to bow the carbonic anhydride ice APPENDIX II. 371 machines are in comparison with the ammonia ice ma- chines. The carbonic anhydride machine people claim their machine far superior to the ammonia machine. They also claim that carbonic anhydride has more freez- ing power than ammonia. Is this in accordance with your statement in Ice and Refrigeration (see same, page 247 of Compend) or not? This question, which was directed to the author of the Compend personally, would indicate that his state- ments with reference to this matter were misunderstood, or at least apt to misconstruction. The superiority of the carbonic acid machine would of course tally with 4.300 and 3, 700 calories per horse power; but these figures were quoted by the author as phenomenal, in fact as mere claims, unsupported, so far at least, by any au- thentical tests. The author of the Compend has taken great pains to find any tests supporting such claims, or to find a carbonic anhydride machine which would give some such results in actual practice, but so far has failed to find any. On the contrary, we have come to the con- clusion that the results of the practical comparative tests given in the tables on page 247 of Compend have not been materially exceeded so far, at least not with machines without expansion cylinder, and only such are in the market at present, as far as we know. As a result of the present status of the theoretical aspect of the questions it appears that at temperatures of 70 before the expansion valve and 20 in refrigeration coils it will take 1.2 horse power in a carbonic anhydride machine to produce the same refrigeration as one horse power in an ammonia refrigerating machine. Hence the advantages of the carbonic acid machine must be looked for in other directions rather than in that of greater effi- ciency. 372 MECHANICAL REFRIGERATION. APPENDIX III. LITERATURE ON THER- MODYNAMICS, ETC. CL.-BOOKS. ATKINSON, E. Ganot's Elementary Treatise on Physics Experk mental and Applied; New York, 1883. BERTHELOT, E. Mecanique Chimique, two vols. ; Paris, 1880. BEHREND, GOTTLIEB. Eis und KalteerzeugungsMaschinen; Halle a.S., 1888, CARNOT, N. L. 3. Reflections on the Motive Power of Heat; trans- lated byThurston; New York, 1890. CLAUSIUS, R. Die Mechanische Warmetheorie, three vols.; Braun- schweig, 1891. CLARK D. KINNEAR. The Mechanical Engineer's Pocket Book; New York. 1892. COOPER, MADISON. Eggs in Cold Storage; Chicago, 1899. DUEHRING, E. Principien der Mechanic; Leipzig, 1877. EWING, S. A. The Steam Engine and Qther Heat Engines; Cam- bridge, 1884. EDDY, HENRY T. Thermodynamics; New York, 1879. FARADAY, M. Conservation of Force; London, 1857. FISHER, FERDINAND, DR. Das Wasser; Berlin, 1891. GRASHOF, F. Hydraulik Nebst Mechanische Waermetbeorie; Leip- zig, 1875. GAGE, ALFRED P. A Text Book on the Element of Physics; Bos- ton, 1885. GIBBS, WILLARD J. Thermodynamisches Studien, translated by W. Ostwald ; Leipzig, 1892. HELM, G. Energetik DerChemischenErscheinungen; Leipzig,1894 HELM, GEORGE. Die Lehfe von der Energie; Leipzig, 1887. HELMHOLTZ, H. Erhaltung der Kraft; Berlin, 1847. HKLMHOLTZ, H. Wechselwirkung der Naturkraefte; Koenigsberg J854. BERING, C. Principles of Dynamo Electric Machines; New York, 1890. HIRN, G. A. Equivalent Mecanique de la Chaleur; Paris, 1858. HIRN, G. A. Th6orie Mecanique de la Chaleur; Paris, 1876. HOFF, J. H. VAN'T. Chemische Dynamik; Amsterdam, 1884, JOULE, J. P. Scientific Papers; London, 1884. JEUFFRET, E. Introduction a la Theorie de 1'Energie; Paris, 1883. KIMBALL, ARTHUR L. The Phj-sical Properties of Gases; Boston and New York, 1890. KENNEDY, ALEX. C. Compressed Air; New York, 1892. LEDOUX, M.-Ice Making Machines: New York, 1879. LEAR, VAN J. J. Die Thermodynamik In der Chemie; Leipzig, 1893 LEASK, A. R. Refrigerating Machinery; London, 1895. LEDOUX, M. Ice Making Machines, with Additions by Messrs. Denton, Jacobus and Riesenberger;-New York, 1892. LORENZ, HANS.-NeuereKuehlmaschinen; Muenchen und Leipzig; MARCHENA, R. E. DE. Machines frigoriflques a gas liquifiable; Paris, 1894. MAYER, J. R. The Forces of Inorganic Nature, 18*2. Translated by Tyndall. MAYER, J. R. Mechanik der Waerme; Stuttgart, 1847. APPENDIX m. 573 MAYER, J. R. Berne rkungen ueber das Mechanische Equivalent der Waerme; Heilbronn und Leipzig-, 1851. MAXWELL, CLBRK J. The Theory of Heat; London, 1891. NYSTROM'S Pocket Book of Mechanics and Engineering; Phila- delphia, 1895. OSTWALD, W. Die Energie und ihre Wandlungen; Leipzig, 1888. OSTWALD, W. Lehrbuch der allgemeinen Chemie, vom Stand, punkt der Thermodynamik, 3 Vols; Leipzig, 1891-94. PLANCK, MAX. Ueber der Zweiten Hauptsatz der Mechanischen Waermetheorie; Muenchen, 1879. PLANCK, MAX. Grundriss der Thermochemie; Breslau, 1893. PLANCK, Max. Erhaltung der Energie; Leipzig, 1887. PARKER, J.-Thermo-Dynamics; Treated with Elementary Math ematics; London, 1894. PECLET, E. Traite de la Chaleur, two vols.; Paris, 1843. PICTET, RAOUL. Synthese de la Chaleur. Geneve, 1879. PEABODY, C. H. Tables on Saturated Steam and Other Vapors; New York, 1888. PUPIN, M. T. Thermodynamics; New York, 1894. REDWOOD, J. Theoretical and Practical Ammonia Refrigeration : New York, 1895. RICHMOND, GEO. Notes on the Refrigerating Process and its plac- in Thermodynamics; New York, 1892. RONTOEN, ROBT. Principles of Thermodynamics; translated by Du Bois; New York. 1889. RUHLMANN, RICHARD. Handbuch der Mechanischen Waerme Theo- rie, two vols. ; Braunschweig 1 , 1876. SCHWACKHOEFER, FRANZ. Vol. II, des Officiellen Berichts der K. K. Osterr. Central Commission fur die Weltausstellung in Chicago, im Jahre 1893; Wien, 1894. SCHWARZ, ALOIS. Die Eis und Kuehlmaschinen; Muenchen und Leipzig, 1888. SKINKLE, EUGKNE T. Practical Ice Making and Refrigerating; Chicago, 1897. TAIT, P. G. Sketch of Thermodynamics; Edinburgh, 1877. TAIT, P. G. Vorlesungen ueber einige neuere Fortschritte in der Physik; Braunschweig, 1877. THURSTON, R. H. The Animal as a Machine and a Prime Motor and the Laws of Energetics. THURSTON, R. H. Engine and Boiler Trials and of the Indicator and Prory Brake; New York, 1890. THURSTON, ROBT. H. Heat as a Form of Energy; Boston and New York, 1890. THOMSEN, I. Thermochemische Untersuchungen, three vols.; Leipzig, 1883. THOMSON, SIR W. Lectures on Molecular Dynamics; Baltimore, 1884. TYNDALL, J. Heat Considered as a Mode of Motion; London, 1883. VERDET, E. Theorie mecanique de la Chaleur; Paris, 1872. VOHHBES, GARDNER T. Indicating the Refrigerating Machine; Chicago. 1899. WALD, F. Die Energie und Ihre Entwerting; Leipzig, 1889. WALLIS-TAYLOR, A. J. Refrigerating and Ice-Making Machinery ; London, 1896. WOOD, DE VOLSON. Thermodynamics, Heat, Motors and Refrig- erating Machines; New York, 1896. WAALS, VAN DER. Die Continuitat des Gasformigen undFlussigen Zustandes; Leipzig, 1881. ZENNER, GUSTAVE. Technische Thermodynamik, two vols.; Leip- zig, 1890. 374 MECHANICAL REFRIGERATION. b.-CATALOGUES. American Insulating Material Manufacturing Co. (Granite Rock Wool and Insulating Materials), St. Louis, Mo. Arctic Machine Manufacturing Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), Cleveland, Ohio. Austin Separator Co. (Oil Separators), Detroit, Mich. Barber^A. H., Manufacturing Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), Chicago, 111.' Buffalo Refrigerating Machine Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), Buffalo, N. T. Carbondale Machine Co. (Ice Making and Refrigerating Machin-. ery, Ammonia absorption system), Carbondale, Pa. Case Refrigerating Machine Co. (Ice Making and Refrigerating Machinery, Ammonia compression systemh Buffalo, N. Y. Challoaer's, Geo., Sons Co. (Ice Making and Refrigerating Machin- ery, Ammonia compression system), Oshkosh, Wis. Cochran Company (Ice Making and Refrigerating Machinery, Carbonic anhydride system), Lorairi, Ohio. De La Vergne Refrigerating Machine Co. (Ice Making and Refrig- erating Machinery, Ammonia compression system), New York City, N. Y. Direct Separator Co. (Water and Oil Separator), Syracuse, N. Y. Farrell & Rempe Co. (Wrought Iron Coils and Ammonia Fittings), Chicago, 111. Featherstone Foundry and Machine Co. (Ice Making and Refriger- ating Machinery, Ammonia compression system, and Corliss Engines), Chicago, 111. Frick Co. (Ice Making and Refrigerating Machinery, Ammonia compression system, and Corliss Engines), Waynesboro, Pa. Gifford Bros. (Ice Elevating, Conveying and Lowering Machinery), Hudson. N. Y. Gloekler, Bernard (Cold Storage Doors and Fasteners), Pitts- burg, Pa. Hall, J. & E., Limited (Ice Making and Refrigerating Machinery, Carbonic anhydride system), London, E. C., England. Harrisburg Pipe and Pipe Bending Co., Limited (Coils and Bends, and Ammonia Fittings and Feed-water Heaters), Harrisburg, Pa. aaslam Foundry and Engineering Co. (Ice Making and Refrig- erating Machinery, Ammonia absorption system), Derby, England. Hohmann & Maurer Manufacturing Co. (Thermometers), Roches- ter, N. Y. Hoppes Manufacturing Co. (Water Purifiers and Heaters), Spring- field, Ohio. Hoppes Manufacturing Co. (Steam Separators and Oil Illumina- tors), Springfield, Ohio. Kilbourn Refrigerating Machine Co., Limited (Ice Making and Refrigerating Machinery, Ammonia compression system), Liverpool,. England. APPENDIX III. 375 Kroeschell Bros. Ice Machine Co. (Ice Making and Refrigerating Machinery, Carbonic anhydride system), Chicago. 111. MacDonald, C. A.' (Ice Making and Refrigerating Machinery, Am- monia compression system), Chicago, 111., and Sydney, N. S* W., Australia. Nason Manufacturing Co. (Ammonia and Steam Fittings), New York City, N. Y. Newburgh Ice Machine and Engine Co. (Ice Making and Refriger- ating Machinery, Ammonia compression system), Newburgh, N.Y, Pennsylvania Iron Works Co. (Ice Making and Refrigerating. Machinery, Ammonia compression system), Philadelphia, Pa. Philadelphia Pipe Bending Works (Wrought Iron Coils and Bends), Philadelphia, Pa. Remington Machine Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), Wilmington, Del. Ruemmeli Manufacturing Co. (Ice Making and Refrigerating Ma- chinery, Gradirworks, Ice Cans, Fittings, etc.), St. Louis, Mo. Siddely & Co. (Ice Making and Refrigerating Machinery, Ammo- nia absorption system), Liverpool, England. Sterne & Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), London, England. Stevenson Co., Limited (Cold Storage Doors), Chester, Pa. Tight Joint Co. (Ammonia Fittings), New York City, N. Y. Triumph Ice Machine Co. (Ice Making and Refrigerating Machin- ery, Ammonia compression system), Cincinnati, Ohio. Vilter Manuiacturiog Co. (Ice Making and Refrigerating Machin- ery, Ammonia compression system and Corliss Engines), Mil- waukee, Wis. Vogt, Henry, Machine Co. (Ice Making and Refrigerating Machin- ery, Ammonia absorption System), Louisville, Ky. Vulcan Iron Works (Ice Making and Refrigerating Machinery, Ammonia compression system), San Francisco, Cal. Wheeler Condenser and Engineering Cq. (Water Cooling Towers) , New York City, N. Y. Wheeler Condenser and Engineering Co. (Auxiliary Devices for Increasing Steam Engine Economy), New York City, N. Y. Whitlock Coil Pipe Co. (Coils and Bends, Feed-water Heaters', Elmwood, Conn. Wolf Co., Fred W. (Ice Making and Refrigerating Machinery, Ammonia compression system), Chicago, 111. Wolf Co., Fred W. (Ammonia Fittings and Ice and Refrigeratic^ Machinery Supplies), Chicago, 111. Wood, Wm. T., & Co. (Ice Tools), Arlington, Mass. York Manufacturing Co. (Ice Making and Refrigerating Machin- ery, Ammonia compression system, York, Pa. TOPICAL INDEX. Absolute boiling point ... 60 Pressure 44 Zero "14, 49 Zero, change of..... 84 Absorber, cleaning of 291 High pressure in. 291 Operating the 291 The .235 Water required for 228 Absorption and compres- sion, efficacy compared. 231 Absorption, heat added and removed in ... ... .223, 224, 225 Absorption machines 86 Capacity of (example) .... 359 Construction of ....... 232, 239 Heat and steam required (example) 359 Miscellaneous attach- ments 237. 238 Tabulated dimensions. . . . 239 Absorption of gas 50 Absorption plant, ammonia required for 284 Charging with rich liquor 285 Installation of 283 Charging of 283 Leaks in 28S Management of. 283, 295 Overcharging of 284 Overhauling of 2H8 Permanent gases in 286 Recharging of 285 Test of 305 Absorption system, actual and theoretical capacity of 230 Ammonia, required in.227, 228 Boil over, remedy for ...'. 290 Correcting ammonia in . ; 290 Cycle of 222 Heat of poor liquor , 226 Heat removed in absorber 225 Heat removed in con- denser 225 Liquid pump in 224 Negative head of vapor . 227 Operation of cycle 222 Poor liquor 224 Rich liquor to be circu- lated 224 Syphoning over 289 The 222, 239 Working of same 223 Absorption vs. compression 231, 238 Acetylene for refrigeration 254 Adhesion g Adiabatic changes .......48. 63 Affinity, chemical 8 % 35 Air machines 85.255, 261 Air, circulation in meat . rooms 215 Air, compressed, use of .;.. 260 Friction in pipes ( table) 260 Air,etc.. liquefied by Linde's method .266, 2tf7. 268 Air refrigerating machines 85 Air required in combustion 30 Saturated with moisture. 110 Air thermometer 76 Air, velocity of .'. 187 Alcoholometers, compar- ison of ( table) 323 Ale breweries, refrigera- tion for 206, 207 Ammonia, anhydrous yi Boiling point of 103, 104 Density of 92 Forms of, properties" of '. '. 91 Heat by absorption (ex- ample) 358 In case of fire.... 276 Latent and external heat of i ; . 93 Pressure and tempera- ture 9,' !4 Properties of 91 Properties of saturated . 93,94,329, 331 Refrigerating effect per cubic foot ( table) -..'. 124 Refrigeration per cubic foot (tables) 124. 125 Required for compression plant 275 .Solubility of, in water 100,101, 102 Specific heat of 92 Specific volume of liquid 93, 94 Table of properties of sat- urated 329, 331 Temperature in expan- sion roil 115 Tests for 103, 104 To be circulated in twen- ty-four hours (table) ... 124 Van der Waals' formula lor 95, 96 Vapor, superheated (table) 90, 311 Waste of, in compression. 275 Wei glit and properties of (tabulated) 4 Dry air for refrigeration.. 185 Dryer for ammonia 143 Drying, air 112 Of egg room, etc 195 Dry vapors 50 Duplex oil trap 133 Dwellings, refrigeration of 219 Dynamics 9, 43 Dynamite works, refriger- ation in 218 Dyne -..,... 7. 346, 347 Dyne centimeter 10 Ebullition 51 Economizing of water 293 Efficiency, of absorption and compression.. 231 Of absorption system 231 Of ammonia compression (table) 348 Of boiler and engine 305 Of compressed air ma- chines ... ..260 Efficiency of compression plant (table) 278 Of ideal cycle .... 66. 67, 68, 69 Of sulphuric dioxide ma- chine 250 Relative, of fuels 350 Eggs, freezing rates of 337 Temperature, etc., for storing, moisture, etc., ..194, 195 Elementary bodies 33 Elementary properties (ta- ble) 34 Elements, properties of (table) 34 Energetics, system of, mod- ern -... 78 Energy, C.G. S., units of ... 10 Chemical, of distance, of surface of volume 78 Comparison of units of (table) .- 346, 347 Conservation of, trans- formation of, kinetic ... 10 Continuous conversion of 83 Dissipation of, radiant 81 Dimensions of. units of. 79 Dissipation of 10, 63, 81 Factors, capacity of, in- tensity of./. 79 Free and latent, charges of . 72, 73 New departure of, me- chanical, electric ( 78 Of a moving body 10 Of gas mixtures 63 Of motion, kinetic 78 Reversible an d irrevers- ible 82 Transformation of 82 Uniform units of 83 Visible, kinetic, potential, mplecular 9 Engine and boiler.efflciency of 305 Engineering and refrigera- tion 221 Engines, dimensions of standard Corliss (table) 340 Pounding 281 Water required for 123 Entropy -72 And intensity principle .. 83 And latent heat 77 Increase of 74 Equalization of pipes 138 Equation of compressed, air cycle .258, 259 Equilibrium of energy, arti- ficial 81 Equivalent units 61 Equivalents in piping 136 Erg; 10, 346, 347 Estimates and proposals for refrigerating plants 306 Ether machine, efficiency of 251 Properties of 251 Properties of hypotheti- cal ; 11, 12 Ethyl chloride machine 249 Ethylene, physical proper- ties of 272 Evaporating water 28, 30 TOPICAL INDEX. Evaporation power of coal (example) 354 Evaporator for carbonic acid plant 243 Examples on natural gas... 361 Exchanger, leak in 288 The, in absorption 236 Expansion, by heat 17 Co-efflcient of (table) 17 Free, latent heat of 48 Of ammonia 134 Of liquids 17 Of liquids and solids by heat 17 Top and bottom feed 294 Expansion coils, size of 184 Expansion valve 133 Experiments on wort cool- ing(table) 352 Explosive bodies 36 External work of vaporiza- tion 62 Extra strong pipe, dimen- sions of (table) 352 Freezing Rates, terms and payment of 337 Rooms in packing houses, calculation of refriger- ation 213 Tank, arrangement and construction of 147 Tank, dimensions of (ta- ble) 145 Tank, pipe in 146 Tank, size of.. . 148 Time for (table) 146, 149 Friction, of gases 49 Of water in pipes (table) 327. 346 Frigorific mixtures Stable ) . 32 Fruits, temperature for storing 188, 189, 190 ,Fuel; economizing of 161 Fuels, heat of, combustion of (table) 38 Relative efficiency of 350 Fusion, latent heat of (table) 31, 332 Factors of energy, of in- tensity and of capacity. 79 Fall of heat 71 Fermentation, heat by 200 Heat of 200, 205 Heat produced by, calcu- lation, rule for ... . 200 Removing heat of 207 Filter, boneblack, blood charcoal ; 164 For distilled water, inter- mediate 160 Filters, number required-, when required.when not 165 Filtration, dangers of 163 Fire and ammonia 276 Fish and oysters, tempera- ture lor storing 192 Fish, freezing rates for .... 336 Specific heat of (table) 182 Flow, of liquid, quantity of 42 Of steam 109 Of water in pipes. 43 Fluids 40 Viscosity of.... 40 Foot-pound 8, 346, 347 Force, measurement of -.... 7 Molecular 7 Unitof 7 Forced circulation 187 Forecooler 131 Free, energy, changes of 72,- 73 Expansion 48 Freezing back 279 Goods'; 183 Time 146, 149 Freezing mixture, capaci- ty of (example) 354 Mixtures 86 Ot meat 21* Rate for butter 336 Rates tor eggs ? 33f Rates, in summer, for fish, for meats .... 336 Gallons contained in cylin- ders (table) 322 Gas and vapor 60 Gaseous products of com- bustion 37 Gas equation, Van der Waals' .;..: ...55, 58, 59 Gas mixtures, energy of 63 Gases, absorption of 50 Adiabatic changes 48, 63 And liquids, general equa- tion 55, 58, 59 Buoyancy of 46 Components of, specific heat of 75 Constitution of 44 Critical data (table ) 47 Critical pressure 46 Critical temperature... .. 46 Critical volume 46, 47 Density of 53 Equation of 55, 56 Expanding into vacuum.. 62 Expansion of 55. Free expansion 48 Friction of, in pipes 49 Internal friction of 54 Isothermal changes 48, 63 I^atent heat of expansion. 48 Liquef action of 46. 60 Mixtures of 46 Perfect 49 Pressure and tempera- ture of , 44, 53 Properties of (table) 272 Relation of volume, pres- sure and temperature of 48, 49 Solubility j>f, in water . (table) 339 Specific heat of, at con- . statit volume and pres- ' J sure S5 Specific heat of (table).... '47 Velocity of sound in . 49 Weight of 45 382 TOPICAL INDEX. Gauges 45 Gauge pressure 44, 45 Gay-Lussac's law 55 Generation of heat 35 Generator, battery 232 Heat required for 327 Still or retort, size of (table) 232 Glue works, refrigeration in 7. 218 Glycerine trap in carbonic acid plant 242 Grains and milligtams per gallon (table)...... 351 Grapes, cold storage of 190 Graphite for lubrication.. . 282 Gravitation 7 Hampson's device for lique- Harvesting ice 148, Head of water In pressure per square inch (table).. Hea^, absorption of (table) Available effect of Capacity By absorption of ammonia (example) By chemical combination By different fuels (table). By mechanical means .... C. G. S. unit of, capacity of .... Changes, components of.. Complicated transfers . . . Cond ucti vitir ( table ) Convection or 23, Conversion of 62, 64, Determination of specific Emission of (table) 22, Emitted by pipes Energy, origin of Energy, transfer of Engines Fall of Generated by absorption of ammonia 101, Generated by ammonia absorption 101, Generation of 35, Latent 30, Latent of fusion and vola- tilization ( table ) 31, Leakage of walls for cold storage 170, Of chemical combinations Of combination (table) 36, 37, Of compression Of fermentation Produced by fermenta- tion, calculation, rule for Heat leakage, of buildings. . Heat, radiation and reflec- tion of (table) Radiation of ..11,12, Sources of Specific, of liquids(tables) 149 171 33 38 46 205 300 170 Heat, specific, of metals and other substances 16 Specific, of victuals... 182, 183 Specific, of water 16 Transfer of 18, 23, 24 Transfer from a.it to wa- ter 30 Transfer, theory of 22 Transmission of, through plates 27,38,29, 30 Unitof 14 Useofspecific 16 Weightof 77 Heater, the, in absorption. 336 Heating surface of boilers. 328 -Helium, physical proper- tiesof 272 Hop storage by artificial refrigeration 211 Hop storage, temperature for 210 vHops, storage of 210 Horse power 8, 43, 346, 347 Of belting, of shafting (ta- ble).... . 324 Of boilers..... 328 For ammonia compres- sors 133 Grate surface . required for 108 Of steam engine(example) 367 Steam required for 108 Of waterfall (example)... 368 Hospitals, refrigeration of . 219 Houses for storing ice 150 Humidity in air, relative, absolute 110,111, 112 Table 1 332 In atmosphere(tables).lll, 112 Hydrodynamics 43 Hydrogen, physical proper- ties of 272 Hydrometers, comparison of (table) 40, 41 Hydrostatics 43 Hygrometers 112 Hygrometry 1 10 Ice, after plate system.. 148, 149 By cell system 167 Cans, sizes of 144 Cost of making 154 Cost of making (tables)154, 155 Devices for making clear 167 Factories, cost of operat- ing (table) 154, 155 Formation of properties of 105 Handling of. 153 Heat conducting power of ..- 152 Harvesting ot 148, 149 Houses, refrigeration of 150, 351 Machines, construction of 86 Machines, measurement of size and capacity 90 Making, amount of water required for same 128 Making and brewing 210 Making, can system 144 TOPICAL INDEX. 383 Ice making capacity 90 Making capacity, exam- ples on 368 Making^ cost of same, 149,164, 155 Making, properties of wa- ter for ... 157,168 Making/plate system. 148, 149 Making, systems of, capa- city of plant 144 Making tanks, dimensions of (table). , 145 Odor of..^., 14 Packing of 151 Quality of .....156, 157 Removing from coils . 295 Rotten 165, 166 Selling of . 152 Shrinkage of.... 152 Specific neat of 107 Storage houses . 150 Storage houses, refriger- ationof 150, 151 Storage of manufactured 149 Taste and flavor of. . . 164 Test for ... 166 Weight and volume of 153 Withdrawal and shipping of - .,./. 152 With core 162, 163 With red core 163 -With white core ; 162 India rubber works, ref rig- . erationin . .< 320 Indicator diagram, inter- pretation of 299-302 Indicator diagram 296, 297 Inertia ...:... 9 Inflammable bodies 36 Installations, actual, of brewery plant 211 Of absorption plant ^ 283 Of compression plant. . . . 273 Insulation 282 Of steam pipes (table ) 20 Insulators (table ) 19 Intensity, and entropy prin- ciple 83 Principle, compensation of... 80 Internal work of vaporiza- tion 52 Isentropic changes 77 Isothermal changes. . 48, 63 Isothermal compression, work required for ...259 Joule.... 846, 347 Kilogrammeter 8 Kinds of aqua ammonia or ammonia liquors 287 Kinetic energy 9 Kinetics, molecular. 53 Latent energy, changes of. 72, 73 Latent heat, of fusion (ta- ble)., 31 Latent neat of solution.. 31, 32 . Of vaporization 51 Leakage of heat in build- ings 1TO Leak in plant discovered by soapsuds 273 Lifting of heat ( example ) . . 355 Lignite r. 39 Linde liquid (oxygen), its uses : 271 Linde's method, for lique- faction of air,etc.266, 267, 268 Rationale of ........... .267, 268 Liquefaction of gases. ..266, 272 History of.,. 266 Liquefaction of vapors 52 Liquefied air by Linde's method ;.....;.... 266, 267, 268 Liquefying air, by Hamp- son's method , 268 By other methods 269 Liquid air,, for motive pow- er, for refrigeration. .. 270 Motive power of ( example) 369 Uses for same 270, 271 Liquid receiver - . ISO In absorption 235 Liquids, 'buoyancy of. 40 Boiling point of 350 Expansion of 17, 18 Flow of., 42 Pressure of 41 Specific heat of 16 Surface tension of 43 Useful data about. ... 341, 342 Velocity of 42 Viscosity of 40 Liquid traps 143 Liquor or ammonia pump.. 237 Liquor pump, in absorption 224 Work done by 227,228 Liquors, temperature for storing (table) 191 Leaking valve and piston packing 300 Leak in rectifying pans 289 Leaks, in absorption plant, in exchanger 288 In brine tank 293 Lemons, cold storage of .... 190 Localities, temperature in different (table) 341 Logarithms, rules for using them 317 Table of, use of. . ..315, 316, 317 Lowest cold storage tem- peratures 196 Lubricating of compressor 282 Malt houses, refrigeration of 211 Management, of absorber. ..291 Of aosorption plant 283-295 Of compression plant . .273-282 Of refrigerating plants. . . 295 Manometers .<, 45 Marsh gas, physical proper- tiesof 272 Mass. 6 Unit of.., 6 Materials, specific weight of (tables) 319,320, 321 384 TOPICAL INDEX. Matter, constitution of 5 General properties of .V. . 5 Solid, liquid, gaseous..... 5 Maximum conversion 64 Maximum convertibility... 83 Maximum principle 85 Mean effective steam pres- sure (tables) .348, 849 Pressure of compressor (table) ...i 298 Measures and weights (ta- - bles) 317,318, 319 Meat, cause of bonestink of 216 Chilling 215 Effect of freezing on.. 214, 217 Freezing from within," de- frosting of..... 316 Freezing of, storage tem- peratures ( table) 214 Mold on, keeping of, ship- ping of..., .. .,. 217 Rooms, circulation of air W i ..,.^...215, 217 Thawing and defrosting of , 216 Time of keeping of. .- 217 Withdrawing fromMstor- - 1 age Y> V .V... 31* Meats, freezing rates for .. 336 Meat Storage, official views on..,.:..... t 214 Mechanisms , 11 Megerg 10- Melting points ( table ) . . . . . . 31 Mensuration, of circle, solids, polyhedrons, etc. 310 Of surfaces (table ) 309 Mercury wells 298 Metals, conductivity of .^ ... 22 Specific heat of 15 Specific weight 6*7 819-321 Me thylic chloride machine. 249 Metric and U. S. weights and measures (table).:.. 323 -Measurement, compari- son .,,.. 319 Milk, specific heat of (table) 182 Temperature, e t c . , f o r storing ......;.. 194 Milky ice 162 Milligrams and grains per gallon, etc. (table)..,... 351 Minerals, metals, stones, specific weight of (table) ......319-321 Miscellaneous goods, tem- peratures, etc., for stor- . age . ( ... 196 Miscellaneous ref r i g e r a - tion 218-221 Mixed vapors 52 Mixtures, frigorific (table). 32 Temperature of .'..... 16 Modern concepts..'... ...... 83 Modern energetics 78 Moisture, in air, absolute . determination of 110 In air (table) 332 In atmosphere (tables) lll t 112 In cold storage ,. 184 J In cold storage (example) 370. Relative, in cold storage. 370 Rules for, cold storage, .. . 187 Mold on meat 211" Molecular dynamics .\.KM5U Forces 7 Kinetic ...,:.... 53 Transfer of energy- ..... . 62 Velocity. ?,..:. .... 54 Molecule 33 Molecules , 58 Heat energy of..,....! 54 Momentum- ^ 8 Motion.. 7 Laws of.. ..:... 9 Perpetual.. 82 Motay and Rossi's system of refrigeration . . . , 254 Motive power of liquid air (example) 369 N Natural gas, expansion, re- frigeration, Work. etc. , 361,362, 363 Negative specific heat 76 Nitric oxide, physical prop- erties of.: .... 273 Nitrogen, physical proper- ties of 272 Noise in engine or pump, how located.. .... ..281 Odor of ice lt>4 Oil trap. , 126 Duplex ........;.. 133 Oil works, refrigeration in. 218 Onions, cold storage of 189 Operation of compression plant 274 Optics . io Overhauling absorption plant...... ..' 238 Oxygen, physical properties Of, .....i 279 Oysters, specific heat of (table) ... 182 Oysters and fish, tempera- ture for storage J92 Packing houses, etc., re- frigeration for, rule for- calculation . , 212, 213 Freezing rooms, piping of same ..'..:. ..212, 213 Packing of ammonia pump, 292 Packing of compressor piston -. 281 Packing of ice 151 Painting brine tanks, etc.. X82 Pascal's law. . . / 40 Passage of heat. 64 Pears, cold storage of . ... 190 Peltry, refrigeration of.... 218 Perfect gases 47 > Equation of 55 Performance of ammonia and carbonic acid svs- . , tem :.. : 246,247 Performance of compressed air machines , 259 TOPICAL INDEX. 385 Permanent gases, examples on '.. .....354,365 In absorption plant 288 In compression plant 279 Origin of 280 Perpetual motion 82 Pf erdekraf t 346, 347 Photography, artificial re- frigeration in 218 Physics, subdivisions of 10 .Pictet's liquid, refrigera- tion by 252 Pictefs liquids, anomalous behavior of 252, 253 Pipe, dimensions of, double extra strong (table). ... 339 Extra strong, dimensions of 352 For condenser 130 Rules for laying 138 Dimensions of (table )?... 136 Plow of steam in (table). 328 Friction of water in (table) 327,346 Table for equalizing.. .... 138 Transmission of heat 135 Pipe required in c o n- denser 127, 129,131 Pipes, dimensions of stand- ard 136 Piping, equivalents in 136 Piping of brine tanks 137 Pipingcold storage rooms.. 172 For, cold storage (exam- ples) 361 Of brewery rooms, rules - ." 204, 205 Required for storage rooms (tables) 174-178 Rooms 134 Rooms in packing houses, etc 213 Rooms, practical rules for 135 Pipe line refrigeration 221 Plants, specification of. 306, 307 Plate and can system, com- parison of 148, 149 Plate ice, size of 149 Plate system for ice mak- ing 148,149 Polygons, surf ace of (table) 309 Polyhedrons, mensuration of (table) 310 Poor and rich liquor (table pt strength) 226 Liquor, heat introduced by 226 Liquor in absorption, strength of 224. 225 Pork.specificheat of (table) 182 Poultry, freezing rates for. 335 And game, rate of freez- ing of . 334,335 Rates for storing un- frozen 336 Pound, Fahrenheit 346,347 Pounding pumps and en- gines 281 Power required for am- monia compressor ..... 133 Furnished by liquid air (example).,,,,,.,. 366 Power' required to raise water (table ) 326 Unit of 8 Practical examples 353-370 Practical tests of ammonia and carbonic acid sys- tem 247 Pressure and temperature of gas. 19 Pressure, condenser and back ,...: 277,278 Critical 46, 47 Gauge, absolute 44 Mean effective, of steam (tables) 348, 849 Mean, in compressor (table) 298 Of liquids 41 Unit of . 44 Principles of energy, regu- lative, intensity 80 Properties of ammonia 91 Of ammonia liquor.. 97. 98, 99 Of gases ( table) 272 Of saturated ammonia (table) :...329,331 Of sulphuric dioxide 249 Proposals and estimates for refrigerating plants 306 Psychrometers. Ill Pumping of vacuum 273 Pump, calculation df (ex- ample.) : 3fi8 Pumps.discharge by (table) 139 Pounding 281 Purge valve:... 132 Radiation of heat... 11, 12, 22, 23 Rates for freezing, in sum- mer, for fish and meats, 336 Poultry, butter, etc.. ..334-337 Rates of cold storage (by months 333, 334 Rationale of Linde's method 267,268 Recharging absorption plant 285 Rectifier, the, in absorption, size of (table) 234 Rectifying pans, leak in .... 289 Red core in ice. - 162, 163 Refrigerating capacity, nominal, actual, com- mercial 302 Refrigerating capacity, of compressor (examples) ...., 356, 357 Units of, British, Ameri- can , 308 Refrigerating duty, exam- ples on 364, 365 Refrigerating effect 52 Net theoretical 117 Per cubic feet ammonia (table) 124 Refrigerating fluids, com- parison of 248 Refrigerating machine,,, ideal, efficiency of * 71 386 TOPICAL INDEX. Refrigerating machinery, etc., catalogues, price lists 373 Testing of 308 Refrigerating ma chines, . different systems,85,86,8T, 88- Refrigeratiag plant, fitting up, for, test of 296 Estimates and proposals for, contracts 306, 307 Testing of 296-308 . Refrigeration, according to Motay and Rossi 254 And engineering 221 And work, by natural gas (examples) ..361,362,363 By cryogene.by acetylene 254 By dry air 185 By liquid air 270 ByPictet's liquid 252 By sulphur dioxide 249 Calculation of, for cold storage 180, 181, 182, 183 Cost of! 167,295 Different systems of 103 During transit 218 Etc., books on 372, 373 For breweries :. . 197-211 For miscellaneous pur- . poses 217-221 For packing houses, etc., rule for calculation 213 In breweries, distribution of 203 in chemical works. . ..;.. 220 In chocolate factories.... 220 In dairies.... 218 In distilleries 220 Indwellings 219 In dynamite works 219 In general, means of pro- ducing 85 In glue works 218 In hospitals 219 In India rubber works 220 In malt houses 211 In oil works 218 In soap works 218 In storing trees 218 In sugar refineries. . . : ... 220 In sulphuric acid works, soda works 221 Means of producing 85 Of brewery storage rooms 201,202 Of photographic supplies, 218 Of silk worm eggs 218 Required for storage rooms (tables) 174, 179 Self -intensifying .265 Transmission of 135 Uses of artificial 90 Refrigeration units, differ- ences between them.... 308 Relative moisture or hu- midity (table) 112 Retort, heat required for. . 227 Or still in absorption, coils in 232.333 Reversible changes . . 82 Reversible cycle v.65, 88 Refrigeration in 89 Rich and poor liquor (table of strength) Rich Ijquor, amount of, to be circulated ... Example on. In absorption, strength of Rooms, construction of, for cold storage.. 169, 170, 171, 172 In brewery, piping of .204, 205 Rotten ice 165, 166 Rules for laying pipe 138 Of moisture in cold stor- age :... 187 S Saccharometers. compari- son of (table) 202 Different 201 Safety valve in carbonic acid plant 243 Salometer, substitute for, comparisonof 142 Salt cake, decomposition of, by refrigeration -221 Salt solutions, properties of ... . 140 Saturated ammonia, table of properties of 329-331 Saturated vapors 50 Scale in coils removed by acid*....'.. 291 Scales, different, of ther- mometers 12, 13 Self-intensifyingrefrigera- tion 265 Shipping provisions, refrig- eration in . . 219 Silk worm eggs, refrigera- tion of 218 Site for brewery 210 Skating rinks 154, 156 Skimmer 161 Soapsuds to discover leaks 273 Solids, mensuration of (table) 310 Solubility, of ammonia in water (table) 102 Of gases in water ( tables X339 Solution, latent heat of.. 31, 32 Solutions, of ammonia, strength and properties (table) 100, 101,102 Of chloride of calcium (table)..... 346 Sound, velocity of 49 Southby's vacuum machine 263 Operation of 264 Space, measurement of 6 Spe-cific gravity and ^ Baume scale ( table) 344 Specific gravity, deter- mination of 40 Specifications of plants. 306, 307 Specific heat, calculation of 183 Determination of. 16 Example on 354 Negative 76 Of ammonia 9J Of beef 182 Of cabbage 182- Of chicken 182 Of cream 182 TOPICAL INDEX. 387 Specific heat of fish 182 "Of gases (table) 47 Of liquids 15 Of metals :. 15 Of milk 182 Of oysters J82 Of pork 182 Of veal 182 Of victuals.. 182 Of water, of ice, of steam. 107 Of wort (table)... 197 Useof. 16 Specific volume of steam... 107 Specific weight Of materials (tables) 319,320, 321 Spontaneous combustion... '66 Square and cubic roots (table) 312. 818 Squares, cubes, roots, etc. (table) ..312, 31S Statics 9 Steam, condensation in pipes (tables). . .21, 24, 25, 86 Condensation of, in tubes. 29 Economizing of, in ab- sorption, amount re- quired 229 Steam engine, horse power of (example) 367 Steam, flow of 109 Flow of. in pipes (table).. 328 Internal and external heat of 106 Latent heat of... -. 106 Steam pipe, condensation in 21 Insulation of ,...20, 21 Steam, production of, work < done by 108 Properties of (table) 107 Saturated 105 Specific heat of...., ^ 106 Specific volume of 107 Total heat of ....-, 106 Steam, pressure of (table).. 107 Steam produced per pound of coal... 108 Steam to produce horse power 108 Steam, volume of 105 St. Charles' law 44 Stiff valve and irregular pressure 800 Storage houses for ice, con- struction, ante-room of. 150 Storage of hops 210 Of manufactured ice .149, 150 Refrigeration for, piping for (tables) 174-178 Storage rooms, drying of, etc 195 Rent of 337 Ventilation 186 Storage rooms, doors for same 179 Strength of brine required 142 Stuffing box for carbonic acid plant....;. 248 Sublimation 62 Sugar works, refrigeration , Sulphuric "acid,' concentra- tion of, by refrigeration 221 Sulphuric dioxide machine, useful efficiency of 250 Sulphur dioxide, proper- ties of, refrigeration by 149 Sulphuric dioxide, prop- erties (table) 250 Refrigerating effect of (example) 356 Superheated ammonia va- por (table) . 811 Superheated vapors 50 Sup.er heating, water to counteract... 125 Surface, tension of liquids. 42 Sweet water 207 For attemperators 207 Syphoning over in absorp- tion plant 289 Symbols, chemical 88 Tables ( appendix I) 809-352 Tanks, capacities of, in bar- rels (tables) 325 Taste of ice 164 Temperature 12 And pressure pf gases 44 Critical 46, 47 Measuring of high 13, 14 Of mixtures 16, 17 Comparison of, Fahr. and Centigrade (table) 343 Etc., for cold storage.. 188-196 Etc., for storing butter. . . 193 Etc., for storing cheese.. 194 Etc., for storing eggs 194 For hop storage 210 For storing fruit.. 188, 189, 190 For storing liquors . ..... 191 For storing milk 194 For storing miscellaneous goods (table) 196 For storing oysters, fish . . 198 For storing vegetables... 191 For storing meat 214 In different localities (table)., 341 Lowest, for cold storage . . 196 Temperatures of cellars... 205 Tension, of vapors 60 Of vapors in air (table). .. Ill Of water vapor (table)... 350 Test for water, for ice 186 Test table, showing items of compressor 806 Testing refrigerating plants 296-308 More elaborate, data of (table) i... 304 More exact, of absorption 305 Results of absorption (table).: 30 Tests, for ammonia 103, 10 Theoretical capacity (maxi- mum) 303 Therapeutics, refrigeration in ; 219 Thermal units 848, 347 Thermo-chemistry 10 Thermodynamics 10, 61 Thermodynamic scale of temperature 76 TOPICAL INDEX, Thermodynamics, first law of 61 Second law of 61 Thermometer, Fahrenheit, Reaumur, Celsius 12 Thermometer scales, com- parison of (table) -18 Fahrenheit and Centi- grade, comparison of (table)., 343 Thermometer, scales of.... II Time, unit of 8 Time for f reezing.water. 146, 149 Top feed and bottom feed expansion 294 Transformation of energy. 82 Transfer of energy, artifl- cial and natural 81 Transfer of heat, compen- sated, uncompensated.. 72 Complicated 23, 24 Prom water to air 30 Transmission of heat through plates of metal ..27,28,29, 30 Transit, refrigeration during 218 Trees, cold storage of 218 Unit, of heat, British ther- mal 14 Of pressure . . 44 Of refrigerating capacity. 90 Units, absolute.. ..;. 7 British and American, re- frigerating capacity of. 308 C. G.S ............. 7 Derived .- 6 Equivalent 61 Fundamental 6 Of energy, comparison of (table F 346, 347 Units of refrigeration, dif- ferences between 308 Universe, future of 73 United States and metric measures (comparison). 323 Usages, cold storage 337 Useful data about liquids 341,342 Useful numbers for approx- imations 338 Uses for liquid air 270, 271 Uses of compressed air .... 260 Vacuum High, produced by liquid Vacuum ' machine*. ! ! ] Compound Efficiency of Objection to sulphuric acid .. Operating expense of Refrigeration by, size of 261, Vacuum, pumping of Valve, leaky, stiff. ..,.'. '. '. '. I \ Lift 271 86 268 262 273 Van der Waals' formula for ammonia 95,96 Vaporization 51, 113 Latent heat of 61 Vaporization machines ... 86 Vapor of water, tension of (tables) Ill, 350 Vapor, boiling points 51 Vapors, dry... 50 Liquefaction of, mixture' of 52 Saturated 60 Superheated 50 Tension of 50 Wet..., 50 Veal, specific heat of (table) 182 Vegetables, temperatures for storing (table) ... ; .. 191 Velocity 8 Of air 187 Ventilation of cold storage rooms 186 Volatilization, latent heat of (table)..... 332 Volt, ampere 346. 347 Volume and pressure and temperature, relations _ of 4? Volume and weight of ice.. 153 Volume, critical 46, 47 W Walls for cold storage, heat leakage of 170, 171 Water cooled by evapora- tion 120 .Constituents, composition of 351 Economizing of 293 Evaporable by coal 38 Evaporating of 28, 80 Expansion and weight of, , at various temperatures (table) 18 Flow of , in pipes . 43 For ice making 157 Friction of, in pipes (tkble) 327, 346 Head of, converted in pressure ( table ) 326 Properties of> for ice mak- ing 157,166 Required to raise same (table) 326 Required for refrigerat- ingplant ; ... 128 Required to make ton of ice 128 Purity of 113, 166 Required for engine 123 Specific heat of 106 Steam, etc .105 Test for, requirements of pure 166 Volume and weight at dif- ferent temperatures ... 18 Volume and weight of..;. 108 Weight and expansion of. 18 Water jacket compressor.. 124 Water motors, useful effect Of . . .368 TOPICAL INDEX. Water power 43 Calculation of (example).. 368 Water pressure 42 Water vapor, tension of (table) 350 Water vapor, table of Ill Watt 346, 347 Watt hour 346, 347 Weight 6 Weight of heat 77 Weights and measures, comparison of 323 Tables 317, 318, 319 Weight, specific 6 Wet compression 280 Wet vapors 50 White core in ice ...162 White or milky ice 162 Wood for storage rooms. 168, 171 Woolen goods, pelts, stor- ing of! 218 Working fluid (influence of) 67 Work of compressor (ex- ample) 367 Work to lift heat (example) 355 Work, unit of, useful 8 Work, useful, lost 19 Wort cooler, dimensions of 203 Direct expansion 204 Wort coolers, special de- vice 208 How to m anipulate 209 Wort cooling, experiments in (table) 352 Wort, cooling of (example) 357 Wort cooling, machine for, efficiency in 199 Wort cooling, refrigeration for, calculation for 198 Wort, specific heat of (table) 197 Zero, absolute 14 UNIVEESITY OF CALIFORNIA LIBRARY BERKELEY THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW Books not returned on time are subject to a fine of 50c per volume after the third day overdue, increasing to $1.00 per volume after the sixth day. 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