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.
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PROPERTIES OF AMMONIA.
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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.
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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
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puooggjad :::::::: : : : r^ M .*
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000
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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-
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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
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