THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES GIFT OF John S.Prell /, REFRIGERATION A PRACTICAL TREATISE ON THE PRODUCTION OF LOW TEMPERATURES AS APPLIED TO THE MANU- FACTURE OF ICE AND TO THE DESIGN AND OPERATION OF COLD STORAGE PLANTS By MILTON W. ARROWOOD GRADUATE, UNITED STATES NAVAL ACADEMY REFRIGERATING AND MECHANICAL ENGINEER WITH THE TRIUMPH ICE MACHINE CO. JOHfU S. PRELL Gvil 6* Mechanical Engineer. SAN FRANCISCO, CAL. ILLUSTRATED CHICAGO AMERICAN SCHOOL OF CORRESPONDENCE 1913 COPYRIGHT, 1913, BY AMERICAN SCHOOL OF CORRESPONDENCE COPYRIGHTED IN GREAT BRITAIN ALL, RIGHTS RESERVED Civil & Mechanical Engineer. A In A/ PAGE Historical 1 Air machine 2 Definitions 3 Heat 4 Units of heat measurement 6 Unit of plant capacity 13 Radiation 18 Convection 19 Conduction 20 Production of cold 20 Tests of refrigerants 33 Systems of refrigeration 36 Cold-air machine 36 Arrangement of air system 37 Commercial form of air machine 38 Compressor cylinder 41 Vacuum process 44 Vacuum pump 45 Absorption system 46 Generator 48 Analyzer 48 Condenser 50 Rectifier 50 Equalizer 50 Absorber 51 Ammonia pump 52 Ammonia regulator 53 Operation 53 Power for absorption plant : 53 Binary systems 56 Care and management ' 57 Charging 7374O1 5 .^ns-.i.e-ilAiE. LflMry 2 CONTENTS Absorption system p AGE Efficiency tests 60 Economy of absorption machine 61 Compression system 61 Operating principle 62 Compressors 64 Essentials in compressors 66 Compressor valves 67 Valve operation 71 Valve proportions 72 Compressor piston 73 Stuffing box 75 Water jacket 76 Lubrication 78 Commercial machines 81 Horizontal double-acting 81 Vertical compressors 85 Carbon dioxide machines 87 Small refrigerating plants 90 Compressor losses 93 Ammonia condensers 94 Submerged condenser 95 Atmospheric condenser 98 Double-pipe condenser. . . 104 Oil separator or interceptor 109 Cooling towers 109 Evaporators 113 Brine tank 114 Brine cooler 118 Auxiliary apparatus 125 Ammonia receiver 125 Pipes 125 Valves : 128 Pressure gauges 128 Methods of refrigeration 131 Proportion between parts of refrigerating plant 132 Testing and charging 134 CONTENTS 3 FACE Operation and management of plant 140 Loss of ammonia 142 Purging and pumping out connection 143 Ice-making plants 145 Can system 146 Can plant equipment 147 Distilling apparatus 148 Steam condenser 149 Hot skimmer and rcboiler 149 Filters 152 Cooling coils and gas cooler . 152 Freezing tank 154 Expansion coils 154 Ice cans 155 Grating and covers 156 Brine agitators 156 Crane and hoist.' 158 Dumping and filling 158 Layout 160 Plate system 162 Storing and selling ice 174 Ice-plant insulation 176 Tank insulation 177 General cold storage 178 Conditions for preservation 179 Insulation 182 Non-conductors 183 Methods of cooling 191 Refrigeration required 197 Cold storage 198 Handling goods 198 Storage rates 201 Applications of refrigeration 202 Breweries 202 Packing houses 202 Creameries 203 Miscellaneous applications. . .- 204. INTRODUCTION r T"'HE production of low temperatures by artificial means is centuries old and even the methods involving the use of lique- fied gases have been known since 1850. It is only in the last few years, however, that cold storage methods have^been extensively applied, and very few of us stop to realize the influence which this means of preserving our meats, fish, poultry, vegetables, etc., has had upon the marketing of our perishable produce. Perhaps we sometimes feel that the cold storage companies often make an unfair use of their powers of control in order to manipulate prices but certainly in the end the results make for the general welfare of the public. * H Ss s nfe ^ 5g tf U < o a } A, QO O "" < 02 t 8 1 .0320 .944 15 1.0614 .895 9 1 .0363 .937 16 1 .0657 .888 10 1 .0404 .930 17 1.0700 .881 11 1.0446 .923 18 1 .0744 .874 12 1 .0488 .916 19 1 .0788 .867 13 1 .0530 .909 20 1 .0832 .861 14 1 .0572 .902 determined, as no process has ever been devised for freezing this liquid. Then, again, the vaporization of tin and lead takes place at such high temperatures as to make accurate measurement impossible by any known means of recording temperatures. Unit of Plant Capacity. Ordinarily the capacity of a refrigera- ting machine or plant is stated in tons that is, one ton is the heat equivalent of a 2,000-pound ton of ice at 32 degrees F., melted into water at the same temperature; or, conversely, the amount of heat that must be abstracted from 2,000 pounds of water at 32 degrees to change it into ice at the same temperature. Since the latent heat of ice is about 142 B. T. U , the ton of refrigerating capacity used in rating apparatus is equivalent to 142 X 2,000 = 284,000 B. T. U. Thermodynamics, as the name implies, is the science treating of heat as a form of energy and of its relation to other forms of energy, particularly its relation to and transformation into mechanical energy 14 REFRIGERATION TABLE IV Fusion and Vaporization Data of Substances SUBSTANCE TEMPERA- TURE OF FUSION F. TEMPERA- TURE OF VAPORIZA- TION F. LATENT HEAT OF FUSION LATENT HEAT OF VAPORIZA- TION Water 32 212 142.65 966.6 Mercury -37.8 662 5.09 157 Sulphur Tin 228.3 446 824 13.26 25.65 Lead'.......'.. ......... 626 9.67 Zinc 680 V,900 50.63 493 Alcohol Unknown 173 372 Oil of Turpentine Linseed Oil 14 313 600 124 Aluminum 1,400 Copper 2,100 C Cast Iron 2,192 3,300 Wrought Iron 2,912 5,000 Steel 2,520 Platinum 3,632 Iridium . 4,892 or work. It is not possible in brief space to enter into a discussion of thermodynamics in detail; but brief mention must be made of the fundamental principles of this science that have to do with the opera- tion of refrigerating apparatus. Some reference has already been made to the first law, which is a special case of the general law expressing the mutual converti- bility of all forms of energy. According to this law, as already mentioned, heat is equivalent to work or mechanical energy, each unit of heat being equivalent to 778 foot-pounds of work, or the amount of work that must be performed to raise 778 pounds a vertical distance of one foot against the action of gravity. This first law of thermodynamics must be qualified to some extent, for, although heat and work when convertible are theoretically equivalent to each other, the actual conversion of one into the other is not, in every case practicable being, in fact, practicable in every case only so far as the conversion of work into heat is concerned. In other words, while it is always possible to change a given amount of work into heat energy, it is not possible in every case to convert heat into work, for there is always a certain amount of unavailable heat which it is found impracticable, with devices at present in use, to convert into work. REFRIGERATION 15 The second law of thermodynamics states, therefore, that it is impossible to transfer heat from a body of low temperature to one of higher temperature without the 'application of some external form of energy. Thus in every case, for a given temperature, there is a certain well-defined portion of the total heat in the substance that can be converted into work, the remaining heat being unavailable for con- version. If this were not true, it would be possible to reduce the temperature to absolute zero, when the substance would have no volume. Thus matter would be annihilated. As this is impossible, however, it is plain that absolute zero temperature can never be attained. In every case where heat is converted into work, there is a lowering of the temperature of the body from which the heat is taken, and the fall in temperature is an index of the amount of heat energy converted into work. The energy existing as heat at low temperature is unavailable and must be dissipated, it being absorbed on discharge from the heat engine by a still colder body, which in the case of steam engines is the atmosphere or condensing water. Much depends on the character of the heat engine, as to just what amount of energy in the form of heat will be transformed into useful work. A conspicuous example of this is the case of low-pressure turbines, which, within the last few months, have been so perfected as to reclaim as much energy from the exhaust steam of reciprocating engines as the engines themselves utilize in the first place. As already pointed out, the molecular activity of a substance is increased by heating or raising its temperature; and it is this molec- ular activity that gives an index to the energy present and available in the form of heat. There are many ways of converting this energy into work; but, in that most commonly used, advantage is taken of the pressure produced by the molecular activity of a gas that has been heated. The gas in its heated state is placed behind a piston; and the molecules in their efforts to get away from each other, or to occupy a larger space, exert a pressure on the piston that moves it forward. As the gas expands, its heat energy is expended, and its temperature is lowered until the force of cohesion acting between the molecules is sufficient to prevent the performance of further external work. The one condition of work being performed is, that there shall be resistance to movement of the piston there being no work, with 16 REFRIGERATION resulting fall of temperature, where a gas has free room to expand, as in a vacuum. This leads to a consideration of the way in which gases may be compressed and expanded ; and it is well for the student to give atten- tion to this subject which lies at the bottom of all efficient work in refrigerating machines. When a gas is expanded or compressed without addition or subtraction of heat, the process is said to be adiabatic, and the temperature of the gas will rise with compression and fall with expansion. If it is desired to maintain the temperature of the gas constant, heat must be abstracted as the gas is compressed, or supplied as it is expanded, except in the case of free expansion, in which case there is practically no change in temperature. In this discussion, however, it is assumed that work is expended in compress- ing the gas, and that the gas performs work in expanding. As the heat abstracted from a gas in a heat engine is the equiv- alent of the work performed, it should be possible theoretically to restore the temperature of the gas to its original state by reversing the operation of the heat engine, there being no loss of heat in the process. In practical work, a certain part of the work obtained from heat in an engine is dissipated at once in overcoming the frictional resistance of the moving parts of the machine, and appears as heat in the bear- ings, etc., so that the theoretical conditions of a complete reversible cycle cannot be carried out. If it were possible to convert heat into mechanical work by direct process without the intervention of heat engines or other mechanism, there would be much greater efficiency than at present; but so far no method of doing this has been found. Where a gas is allowed to expand freely without performing work, its energy is dissipated, and there is no way to restore it to its original condition without the expenditure of some external form of energy. It is possible, therefore, for the entire heat energy of the world to be dissipated, as the only way in which waste heat is reclaimed is in its indirect effect on growing vegetable matter which can be used as fuel. In the operation of a refrigerating machine, it is necessary to have a continuous conversion of heat into work. This presupposes dissipation of a certain amount of heat energy, as it is impossible to carry on continuous conversion without the loss of the unavailable heat that must be rejected by the machine. Thus the heat pump of a refrigerating establishment is a machine designed to abstract a REFRIGERATION 17 certain amount of heat from the body to be cooled by changing the form of the surrounding medium used in the abstraction so that its temperature becomes lower than that of the body itself. It is there- fore evident that, with the possible exception of the vacuum pro- cess, in which the evaporation of a portion of a body of water absorbs sufficient heat to freeze the remaining part of the water, it is impossible for a machine, however designed, to refrigerate the body to be cooled without using some working medium. Several kinds of mediums are used, and will be discussed in detail later. In practically all cases, water is used for the cooling body to absorb the waste heat, the water being circulated over the condensers and cooling coils of the machine, so as to take up the heat that has been concentrated in a comparatively small volume of the working medium by the action of the refrigerating machine. It is therefore in order to see how the machine effecting this result is constructed; but before doing this, it is well to see in what way heat transfers are made. Heat transfers may be made in three ways by radiation, by convection, and by conduction. An illustration of the meaning of these terms is had in the case of an iron bar thrust into the fire until one end becomes hot. When the bar is withdrawn from the fire, it loses heat in each of the three ways mentioned, part of the heat being radiated into space, part of it being conducted along the length of the bar, and part being carried off by air currents which circulate around the bar, the heated air rising. At first the temperature of the iron will fall rapidly ; but as it becomes cooler, the transfer of heat to the atmosphere and surrounding objects becomes less rapid. This brings us to the law of Newton, which holds good for mod- erate temperatures such as those used in refrigerating work namely : "The rate of cooling of a body is proportional to the difference between the temperature of its surface and that of its surroundings." In the case of liquids, we have the similar law, also evolved by Newton, in the words : "The amount of heat lost in a given interval of time by a vessel filled with liquid is proportional to the mean difference of temperature between th*> liquid and its surroundings." 18 REFRIGERATION Radiation. Taking again the illustration of the hot bar of iron, if the hand is placed at a certain distance above the bar, a greater intensity of heat is felt than if it is placed at the same distance below the bar, this being due to the fact that in the first case the hand feels heat emitted from the bar both by radiation and convection, while in the second case with the hand underneath the bar, the heat or radia- tion alone is felt. Another illustration of radiant heat is the common experiment performed with the optical lens by means of which the rays are focused on a given point, when the heat becomes so intense as to burn the flesh or ignite a dry substance. Radiant heat rays pass readily through glass, but are reflected by smooth polished surfaces; while, on the other hand, a rough surface covered with lamp black will absorb the rays. The rays" pass readily through air, but are absorbed to some extent by carbonic acid gas, and still more so by ammonia gas. A warm body exposed to the air will lose a certain amount of its heat by radiation; but when placed in a closed chamber the walls of which are at the same temperature as itself, will lose no heat. This does not mean, however, that radiation of heat from the body stops under such circumstances, but simply that as much heat is radiated from the walls of the containing chamber to the body as is radi- ated from the body to the walls, so that the temperature of walls and body remains constant. This is known as Prevost's theory of radiant heat exchanges; and in the case cited, the radiation of heat is equal from the body and from the walls. Where bodies are at different temperatures, the exchange of radiant heat goes on in the same man- ner; but the amount radiated from the warmer body is greater than that from the cooler body, so that there is a tendency to equalize the temperatures of the two bodies. Where two bodies covered with lamp-black are enclosed in a chamber the walls of which are at the same temperature as the bodies, the temperatures throughout will remain constant; but as the black surface of one body will absorb heat readily and this heat must be supplied from external sources, it is evident that the other body must emit heat rapidly. In other words, the exchange process of radiant heat goes on much more rapidly between bodies covered with lamp- black and, in general, between all dark bodies than between bodies of lighter color and those that are polished. Thus good REFRIGERATION 19 absorbers of heat are also good radiators; and surfaces designed to absorb or radiate heat should preferably be of a dark color, while those designed to prevent radiation should be smooth and of as light color as practicable Thus a polished copper steam pipe radiates much less heat than a similar black pipe, and a pL:n cast-iron radiator is better than the same radiator covered with one of the bright metallic paints so frequently used. For this reason, also, the walls and sides of a cold storage house should be whitewashed or constructed of white enamel brick to reflect radiant heat that otherwise would be absorbed by the walls and conducted through the insulating material of the rooms to the cold stores from which it would have to be ab- sorbed by the expenditure of considerable work in refrigerating. Convection. It is by this process that heat is readily diffused through liquids and gases; for, when one portion of the liquid is heated, its density is decreased and it is displaced by the heavier and colder portions of the liquid, w r hich in turn are themselves displaced as the heating process continues, until finally the temperature is practically uniform throughout. The currents set up in this process of heating are known as convection currents. The same thing takes place in the case of heat applied to a body of gas. Thus the air in a room, for example, being heated by a stove or other means, rises to the ceiling of the room and displaces the colder air, which, being heavier, falls to the floor to be heated in its turn. In this case we have convection air currents; and it is owing to currents of this character that great care must be taken in construc- ting insulating walls, where air spaces are used, in such a manner that the spaces will be comparatively small, thus not allowing room enough for the setting up of such currents, which, if formed, would be a means of transferring heat to the cold stores instead of acting as an insulation. Neglect of this matter has frequently resulted in disappointment with insulation where dead air spaces have been depended on to a considerable extent. The air in contact with the warm wall on the outside of the chamber becomes heated and rises to the top of the space, whence, as it is gradually cooled, it falls down along the com- paratively cold inner wall, imparting its heat to this wall during pas- sage. By the time the air has passed down this inner wall to the bottom of the space, it is comparatively cold, and then comes in con- 20 REFRIGERATION tact a second time with the outer wall. In this way a continuous current is set up, and acts as a conveyor of heat from the outer to the inner wall of the building. Having these facts in view, insulating men have agreed that the smaller the air space can be made, the deader it is; and in modern work, this is reduced to a nicety where there are no air spaces larger than the minute cells in the structure of cork, which is used for insulating purposes in the best work of the present time. Conduction. This term has reference to the manner in which heat is propagated through a substance, or from one substance to another where the two substances are in contact. Taking again the case of the iron bar heated at one end, the molecules at the heated end may be considered as being in a state of violent agitation so that each possesses a definite amount of kinetic (active'or moving) energy. In the cooler portion of the bar, the molecules will be agitated to a less extent; but those molecules in contact with the similar molecules in the hotter portion of the bar are gradually affected by the impact of these latter molecules, by which means their rate of motion among themselves is gradually increased, they receiving in the contact a portion of the energy of the more violently agitated molecules. In this way the heat energy of the molecules in the cooler portion of the bar is considerably increased; and the heat gradually passes thus from molecule to molecule toward the cooler end of the bar, until finally the temperature has been made uniform throughout the entire length of the bar by the process of conduction. PRODUCTION OF COLD Production of cold is in general effected by transfer of heat from one body or substance to another at lower temperature. Something has already been stated as to the manner in which heat transfers take place and the effects produced by such transfers. It remains to be seen, then, how the transfers are brought about in practice in such a way as to give the desired results. There are three ways in which heat transfers may be made to produce cold, the first of these being by chemical action as exemplified in the so-called freezing mixtures. It has already been seen that when a solid changes to the liquid form, the heat becomes latent and the temperature correspondingly lowered, the change being REFRIGERATION 21 effected by separation of the molecules of the substance in melting. It is equally true that the latent heat is absorbed when the change of state to the liquid form is made otherwise than by melting, as in the case where a solid is dissolved in water. Heat, then, may be- come latent with change of state by the process of 'dissolving as well as by that of melting, the fall in temperature in either case being brought about by the expenditure or exchange to the latent fofrn of the heat energy necessary to separate the molecules of the solid sub- stance so that it assumes the liquid form. To illustrate the lowering of temperature produced by solution, take a glass of water and place in it a thermometer. On dissolving sugar or salt in this water, the temperature will be seen to fall, the effect being much more marked if the disolving process is hastened TABLE V COMPOSITION OF FREEZING MIXTURES RED. OP TEMP. IN DEO. F. AMT. OF FALL IN DEO. F. FROM To Sn aw 4 pa 2 3 3 7 ' 8 2 3 ts; Muriate of lime 5 parts Common salt 1 part Muriate of lime crys. 3 parts Dil. sulphuric acid 2 parts Hydrochloric acid 5 parts Dil. nitric acid 4 parts Chloride of calcium 5 parts crystallized 3 parts Potassium 4 parts 32 32 32 32 32 32 32 32 32 -40 -50 -23 -27 -30 -40 -50 -51 72 32 82 55 59 62 72 82 83 by stirring, so that the heat will not be absorbed from the surround- ing subjects before the reduction of tempeyature occurs. One part nitrate of ammonia mixed with one part of water at 50 F. gives a re- duction of 46 degrees, or to 4 F. Where two solids are mixed, one of them being at the freezing point, the cooling action is still more marked. Two parts of snow mixed with one part of common salt gives a reduc- tion of 50 degrees; while four parts of potash mixed with three parts of fine snow or crushed ice gives a drop from 32 to 51, or a total of 83 degrees. Table V gives the reduction in temperature for a number of other mixtures, and is of considerable value to manufac- turers of ice cream, in enabling them to determine what materials may be used with greatest economy in freezing or packing cream. 22 REFRIGERATION It is in work of this kind that freezing mixtures have their chief value, the cooling produced being too slight in proportion to the amount of material used to be of any value in producing refrigeration on a large scale in commercial work. A more practical and at the same time a rather expensive method of producing refrigeration for commercial purposes, is that in which a non-condensable gas is expanded adiabatically, or without the ad- dition or subtraction of heat. The gas, after being compressed and cooled, is allowed to expand while doing work against a piston, with the result that its temperature is lowered. In this machine the gas is never condensed to the liquid form, but merely compressed to greater density than its natural condition. Air is used in all practical machines employing the principle of adiabatic expansion; but in no case is the air reduced to liquid form, as liquid air has far too low a temperature to be of any practical use for refrigeration under normal conditions. It is this difference in handling the working medium that distinguishes the compressed-air machine from other compression machines in which the liquid is compressed and then condensed to the liquid form by cooling. The third and most important method of refrigeration is that in which a volatile liquid is vaporized to absorb heat, as represented by the latent heat of the medium used. The heat of vaporization is absorbed from objects surrounding the working medium; and these objects are cooled to the temperature desired, the material used for the cold body in most refrigerating plants being a strong brine solu- tion. Thus the liquid expanding in the cooling coils absorbs heat from the brine in the tank surrounding these coils, and the cold brine is used to freeze ice or is circulated through the cold storage rooms, the application of the cold produced by the expansion of the working medium varying according to the circumstances and requirements of each case. In the special case of vaporization or latent-heat machines operating on what is known as the vacuum system, water is at once the working medium and the cold body, the cooling being done by evaporating part of a body of water under a vacuum so that the latent heat taken up in evaporation reduces the temperature until the por- tion of water remaining in the apparatus is frozen. Owing to the fact that the latent heat of water is large as compared with other REFRIGERATION 23 liquids used, the freezing is very rapid, so that the ice produced is usually opaque, there not being time for separation of the air from the water. It should be noted that this system depends for its operation on a vacuum being produced, as otherwise the boiling point of water is at 212, which is altogether too high a temperature for refrigeration work. The chief difficulty, then, with the vacuum process, is the necessity of maintaining the vacuum, for which complicated apparatus is required. In the vacuum process, external energy is expended to drive the vacuum pumps and other machinery connected therewith; and a moment's consideration will show that in every system external energy is utilized at some point in the cycle, thus obeying the thermo- dynamic laws. It is seen at once that pressure and temperature .tell the w-hole story in refrigerating \vork, the whole object of such work being the reduction of temperature, which reduction depends on the pressures and corresponding temperatures in the different parts of the system. As already pointed out, w r ater cannot be used except in a vacuum on account of its high temperature of vaporization at ordinary pressures. Since it is not desirable to operate with a vacuum in all cases, other working mediums or refrigerants than water must be chosen, and thus it comes about that the temperature at which a substance will vaporize at a given pressure is of first importance. For any given substance in the form of vapor that is, a fully expanded gas containing no moisture there is' a certain temperature above which it is impossible to liquefy the substance no matter how great the pressure. This is the critical temperature. The pressure that w T ill cause liquefaction at the critical temperature is known as the critical pressure. These tw r o critical points of temperature and pressure determine largely whether or not a given substance is suit- able as the working medium in refrigerating machines. Aside from its latent heat, which should preferably be high, the substance should have such critical data as to make it possible to work it in the refriger- ating machine at ordinary pressures and temperatures, for otherwise the special apparatus required to manipulate it will be too expensive to be practical. Table VI gives the critical pressure and temperature, with the corresponding density, for a number of substances. It is seen that ammonia, carbon dioxide, and sulphur dioxide are the only 24 REFRIGERATION three substances that have the critical points at anything like normal conditions of temperature and pressure. Hence the choice of a re- frigerant from among the many volatile liquids known to chemistry is narrowed down to these three substances. There is considerable discussion and expression of opinion among engineers as to which of these three is best. Generally speaking, the choice of any substance from an engineering standpoint depends on the latent heat of the liquid per pound ; the boiling point at ordi- nary pressures; the number of cubic feet that must be compressed TABLE VI Critical Data H Kb S.s w i fa g H fe * w " 1 "t^ P i-3 -K K H CL M ^ a ^ ^ s w ^ ' o rt SUBSTANCE PH a. p g) ogg IfiS J I 8 fl mi ffH 5 K H * I S(2 s^ ^g 55-5 j jj O rt Water H 2 O + 212 + 32 + 657 205 037 Alcohol C 2 H 6 + 172 -148 + 423 67 0.114 Sulphur dioxide SO 2 - 14 -105 + 313 81 Ammonia NH 3 - 27.4 -106.6 + 266 115 0.048 Carbonic acid (carbon dioxide) . . . CO 2 Oxygen O -110 -296 -110 -269 + 88 -180 75 52 0.035 Atmospheric air -312 -220 39 Nitrogen N -317 -353 -231 36 -400 -382 -231 9 21 45 0.037 Air ... Nitrous oxide + 96 75 to produce a certain refrigerating effect (or, in other words, the size of the compressor necessary); the pressure required to produce lique- faction of the gas at certain temperatures ; and the specific heat of the liquid. Table VII gives the boiling point and latent heat of a number of substances at 14.7 pounds, and also gives the specific heat of the liquids used in refrigerating work. Under atmo'spheric pressure, carbon dioxide boils at 110 F., or far below the temperatures required in ordinary refrigerating work. By reference to Table VI, it is seen that this refrigerant must be lique- fied under about 900 pounds pressure, and in view of this it would seem advisable to carry a higher pressure on the suction line to the compressor than is carried with the machines using the other refriger- REFRIGERATION 25 ants, which are liquefied at lower condensing pressures. With a pressure of 342 pounds a square inch, carbon dioxide toils with a temperature of 5 F., its latent heat under these conditions being 121.5 B. T. U. This temperature is about as low as is usually re- quire:! in refrigerating work, and gives, thererore, an index of the suction pressure that may be carried. Passing by, then, those refrigerating agents that have been tried and found wanting, such as the various forms of ether and its com- TABLE VII Boiling Point and Latent Heat of Substances SUBSTANCE TEMPEHA- TURE OF BOILING POINT LATENT HEAT B. T. U. SPECIFIC HEAT OP LIQUID Nitric acid Saturated brine 248 P. 220 F. Water Alcohol Chloroform Ether, sulphurous Ether, methyl Sulphur dioxide Anhydrous ammonia Carbon dioxide 212 F. 173 F. 140 F. 95 F. -10 F. 14 F. -28. 5 F. -110 F. 966 i70 ies.7 573 141 1 .0000 .5299 ' .4100 1 .0058 .9550 binations with sulphur dioxide; and also such agents as cryogene, acetylene, naphtha, and gasoline, it will be sufficient to give in some detail the properties of sulphur dioxide, carbon dioxide, and am- monia, which are in common use as refrigerants. Table VIII gives the qualities of these three refrigerants, and should be given careful study, as it shows up the good and bad points of each refrig- erant in the clearest manner. It will be seen in the column next to the last, that the size of the sulphur dioxide compressor is about twenty times that of the carbon dioxide machine, or three times as large as the ammonia machine, which itself is something like five times the size of the carbon dioxide machine. The size of machine, of course, determines to a large extent the amount of fric- tion losses. Other things being equal, the smaller the machine, the better. The great disadvantages of the carbon dioxide machine are the high pressures required and the comparatively high specific heat of the liquid, which means that considerable of the cooling effect pro- 26 UEFRIGERATION J > w 3 - ~ (Q13J3X3ig 'ZM3HO--[) 3WQ1OA 'HdWOO xj -a^Had "ziHOdVA^o xvajj a'fljaefj O OO O O C^ GO 1C amOr^aHx DNnooQ ox aaQ % NI ssoq j> 1C Tf (aiajaxaxg) -,j O f-i xv XJ -aQ H3d NOIXVZIHOdVA ^O XV3JJ co c^ co 00 CO GO (VXVQ 01Q) xj - aQ aad NoixvziHOdVA -*o xvajj i> co t * t^ 1C t^ IM rH rH (VXVQ Q1Q) QIQbiq 3HX JO XV3JJ .il 1 1 i 1. Iv; !" (aiaj3xaxg 'ZNanoq) '>! oO -iv -aq H3d -x^ -03 NI swmoA co -^ ic t- OS (VXVQ QiQ) 'J oO iv annoj Had xas^ oiaa^ NI awmoA t^ iC O (N CO rH t-' Os' (ZN3HOq) -J Q XV rH rH 1C (VXVQ aiQ) 'J iv (N d "3 a aoj NOIX zi A * * 'iJ oO iV HONJ ftg H3d 'saq NI aanesaaj axaiosay 000 rnrHCO ' 1 oo Carbon dioxide CO 2 Sulphur dioxide SO 2 Ammonia NH 3 REFRIGERATION 27 duced by evaporation will be absorbed in reducing the temperature of the liquid from that of the condenser to that in the expansion coils or cooler. This is shown up clearly in the last column of the table, where it is seen that the loss due to cooling the liquid as shown in percentage for every degree difference of temperature between the condenser and cooler is less for ammonia than for any other liquid, the loss being high with carbonic acid. The chief point in favor of sulphur dioxide or sulphuric acid is the low pressure of its vapor, but the large size of machine required for this refrigerant has pre- vented its coming into general use. Table IX gives the comparative refrigerating values of the refrigerants most in use, and shows at a glance the standing of each on the principal scores of value. TABLE IX Comparative Values of Three Refrigerants g. , K ^ B W OH K P P ",- ^ H . o| a PU 11 H & |- s3( W g2 ice S5 H & ? ,8$ 6 sz ij z ' w i! 22 tf z ;> , 2 oli PfH[^ ftp SUBSTANCE K H 04 CU - 2 V ^ W O d ^ T> I 1 S2 ^gP S H s^ o o i-j p* P o ^H j tf < a U B. H K H W p Q SSj3 ?: " H O H II g ?* o M e U B E h W J H^rJ P O J w CO tf w ^ Ko as 1 tar Q P E^ 1 i i f< ! 1 1 ^2 I 5 a -< PH Carbon dioxide CO 2 0.49 6 5 4 9 24 0.60 0.61 14,855 13,370 Sulphur dioxide .... SO, Ammonia NH 3 7.04 2.4 6 6 6 6 14 11 25 49 48 10.556 3.56 10.6 4.00 16,673 16,673 13,300 13,300 In case of the carbon dioxide machine, particular attention should be given to the temperature of the cooling water, as the critical temperature of this refrigerant is not much above the ordinary sum- mer temperature of river water from natural sources of supply. Where the initial temperature at the condensers is 70 or more, it is advisable to increase the supply of cooling water so as to maintain an average condenser temperature of 75. With temperatures greater 28 REFRIGERATION than this, the efficiency of the carbon dioxide machine falls off as compared with the other two systems, but even with water at 90 degrees, the machine will develop about 70 per cent of its normal capacity. Theoretically the efficiency of the carbon dioxide machine is about 12 per cent less than that of the ammonia and sulphur dioxide machines, but practical compensating features enable the machine to make up for this. Stetfeld has found that the losses resulting from radiation in the clearance spaces of the refrigerator, the resistance of the gases on their way from the refrigerator to the compressor and in passing the suction valve, and friction and valve leakage, all together, average 49 per cent of the losses in the ammonia and sulphur dioxide systems, and not more than 25 per cent when carbon dioxide is used. With the carbon dioxide machine, for example, the piston leak- age averages about 9 per cent, as against 25 per cent in the ammonia and sulphur dioxide machines. In carbon dioxide machines, the great density of the gas permits making the valves, passages, and suction pipes large enough to materially reduce frictional losses, and yet not so large as is necessary in the other machines. In view of these facts, engineers have generally concluded that the practical efficiency of the three refrigerants mainly employed is about equal when each is used to best advantage. This is shown in the last column of Table IX. The choice therefore depends on circumstances and the local conditions in any case. To determine the fitness of the refrigerant for any set of conditions, its natural characteristics must be taken into consideration. While ammonia and sulphur dioxide have a sharp penetrating odor, carbon dioxide is odorless; and if leaks are to be detected readily, the charge must be made odoriferous by adding a small amount of alcohol impregnated with camphor. At high tempera- tures, ammonia dissociates into its constituent gases and loses its value as a refrigerant, while the gases formed have a detrimental effect on the working of the machine. It is not definitely settled as to the exact temperature at which this dissociation takes place; but it is certain that above 900 F., ammonia gas is gradually decomposed, until at about ] ,600, complete dissociation takes place. It is believed that the action goes on to some extent at lower temperatures, but just under what conditions and to what extent are not definitely known. REFRIGERATION 29 Carbon dioxide does not decompose under any conditions, and is a fire extinguisher, while ammonia mixed with lubricating materials, etc., may support combustion in case of an explosion. Ammonia to some extent, and sulphur dioxide particularly, have a corrosive effect on metals, and the machines must be designed with this in view, a special close-grained steel cylinder being used in ammonia com- pressors of the best manufacture. Carbon dioxide is entirely neutral in its action on metals, and in the event of accidents resulting in large leaks, it has a marked advantage, as 8 per cent of the gas in the air can be inhaled with safety while less than 1 per cent of ammonia gas is dangerous to life. Large losses have frequently resulted by damage to goods in store where ammonia has escaped, but this can- not happen where carbon dioxide machines are employed, as the gas does no damage. Sulphur dioxide was used as a refrigerant in the early stages of modern machine development after the ether machine had its day. Owing to the high cost of ether, and other disadvantages connected with its use principally its inflammability investigators took up sulphur dioxide and studied its properties as a refrigerant. It was found to require a higher condensing pressure than ether, but did not need to be evaporated under a vacuum, so that the compressor could be made smaller for a given capacity. On account of the higher condensing pressure, it was necessary to build the compressor stronger than had formerly been done, and more attention was given to the elimination of clearance spaces. Even though the machine for use with this refrigerant is smaller than that formerly used with ether as a refrigerant, it is still much larger than ammonia and carbon dioxide machines, as has been shown in the tables. Table X gives the properties of sulphur dioxide. Carbon dioxide, although not used extensively until within a comparatively recent period, is coming into favor, for it is made as a by-product in certain industries and can be obtained cheaply. The gas is not readily absorbed by water or by lubricating materials; and, not being easily dissociated, the system using it remains free of non-condensable gases and in efficient condition. Table XI gives the properties of this refrigerant. Ammonia, the most widely used of all refrigerants, is composed of one part of nitrogen in combination with three of hydrogen, this 30 REFRIGERATION TABLE X Properties of Saturated Sulphur Dioxide TEMPERA- TURE OF EBULLITION IN DEO. F. ABSOLUTE PRESSURE IN I. US. PER SQ. IN. TOTAL HEAT RECKONED FROM 32 FAHR. HEAT OF LIQUID RECKONED FROM 32 FAHR. LATENT HEAT OF VAPORIZA- TION DENSITY OF VAPOR. OR WEIGHT OF 1 CUBIC FT. DEO. F. LBS. B. T. U. B. T. U. B. T. U. LBS. -40 3.16 155.22 -17.76 172.98 .048 -31 4.23 156.39 -16.55 172.94 .062 -22 5.56 157.55 -15.05 172.60 .079 -13 7.23 158.69 -13.26 171.95 .099 - 4 9.27 159.82 -11.18 171.00 .124 5 11.76 160.93 - 8.82 169.75 .154 14 14.75 162.02 - 6.17 168.19 .190 23 18.31 163 . 10 - 3.23 166.33 .232 32 22.53 164.16 0.00 164.16 .282 41 27.48 165.21 3.52 161.69 .341 50 33.26 166.24 7.32 158.92 .410 59 39.93 167.25 11.41 155.84 .491 68 47.62 168.25 15.79 152.46 .584 77. 56.39 169.23 20.45 148 . 78 .692 86 66.37 170.20 25.41 144.79 .819 95 77.64 171.15 30.65 140.50 .965 104 90.32 172.08 36.18 135.90 1.131 TABLE XI Properties of Saturated Carbon Dioxide TEMPER- ATURE OP EBULLITION IN DEO. F. ABSOLUTE PRESSURE IN LBS. PER SQ. IN. TOTAL HEAT FROM 32 F. HEAT OF LIQUID FROM 32 F. LATENT HEAT OF VAPORIZA- TION DENSITY OF VAPOR, OR WEIGHT OF 1 Cu. FT. -22 210 98.35 -37.80 136.15 2.321 -13 249 99.14 -32.51 131.65 2.759 - 4 292 99.88 -26.91 126.79 3 265 5 342 100 . 58 -20.92 121.50 3.853 14 396 101.21 -14.49 115.70 4.535 23 457 101 .81 - 7.56 109.37 5.331 32 525 102.35 0.60 102.35 6.265 41 599 102.84 8.32 94.52 7.374 50 680 103.24 17.60 85.64 8.708 59 768 103.59 28.22 75.37 10.356 68 864 103.84 40.86 62.98 12.480 77 968 103.95 57.06 46.89 15.475 86 1,080 103 . 72 84.44 19.28 21.519 being the only proportion in which these two gases combine. Anhy- drous ammonia thus formed, when dissolved in water, gives the aqua ammonia of commerce, used in absorption machines. When heat is applied to this aqua ammonia in the generator of the absorption REFRIGERATION 31 TABLE XII Properties of Saturated Ammonia Gas DE VOLSON WOOD AND GEO. DAVIDSON M , M * 8 ~ *8 o 1.8 * OJ ffi iS W H ^ M z P& o mm II: rJ IPERATUR :OREES F. ||| III B. H g ss* ooS )LUME OF ND OFLlQ !UBIC FEI SH :!.< 1*5 wSa ill O OS 32 EH Q ^|o H! B >l& 2 w pw *-! C5 xes being fitted with wedge and screw adjustments. Something has already been said of the valve adjustment which is made by means of a nut on the stem, the tension of the cushion spring being regulated by turning the nut after the lock nuts have been loosened. On the collar under the adjusting nut is a secondary collar with which the working spring is adjusted, and these two collars are held in their correct positions by keepers. This adjustment 82 REFRIGERATION feature of the valves has an important bearing on the economy cf the compressor, as it is evident that the same pressures cannot be used under varying conditions with maximum economy at all times. Particular attention is directed to the stuffing box of this machine, which is divided into three parts separated by two cages, which are of spider frame construction as shown in the figure. One of the cages forms a relief chamber from which any gas that may leak past the first packing is returned to the suction manifold, while the other serves Fig. 19. Section of Triumph (Compressor. as an oil reservoir that keeps the rod and packing well lubricated. Oil is circulated through the gland by means of a small power pump driven from the shaft of the machine. The oil is drawn from a cham- ber provided in the base of the machine under the cylinder. Thus there is a continuous circulation of oil and it is necessary to pump against only the suction pressure. Fig. 20 shows an outside view of a 70-ton Triumph unit, in which the stuffing-box connections and lubricating apparatus are shown more in detail. It is noted that all the bolts of the gland are connected by inside gear so that in turning one nut, uniform adjustment is given to all. Thus there can be no trouble from cocking the gland by unequal adjustment. REFRIGERATION 83 Linde. This machine is similar in many respects to the Triumph, and is manufactured by the Linde Refrigerating Co., New York, with the usual heavy-duty type of frame and bored guides for the cross- head. The piston is of the spherical form used in all the best hori- zontal machines of the double-acting type, and enables the valves to be set close in the head so as to reduce clearance to a minimum. To facilitate handling, each valve is made so as to form virtually a single Fig. 20. Exterior Triumph Machine Showing Stuffing-Box Arrangement. part with its seat, enabling the valve and seat -to be removed together with the same labor that would be necessary to remove either sep- arately. The valve-seat casting rests on the cylinder head and is held in place by the valve-stem guide which is secured in position by the cap or bonnet. With the bonnet oil, the valve and all its parts can be removed practically as one piece and without disturbing any part of the machine. Two self-expanding rings make the piston tight, and strength is given by heavy reinforcing ribs. The stuffing-box packing may be seen readily in Fig. 21, which is a sectional view of the cylinder of this machine. It will be seen that the arrangement is similar to the other 84 REFRIGERATION double-acting stuffing boxes already described, the outer packing having to withstand only the pressure of the suction gas. Particular Fig. 21. Sectional View of the Cylinder of the Linde Compressor. note should be made of the fact that there is no water jacket on the cylinder of the Linde machine. The distinctive feature of this ma- chine is its operation on the wet system, where the cylinder is kept cool Fig. 22. Longitudinal Sectional Elevation of York Machine. by the injection of a small amount of liquid ammonia at the beginning of the compression stroke; or, arranging the system so that a small part of the liquid is not evaporated and goes back to the compressor. REFRIGERATION 85 Vertical Compressors. Although some manufacturers make a vertical double-acting machine, the most notable being that of the De La Vergne Machine Co., the great majority of such machines are single-acting. The discussion will therefore be confined to this type of apparatus. Fig. 23. Cross-Sectional Elevation of the York Machine. York. Figs. 22 and 23 show longitudinal and cross-sectional views of the York machine direct-connected to its steam engine. It consists of two single-acting compressor cylinders mounted on vertical /1-frames and driven from a Corliss engine of the horizontal type. A fly-wheel is mounted on the middle of the crank-shaft, and a crank on each end of the shaft drives the compressor cylinders, the cranks being set 180 degrees apart for reasons already mentioned. The con- REFRIGERATION iiecting rod of the engine is attached to one of the cranks, as shown in the illustrations. Gas enters the cylinders through valves at the bot- tom underneath the piston and, on the down stroke of the piston, is forced through the valve in the piston to the space above so as to fill the cylinder. On the return or compression stroke of the piston the gas is compressed and, at the end of the stroke, is forced out through the valve in the up- per head, going thence through the pipe connec- tion to the condenser. The upper head itself, being of the safety type, may be considered as one huge valve, as in case anything should get in the cylinder, or the clear- ance become too small for any reason, the piston may strike the head with- out doing damage. The effect is similar to lifting the head against the ac- tion of heavy buffer springs, shown in the il- lustration, and allowing the charge in the cylin- der to pass over to the condenser by the regular connections. Great Lakes. In this machine, which is made by the Great Lakes Engineering Works, there is no valve in the piston. Separate suction and discharge valves are provided in the head of the machine, as shown in Fig. 24, there being two valves of each kind. Sight-feed lubricators are provided, as shown, and the cylinder has a specially arranged water-jacket around the upper end. One of the special features is the arrangement of the suction and discharge passages, which are connected to the piping system of the plant by a system Fig. 24. Cylinder of Great Lakes Refrigerating Machine. REFRIGERATION S7 of manifolds and by-passes that permit of handling the gas in any way desired. Like the York machine this compressor is single-acting, gas being drawn in through the right-hand valve, on the down-stroke, as seen in the illustration, and discharged through the other valve on the up-stroke. The two suction and the two discharge valves work, each pair, as one valve, they being made in pairs owing to the fact that there is not room enough within the head to give the proper diameter for the necessary valve opening for a single-suction and a single-discharge valve. Carbon Dioxide Machines. Owing to the difficulty in getting sound castings suitable to withstand the pressure necessary to liquefy Fig. 25. Sectional View of Cylinder of Carbon-Dioxide Machine. Suction Passages are so arranged that coal gas passes around cylinder before entering suction valve. carbon dioxide, manufacturers in the United States have largely adopted soft forged steel for the cylinders. With summer temperature of water the pressure may be as much as 1,000 pounds or more, and it is seen at once that the cylinders and piping must be very strong. The diameter of the gas cylinder must be small as compared with that of the steam cylinder. In some cases the compressors are made to compress the gas in stages. The gas leaves the first cylinder at a pressure of from 400 to 600 pounds per square inch, and is cooled before entering the second cylinder where it is compressed to the final pressure. Owing to the difficulty in keeping stuffing boxes tight with the high pressures, compressors are usually made single-acting, but some manufacturers have been successful with the double-acting machine. 88 REFRIGERATION Fig. 26. Small Vertical Carbon-Dioxide Machine. 90 REFRIGERATION Ordinarily the length of the stroke should be about four times the diameter of the cylinder, and, if the piston is to be kept tight, it should be at least two and one-half times the cylinder diameter. Fig. 25 is a sectional view of the typical cylinder in which it will be seen that the suction passages are arranged to pass the cool gas around the cylinder before entering it. Although the suction valves are usu- ally placed in a horizontal position, they are easily closed by light springs as they are small and have little inertia. Guides are used to keep the valves in line with the seat; and the discharge valves, being set vertical, easily come to a true seating. Suction valves should have an area of about one-half that of the piston and the area of the discharge valves should be about one-seventh that of the piston. Owing to the limited space on the crank end of the cylinder, it is usually necessary to have two suction valves for this end. For the discharge valves, the seats should be beveled at from 70 to 80 degrees, while for the suction valves the seats should be beveled from 60 to 75 degrees; and the seats for both valves are from 0.1 to 0.12 of the disk diameter in width. On the suction valve the lift should be about 0.33 of the disk diameter while that for the discharge valve should be about 0.28 of the diameter. Spring tension is 8 or 9 pounds on the suction and 10 or 11 pounds on the discharge valve. Stuffing boxes are made on the same general principles as those for the double- acting ammonia compressors, bearing in mind that the greater pres- sures call for more compartments. Cup leather packings are used except for the outer packing which is merely a wiper for the rod. Small machines are usually made vertical, Fig. 26, which shows a direct-connected vertical unit built by the Brown-Cochrane Co. Above 2 tons capacity, the machines are usually made horizontal, as shown in Fig. 27, which is an illustration of the double-acting com- pressor built by Kroeschell Bros., Chicago, 111. Small Refrigerating Plants. In recent years large consumers of ice have created a demand for small plants to be used on their premises and thus do away with the "ice man." As a result, machines are now made in capacities ranging upward from |-ton refrigerating duty. Such apparatus is used for a number of purposes. Where the consumer can obtain cheap electric power and is able to stand the first cost of the apparatus, there is some economy in operating a refrigerating plant by electricity. Where electric power is not avail- REFRIGERATION 91 able and a special engine equipment must be used gasoline engines as a rule there will be no economy, and the matter of installing such a plant must be decided on other grounds. Where temperatures below 32 are required, the installing of such a plant is a necessity. Hospitals, restaurants, cafes, and saloons use the small refrigerating plant to advantage because they can keep the coolers drier, colder, Exterior of Brunswick Machine. and more sanitary than by the use of ice. Residences and country clubs use such machines, owing to the fact that ice cannot be obtained readily. Where it is a mere question of refrigeration of cooler boxes there is an economy in using the refrigeration direct instead of melting ice. The machine thus used gives about twice as much cooling for a given amount of power expended as is secured by using the ice made by refrigeration. As the small machine must be operated by servants and other unskilled persons, it is made as near automatic as possible, this being particularly the case with the machines designed for household use. 92 REFRIGERATION In the larger hotels and clubs the machine will be looked after by the engineer of the steam plant, and for machines above 1 ton refrigerating duty, it is generally sufficient to have a reliable source of water supply and a thermostat in the cooler to regulate the operation of the motor. Arrangements should be made so that the power and water are turned off or on simultaneously. Lubrication can be looked after by the attendant, but for machines smaller than 1 ton, as used in residences, it is advisable to have automatic lubricating devices and, in fact, have the whole machine practically take care of itself, Fig. 28 is an exterior view of the complete Brunswick refrigera- ting machine made in New Brunswick, N. J., in sizes of 200 pounds Fig. 29. Construction of Brunswick Compressor. to 10 tons refrigerating duty or half as much ice-making capacity. Power is furnished by a motor belted to the band wheel seen in the illustration at the right-hand end of the shaft. The compressor is entirely self-contained in an enclosed crank case, which contains oil for lubricating purposes. An idea of the construction may be had from the sectional line drawings in Fig. 29. The machine is single- acting, the suction and discharge valves being of special design and made of steel, with the suction valve carried on the discharge valve and seating on its face. This construction makes it possible to have the REFRIGERATION 93 discharge valve the full diameter of the cylinder so that it becomes a lifting head similar to the safety heads of large single-acting machines. Thus, there is no clearance and all the gas in the cylinder is forced out at each stroke, the piston, in fact, passing beyond the discharge port in the side of the cylinder and at once shutting off the port so that there can be no back slip of gas. As the piston reverses, it is followed by the discharge valve, which rests on its upper end, and as this valve comes to its seat with a slight impact there is no chance for the suction valve, which seats on its face, to get stuck and not open promptly. The lift of the suction valve is limited by a nut on the stem; but the discharge valve may lift as much as necessary to pass any obstruction that may get into the cylinder. Other details of the construction are made plain by the illustration which shows the eccentric (used instead of a crank on the sha^t), and the arrangements made for lubrication. There are a number of automatic and semi-automatic machines on the market, in all of which the arrangements are more or less similar, the smallest units being self-contained with all parts mounted on a common base. COMPRESSOR LOSSES Having described the compressor and its parts, let us take up the losses clue to the improper working or assembling of the parts of the machine, before proceeding with the description of the rest of the plant. As has been stated in a general way, the economy of the compressor lies in its filling at the nearest possible point to the evaporating pres- sure, and then compressing and discharging at the lowest possible pressure, as much of the entire contents of the cylinder as possible. If the compressor piston does not travel close to the upper end of a single-acting machine or the machine has excessive clearance,the com- pressed gas remaining in the cylinder re-expands on the downward stroke of the piston, and the gas from the evaporator will not be taken into the compressor until the pressure falls to, or slightly below, this point, and the loss due to this fault is equal to the quantity of gas thus prevented from entering the compressor plus the friction of the machine while compressing the portion of the gas thus expanding. If we make a full discharge of the gas and there is a leak}' outlet valve in the compressor, the escape and re-expansion into the com- pressor affects not only the intake of the gas at the beginning of the 94 REFRIGERATION return stroke, but continues to affect the amount of incoming gas during the entire stroke and the capacity of the machine will be corre- spondingly reduced. If the inlet valve is leaky or a particle of scale or dirt becomes lodged on its seat, as the piston moves upward the portion of the gas which may escape during the period of compression is forced back to the evaporator and a corresponding loss is the result. A piston which does not fit the compressor, faulty piston rings, or a compressor which has become cut or worn to the point of allowing the escape of gas between the cylinder and piston has the same effect as the ill conditioned suction valve. The loss due to leaky or defec- tive cylinders, joints, or stuffing boxes, are not included under this head, as these more generally effect the loss of the material than the efficiency of the compressor. AMMONIA CONDENSERS The ammonia condenser, or liquefier, as briefly stated in the description of the system, is that portion of the plant in which the gas from the evaporator, having been compressed to a certain point, is cooled by water and thereby deprived of the heat which it took up during evaporation; consequently it is reduced to its initial state, that is liquid anhydrous ammonia. Condensers for other refriger- ants are constructed in the same general way as those for ammonia, due regard being had to the pressures to be carried. Let us consider the general principles governing the action before describing the types. On account of its duty having been performed, the ammonia as it leaves the evaporating coils is a gas at low temperature, usually 5 to 10 below that of the brine, or other body upon which it has been doing duty, yet it is laden with a certain amount of heat, although at a temperature not ordinarily expressed by that term. It is a well- known fact that we cannot obtain a refrigerating agent which can absorb heat from a body colder than itself, and it is therefore necessary to bring the temperature of the ammonia gas to a point at which the flow of heat from the one to the other will take place. This is done by withdrawing part of the heat in the ammonia in the following manner: The cold gas is compressed until its pressure reaches such a point that at ordinary temperatures it will condense to liquid form ; as it leaves the compressor it is very hot because of the fact that it REFRIGERATION 95 still contains nearly all of the heat it had when it left' the evaporator, in only a small portion of the space occupied before. Thus when it reaches the condenser it is much warmer than the cooling water and will readily give up its heat to the cold water so much that its latent heat is absorbed by the water and it condenses into anhydrous am- monia. The temperature of water if pumped from surface streams will average about 60 F., and since we cannot expect to get the ammonia any colder than this, it must be compressed until the boiling point corresponding to the pressure obtained is at about 75 F. In Table XII, p. 31, we find that this temperature corresponds to a pressure of 141.22 pounds per square inch (absolute), or 126.52 pounds per square inch (gauge). Thus if the gas is compressed until the gauge reads 126.52 and then passed into a condenser where the temperature of the water is less than 75 F., the water will absorb the latent heat and we have accom- plished our object which was to remove some of the heat contained in the ammonia. In this condition it is drained from the condenser into the ammonia receiver to again repeat the cycle of operation. The forms of condensers may be divided into three classes the submerged, the atmospheric, and the double-pipe. Of each of these classes a number of different types and constructions are in use. To illustrate the general principles, however, it is only necessary to pre- sent one of each type. Submerged Condenser. The submerged condenser consists of a round or rectangular tank with a series of spiral or flat coils within, joined to headers at the top and bottom with proper ammonia unions. In Fig. 30 is shown a sectional elevation of a popular type of sub- merged condenser. A wrought iron or steel tank A is formed by plates from T \ to T 6 T inch thick, of the necessary dimensions to contain the coils, and sufficiently braced around the top and sides to prevent bulg- ing when filled with water. A series of welded zigzag pipe coils B are placed in the tank and joined to headers C with ammonia unions D. The ammonia gas enters the top header through the pipe E, and an outlet for the liquefied ammonia is provided at F with a proper stop valve. Water is discharged or admitted to the tank at or near the bottom and overflows at outlet M. It will be seen that in this type of condenser a complete reverse flow of the current is effected,, the 96 REFRIGERATION gas entering at the top and the liquid leaving at the bottom, while the water enters at the bottom and leaves at the top. This brings the cold water in contact with the cool gas, and the warm water in contact with the incoming or discharged gas from the compressor, thereby presenting the ideal condition for properly condensing am- monia. Owing to the necessarily large spaces between the coils and the distance between the bent pipes, the portion of water coming in contact with the surface of the pipes must be small compared with the total amount passing through; it is, therefore, uneconomical as regards amount of water used. With water containing a large amount of float- ing impurities the deposit on the coils is considerable and not easily Fig. 30. Submerged Condenser. removed owing to the limited space between the coils; and further- more, the dimensions of the tank necessary to contain the requisite amount of pipe for a plant of considerable size is so great and its weight, when equipped with coils and filled with water, requires such a strong support, that its use is now limited to certain requirements and localities. A better shape for a condenser of this type is one of considerable height or depth, rather than low and broad. This is owing to the fact that the greater length of travel of the water and gas in opposite directions, the greater the economy. The number of coils used should be such that the combined internal area of the pipes equals or ex- ceeds the area of the discharge pipe from the compressor. The circular REFRIGERATION 97 submerged condenser is similar to the above described except that the tank is circular and the coils bent spirally. In the circular type of submerged condenser the pipes are 1^ to 2 inches in diameter, and the separate coils are made in lengths up to 350 feet. A number of coils are used in a single condenser, the in- lets and outlets being connected to manifolds with valves provided to shut off any individual coil. Where the water comes to the con- denser at 70 and leaves at 80 a range of 10 degrees about 40 square feet of condensing surface, corresponding to 64 running feet of 2-inch pipe or 90 feet of l|-inch pipe are allowed per ton of refrig- eration. Less surface than this means excessive condensing pressure. Siebel gives the following empirical formula for calculating the square feet of cooling surface F required in submerged condensers: m(t-t'} In this formula, h = the heat of vaporization of 1 pound of ammonia at the temperature of the condenser; k the amount of ammonia pass- ing through the condenser in one minute; m = 0.5 = the number of heat units transferred per minute per square foot of iron surface where the pipe contains ammonia vapor and is cooled by water; t = the temperature of the ammonia in the coils; t' = the mean tem- perature of the inflowing and outflowing cooling water. The heat taken up by the ammonia, in producing refrigeration, added to that corresponding to the work done on the ammonia in the compressor, less any heat expended in superheating the gas, is equal theoretically to the heat of vaporization of ammonia at the tempera- ture of the condenser and is the amount of heat that must be re- moved by the cooling water. This then gives a gauge on the amount of cooling water that should be used in the plant. For finding the number of pounds A of cooling water, Siebel gives the formula : MX 60 A T=r in which the notation is the same as in the formula above, except that t is the temperature of the outgoing cooling water, and If that of the incoming water. The result is converted into gallons by dividing by the factor 8.33. Usually from f to 3 gallons of water are required per minute per ton of refrigeration in 24 hours. 98 REFRIGERATION Atmospheric Condenser. This type of condenser most gener- ally used is made of straight lengths of 2-inch extra strong, or special pipe, usually 20 feet long, screwed, or screwed and soldered into steel return bends about 3^-inch centers and usually from eighteen to twenty-four pipes high. The coil is supported on cast or wrought iron stands and placed within a catch pan, or on a water-tight floor, having a proper waste water outlet, and supplied with one of the several means of supplying the cooling water over their surfaces. REFRIGERATION 99 Stop valves, manifolds, and unions connect with the discharge of the compressor and the liquid ammonia supply to the receiver. In the manner of making the connections to this type of con- denser and the taking away of the liquefied ammonia as well as in the devices for supplying the cooling water, a great variety exists. Fig. 31 represents a side elevation of an ammonia condenser with 100 REFRIGERATION the discharge or inlet of the gas from the compressor entering at the top A, and the liquid ammonia taken off at the bottom B, while the water is supplied over the coils flowing down into the catch-pan or water-tight floor, where it accumulates and is taken away by any of the usual means. It will be noticed that the flow of the water and the gas with this type of condenser is in the same direction, the coldest water coming in contact with the warmest ammonia. The tempera- ture governing or determining the point of condensation will be that at which the ammonia leaves the condenser, or the temperature in REFRIGERATION 101 the bottom pipe from which the liquid ammonia is withdrawn. Owing to this arrangement it is not favorable to a low condensing pressure or economy in the water used. Fig. 32 represents a type in which an attempt is made to eliminate this undesirable feature, and in which it is expected to use the waste from the condenser proper, in taking out the greater part of the sensible heat from the gas leaving the compressor. The construction of this condenser is identical with that shown in the preceding figure except that its uppermost pipe is continued down and under the pipes forming the condenser proper; it passes backward and forward in order that a large proportion of the heat may be removed by the water from the condenser proper, before the ammonia enters the condenser. A supplemental header is sometimes introduced in connection with this pipe for removing any condensation taking place in it. A third type of this condenser is shown in Fig. 33. In this type a reverse flow of the gas and water takes place. The gas en- ters the condenser through a manifold or header A at the bottom and continues its flow upward through the pipes to the top; at several points drain pipes are provided for taking off the condensation into the header B. The condensing water flows downward over the pipes. This type of condenser is the most nearly perfect of its class. The atmospheric condenser is a favorite, and possesses many features that make it preferable to the submerged. Its weight is a minimum, being only that of pipe and supports and a small amount of water. The sections or banks may be placed at a convenient dis- tance apart to facilitate cleaning and repairs. The atmospheric effect in evaporating a portion of the condensing water during its flow over the condenser, makes use of the latent heat of the water in ad- dition to the natural rise in its temperature. The various devices for distributing the water over the condenser are numerous. Fig. 34 represents the simplest and most easily ob- tained a simple trough with perforations at the bottom for allowing the water to drip over to the concenser. Fig. 35 is a modification of the- one shown in Fig. 34. This is intended to prevent the clogging of the perforations, by allowing the water to flow into the space at one side of the partition, and then 102 REFRIGERATION through a series of perforations into the second, and thence through a second set of perforations in the bottom to the pipes in the con- denser. Fig. 34. Simple V ; Shaped Water Trough. Fig. 35. Modification of the V-Shaped Trough. Fig. 36 is a type of trough, or water distributor, designed to overcome the objections to a perforated form of trough, and the consequent difficulties due to the clogging or filling of the perfora- REFRIGERATION 103 tions. As will be readily understood from the illustration, this is also made of galvanized sheet metal with one side enough higher than the other to cause the water to overflow through the V-shaped notches or openings along the top of the straight or vertical side of the trough, and down and off the serrated bottom edge to the pipes. The object of the serrated edges, as will be apparent, is the more even distribution of the water, owing to the fact that while it would be practically impossible to obtain a uniform flow of water over a Fig. 36. Serrated-Edge V-Trough. straight and even edge of a trough, particularly if the amount is limited, it is an easy matter to regulate the flow through the V-shaped openings. Fig. 37 is termed the slotted water pipe. It is a pipe slotted between its two ends, from which the water overflows to the series of pipes below. It is good practice to lead the water supply to a cast-iron box at the center of the condenser, into the sides of which is screwed a piece of pipe- usually 2-inch reaching the ends of the condenser, and having its outer ends capped, which may be removed while a scraper is passed through the slot from the center towards the ends while the water is still flowing, thereby carrying off any deposit within the pipe. This forms a very durable construction, and one not liable, as with the galvanized drip trough, to disarrange- ment or bending out of shape due to various causes. It is impossi- 104 REFRIGERATION ble, however, to obtain the uniform flow of water over the condenser with this, as with the serrated or perforated troughs, particularly if the supply is limited, from the fact as stated in describing the over- flow trough, viz, the impossibility of obtaining a sufficiently thin stream of that length. Double=Pipe Condenser. This is a modern adaptation of an old idea, given up owing to its complex construction and the imperfect facilities available for its manufacture. It has come into use with great rapidity, and has brought forth many novel ideas of principle and construction. It combines the good features of both the atmos- Flg. 37. Slotted Water Pipe. pheric and the submerged types, having small weight and being accessible for repairs. It has the downward flow of the ammonia and the upward flow of the water, effecting a complete counter flow of the two, minimizing the amount of water required and taking up the heat of condensation with the least possible difference between the ammonia and the water. The two general forms of construction are a combination of a 1^-inch pipe within a 2-inch pipe, or a 2-inch pipe within a 3-inch. The water passes upward through the inner pipe, while the gas is discharged downward through the annular space; or, the position of the two may be reversed, the ammonia being within the inside pipe while the water travels upward through the annular space. REFRIGERATION 105 106 REFRIGERATION REFRIGEEATION 107 108 REFRIGERATION They are also constructed in series, in which the gas enters a number of pipes of a section at one time, flowing through these to the opposite end to a header or manifold, at which point the number of pipes is reduced, and so on to the bottom with a constantly reduced area. The theory of this construction is, that the volume of the gas is Fig. 41. Fig. 42. Types of Oil Interceptors Fig. 43. constantly reduced as it is being condensed. Figs. 38, 39, and 40 illustrate a general range of the various types in use. It is usual in the construction of this type to make each section or bank twelve pipes high by about 17 feet long; they are rated nominally at ten tons refrigerating capacity each, although for uneven units the construction is made to vary from 10 to 14 pipes in each. REFRIGERATION 109 Oil Separator or Interceptor. This is a device or form of trap, placed on the line of the discharge between the compressor and the condenser to separate the oil from the ammonia gas. It is to prevent the pipe surface of the condensing and evaporating system from becoming covered with oil, which acts as an insulator and prevents rapid transmission of heat through the walls. There are many forms of this device in common use, including the plain cylindrical shell with an inlet at one side or end and an outlet at the other, an almost endless variety of baffle plates, spiral conductors, and reverse-current devices. The object is similar to that obtained in the steam or exhaust separator, and generally speaking, that which would be effective in one sendee would be so in the other. Figs. 41, 42, and 43 illustrate three of the most com- mon types in use; from these the student will understand the general principles. COOLING TOWERS In cities and other localities where water is scarce or of high temperature, it becomes important to conserve the supply brought to the plant. In order to do this it is necessary to cool the water after it has passed over the condensers and coolers of the refrigera- ting plant. This is done by evaporation of a part of the water under atmospheric pressure so that the remaining water will be cooled, owing to the abstraction of heat that becomes latent in the water evaporated. The process may be employed to advantage, even where there is plenty of water, in order to save pumping; or where the water is taken from muddy streams to a settling basin, to avoid the use of more muddy water than absolutely required. The effi- ciency of any apparatus for this purpose depends on the extent of the water surfaces exposed and on the amount of air brought in contact with the water. Also to some extent the pressure of the air and, to greater extent, the dryness of the air are factors having their influence, but acting alike on any apparatus however constructed. Apparatus designed to cool water for re-use in refrigerating plants are known as cooling towers and of these there are many types on the market. All such towers may be divided into two classes according to whether the circulation of air is by natural or artificial currents. Also towers are classified as to material used, whether 110 KEFRIGERATION steel or wood. Both materials are used for towers operating with both kinds of air circulation. An efficient tower can, in fact, be made Fig. 44. Atmospheric Wood Cooling Tower. very cheaply by throwing brush into a framework arranged to pre- vent the brush packing, thus leaving space for air currents. Where REFRIGERATION 111 wood is used, the tower may be anything from a cheap slatted struc- ture made of rough lumber to an elaborate tower such as shown in Fig. 44. Here No. 1 lumber is used and treated by a preservative process before being put into the tower, and the structure is painted 112 REFRIGERATION with mineral paint when finished. This illustration represents the tower constructed for the Bauer Ice Cream and Baking Co. of Cin- cinnati, O., by the Triumph Ice Machine Co., for a 75-ton refrigera- ting plant using city water. Fig. 45 shows a circular steel tower using forced air circulation installed by the Triumph people for the Cincinnati Ice Co. A good form of the atmospheric or natural draft steel tower is made by B. Franklin Hart Jr. and Co. of New York, as shown by Fig. 46, complete with spray preventors. In towers using natural Fig. 46. Cooling Tower Installed at a Large Brewery in Monterey, Mexico. air currents, care should be taken to set the apparatus clear of all buildings, etc., so that there is free access of the air. Such towers should be designed with about 12 square feet of cooling surface for each 5 gallons of water to be cooled per minute, with which surface the temperature of the water will be lowered from 7 to 15 degrees depending on conditions. From 1^ to 7 per cent of the water passed over the tower is evaporated, and with losses by leakage, etc., this may be increased to 10 or 12 per cent, which represents the amount of make-up water that must be supplied. With artificial draft from 5 to 25 horse-power is required to operate the fans, according to the size of the tower and the type of fan used. Either suction or pressure fans may be used in such towers, as it is not definitely settled whether best results are had by forcing air in at the bottom of the tower or drawing it down from the top. Most towers, however, REFRIGERATION 113 force the air in at the bottom, thereby getting the flow in the opposite direction to that of the water. EVAPORATORS Evaporators may be divided into two classes. The first is operated in connection with the brine system. In this evaporator salt brine, or other solution, is reduced in temperature by the evapo- ration of the ammonia or other refrigerant, and the cooled brine circulated through the room or other points to be refrigerated. In the second, the direct-expansion system, the ammonia or refrigerant is taken directly to the point to be cooled, and there evaporated in . Fig. 47. Rectangular Brine-Cooling Tank. pipes or other receptacles, in direct contact with the object to be cooled. Which of the two systems is the better, is a much disputed and debated point; we can state, in a general way, that both have their advantages, and each is adapted to certain classes of duty. The cooling of brine in a tank by a series of evaporating coils one of the earliest methods is common to-day. A description of the many methods of construction and equipment would require much space. Let us, therefore, discuss the two most general types, viz, the rectangular with flat coils, and the double-pipe cooler the spiral-coil cooler being practically obsolete. 1 1 4 REFRIGERATION Brine Tank. Fig. 47 shows a sectional view of a brine-cooling tank. Flat or zigzag evaporating coils are connected to manifolds or headers; the pipe connections leading to and from these manifolds for the proper supplying of the liquid ammonia and the taking away or return of the gas to the compressor are also shown. For coils of this type, 1-inch or IJ-inch pipe is preferable, owing to the impos- sibility of bending larger sizes to a small enough radius to get the required amount into a tank of reasonable dimensions. It is pos- sible to make coils of this construction of any desired length or num- ber of pipes to the coil, "pipes high," the bends being from 3^ in. to 4 in. centers for 1-inch pipe, and 4 in. to 5 in. for lj-inch pipe. It is preferable to make the coils of moderate length not less than 150 feet in each and there is no disadvantage, other than in handling, in making them to contain up to 500 or 600 feet each. It will be observed that there is a slight downward pitch to the pipes with a purge valve at the lowest point of the bottom mani- fold, which is valuable and an almost necessary provision. This valve is for removing foreign matter that may enter the pipes at any time. By opening the valve and drawing a portion of their contents, the condition of cleanliness can be determined without the necessity of shutting down and removing the brine and ammonia for inspec- tion. The coils are usually strapped or bound with flat bar iron about | inch X 2 inches, or a little heavier for the longer coils, and bolted together with J-inch square-head machine bolts. The coils are painted with some good water-proof or iron paint. The brine tank is usually constructed of iron or steel plates, varying from T \ inch to f inch in thickness; the average being ^ inch for tanks of ordinary size. The workmanship and material for a tank of this kind should be of the very best; without these the result is almost certain to be disastrous to the owner or builder. The general opinion with iron workers, before they have had ex- perience, is that it is a simple matter to make a tank which will hold water or brine, and that any kind of seam or workmanship will be good enough for the purpose. On the contrary the greatest care and attention to detail is necessary. It is customary, and good prac- tice, to form the two side edges at the bottom by bending the sheets, thereby avoiding seams on two sides; while for the ends an angle iron may be bent to conform to this shape and the two sheets then REFRIGERATION 115 riveted to the flanges of the angle iron. The edges of the sheets should be sheared or planed bevel, and after riveting, calked inside and out with a round-nosed calking tool. The rivets should be of full size, as specified for boiler construction, and of length sufficient to form a full conical head of height equal to the diameter of the rivet, and brought well down onto the sheet at its edges. An angle iron of about 3 inches should be placed around the top edge and riveted to the side at about 12-inch centers. One or more braces, depending on the depth, should extend around the tank between the top and bottom, to prevent bulging; without these it would be impossible to make the tank remain tight, as a constant strain is on all its seams. A very good brace for the purpose is a deck beam. Flat bar iron placed edge-wise against the tank w r ith an angle iron on each side and all riveted through and to the side of the tank with splice plates at the corners, or one of each pair long enough to lap over the other, makes a good brace. Heavy T-iron is also used to some extent. It is usual to rivet the bottom of the tank and a short distance up the sides, then test by filling with water; if tight, lower the tank to its foundation and com- plete the riveting and calking. It may then be filled with water and tested until proven absolutely tight, when it may be painted with some good iron paint; it is now ready for its equipment of coils and insulation. A washout opening with stop valve should be placed in the bottom at one corner; for this purpose it is well to have a wrought iron flange, tapped for the size of pipe required, riveted to the outside of the bottom. If the brine pump can be located at this time, it is well to have a similar flange for the suction pipe riveted to the side or bottom of the tank, as a bolted flange with a gasket is never as durable as a flange put on in this manner. After the tank has been made absolutely tight and painted, the insulation may be put around it, the insulated base or founda- tion having been put in previous to the arrival of the tank. The insulation should be constructed of joists 2 in. or 3 in. X 12 in., on edge, and the space should be filled in with any good insulating ma- terial and floored over with two thicknesses of tongued and grooved flooring with paper between the thicknesses. In putting the insula- tion on the sides and ends of the tank, place joists, 2 in. X 4 in., 116 REFRIGERATION so that they rest on the projecting edges of the foundation about 2 feet apart. The upper ends should be secured to the angle iron at the top of the tank, its upper flange having been punched with f-inch holes, 18 in. to 24 in. centers, and to which it is well to bolt a plank, having its edge project the required distance to receive the uprights. Between the braces around the tank, block- ings should be fitted to secure the framework at the middle, as the height of some tanks is too great to depend on the support at the top and the bottom alone. After the framework has been properly formed and secured to the base and tank, take 1-inch flooring, rough, or planed on one side, and board up on the outside of the uprights. Fill in the space, as the work progresses, with the insulating material which may be any one of the usual materials. Granulated cork is about the best, all things considered, although charcoal, dry shavings, saw- dust, or other non-conductors may be used with good results. When the first course of boards is in place, it is well to tack one or two thicknesses of good insulating paper against the outer surface, care being taken that the joints lap well and that bottoms and corners are filled and turned under at the junction with the bottom insula- tion. It is then in shape for the final or outer course which is very often made of some of the hard woods in 2^-inch or 3-inch widths, tongued, grooved, and beaded. It is finished off with a base board at the bottom, moulding at the top, and given a hard wood finish in oil or varnish. If the tank is located in a part of the building in which appearance is of no importance, the outer course may be a repetition of the first, except that the boards are put on vertically instead of horizontally. It is well to make the top of the tank in removable sections to facilitate examination or cleaning; for this purpose make a num- ber of sections, about 2 J to 3 feet wide, of the length or width of the tank, using joists about 2 in. X 6 in. placed on edge, floored over top and bottom, and filled in with the selected insulating ma- terial. It is also well to have a small lid at one end of each, prefer- ably over the headers or manifolds, which will allow of internal examination of the tank to ascertain the height or strength of brine without removing the larger sections. The tank is now fully equipped and ready for testing and filling with brine. REFRIGERATION 117 For a circular tank, the general instructions regarding construc- tion and insulation may apply as with the rectangular tank just described; therefore only its special features will be considered. If the tank is small and there is sufficient head room above it for handling the coils there cannot be serious objection to this type, as its cost is lower than that of the rectangular tank. This is often an Fig. 48. Circular Brine-Cooling Tank. important item in a small installation, but when the tank is of con- siderable size and the coils large it is not as readily handled and taken care of as the other type. The usual construction of a nest of coils for a round tank is to bend the inside coil to as small a circle as possible, which, if it be of 1-inch or 1 J-inch pipe, may be 6 to 8 inches. Increase each successive coil enough to pass over the next smaller until the required amount of pipe is obtained. The ends may then be bent up or out and joined to headers at the top and the bottom 118 REFRIGERATION and the tank insulated in the manner previously described; it is then ready to test and charge with ammonia and brine. Fig. 48 represents an evaporator of this type. Other constructions of tanks and coils are too numerous to de- scribe in detail, and with one exception may be properly classed in one of the preceding types. The one exception referred to is illustrated in Fig. 49. It is quite common and is adopted for large pipe; it is often called oval, although not of that shape, but rather a combination of the flat and circular form. It has some good Pig. 49. Oval Brine-Cooling Tank. features; it allows the maximum amount of pipe in the smallest space and a large amount of pipe in a single coil. Brine Cooler. The brine cooler at present is a popular and efficient method of cooling brine for general purposes. Owing to mechanical defects and the impossibility of obtaining a brine solu- tion which would not freeze, it was abandoned only to be taken up again, and with the aid of modern ideas and better material it has become highly successful. The great advantage of the brine cooler over the tank method of cooling brine is the fact that the brine and gas are both in circulation, passing through the double-pipe cooler in opposite directions so as to get the greatest efficiency as well as REFRIGERATION 119 120 REFRIGERATION the most rapid transfer of heat and resulting rapid cooling. The double-pipe cooler is almost universally used at the present time in preference to the spiral enclosed shell cooler, notwithstanding the fact that the latter is more easily insulated and has a larger space for evaporation of the gas. Double-pipe coolers must be set up in TABLE XVII Properties of Calcium Brine Solution DEG. X BAUME 60 F. DEO. SALOM- ETER 60" F. PER CENT CALCIUM WEIGHT LBS. PER Cu. FT. SOL. LBS. PER GAL- LON SPECIFIC GRAVITY SPECIFIC HEAT FREEZING POINT F. AMMONI.. GAUGE PRESSURE 1 1 32 47.31 1 4 .943 1.25 i 1.007 .996 31.1 46.14 2 8 1 .886 2.5 } 1.014 .988 30.33 45 . 14 3 12 2.829 3.75 4 1.021 .98 29.48 44.06 4 16 3.772 5 I ^ 1.028 .972 28.58 43 5 20 4.715 6.25 % 1.036 .964 27.82 42.08 6 24 5.658 7.5 1 1.043 .955 27.05 41.17 7 28 6.601 8.75 if 1.051 .946 26.28 40.25 8 32 7.544 10 H 1.058 .936 25.52 39.35 9 36 8.487 11.25 H 1.066 .925 24.26 37.9 10 40 9.43 12.5 1$ ' 1.074 .911 22.8 36.3 11 44 10.373 13.75 it 1.082 .896 21.3 34.67 12 48 11.316 15 2 1.09 .89 19.7 32.93 13 52 12.259 16.25 2i 1.098 .884 18.1 31.33 14 56 13.202 17.5 2i 1.107 .878 16.61 29.63 15 60 14.145 18.75 2J 1.115 .872 15.14 28.35 16 64 15.088 20 2 1.124 .866 13.67 27.04 17 68 16.031 21.25 2f 1 . 133 .86 12.2 25.76 18 72 16.974 22.5 3 1.142 .854 10 23.85 19 76 17.917 23.75 3* 1.151 .849 7.5 21.8 20 80 18.86 25 3i 1.16 .844 4.6 19.43 21 84 19.803 26.25 3i 1.169 .839 1.7 17.06 22 88 20 . 746 27.5 3J 1.179 .834 - 1.4 14.7 23 92 21.689 28.75 3f 1.188 .825 4.9 12.2 24 96 22.632 30 4 1.198 .817 8.6 9.96 25 100 23.575 31.25 4 1.208 .808 11.6 8.19 26 24.518 32.5 4i 1.218 .799 17.1 5.22 27 25.461 33.75 4i 1.229 .79 21.8 2.94 28 26.404 35 4 1.239 .778 27. 65 29 27.347 36.25 *! 1.25 .769 32.6 1" Vac. 30 28.29 37.5 5 ' 1 261 .757 39.2 8.5"" 31 29.233 38.75 si 1.272 46.3 12 32 30.176 40 6J 1.283 54.4 15 33 31.119 41.25 * 1.295 52.5 10 34 32.062 42.5 5f 1.306 39.2 4 35 33 43.75 6| 1.318 25.2 1.5 REFRIGERATION 121 insulated rooms at considerable expense, but the comparative sim- plicity of the construction and the fact that all parts are open and subject to inspection, has made this form of cooler the choice of prac- tically all refrigerating engineers in recent years. Owing to the fact that salt brine may freeze and burst the pipes of the cooler, it should not be used if avoidable. Calcium chloride brine is preferred for several reasons, but particularly on account of the fact that its freezing point for ordinary densities is 54 below zero F.; while that of salt brine is about F. The construction of TABLE XVIII Properties of Salt Brine Solution DEGREES ON SALOM. r^ir R WEIGHT Cu ' FT ' POUNDS SALT PER GALLON SPECIFIC GRAVITY SPECIFIC HEAT FREEZING POINT F. AMMONIA GAUGE PRESSURE 1 1 32 47.32 5 1.25 .785 .015 1.009 .99 30.3 45.1 10 2.5 1.586 .212 1.0181 .98 28.6 43 .03 15 3.75 2.401 .321 1.0271 .97 26.9 41 20 5 3.239 .433 1 .0362 .96 25.2 38.96 25 6.25 4.099 '.548 1.0455 .943 23.6 37.19 30 7.5 4.967 .664 1 .0547 .926 22 35.44 35 8.75 5.834 .78 1.064 .909 20.4 33.69 40 10 6.709 .897 1.0733 .892 18.7 31.93 45 11.25 7.622 1.019 1 .0828 .883 17.1 30.33 50 12.5 8.542 1.142 1 .0923 .874 15.5 28 73 55 13.75 9.462 1.265 1.1018 .864 13.9 27.24 60 15 10 . 389 1.389 1.1114 .855 12.2 25.76 65 16.25 11.384 1.522 1.1213 .848 10.7 24.46 70 17.5 12.387 1.656 1.1312 .842 9.2 23.16 75 18.75 13.396 1.791 1.1411 .835 7-7 21.82 80 20 14.421 1.928 1.1511 .829 6.1 20.43 85 21.25 15.461 2.067 1.1614 .818 4.6 19.16 90 22.5 16.508 2.207 1.1717 .806 3.1 18.2 95 23 . 75 17.555 2.347 1.182 .795 1.6 16.88 100 25 18.61 2.488 1.1923 .783 15.67 the double-pipe brine cooler is shown in Fig. 50, in which it is seen that one pipe is within the other, the brine being discharged by the pumps into one or more pipes as at A and issuing at B. This con- nection leads from the main to the point to be refrigerated, and the ammonia is expanded or fed into the annular space between the two pipes and takes up the heat of the brine in evaporating, issuing as gas from the opening D at the top of the cooler. From thence the ammonia flows to the compressor and passes through the cycle of compression, condension, and return to the liquid ammonia receiver as 122 REFRIGERATION before. The ammonia evaporating between the two pipes will naturally absorb as much heat from the outside surface as from the inner or brine, if allowed to do so, and it therefore becomes necessary to insulate the outside of the cooler or to build an insulated room in which the cooler is erected. Although preferable in all cases, calcium brine is a necessity for very low temperatures. The proper density or strength of either salt or calcium brine is determined by the temperature to which it is necessary that the brine be reduced. In determining the proper strength for different requirements, Tables 17 and 18 are of value. It should be remembered, however, that a difference of from 5 to 10 degrees F. exists between the temperature of the brine and that of the evaporating ammonia; and that while the strength of the brine may appear ample for the temperature carried, the lower temperature of the liquid ammonia may cause it to solidify within or upon the surface of the evaporator, thus causing it to separate, or freeze, and act as an insulator, preventing the transmission of heat through the surface. It is, therefore, necessary in examining into the strength of the brine to consider it with reference to the evaporating pres- sure of the ammonia as well as its own temperature. In the last columns of Tables 17 and 18, the gauge pressures, correspond- ing to the freezing point of the brine for different strengths, are given. The usual and proper instrument for determining the strength of brine is the Baumd scale already described in discussing aqua ammonia and its strength, but an instrument known as the salometer is sometimes used. This instrument is similar in appearance to the Baume" hydrometer, the difference being the way in which the scale is graduated, which in case of the salometer is from to 100, the lower point being that at which the tube stands when floating in pure water, while the 100 point is that at which it stands in a saturated solution of salt brine, i. e., a solution which can be made no stronger, owing to the fact that the water has dissolved all the salt it will take up. In the table giving the properties of calcium brine, the two scales are compared so that the student should have no trouble in converting readings of one scale to the corresponding readings of the other. It will be seen that the scales are to each other as 1 to 4. In testing the strength of brine a sample is drawn REFRIGERATION 123 into a test tube and the temperature adjusted to 60 degrees, when the reading of the scale is taken at the surface of the liquid. In making brine it is well to fit up a box with a perforated false bottom, or, a more readily obtained and equally effective mixer may be made by taking a tight barrel or hogshead, into which is fitted a false bottom four to six inches above the bottom head, and which is bored with one-half inch holes. Over the false bottom lay a piece of coarse canvas or sack to prevent the salt falling through. A water connection is made in the side of the barrel near the bottom, between the bottom head and the false bottom, and a controlling valve placed nearby to regulate the amount of water passing through. Fig. 51. Apparatus for Preparing Brine. An overflow connection is made near the top of the cask, with its end so placed that the brine will flow into the tank, and a wire screen placed across its end inside the cask with a liberal space between it and the opening, to allow of cleaning, as shown in Fig. 51. The cask or barrel is now filled with the calcium or salt, which dissolves and overflows into the brine tank. A test tube and Baume scale, or salometer, should be kept at hand, and frequent tests made; the strength of the brine may be regulated by admitting the water more or less rapidly. After the first charge it is well to allow the mixer to remain in position for future requirements. A connection should be made between the return brine line from the refrigerating system and the cask with 124 REFRIGERATION a controlling valve; by the use of this valve the strength or density of the brine may be increased without adding to the quantity. The cask should be kept full of the calcium or salt, and a portion of the return flow of brine should be allowed to pass through the cask, which will dissolve the contents and flow into the tank. Calcium is usually obtained in sheet-iron drums, holding about 600 pounds each, and is in the shape of a solid cake within the drum. It is advisable to roll these onto the floor or top of the tank' in which the brine is to be made and pound them with a sledge ham- mer before removing the iron casing, this process breaking it up into small pieces without its flying about the room. After breaking it up the shell may be taken off and the contents shoveled into the mixer. It is also sold and shipped in liquid form, in tank cars, generally in a concentrated form, on account of freight charges, and diluted to the proper point upon being put into the plant. Where proper railroad facilities exist, this is probably the most desirable way of obtaining the calcium. Salt is sold and may be obtained in a number of forms. The usual shape for brine is the bulk, or in sacks of about 200 pounds each. Where it is possible to handle salt in bulk, direct from the car to the tank, this is most generally used on account of the price, being about $1.00 per ton less than if sacked. If it is necessary for it to be carted or stored before using, the sack form is preferable. The coarser grades of salt are used for this purpose, No. 2 Mine being the grade commonly used. The finer salts are higher in price, without a corresponding increase in strength of the brine formed. As a rule the freezing point of brine should be equal to, or slightly below, the temperature of the evaporating ammonia, rather than the temperature of the coldest brine, as is common. In referring to the table of salt brine solution, page 121, we find that if we wish to carry a temperature of 10 F. in the outgoing brine, it is necessary that the temperature of the evaporating ammonia be from 5 degrees to 10 degrees below this point, in order that the transfer of heat from the brine to the ammonia will be rapid enough to be effective, which would mean that the ammonia would be evaporating at a temperature of practically degrees F. To prevent the brine freezing against the walls of the evaporator, its strength or density should be made to cor- respond with this, or from 95 degrees to 100 degrees on the salometer. REFRIGERATION 125 In examining into the causes of failure in a plant to perform its usual or rated capacity, it is advisable, unless there is every evi- dence that the trouble is elsewhere, to make an examination of the brine and determine whether its strength and condition is suited to the duty to be performed. AUXILIARY APPARATUS Ammonia Receiver. The ammonia receiver, or storage tank, is a cylindrical shell with heads bolted or screwed on, or welded in each end, and provided with the necessary openings for the inlet and outlet of the ammonia, purge-valve, and gauge fittings. They may be vertical or horizontal; the former type is generally used on account of the saving of floor space, while the horizontal is necessary when the condenser is located so low as to make the flow of the liquid ammonia into the vertical type impossible. A con- venient location for the receiver in a plant in which the condenser is located above the machine room, is against the wall, or at one side of the room on a bracket or stand at one side of the oil interceptor, the sizes of the two being generally the same. They are then more readily under the control of the engineer than if at some out of the way place. Fig. 52 illustrates a receiver of the vertical type with the usual valves and connections for the proper equipment. The liquid ammonia enters at the top and is fed to the evaporator from the side near the bottom. The space below this opening has been provided for the accumulation of scale, dirt, or oil, and means are furnished for drawing it off rig. 52. vertical Type of through the purge valve in the bottom. Pipes. Extra strong, or extra heavy pipe is the generally ac- cepted pipe for connecting the various parts of the refrigerating system. Wrought-iron pipe is generally preferred to steel. Fre- 126 REFRIGERATION quently, however, and particularly for the evaporating or low-pres- sure side of the system, a special weight or grade of pipe is used, also standard or common pipe is sometimes employed for this pur- pose. Without knowing the particular conditions under which this is to be used, or the rela- tive value of the material, or manner in which the pipe is made, it is always better to use and insist on having the standard extra strong grade. The threads should be carefully cut with a good sharp die, making sure that the top and bot- tom of the threads are sharp and true. With this precaution, and an equally good thread in the fitting, it is not difficult to form a good and lasting joint. Particular care should also be taken that the pipe screws into the fitting the proper distance, and forms a contact the entire length, rather than to screw up against a shoulder without a perfect fit in the thread. This latter often causes leaky joints some time after the plant has been operated; the tem- porary joint formed either by screwing in too deep against the shoulder, or by ill-fitting threads, very often passes the test, and is used for some time until, after the alternate effects of heat and cold, and the chemical action of the ammonia cause it to break out. It is a safe rule that no amount of solder or other doctoring that is not backed up by a good fitting thread to support it can make an ammonia joint. This is particularly true of the discharge or compression side of the plant. Fig. 53. Boyle Union. REFRIGERATION 127 The manner of making these joints may be divided into those having a compressible gasket between the thread on the pipe and the fitting into which it screws, and the screwed joint formed by a threaded pipe screwed into a tapped flange or fitting. The latter may be divided into those having a soldered joint, or "one in which the union is formed by the threads only, with some of the usual cements to assist in making a tight joint. The two most prominent types of gasket fittings are shown in Figs. 53 and 54. The former is known in this country as the Boyle Union, and is extensively used. As will be observed, the drawing together of the two glands by the bolts, compresses the gaskets, Fig. 54. Gland Type of Union. usually rubber, against the threaded sides of the pipe, the bottom and sides of the recess in the flanges, and the edges of the ferrule be- tween the two gaskets. Figure 54 represents a union or joint quite frequently used, although not as commonly as the former. In this the pipe is threaded and screwed into the body of the fitting, in such a way that it does not form an ammonia-tight joint; leakage is prevented by a pack- ing ring compressed by the gland against the pipe thread and the walls of the recess. In Fig. 55 a type of ammonia coupling the contact between the pipe and fitting is made to withstand the leakage of the gas with- out the aid of packing or other material other than solder or some of the usual cements; the two flanges are bolted together with a tongue 128 REFRIGERATION and grooved joint having a soft metal gasket. This makes a per- manent and durable fitting. Other fittings of the class as ells, tees, and return bends are usually provided with one of the above methods of connecting with the system, and the different types described may be obtained of the builders of refrigerating machines. Valves. The valves for the ammonia system of a refrigerating plant are of special make and construction, being of steel or semi- steel, with a soft metal sent which may be renewed when worn, and metal gaskets between the bonnets and flanges. The usual types are globe, angle, and gate, subdivided into screwed and flanged. Fig. 56 is a generally adopted type of the flanged globe ammonia valve, while Fig. 57 represents the angle valve of the same construction. This seems to represent the best ele- ments of a durable and efficient valve. For a valve or cock requiring a fine adjustment, as is frequently the case in direct-expansion systems, particu- larly where the length of the evap- orating coil or system is short, a V-- shaped opening is desirable. Fig. 58 represents a cock for this purpose which will be found to be effective and meet the most exacting require- ments. Pressure Gauges. Two gauges are necessary for an ammonia plant of a single system; one to indicate the discharge or condensing pressure, and one for the evaporator or return gas pressure to the compressors. Owing to the action of ammonia on brass and copper, the gauges for this purpose differ from the ordinary pressure gauge in that it is made with a tube and connections of steel instead of brass, and this construction is the general choice of gauge makers; in other respects the construction is similar. For machines of small capacity instru- Fig. 55. Metal Gasket Coupling. REFRIGERATION 123 Fig. 56. Ammonia Globe Valve. Fig. 57. Ammonia Angle Valve. 530 REFRIGERATION ments with 6-inch dials are common, while for larger plants 8-inch is the generally adopted size. The graduation for the high-pressure gauge is usually to 300 pounds pressure, and if a compound gauge is used, it is made to read to a vacuum also. This latter is only needed on certain occasions and frequently omitted from the high- pressure gauge. Owing to the necessity of removing the contents of the system at certain times, and usually through the evaporating side of the plant, the gauge for this portion of the system is graduated to read from a vacuum to 120 pounds pressure. In connecting the gauges to the system, it is customary to locate the opening in the discharge and return gas lines near the machine within the engine room, placing a stop valve at some convenient point and carrying a line of j- or ^-inch extra strong pipe to the gauges, making the joints with the usual ammonia unions. On account of the possibility of leakage of ammonia gas from the gauge tube, it is often considered advisable to fill the g.iuge pipe with oil of the kind usd for lubricating the ammonia compressor for Fig 58. v-pon Expansion cock. a short distance above the gauges, upon which the pressure of the gas will act, causing the gauge to move properly but without allowing the ammonia gas to enter the gauge. This is an application of the same principle as the steam syphon or bent-pipe arrangement in use with steam gauges, for the purpose of keeping the heat and action of steam from the gauge mechanism by the retaining of water in the gauge con nection. Other gauges used about the refrigerating plant are of the ordinary pressure or vacuum types and do not need a special descrip- tion, as their construction and manner of applying to the different REFRIGERATION 131 parts of the system are well known to the engineer. It may be well, however, to caution the user on the importance of testing the gauges often enough to be sure they are accurate, as serious damages may result from a wrong indication of pressure. METHODS OF REFRIGERATION Various systems are in use for applying the cooling effect pro- duced by a refrigerating machine in general. work and in the special applications of refrigeration. All systems may be classified as either direct in which the gas is expanded in pipes located so as to permit of direct abstraction of heat from the bodies to be cooled; or indirect in which brine is cooled and then circulated in pipes, or by other means, so as to absorb heat from the bodies it is desired to cool. Methods of making and cooling brine have been described and it is only necessary to provide a brine pump and the necessary brine piping. The pump should be bronze fitted and the pipe should be of wrought iron. In some cases cold brine is made to cool air and the air is circulated through the cold stores. Direct refrigeration is applied by two methods, the most general being simple evaporation oj liquid in the pipes, there being nothing but gas in the piping, as the supply of liquid is regulated "by the expansion valve. In the other method the so-called flooded system the pipes or evaporators are almost full of liquid, or at least have the inner surfaces wet. Regulation is effected by the inlet valve and the gas trap of special design on the outlet, this trap being arranged to return the gas to the compressor and at the same time guard against allowing the liquid to reach the suction of the machine in any quantity that might be dangerous. Of course in the wet system of operation devised by Prof. Linde a certain amount of liquid is passed into the suction, but this is and must be under entire control. There are reasons for and against each of the two methods of applying refrigeration, but generally the indirect or brine system, is best for small plants, while large plants should use the direct-expansion system. The chief reason for retaining the brine system in large plants thus far has been the fear of ammonia leaks that mean damage to goods in store. Such leaks are com- paratively rare where reasonably good pipe work is used, and the man who uses any other kind of piping deserves to foot up the loss rather 132 PEFIUGEPATION than be behind the times with his whole system. Small plants must use brine to guard against shut-downs as the refrigeration stored in a comparatively large body of brine is of considerable value in keeping temperatures down at such times. Also the small machine may be shut down at night and the brine pump kept going to circulate the brine, thus effecting considerable saving in operation costs. The same results can be had to a certain extent by having shallow pans of brine placed over the pipes in the coolers. Where very low tem- peratures are required, as in the case of fish and poultry freezers, the direct-expansion system is a necessity. PROPORTION BETWEEN THE PARTS OF A REFRIG- ERATING PLANT There is necessarily a certain ratio or proportion between the several parts of a refrigerating plant, as there is between the boiler engine, and parts of a steam or power plant, in order to obtain the most economical results. It is first necessary that the evaporator be provided with heat-transmitting surface sufficient to conduct 284,000 B. T. U. from the brine to the ammonia, for each ton of refrigeration to be performed. Without going into a theoretical calculation of this amount, we shall state, in both lineal feet of pipe and square feet of pipe surface, the commercial sizes and amounts ordinarily in use. The coil surface in a brine-tank system of refrigeration, should contain approximately 50 square feet of external pipe surface, to each ton in refrigerating capacity of the plant, when it is to be operated at a temperature of 15 degrees F. This is an ample allowance and will be found under general working conditions to give readily the required capacity. While tests have been made in which 40 square feet of pipe surface has been found sufficient for one ton of refrig- eration, it will be safer to use the former amount, owing to the varied conditions under which a plant may be operated. This would amount in round figures to 150 lineal feet of 1-inch pipe, 115 feet of 1^-inch 100 feet of H-inch, or 80 feet of 2-inch pipe. For each ton in re- frigerating capacity, the pipe surface of the brine tank should vary from 40 to 60 cubic feet, depending on the amount of storage ca- pacity desired. The submerged type of ammonia condenser should contain REFRIGERATION 133 approximately 35 square feet of external surface which nearly cor- responds to 100 lineal feet of 1-inch, 80 feet of 1^-inch, 70 feet of 1 ^-inch, and 56 feet of 2-inch pipe. The atmospheric type of condenser should contain 30 square feet of external pipe surface which corresponds to 87 lineal feet of 1-inch, 69 feet of l|-inch, 60 feet of H-inch, and 48 feet of 2- inch pipe. The double-pipe type of condenser, as usually rated, contains 7 square feet of external pipe surface for the water circulating pipe and about 10 square feet of internal pipe surface for the outer pipe, and corresponds to approximately 20 lineal feet each of \\- inch and 2-inch sizes for each ton of refrigerating capacity. The above quantities are based on a water supply of average temperature 60 degrees and quantity. In cases of a limited supply or higher temperature than ordinary, a greater amount should be used. The ammonia compressor should be of such dimensions that it will take away the gas from the brine cooler, evaporating coils, or system, as rapidly as formed by the evaporation of the liquid ammonia; and unless the temperature at which the plant is to be operated be known, it is impossible to determine the volume of gas to be handled and the necessary size of the compressor. As stated before, the unit of a refrigerating plant is usually expressed in tons of refrigeration equal to 284,000 B. T. U. Up to the present time, however, a standard temperature at which this duty shall be performed has never been established, and therefore the rating of a machine, evaporator, or condenser by tonnage is a merely nominal one and misleading to the purchaser, a range of as great as 50 per cent very often existing in the tenders for certain con- tracts. Upon the basis, however, of the average temperature required of the refrigerating apparatus that of 15 degrees F. is probably the mean; and at this temperature in the outgoing brine, it is necessary to take away from the evaporator nearly 7,000 cubic inches of gas per minute for each ton of refrigeration developed in twenty-four hours. This may be considered as a fair basis for the rating of the displace- ment of the compressor or compressors of the plant, unless a specific temperature is stated at which the plant is to operate. At degrees F. it is necessary to calculate on approximately 9,000 cubic inches, while at 28 degrees F. about 5,000 will be the required amount. 134 REFRIGERATION For example, if we have two single-acting compressors 12 inches diameter by 24 nches stroke, operating at 70 revolutions per minute, we would have 113.09 (inches, area of 12-inch circle) X 24 (inches stroke) X 2 (number of compressors) X 70 (revolutions) -f- 7,000 (cubic inches displacement required) = 54.28 (tons refrigeration per 24 hours of operation) ; while if the same machine is to be operated at or near a temperature of zero and we divide the product by 9,000, we have a capacity of 42.22 tons only, in the same length of time. The above quantities are given as approximate only, but they have been deduced from the average results obtained from years of prac- tice and will be found reliable under average conditions. It is to be hoped, however, that a standard will soon be adopted which will rate machines or plants by cubic inches displacement at a certain number of revolutions or a stated piston speed, and the cooling of a certain number of gallons of brine per minute through a certain range of temperature. TESTING AND CHARGING Having described the different parts of the refrigerating plant and their relations to one another, let us consider the process of testing and charging, or introducing the ammonia into the system. After the connections are made between the different parts, whether the system is brine or direct expansion, it is necessary to introduce air pressure into it to determine the state of the joints. This may be done in sections or altogether. It is customary, however, to put a higher pressure on the compression side of the plant than on the evaporator owing to the difference in the pressure carried in opera- tion. Adjacent to each compressor is placed a main stop valve, on both the inlet and outlet sides, while on either side of these it is customary to place a by-pass or purge valve. Before starting the compressor, the main stop valve or valves if there be two on the inlet or evaporating side of the compressor, is closed, the small valve between the compressor and the main stop valve opened, and all of the other valves on the system opened except those to the atmosphere. The compressor may then be started slowly, air being taken in through the small by-pass valves and compressed, into the entire system. It is well to raise a few pounds pressure on the entire system before admitting water into REFRIGERATION 135 the compressor water jackets or other parts of the system, because if a joint were improperly made up, it would be possible for the water to enter the compressors, or coils of the condenser or evap- orator, and serious damage or loss of efficiency in the plant occur, which it might be impossible to locate afterwards. While if pres- sure exists within the system when the water is admitted, its en- trance into the coils or system is impossible while the pressure exists, and the leak is at once visible and may be remedied before proceed- ing further. In starting the test it is also well to try the two pressure gauges and see that they agree as to graduation; as it has happened that owing to a leakage between the discharge pipe and the high pres- sure gauge, an enormous pressure has been pumped into the system causing it to explode, with a consequent result of loss of life and property. If, however, the pressures are found to be equal on the two gauges it is safe to assume that they are recording properly and their connections are tight. After these preliminaries it is safe to put an air pressure of 300 pounds on the compression side of the plant, care being taken to operate the compressor slowly, not rais- ing the temperature of the compressed air too much, as, with the utmost care in making up joints and in selecting material, certain weaknesses may exist and under such high pressure it is well to pro- ceed with caution. After the desired pressure has been reached, the entire system should be gone over repeatedly until it is absolutely certain that it is tight. Parts which can be covered with water, such as a sub- merged form of condenser or brine tank with evaporating coils, should be so covered that the entire surface may be gone over at once and with almost absolute certainty. The slightest leakage will cause air bubbles to ascend to the surface. This leakage may be traced by allowing the water to flow from the tank while the air pressure is still on the coils or system, marking the points where the bubbles occur. The coils may then be taken up or repaired when empty. For parts which cannot be covered with water, it is customary to apply with a brush a lather of such consistency that it will not run off too readily; upon coming in contact with a leak, soap bubbles are formed, and by tracing to the starting point the leak may be located. After the compression system has been subjected 136 REFRIGERATION to a pressure of 300 pounds and found to be tight, the air may be admitted through the liquid ammonia pipe to the evaporating side of the plant, care being taken that the pressure does not rise above the limit of the gauge which, as previously stated, is usually 120 pounds and the same process of testing as applied to the opposite side of the plant gone over. Many engineers require the vacuum test as well as the fore- going, and although if the former is gone over thoroughly, there can be little chance of leakage afterwards, it is better to be over-exacting than otherwise in the matter of testing and preparation of the plant, thus preventing the possibility of leaks that may prove disastrous. Open the main stop valves on the inlet line and close the main valves above the compressor on the discharge line, closing the by-pass valves in the suction line, and opening those in the discharge line between the main stop valve and the compressor. Have all the other valves on the system open as before for testing. Starting the compressor draws in the air, filling the system through the com- pressor and discharging it at the small valve left open. Assum- ing the system to be tight, continuing the operation will finally ex- haust the air, or nearly so, when the small valves should be closed and the pressure gauges watched to determine whether or not leakage exists. Assuming that the system and apparatus is tight in every par- ticular and that it is otherwise ready to be placed in operation, we are now ready to charge the ammonia into the plant. If the air has been exhausted from the system in testing, this usual step need not be taken before charging, and it is only neces- sary to put the machine in proper condition to resume the pump- ing of the gas, and to attach a cylinder of ammonia to the charging valve to enable the refrigeration to be commenced. The main stop valves above the compressor, which were closed in expelling the air, should now be opened, and by-pass and other valves to the atmosphere closed. Close the outlet valve from the ammonia receiver and start the machine slowly, at the same time opening the feed valve between the drum of ammonia and the evaporator. The anhydrous liquid am- monia will flow into the evaporator through the regular supply pipe, the gas resulting from evaporation being taken up by the compress- ors and discharged into the condenser and finally settling down into REFRIGERATION 137 the receiver, when a sufficient quantity has been introduced to form a supply there. Upon closing the valves between the drum from which the supply is being drawn, and opening the outlet valve from the receiver, the process of refrigei ation by the compression system is regularly in operation. 6 'i REFRIGERATION PART III OPERATION AND MANAGEMENT OF THE PLANT Assuming that the plant has been properly erected, tested, and charged with ammonia of a good quality and if a brine system, with brine of proper strength or density, as already explained it only remains to keep the system or plant in that condition. As all forms of mechanism are liable to disarrangement and deterioration from various causes, repairs and corrections from time to time must be made to keep them in good condition. Let us now consider the most important points requiring attention. It is absolutely necessary for the good working of any type of plant or apparatus that it be kept clean. As a steam boiler must be clean to obtain the full benefit of the fuel consumed, so must the surfaces of the condenser and evaporator be clean to obtain the proper results from the condensing water and evaporation of the ammonia or other refrigerant. For satisfactory work, the system should be purged of any foreign element present in the pipes, such as air, water, oil, or brine. For- eign matter is the most common among internal causes for loss of efficiency, and the valve openings which have been shown and de- scribed should be used for cleaning the system. Oil is used as a lubricant in nearly if not quite all compressors, and the quantity should be the least amount that will lubricate the surfaces and prevent undue wear. This is considerably less than the average engineer is inclined to think necessary, and consequently a coating forms on the walls of the pipes or other surfaces of the con- densing or evaporating systems, and a proportionate decrease in the duty is obtained. It is also necessary that the oil be of such a nature that it is not saponified by contact with the ammonia. Such a change would choke or clog the pipes, coating their surfaces with a thick paste which causes a corresponding loss as the amount increases. 140 REFRIGERATION The purge valve in the bottom of the oil interceptor may be opened slightly about once each week, and the oil discharged from the com- pressors drawn off into a pail or can, unless a blow-off reservoir is provided. After the gas with which it is charged has escaped, the oil should be practically the same as when fed into the compressors. If, however, the oil is not of the proper quality it will remain thick and pasty, or gummy, showing it to have been affected by the am- monia. Its use should not be continued. By opening the purge valves, which are usually provided at the bottom manifold or header of the brine tank and the bottom head of the brine cooler, oil or water, if there is any in that part of the system, may be drawn off. These valves, however, should not be opened unless there is some pressure in that part of the system, as air would be admitted if the pressure within the apparatus is below that of the atmosphere. Air may enter the system through a variety of causes and its presence is attended with higher condensing pres- sure and a falling off in the amount of work performed. For the removal of air from the apparatus, a purge valve is placed at the highest point in the condenser or discharge pipe from the compress- ors near the condenser, which may be tried when the presence of air or foreign gases is suspected. This should be done after the compressor has been stopped. When the condenser has fully cooled and the gases separated, a small rubber hose or pipe may be carried into a pail of water and the purge valve or valves slightly opened. If air or other gases exist in the system, bubbles will rise to the surface of the water so long at it is escaping; while, if ammonia is being blown off, it will be absorbed in the water and not rise to the sur.ace. To prevent the possibility of air getting into the system the evaporating pressure should never be brought below that of the atmospheric, or degree on the gauge, as at such times, with the least leakage at any point, it is sure to enter. Should it become necessary to reduce the pressure below that point, it is well first to tighten the compressor stuffing boxes and allow the pressure to remain below degree only the shortest possible time, as not only air may enter, but if it be the brine system and a leak exists, brine also will be drawn in. From the foregoing it is evident that in order to obtain satis- factory results, the interior of the system must be kept clean by REFRIGERATION 141 purging at the different points provided for this purpose; and it need only be added in this connection, that when the presence of oil or moisture becomes apparent in any quantity, the coils or other parts should be disconnected and blown out with steam until thor- oughly clean, and afterwards with air to make certain that conden- sation from the steam does not remain. After this the parts may again be connected and tested ready for operation. If the plant be a brine system, it is necessary that the brine be maintained at a proper strength or density to obtain satisfactory results; for if it becomes weakened, it freezes on the surfaces of the pipes or evaporator, thereby acting as an insulator and preventing the rapid transmission of heat through the walls. It is of great importance to know at all times whether or not the gas taken into the compressors is fully discharged into the con- denser, as the slightest loss at this point is certain to make itself felt in the operation of the plant. The compressor and valves seldom need be taken apart to determine their operation. The engineer should be able to discern when the compressors are working at their best, by placing the hand on the inlet and outlet pipes or on the lower part of the compressors so as to detect slight change from normal temperature. Should the inlet pipe to one compressor be warmer than that to the other (of a pair), or the frost on the pipe from the evaporator reach nearer one compressor than the other, it is then certain that the one with the higher temperature, or, from which the frost is farthest, is not working properly or doing as much duty as the other; and it is equally certain that some condition exists which prevents the complete filling and discharge of its contents; possibly it has more clearance or leaky valves. The most common difficulties experienced with ammonia con- densers are those of keeping the external surfaces clean and free from deposits, and preventing the accumulation of air or foreign gases within. Deposits on the surface are usually of two kinds one, a soft deposit which may be washed off with a brush or wire scraper such as is used for cleaning castings in a foundry; the other, a hard deposit which must be loosened with a hammer or scraper. It is hardly necessary to explain in detail the methods employed in cleaning the condenser as this is a matter that each engineer will be able to accomplish in his own way. It should not, however, be over- 142 REFRIGERATION looked, and with a condensing pressure higher than ordinary, this should be the first point to be examined after the water supply. Air and foreign gases due to decomposition of the ammonia or other causes, find their way into the condenser and make themselves manifest generally in a higher condensing pressure, or a falling off in the duty to be obtained from the plant. They should be blown off through the purge valve at the top of the condenser in the man- ner already described. It is possible, through leakage of the coils or other parts of the apparatus, that the ammonia may become mixed with brine or water, thereby retarding its evaporation and interfering with the proper or usual operation of the plant. If this is suspected, a sample may be drawn off into a test glass through the charging valve or purge valve of the brine tank or ammonia receiver and allowed to evaporate, in which case the water or brine will remain in the* glass and the relative amount be determined. Through careful evaporation and con- tinued purging of the evaporator at intervals, this may in time be eliminated, and care should be taken to prevent future recurrence. Loss of Ammonia. This should be constantly guarded against. It is watchfulness which determines between a wasteful and an economical plant in this particular, and the engineer who allows the slightest smell of ammonia to exist about the plant is certain to be confronted with excessive ammonia bills; while he who is constantly on the alert and never rests until his plant is as free from the smell of ammonia as an ordinary engine room, will be referred to as the one who ran such and such a plant without addition of more ammonia for so many years. The escape of ammonia into the atmosphere is readily detected; but where a leakage occurs in a submerged condenser, brine tank, or brine cooler it is necessary to examine the surrounding liquid to determine whether or not it exists. For this purpose various agents are employed, and may be obtained of druggists or from the manu- facturers of ammonia. Red litmus paper when dipped into water or brine contaminated with ammonia will turn blue. Nessler's solution causes the affected water to turn yellow and brown, while phenolphthalen causes a bright pink color with the slightest amount of ammonia present. The stopping of a leakage of ammonia in the brine tank or REFRIGERATION 143 cooler may be possible while the plant is in operation, by shutting off the coil in which it occurs, or, if the point is accessible a clamp and gasket may be put in place temporarily. Purging and Pumping out Connection. A common cause of failure to operate properly and effectively is the introduction of some foreign substance into the system. This will be readily understood and appreciated by engineers and those familiar with the require- ments of a steam boiler. Clean surfaces on the shell or tubes are necessary for the maximum evaporation of water, or for the transfer of heat through the walls of pipe or other forms of heat-transmitting surface. The most common difficulty encountered in a refrigera- ting plant is oil, either in its natural condition, or saponified by con- tact with the ammonia, water, or brine. It enters the system in many ways; through leakage, condensation in blowing out the coils or system, foreign gas arising from decomposition of the ammonia through excessive heat and pressure, or the mingling of air which may enter the system through pumping out below atmospheric pres- sure, or the air may have remained in the system from the time of charging, never having been fully removed. It is also probable, though hard to determine with certainty owing to the various con- ditions surrounding the operation of plants, that impurities are in- troduced with the ammonia, either in the form of liquid, gas, or air, which afterward become impossible to condense. The oil in a system forms a covering or coating on the evap- orating surface which acts as an insulation and prevents the ready transfer of heat through the walls of the evaporator. The presence of water or brine causes an absorption of a portion of the ammonia into the water or brine, forming aqua ammonia which raises the boiling point of the ammonia and causes material loss in the duty. Air or other non-condensable gas in the system, excludes an equ?l volume of the ammonia gas, thereby reducing the available condens- ing surface in that proportion. For the purpose of cleaning the system and removing the dif- ferent impurities which may appear, purge and blow-off valves and connections are provided. One of these is placed at or near the bottom of the oil interceptor, which is located between the com- pressors and the condenser; it is used to draw off the oil used as a lubricant in the compressor and which is precipitated to the bot- 144 REFRIGERATION torn. This oil should not be allowed to accumulate to any great extent as it may be carried forward to the condenser by the current of gas. If the liquid ammonia receiver be placed in a vertical position it is customary to place a purge valve in the bottom for drawing off oil or other impurities. The supply of liquid to the evaporator \s taken off at a short distance above the bottom say, 4 to 6 inches. The next point for the removal of impurities is at the bottom of the brine cooler, or the lower manifold of the coil system in a brine-tank refrigerator. Tests at these points may be made as often as necessary to determine the state of cleanliness of the system. If the system is charged with any of the common impurities, they should be blown out and the system cleansed at the earliest possible mo- ment, as they cause a decided loss. Air and foreign gases accumulate in the condenser because the constant pumping out of the evaporating system tends to remove them from that part of the system to the condenser. This point, therefore, is the most natural place for their removal. For this purpose it is customary, on the best condensers, to place a header or manifold at the top at one end, and connect each of the sections or banks with a valve opening. A valve is also placed at each end of the header, and a connection made from one end of this header to the return gas line between the evaporator and the compressors. By closing the stop valves on the gas inlet and liquid outlet of any one of the sections and opening the purge or pumping-out line into the gas line to the compressors, the section or tank may be emptied of its contents for repairs or examination and then connected up and put into service without either shutting down the plant, or losing a material quantity of ammonia. For purging of air or gas, the valve between this header and the machine should be closed, and the valve on the opposite end opened to the atmosphere, the valves on each section in turn opened slightly while the foreign gases are ex- pelled. This process should not be used while the compressor is in operation, as the discharge of the ammonia into the condenser would keep the gas churned to the extent that it would become impos- sible to remove the foul gases without removing a considerable por- tion of the ammonia also. For this reason it is customary before blowing off the condenser REFRIGERATION 145 to stop the compressor and allow the water to flow over the condenser until it is thoroughly cooled. Sufficient time should elapse for the ammonia to liquefy and settle towards the bottom, while the air and lighter gases rise to the top, at which point they may be blown out through the purge valve to the atmosphere. If doubt exists as to whether ammonia or impurities are being blown out, attach a piece of hose to the end of the purge valve and immerse its other end in a pail of water. If it is air, bubbles will rise to the surface, while if it is ammonia, it will be absorbed into the water; the mingling of the ammonia with the water will cause a crackling sound, and the tem- perature of the water will increase owing to the chemical action. ICE= MAKING PLANTS One of the most important applications of refrigeration is in the production of artificial ice. Thus refrigeration, which in former times was produced only by the melting of ice, is now pro- duced artificially and used in making ice. In order to freeze water, it is only necessary that its temperature be lowered to the freezing point and tfre latent heat of liquefaction abstracted. In practice, to get rapid freezing, the temperature of the ice formed is carried below the freezing point, so that calculations of the heat to be ab- stracted must cover this. Assuming that the water supply has a temperature of 60 F., 28 B. T. U. will have to be removed from 1 pound of water to reduce it to freezing temperature. Then, since the latent heat of ice is 142.65, this number of heat units must be abstracted to freeze the pound of water, and since the temperature of ice is usually about 20 F. or 12 degrees below freezing and its specific heat 0.5, we have 6 B. T. U. to be removed on this ac- count. Thus altogether 176.65 B. T. U. must be removed from one pound of water to freeze it. Of the many more or less impracticable schemes that have been devised to freeze ice, only three are to any extent in use at the pres- ent time. These are known as the can, the plate, and the cell systems. The latter is used in England but not to any extent in the United States, where the great majority of the plants are on the can system with a few working on the plate plan. Indeed, the can system is most in use the world over, in spite of the fact that there are a num- ber of disadvantages connected with its use. As good ice can be 146 REFRIGERATION made by one system as by the other when both are operated properly, but it costs more to make ice with the can system owing to the purify- ing apparatus that must be employed if the ice is to be made clear and firm. The plate plant costs from 30 to 75 per cent more to con- struct and requires considerably larger buildings and more ground space. This means greater fixed charges, but the disadvantage is offset in part, at least, by the fact that the plate plant will make from 10 to 14 tons of ice per ton of coal burned, while the average for good can plants is from 6 to 8 tons. The practical skill required to operate the two plants is about the same, but somewhat more technical knowledge is required in the case of direct-expansion plate plants. As a rule it never pays to build small plate plants and in the larger plants a high grade of equipment, consisting of compound condensing engines and power-driven handling devices, must be employed to get the economy that will justify the building of such a plant. Such machinery requires a high degree of skill for proper operation. Fixed charges and depreciation are greater with the plate system. Where a large plant is to be operated by hydro- electric or other cheap power, it will pay to build a plate plant, the system requiring no steam to freeze the water, as in the case of the can plant. Can System. As the name implies, this system uses cans in which the ice is frozen, the cans being filled with water and partially immersed in a mechanically-cooled non-freezing brine bath. Freez- ing proceeds from the four sides and the bottom, and the impurities in the water, which have not been removed during the first stages of the freezing process, are finally frozen into the center of the block. The central opaque core formed in this way is undesirable, and it is to the necessity for eliminating it that all the complica- tions of the can system are due. Distilling, reboiling, and filtering apparatus must be employed except where porous opaque ice is not particularly objectionable, as in packing fish and icing cars. By freezing ice at a comparatively high temperature, say 25, clear ice can be made by the can system with natural water, but it is not practicable to use so high a temperature, owing to the length of time required to freeze the ice and the comparatively large tanks that would have to be employed. On this account ice is frozen at from 12 to 20, the usual working temperature being from 14 to 16. REFRIGERATION M7 At very low temperatures the ice crystals are formed so rapidly that they do not have time to solidify so that the block is rather porous, being made up of the separate crystals. With a freezing temperature of 15, the tank for holding the cans should be large enough to contain from 2 to 2^ times the number of cans necessary to make up the daily output. Thus what is called a 15-ton tank will really contain cans sufficient to hold about 38 tons of ice. This factor by which the number of the cans in the tank is increased is known as the tank surface. The time of freezing depends, of course, on the thickness of the ice, as the first inch of thickness is formed much quicker than the rest of the block. Thus, with a temperature of 20, a 1-inch thickness can be frozen in an hour or less; while a 4- inch thickness will require about 10 hours, the cooling being from one side only. For this temperature, the time in hours required to freeze can be found approximately by adding 1 to the inches of thickness, multiplying this sum by the thickness in inches, and divid- ing the result by 2. Thus to freeze ice 8 inches thick from one side, we have 8 (8 + 1) -J- 2 = 36 hours. For a temperature of 15 the results obtained by the rule should be decreased by 20 per cent for all thicknesses under 8 inches, and by 25 per cent for thicker ice. Can Plant Equipment. The complete can ice plant is made up of a steam boiler plant, a refrigerating or ice-making machine, dis- tilled water system, and freezing tank with accessories. In addition to this equipment, it is customary to provide ice storage rooms and the necessary brine cooling and circulating apparatus. Pumping apparatus is also required to supply water to the plant, and in cases where water is scarce or obtained at great expense, cooling towers are employed. The steam boiler plant will not be described in de- tail as it should differ in no way from a first class steam power- plant equipment. It consists of a good boiler with fixtures and stack, a boiler feed pump, an injector, and a feed-water heater to- gether with water softening or purifying apparatus in case the water is^bad. For small plants, ordinary return tubular boilers are about the most practical type and should be installed so as to have a reserve unit if possible, particularly if the water is bad. Larger plants may use the more expensive water-tube boilers to advantage but there is little need of these except where con- densing or compound engines are employed as in plate plants. 148 REFRIGERATION The engines are of standard manufacture and in no-wise specially constructed for the ice plant. The refrigerating machine has already been discussed in detail so that it only remains to describe the dis- tilling and freezing apparatus and show how all the apparatus is assembled to form the complete ice plant. Distilling Apparatus. This consists of an oil separator, a back pressure or relief valve, an exhaust steam condenser, a reboiler and skimmer, a hot filter, a cooling coil, a gas forecooler, and a cold filter. Fig. 59 shows the course of the steam from the engine through ttae various parts of the apparatus. From the engine cylinder A, the steam passes directly to the oil separator, or, if a receiver is used, to the receiver, and then to the separator. The separator should be of Fig. 59. Diagram of Distilled- Water Apparatus. ample size and never less than the size of the pipe to which it is con- nected. In the separator the oil and priming water that may have come over are separated out and the purified steam carried to the exhaust steam condenser B. Any steam that is not condensed im- mediately escapes through the relief valve C\ and the vent cock D serves to rid the steam of any air and other gases that may be present. Water from the steam condenser passes to the reboiler E, which is provided with a skimming diaphragm near one end over which scum and light impurities can pass off to the waste pipe F. A float valve regulates the water level in the reboiler and a live steam coil furnishes the heat for boiling. After the water is boiled. REFRIGERATION 149 it passes through the pipe G to the hot filter H, and thence to the cooling coil / over which cooling water runs. From the cooling coil the water passes to the tank J which contains a coil of pipe con- nected at its two ends into the suction line of the compressor. Thus the return gas from the expansion coils passes through the coil, and the water in the tank, which is known as the forecooler, is cooled down to a temperature of 45 to 50. From the forecooler, the water goes through the cold filter and thence passes through a hose to the can filter and thence to the cans. Steam Condenser. This usually consists of pipe coils over which water is run as in the atmospheric type of ammonia condenser. Either IJ-inch or 2-inch pipe may be used, care being taken to have sufficient coils to give a condensing area equivalent to about twice the area of the exhaust pipe. This will be found satisfactory where the oil separator is of such design as to act as a receiver, or where a receiver is connected in the exhaust pipe. The idea is to avoid throwing back pressure on the engine, and if the exhaust pipe is long or has a number of unavoidable bends, the aggregate area of the condenser pipe coils must be made larger in proportion. About 80 square feet of pipe surface should be allowed for each ton of ice making capacity in 24 hours. This means 128 running feet of 2-inch or 180 running feet of 1 j-inch pipe per ton of capacity. Many plants do not use this amount of pipe, and in cases where the cooling water has a low temperature the use of less pipe surface may be justifiable. In addition to the pipe coil condenser, there are a number of special designs on the market, most of them designed to economize space. These generally consist of some form of receiving tank made of galvanized iron, water being run over the outer surfaces of the tank. It is claimed that the thin metal gives rapid and economical transfer of heat and that the cooling water is used to the best advan- tage so that less of it is required. A steam condenser of this type made by the Triumph Ice Machine Co. is shown in Fig. 60. In some cases local conditions make it desirable to use the regular standard surface condensers, this being particularly the case where the ice plant is operated in combination with a power plant. Hot Skimmer and Reboiler. Cleansing of the water formed by condensing the steam is done by driving off all volatile matter, dur- ing the process of boiling, and skimming such of the impurities as 150 REFRIGERATION REFRIGERATION 151 cannot be volatilized. These processes may be carried on in two separate pieces of apparatus or the hot skimmer and reboiler may be combined as shown in Figs. 59 and 61. The combined apparatus requires fewer pipe connections and is somewhat more simple and in- expensive. As seen in Fig. 61, the skimming is accomplished by a heavy galvanized-iron diaphragm near one end of the rectangular tank containing the water to be boiled. The impurities and refuse water flow over this diaphragm and out through the pipe connection made to the end of the tank. Distilled water is brought to the tank by the connections A, the pipe being extended into the tank and per- forated so that the water escaping through the holes is evenly difr A Fig. 61. Keboiler and Skimmer. fused and, rising to the surface level of the water in the tank, gets rid of any entrained air. Live steam is supplied to the zigzag coil in the bottom of the tank by means of the connection B, and being condensed in its pas- sage through the cpil is allowed to escape through the perforations shown at C in the last turn of the coil. It will be seen from this that all water enters the tank at the end nearest the skimming diaphragm and must pass to the other end of the tank before going through the outlet valve D to the hot filter. During this passage the water is thoroughly boiled by the heat from the live steam coil and is freed from any impurities and air it may have contained. The outlet valve is controlled by a float and is so constructed that it is wide open while the tank is full and closes gradually as the water level falls until, when the level is about 3 inches above the outlet, the valve is entirely closed. Thus there is no chance for air to be drawn off with the water 152 REFRIGERATION as would be the case if the valve remained open until the water level should fall as low as the outlet opening. Filters. Filters usually consist of vertical cylindrical tanks made of heavy sheet iron or cast iron with the interior surfaces well galvanized. A perforated false bottom supports the filtering ma- terial in place, crushed quartz, sand, or good charcoal being used for this purpose. Quartz is preferable for the hot filter but charcoal is frequently used for this as well as for the cold filter. All pipe con- nections are made to the side of the tank so that the covers can be removed for cleaning and recharging and, in addition to stop cocks and valves on the pipe connections, a by-pass with proper valves should be provided so that cleaning can be done without interfering with the operation of the plant. The frequency with which the filtering material must be renewed depends altogether on local con- ditions, and varies from every week or ten days to once a season. Under average conditions renewal once a season or, at most, twice will be found satisfactory. The water may run through the filter from the top down, as is usually done, or the direction of flow may be reversed according to the preferences of the engineer in charge. In the average filter, the depth of the filtering material is about 5 feet. The surface area required depends on local conditions. Filters are ordinarily from 30 to 40 inches in diameter and one hot filter of this size, 7 feet high over all, is about right for a 15-ton plant. For the cold filter, 1 square foot of surface will suffice for a plant of the same size. In small plants the cold filter is often a very small affair known as a sponge filter and may consist of nothing more than a sheet-metal cylinder about 20 inches long and 8 or 10 inches in diameter with proper connections at its two ends for the water pipes. Charcoal, grass sponges, or other filtering material is placed in one end and the other end is filled with alternate layers of cotton and cloth of fine weave. This arrangement is considered very effective in catching rust and other material that gives red core ice. Cooling Coils and Gas Cooler. After leaving the hot filter, the distilled water goes to the cooling coils constituting the fiat cooler, in the manner already described. These coils are built like the steam condenser but are usually of a smaller sized pipe. In fact the coils are nothing more than an atmospheric condenser used to cool water REFRIGERATION 153 instead of to condense steam. About 4 square feet of pipe surface should be allowed for each ton of ice-making capacity. As the cool- ing coils may be compared to the atmospheric condenser, so also the gas forecooler may be likened to the submerged condenser. In the case of the forecooler, however, the cooling medium expanded gas flows through the coils and the water to be cooled fills the tank, whereas with the condenser the water filling the tank does the cool- ing and the gas inside of the pipe coil is condensed. For small plants the tank for the forecooler should preferably be cylindrical and the pipe coil be made in the form of a spiral without joints. Such a cooler is illustrated in Fig. 62, showing the Triumph construction. Larger plants have the cylin- drical or rectangular tank as best suits local con- ditions. The combined area of the coils in every case should not be less than the area of the suc- tion pipe of the com- pressor and should pre- ferably be from 1| to 2 times greater. This pro- portion will ordinarily give from 4 to 5 square feet of cooling surface per ton of ice, which is about right for average conditions. Care should be taken to see that all the connections of the distilled water apparatus are of block tin or galvanized iron so that no trouble will be had with rust. The reboiler and other vessels should be made of gal- vanized iron or have the surfaces in contact with the water thoroughly galvanized. Valves should be of composition. Connections should be made to blow out all parts of the system with live steam as occasion may require, andblow-off cocks should be provided at convenient points. Fig. 62. Distilled Water Storage Tank. 154 REFRIGERATION Freezing Tank. The freezing tank with its accessory apparatus is the center of operations in the ice plant. The complete equipment includes ice cans, with covers to be placed over them in the spaces of the floor grating that holds them in position; a brine agitator; a crane with geared hoist and can lift; an ice can dump with thawing apparatus; a can filler with hose to reach any part of the tank room floor; expansion coils with headers and valves; a brine hydrometer and a thermometer. The tank itself is made of metal or wood and should be well insulated, one method of doing which has been de- Fig. 63. Construction of Tank Grating and Covers. scribed in discussing brine cooling tanks. For tanks up to 30 inches deep, fV-inch steel is thick enough, but for deeper tanks up to about 4 feet the thickness should be |-inch. The sides and ends should be well braced with angle irons and an angle-iron rim should be put around the top. Sufficient holes should be punched in this rim to make sure that the grating can be bolted securely in position. Expansion Coils. The expansion coils should be of extra heavy welded pipe running the full length of the tank if possible and held in position, a coil between each two rows of cans, by iron straps. These straps also support the grating, as seen in Fig. 63. The inlet of each coil is fitted with an expansion valve and each of the outlets is provided with a stop valve. Thus any coil may be cut out of opera- tion, if it is found to be leaking, without interfering with the operation of the plant. All of the coils of the tank are connected to a manifold at the inlet end, the connection being made so that the expansion REFRIGERATION 155 valve is between the coil and the manifold. A similar manifold is used to connect the outlets of all the coils with the suction of the com- pressor. Ordinarily the bottom jeed is used, the liquid ammonia entering the bottom pipe of each coil and passing off to the suction manifold from the upper pipe of the coil; but this method of feeding is reversed where the wet system of operation is used. Thus there are two methods of feeding the coils, each of which has its advan- tages and disadvantages. There is also a third system of operation known as the top jeed and bottom expansion which is a combination of the two methods just described. At the feeding end of the coils a manifold is connected to each alternate coil and the ammonia is fed downward in these coils as in the wet system. The bottom ends of all the coils are con- nected to a common manifold so that the liquid after flowing down through half of the coils, rises and evaporates through the other coils and finally passes to a third or suction manifold which is connected to the upper ends of the coils not connected to the feeding manifold. The gas passes from this third manifold to the suction of the com- pressor. There should be 220 lineal feet of 2-inch pipe or 350 feet of l|-inch pipe for each ton of ice to be made in 24 hours, due regard being had for the temperature of the brine and the most economical capacity of the machine. It is true that many tanks are installed with much less pipe surface than this, but the plants so installed are necessarily operated extravagantly, as the back pressure must be carried very low to get capacity. This low pressure calls for more coal, and is the cause of increased depreciation of the apparatus. Ice Cans. Ice cans are made in 50-, 100-, 200-, 300-, and 400- pound standard sizes, the top and bottom dimensions for each of the sizes respectively being 8x8 and 1\ x 7$ inches, 8x16 and 1\ x 15 \ inches, 11^x22$ and 10$ x 20$ inches, Il$x22$ and 10 x 21$ inches, and 11$ x22$ and 10$ x 21$ inches. For the 50- and 100- pound can, the inside and outside depths are respectively 31 and 32 inches, while for the 200- and 300-pound cans the depths are 44 and 45 inches, and the 400-pound can has an inside depth of 57 inches with an outside depth of 58 inches. Reinforcing rings are used around the tops of the cans which are made of iron bands f-inch thick by 1$ inches wide. All except the 400-pound cans are made of No. 16 steel, U. S. gauge, and these cans are made of No. 14 material. 15C REFRIGERATION The metal should be of good quality and of uniform thickness and all except the largest cans should be made with but one side joint. All joints are riveted on 1-inch centers, the rivets being driven close and the seams soaked with solder and floated flush. The bottoms are flanged and inverted 1 inch into the body of the can. All bands are welded and galvanized and should be punched in the middle of the long sides with f-inch holes placed 1 T V inches from the top of the band. Cans made of No. 16 steel should have the sides turned over at the top and bottom. Grating and Covers. Gratings and covers for holding the ice cans in position are constructed as shown in Fig. 63. The rim of the can rests on a galvanized-iron cross-strap A which is mortised into the oak strip B. Above and below the strip B are strips C and G, and all three of the strips are held together by through bolts, as shown in the illustration. The whole structure is supported on the iron straps that hold the expansion coils in position, these traps being mortised into the strip G as shown. Grooves E are cut into the sides of the strip C and a stick F, having its ends set in these grooves, serves to hold the cans down so that they cannot float. The covers D rest on the strips C and in common with the other parts of the grating are made of oak, two thicknesses being used with good insulating paper between them. These boards must be thoroughly nailed together, as they are subjected to rather severe usage and have a tendency to warp out of shape. Some means should be provided for lifting them and this may be done by hollowing out hand holes at the ends or by providing regular plates and handles. Brine Agitators. Brine agitators are of three classes, using centrifugal pumps, displacement pumps, and propellers respectively. As the object in all cases is to get a steady, uniform circulation of the brine in all parts of the tank, it is plain that the propeller is well adapted to the work and for this reason it is used in the great majority of cases. Where brine coils are placed in the ice storage house or where coolers are operated in connection with the ice plant, there is an advantage in using a displacement pump, as the brine when drawn from the tank may be pumped through the cooling coils before being returned. When this method of circulating the brine is adopted, discharge pipes must be put in the tank so that the return- ing brine will be distributed throughout the entire tank. One of these REFRIGERATION 157 pipes is placed under each of the expansion coils and small holes in the pipes distribute the brine all along the coils. In this way a cur- rent is set up at each of the coils and the comparatively warm brine returned by the pump from the cooler coils is brought in direct con- tact with the expansion coils, with a resulting high efficiency of heat absorption by the expanding gas. In the use of the centrifugal pump, the chief point of advan- tage lies in the fact that a large quantity of brine can be circulated. The brine is taken from one corner of the tank and discharged into a header on the side of the tank opposite the suction connection of the pump. The rapid circulation set up in this way causes rapid freezing which is a great advantage when ice is needed in increased quantities to meet the demands of the market in hot weather. Fig. 64. Construction of Freezing Tank. Where a propeller is used for circulating the brine, as shown in Fig. 64, which is a longitudinal section through a freezing tank, one or more wooden partitions are constructed in the brine tank be- tween the cans and along the expansion coils for almost their entire length. The propeller is driven by a direct-connected engine or by a motor, and forces the brine to circulate by moving from the dis- charge side through the length of one compartment, around the end of the wooden partition and back through the other compartment to the suction side of the propeller. Thus it is seen that there are two passages essential to the operation of the system, one of the pas- sages being open to the suction and the other to the discharge side of the propeller. Where only one propeller is used on a tank, it is advisable to use two partitions so that the suction passage of the 158 REFRIGERATION propeller is divided into two parts. The propeller is placed near the center of the tank at one end and discharges through the middle com- partment between the two partitions, and the brine, arriving at the far end of the tank, is divided into two streams that flow back by the side passages outside of the partitions to the suction of the propeller. For a 10-ton tank, a 12-inch propeller of ample size, and for a 15- ton tank an 18-inch propeller should be used. Larger tanks re- quire more than one propeller. In planning a method for circula- ting the brine, one should remember that a comparatively large amount of power is required to operate the propeller system. Crane and Hoist. The great majority of small. and medium sized plants use hand cranes, consisting of a light channel iron car- ried on four wheels, which run on suitable rails placed at a con- venient height on the side walls of the tank room. The channel iron carries a four-wheeled trolley provided with a geared hoist on the drum of which is wound the hoisting chain or rope. A can latch, one form of which is shown in Fig. 65, is attached to the end of the chain. The apparatus consists of a board mortised out at the ends so as to drop into the top of the can. In the middle is an eyebolt to which the hoisting chain is connected and hook latches a* the two ends are adapted to catch in the holes in the sides of the can. When the can has been lifted and is to be set down on the dumping table the latches are pulled outward so as to release the hooks. With the hand crane and an apparatus of this kind, a man can handle about 15 tons of ice in a day of 12 hours. For plants of larger capacity it is advisable to use a pneumatic hoist and when this is done a special latch may be used so that two or more cans may be lifted at the same time. With this kind of hoist, one man can handle from 40 to 50 tons of ice in 12 hours. In still larger plants, special means are used to hoist the cans and dump the ice. Dumping and Filling. The dumping and filling of the cans should be done according to some regular, well-ordered system of rotation. Numbers should be plainly stenciled or cut on the covers of the cans so that the tankmen need make no mistake in pulling the proper cans. All the cans should not be pulled from any one part of the tank at the same time, and except in large tanks it is not well to take all the cans of any one row at a single pull. As an example of what may be done, suppose that the cans are numbered REFRIGERATION 159 in consecutive order over the entire tank. The tankman could then pull every fourth can, taking the numbers 1, 5, 9, etc. At the next pull he would take the numbers 2, 6, 10, etc. Various styles of dumping tables are in use, varying from a simple home-made apparatus designed to handle one oan at a time, to the elaborate apparatus of a large plant dumping a number of cans at one operation. The can may be dipped into a hot-water tank to thaw the ice block loose, or tepid water may be sprinkled over it to accomplish the same purpose, as is done with the style of apparatus illustrated in Fig. 66. n n Fig. 65. Can Latch. \ Fig. 66. Automatic Can Dump. The table here shown is constructed of metal and consists of a drip pan A on the bottom of which are riveted two pairs" of support- ing brackets B, made of pipe. Hollow trunnions C are connected to the water supply and sprinkler pipes and support the box D, in which the can is placed. The ports in the hollow trunnion are so arranged that when the box is in the position shown by the full lines, the water connection is shut off. However, as soon as the box is tilted to the dumping position shown by the dotted lines, the con- nection to the water supply is made and water flows over the can from the sprinkler pipes until the block of ice is thawed out. When this occurs, the weight of the can, which is not evenly bal- anced on the trunnions, acts to return the box to the first position, in doing which the water is shut off. Thus the operation is auto- 160 REFRIGERATION matic and the tankman, having placed a can in the tilting position, gives it no further attention until he pulls and brings up another can to be put in the place of that from which the ice has been dumped. The empty can is then returned to its place in the tank and filled with distilled water from the supply hose by means of an automatic can filler which is placed in the can and the trigger pulled, after which the attendant leaves it and goes about his business. When the water rises to the desired level, it raises a float that automatically moves the trigger to shut off the water supply. By using this apparatus all cans are filled to the same level without special attention. Layout. The layout of a plant should be given the most care- ful consideration as success or failure depends to a large extent on Fig. 67. Layout of Wolf Plant. the arrangement of the different parts with reference to convenience and economy in operation. No set designs can be given which will meet the local conditions of every case, but plans of a few typical plants are given to show what should be sought for in constructing a plan suitable for any particular case. Where local conditions do not require specially constructed buildings, the whole plant may be housed in a single building of rectangular form such as that shown in Fig. 67. This design is by the Fred W. Wolf Co. and has been used as a basis of work in designing a large number of successful plants. The boilers are in the end of the building remote from the freezing REFRIGERATION 161 tank, and the ice machine is so set that as little as possible of the heat radiated from steam pipes, etc., will get to the tank room. The overall dimensions for a plant of this kind are given in Table 19 for capacities ranging from 5 to 100 tons. Fig. 68 shows a diagram plan and elevation of a design used by the Arctic Ice Machine Co. The dimension letters refer to Table 20 which gives a complete schedule of dimensions for plants ranging in capacity from 2 to 200 tons daily output. All dimensions given in the table are in feet. TABLE XIX Dimensions for Fig. 67 DAILY CAPACITY DIMENSIONS A B 5 tons 30 feet 56 feet 10 35 73 " 15 37 78 20 40 85 25 42 95 30 " 42 107 35 42 117 40 49 120 50 49 135 60 54 150 80 59 154 100 73 160 Fig. 69 shows another arrangement for a small factory. This is a design of the Frick Co. and is suitable for a plant having a daily output of from 6 to 10 tons. For a plant of about 35 tons capacity, the Frick Co. uses the design shown in Fig. 70, which gives sec- tional side and end elevations and a plan view. Another design by the same company for a ICO-ton plant is shown in Fig. 71. These three illustrations give an idea of the necessary changes in arrange- ment for plants of different sizes. Fig. 72 shows in plan and elevation a modern ice factory as constructed by the Triumph Ice Machine Co. Where absorption machinery is used, the arrangement of ma- chinery may be modified if desired so as to make the plant somewhat more compact, for the same capacity, than a plant operating with compression machinery. This ability to compact the arrangement is due principally to the fact that in the absorption machine there are no moving parts, the only moving machinery being the pumps. A good plan for an absorption plant is that used by the Henry Vogt Machine Co., an isometric view of which is shown in Fig. 73. 162 REFRIGERATION Plate System. Although plate ice may be produced by freez- ing from two sides of the compartment containing the water and allowing the ice cakes to meet, thereby reducing the time of freezing, this has not been done to any extent. Practically all plate ice is frozen from one side only and on this account a great deal of time is ienses Weight /oolbs pertf " * N ^Better Room M JE'/ipt/ie Q ftoom Ammonia Condenser - Weiyht /ce Tank Room Fig. 68. Arrangement of Arctic Plant. required, about eight or ten days being necessary to freeze 11 -inch ice. The time of freezing for a 20-degree temperature is determined by a rule similar to that given for the can system, viz : Multiply the thickness to be frozen by twice itself plus one. For a temperature of 15, deduct one-fourth from the result thus found. Thus for 11-inch ice we have 11 (2x11 + 1)= 253 hours and deducting one- fourth the freezing time at 15, is about 190 hours. The freezing REFRIGERATION 163 TABLE XX Dimensions for Fig. 68 CAPACITY n TONS ICE A B c D E p G H J K L M N o p Q R s T 2 47 28 17 10 18 10 10 28 12 8 18 16 20 6 9 16 5 12 10 5 48 42 17 10 82 10 10 42 13 8 32 16 20 6 9 16 5 12 10 8 61 34 19 12 24 12 10 34 22 8 24 16 20 6 10 16 5 12 10 10 72 34 21 15 24 15 10 34 26 10 24 16 20 6 10 16 5 12 10 12 72 38 21 15 28 15 10 38 26 10 28 16 20 6 10 16 5 12 10 15 78 44 24 18 34 18 10 44 26 10 34 10 20 6 12 20 5 12 10 18 80 50 24 18 40 18 10 50 26 12 40 16 20 6 12 20 5 12 10 20 87 46 25 18 36 18 10 46 32 12 36 16 22 6 12 20 5 12 10 25 89 54 25 20 44 20 10 54 32 12 44 16 22 6 12 20 5 12 10 30 92 62 25 20 50 20 12 02 32 15 52 16 22 6 12 20 5 12 10 35 93 70 26 20 68 20 12 70 32 15 60 16 22 6 12 22 5 12 10 40 93 79 26 20 67 20 12 79 32 15 6!) 16 22 6 12 22 5 12 10 50 144 54 35 25 39 25 15 54 64 20 44 20 22 6 12 24 5 12 10 60 145 62 86 25 47 25 15 62 64 20 52 20 25 6 12 24 5 12 10 75 160 79 46 80 64 30 15 79 64 20 69 20 25 6 12 27 5 12 10 100 173 59 54 80 80 30 15 95 64 25 85 20 25 6 12 30 5 12 10 150 247 95 76 40 80 30 15 95 96 35 85 20 25 6 12 30 5 12 10 200 333 95 100 40 SO 30 15 1)5 128 45 85 20 25 6 12 30 5 12 10 THROU6H D/JT/LL/nG ROOM Fig. 69. Prick 10-Ton Plant. Fig. 70. Frick 35-Ton Plant. 166 REFRIGERATION apparatus of the plate plant consists of a tank divided into compart- ments and fitted with freezing plates; a forecooling tank with coils; a crane and hoists; a tilting table; cutting-up saws; water filters and pipe connections for supplying water. Mac 5/OE. JLLLVATION dffl ffeezi'ncf Tank fee. Pt.An Fig. 71. Frick 100-Ton Plant. There are two methods of operation. The first method, which is known as the dry-plate system, is that in which ammonia gas is ex- panded directly in pipe coils that make up the freezing plate, the spaces between the pipes being filled in with wood or other material to form a smooth freezing surface on the two sides of the coil. In the wet- 168 REFRIGERATION REFRIGERATION plate system, brine is used and is closed up in a metal cell or tank from 4 to 6 inches thick and of the size necessary to form the freezing plate. This imprisoned brine is kept cold by ammonia expanding in a pipe coil placed in the tank. In some cases the plate and the attached blocks of ice are removed from the tank bodily, by disconnecting the pipe connections to the expansion coil after drawing off the am- monia in the coil. Where this is done, provision is made to drain the cold brine into another of the hollow plates which is immediately placed in the tank so that the freezing process goes on while the ice is being detached from its plate and disposed of. In another form of the wet-plate system the cells forming the freezing plates are designed to have cold brine pumped in at the top Fig. 74. Coil Plate with Wood Filling. and run down in a thin sheet over the inner surfaces of the plate and collect at the bottom of the cell, from which it is drawn off by the brine circulating pump. The great difficulty with all applications of the wet-plate system is that of making the cells tight. It is almost impossible to roll large plates which will not show up small leaks and a few such leaks turn enough brine into the water to ruin the ice. This difficulty of obtaining tight plates stands in the way of freezing by expansion of ammonia direct into a cell on the sides of which the ice is frozen. The cells can easily be made tight against the es- cape of brine under small difference of pressure but to make them tight enough to retain expanding ammonia gas is impossible except at 170 REFRIGERATION prohibitive expense. In the dry-plate system, pipe coils can be made to hold the gas where care is taken in welding the pipe and in making the joints; the chief difficulty has been that of getting suit- able surfaces against which to freeze the ice, while using the coils. In small plants the ice is allowed to freeze directly to the coils and is then cut loose, but this is wasteful of ice and of labor. Wood filling between the pipes of the coils is not stable enough to with- stand the rough usage to which the plates are subjected, and on this account smooth metal plates are bolted on each side of the coil and its wood filling, as shown in Fig. 74. Plates of this kind are placed in the compart- ments of the freezing tank about 30 inches apart on centers, and the tank is filled with water to within about 9 inches of the top of the plate. As the am- monia is expanded directly into the coil, the cooling is very rapid and on this ac- count great care must be taken in feeding or the ice will be frozen before the air and impurities have had time to be separated out. Another difficulty with the dry-plate system of operation is the fact that the ice forms thicker where the ammonia is fed into the coil than over the rest of the plate so that the block is not of uniform thickness. These difficulties are avoided to some extent by expand- ing the gas into a forecooler before turning it into the plate coils, but after all the dry plate is difficult to operate successfully. This difficulty is offset, at least partially, by the fact that the dry- plate apparatus is comparatively inexpensive to install while the wet- plate system with its brine storage tank, brine pump, and extra piping for the brine is expensive to install and somewhat extravagant in Fig. 75. Cell Plate. REFRIGERATION 171 operation on account of the extra transfer of heat to the brine. Fig. 75 shows a cross section of a cell such as is used with the wet- plate system. The quantity of brine in the cell acts as a kind of fly-wheel or balancer for the system and aids materially in regula- ting the temperature to the uniform standard required for making good ice with the water available. Different waters require different brine temperatures, more time being allowed where the water is impure. Practice with the given plant is the only way to determine the best temperature for getting good ice in a given case. Slabs of ice frozen on the plate system may weigh from 1 to 10 tons, the maximum dimensions being about 16 x 9 feet by 12 inches Jec ional End View Sectional -Side View Fig. 76. Eclipse Plate System. thick. In the United States the cakes are usually about 14 x 8 feet by 11 inches. During the process of freezing the impurities elimi- nated and thrown out settle to the bottom and may be washed out before refilling the compartment with fresh water, if considered neces- sary. Heavy traveling cranes are used to lift the ice when frozen and transport it to the cutting floor to which it is lowered from the vertical position by the tilting table. Power-driven gang saws are now made to cut the cakes up automatically into any size blocks desired, and chain conveyors take the blocks from the table to the storage room or loading platform. The whole process of lifting is done as readily as one lifts a single can from a tank, everything being done by power. Fig. 76 shows a sectional elevation of a plate plant REFRIGERATION 173 built on the Eclipse plan used by the Frick Co., while Figs. 77 and 78 show plan and sections in outline for a 25-ton plate plant as designed by the Vilter Mfg. Co., for electric-motor drive. The tfacuyft fonn ROOM ancCLne/ Fig. 78. Front and Side Views of Vilter Plate Plant. drawings, it will be noted, show complete details and dimensions, while the notes are self-explanatory. There is only one bulkhead in the freezing tank, so that only two compartments are formed. It would be better to increase the length of the tank so that additional bulkheads could be inserted to divide the tank into eight compart- ments, each containing four double-face cells as required to freeze a day's pull of ice. 174 REFRIGERATION STORING AND SELLING ICE Distribution is the one great problem of the ice manufacturer. The product of his factory is perishable and cannot be held except at considerable expense. It must be disposed of as made if the ledger is to show a profit. Some manufacturers, it is true, find it advisable to have a smaller plant than required to meet the demands of the summer trade and arrange to run all the year round, storing up the ice made during the winter so as to have it available when needed. The cost of such storage is about as much as the interest on the larger plant, and there is considerable loss of the ice put in store unless it is refrigerated. This necessitates using part of the capacity of the machine on the cooling coils of the storage rooms. Then again there is no opportunity to overhaul the plant when run continuously and the item of depreciation is larger than it should otherwise be. On the other hand the best machine and the wisest manager cannot regulate production to exactly meet demand, for two successive summer days may bring very different demands for ice. Some days the manager has ice melting on his hands or his machine killing time, while at other times he sits up nights wondering where he is going to get the ice. All things considered it is best to store a moderate amount of ice and have a medium-sized plant, arranging things so that there will be opportunity to overhaul, repair, and repaint the system during the winter. Ice plants, then, are usually provided with a temporary storage room and a larger room for permanent storage. Any over- plus of production from day to day goes into the small storage room and in seasons of very light demand practically all^the output will go into the large store-room. In most cases, and wherever possible, it is best to have the storage rooms on a floor level lower than the top of the tank so that the ice can be passed by chute to the stores. Otherwise conveyors are used, these being of several forms, but all built on the endless chain plan. A chain having catch lugs passe? along a slot in the floor of the slide or chute and carries the ice up to the storage room. In storing large quantities of ice, as in plants where fruit and produce cars are iced, it is necessary to pack the ice in tiers and for more than two tiers some form of hoisting appa- ratus should be used in the storage room. About 50 cubic feet of space are allowed per ton of ice to be stored, and 1 running foot of If- inch brine piping should be allowed for every 6 to 10 cubic feet of REFRIGERATION 175 space, depending on the latitude and the size of the room. Owing to the low temperature of the ice, it is safe to allow at least one- third less pipe-cooling surface than is provided for ordinary stores. A temperature of 28 degrees is ample to prevent melting but some authorities prefer to carry as low as 22 degrees, for they consider the low temperature keeps the ice firm. Methods of packing ice vary, some preferring to allow space be- tween the blocks for ventilation and others packing the blocks close to- gether and exactly over each other in successive tiers i.e., no break- ing of joints with packing material provided where the store-room is not to be cooled artificially. Where spaces are left, wood spacing strips are placed between tiers and blocks in all directions. If hard dry ice is put in store at or below freezing and the temperature is kept down or, even packed simply, without cooling coils in the rooms it will come out in good condition without the strips, which are little used in the United States. The rooms should have ven- tilators so that all foul, damp air may be removed, and good drainage should be provided. In permanent store-rooms good insulation should be provided and this is done almost universally in ice plants, there being no need of packing materials except in the case of natural ice storage. Materials used for such purpose are hay, rice straw or chaff, soft wood shavings, sawdust, and similar substances. About six inches of this material is packed around the walls in storing ice where cooling coils are not used. Also a good thick layer is placed on top of the upper tier. When coils are used they should be placed in racks hung from the ceiling and provided with drip pans having proper drainage connections to the sewer. In some cases it is neces- sary to place the coils on the walls of the room. Where ice taken from the stores is to be used in icing cars, it is put through a crusher and sent by barrow or chute to the car box. In delivering ice to the retail trade, care should be taken to be regular and systematic in all arrangements and dealings with customers. Go to the same house at the same time on the day when it is known that ice is wanted and don't go any other time. Endeavor to have the men satisfied so that they will stay on the job long enough to learn their business and the little traits of the customers. Have everything about the wagons and the men clean, and use tested scales with the coupon system of selling. Let each team have its regular 176 REFRIGERATION route and let the drivers understand that they are responsible for what happens on their respective routes. In shipping small lots of ice, blocks may be packed in sawdust in bags. Where car loads are to be shipped get refrigerator cars if possible. If not, pack the ice in an ordinary car with sawdust using heavy paper around the blocks after they are in position so as not to foul the ice with the dust. The paper also helps to keep out heat. Suitable hand tools should be provided in plenty as they are worth their cost several times over in saving the time of drivers and help, not to speak of insuring accurate cut of ice which means less loss and better satis- faction to customers. ICE=PLANT INSULATION The most important piece of insulating work in an ice plant is on the freezing tank. Aside from this the ammonia line from the tank to the compressor as well as the suction headers, where ex- posed, and all brine circulation lines should be insulated. The steam lines should be covered to prevent undue radiation. For this purpose a good magnesia covering should be employed. For the ammonia and brine lines, cork pipe covering should be used. Cork is now prepared for such work with parts made to fit all pipe fittings, as well as any bends and turns. Next to the tank in impor- tance the ice storage rooms should be protected with insulating ma- terial, more or less care being used in this work depending on the use to which the room is to be put. For a temporary small storage it is not worth while to spend a large amount of money, but for permanent storage rooms the insulation should be done well. This may be done in any of the ways usual for cold storage rooms, care being taken to provide drainage for any water that may result from melting. Owing to the dampness, cork insulation finished with cement plaster is about the most satisfactory material for an ice storage room. On a concrete foundation, from 4 to 6 inches of Acme corkboard is laid in cement, coated with asphalt, and finished over by laying 3 inches of concrete having cement finish on top. The ceiling and walls are insulated with from 3 to 6 inches of corkboard laid in Port- land cement, with asphalt between layers, and finished with Port- land cement plaster. This method of insulation gives a permanent water-proof finish and is effective and durable. REFRIGERATION 177 Tank Insulation. There are a number of ways to insulate a tank and various insulating materials that may be used, but planer shavings, when perfectly dry, give about as good insulation as can be had at moderate cost. Cork is better but is more expensive, though by using it in granulated form for the sides of the tank the expense is reduced considerably. Other manufactured products are too expensive, as a rule, in proportion to the benefit to be derived from their use. Sawdust lies so close that there is not enough dead air space, and takes up water readily so that its insulating properties become greatly impaired. Ground tan bark is subject to the same objection. Since good insulation cuts down operating expenses, it is economy to use as thorough insulation as circum- stances permit. This does not necessarily mean the most expensive job that can be had. Where shavings are used, the thickness be- neath the tank should not be less than 12 inches and on the sides it should be at least 10 inches, greater thickness being desirable if space can be had. Matched flooring is used for partitions, with tarred paper laid on the flooring when in place to make it air tight. A simple construc- tion is obtained by coating the outside surface of the tank with as- phalt or pitch, and pack shavings between it and the air-tight wall built up of matched boards on studs set on 18-inch centers. In the case of metal tanks, which are used almost universally in preference to wood, a layer of pitch and 1 or 2 inches of shavings should be laid on the floor so as to form a cushion on which the tank sets, thus pre- venting possible strain due to irregularities of surface. Although wood tanks have been in use for some time and cement has more recently come into use as a material for tank construction, neither of these ma- terials may be considered as satisfactory in all respects as the steel tank. More framing must be used with the wooden tank to withstand the pressure of the water and great care must be taken to make the cement or concrete tank waterproof. For plate plants, the freezing tanks are commonly constructed of wooden compartments, the framing being made ample to withstand the pressure. Where the water is bad and it is necessary to wash out the freezing compartments often, it is well to have each compartment insulated from the others. Cork insulation is largely used on tanks, owing to its waterproof qualities and the fact that it requires much less space than other in- 178 REFRIGERATION sulation. Where this material is used, the foundation on which the tank is to be made is constructed of concrete, preferably laid on cinders, on top of which Acme corkboard is laid in Portland cement. This insulation is from 3 to 6 inches thick and is coated on top with asphalt, the tank being set directly in the asphalt. The sides are then insulated with Acme or Nonpareil board laid on in cement, with asphalt between layers and finished outside with Portland cement plaster. This insulation is usually about 6 inches thick and is quite as effective as the thicker insulating walls made with other materials. Where it is desired to reduce expense, and space is of no particular account, regranulated cork may be used around the sides packing it between the tank and a wooden wall, as in the case of shavings. GENERAL COLD STORAGE After ice-making, cold storage is the most important and widely used application of mechanical refrigeration. By means of low temperatures, fruits and perishable products may be preserved dur- ing periods of plenty until such time as the supply falls off and the demand increases, when the products, coming from store in good condition, may be sold at a profitable figure. Thus decay is pre- vented, the product is preserved in its natural form quite another matter from goods preserved by drying or salting and the dealer is able to make a profit. The producer at the same time is able to market his crops to better advantage than when all the goods have to be sold on a glutted market. Owing to the fact that the period of consumption for any given product is greatly increased, produc- tion can be increased accordingly with a corresponding increase in profits to the farmer and fruit grower. The owner of perishabb goods is not compelled to market them for fear that they may spoil but may choose his market and hold his goods irrespective of time and distance. For these reasons, cold storage establishments are coming into use the country over. Refrigerator cars make possible the shipping of goods to distant markets where good prices prevail, and in case markets are not satisfactory in the country of , production, goods may be exported in carefully constructed storage rooms on board the large steamers. Thus it is possible to place perishable products in the hands of consumers in such quantity and at such time as the REFRIGERATION 179 owner desires so that the market conditions are steady and the con- sumer is able to obtain articles of food that could not be had without the aid of refrigeration. Meats produced in Australia are shipped to England and fruits grown in California are sold in New York and Europe. On a bleak winter day one may have the freshest vege- tables and fruits on his table, in any part of the world. Peaches grown in Australia have been served at millionaire feasts in New York during the months of January and February. Apples, butter, eggs, and other such products are sent abroad by the ship-load. In a word there is no perishable product that cannot be handled to advantags by means of refrigeration. But food products are not the only things kept in cold storage. Many articles not classed as perishable are kept at low temperatures. Furs, for example, are placed in storage to prevent damage from moths and to preserve the skins. On coming out of store the luster of the furs is greatly improved, the articles becoming more valuable in some cases than before storage. Clothing and woolens are also stored. Dried fruits are kept during the warm months of summer. Seedsmen find it profitable to store their stock so as to prevent deteri- oration by the seed drying out, owing to evaporation of the oils. Thousands of dollars are saved in this way, as the germinating value of the seed may be kept unimpaired and the seedsman has good insurance against failure of any year's crop. Peanuts, walnuts, and other like goods are carried through the summer and, during ^he winter, potatoes and cabbage are put in store. Each year some new product is added to the list of articles carried in cold stores and there seems to be no limit to the growth of the ever-widening field for the cold storage industry. Conditions for Preservation. In any cold storage room, three things are essential if the goods are to be cared for properly. The air in the rooms should be renewed frequently by a good system of ventilation; all air entering the rooms should contain an amount of moisture suitable to the temperature and the goods carried; and the temperature should be suited to the given products, not varying outside of certain limits. A hygrometer is used for measuring the amount of moisture in the air and this should be done accurately as too little moisture will cause the goods to be damaged by evapora- tion, while too much moisture will cause mold to be formed. One 180 REFRIGERATION of these evils is about as bad as the other. Products that are dried to the mere fibre are of no value for food and those that are musty are not palatable. The lower the temperature, the less moisture the air can carry and if the air is brought into the rooms with more moist- ure than corresponds to the amount it can carry at the temperature of the room, the excess will be condensed and form ice on the pipes and other places. This frost should be kept off the pipes where pipe coolers are used in the rooms as far as possible, as ice is a good insulator and prevents the heat being absorbed by the gas or brine in the pipes. The temperature is entirely under the control of the operator and can be raised or lowered at will by circulating more brine or expanding more gas, according to the system used. There is a wide difference of opinion among authorities as to the temperatures required for the best results with different products. A number of conditions complicate the question so that, except for a few of the articles most handled, no definite rule can be laid dow r n. Where- the goods have been shipped, consideration must be taken of the temperature before and during shipment and particularly whether or not the temperature has been excessively high or low at any time during shipment. Furthermore the condition of the goods must be taken into account, and the time they are to be kept in store, as well as the purpose for which they will be used when taken out of store. Thus for example, if decay has set in with a shipment of peaches which is being unloaded into the storage rooms and they are to be kept only a short time and then disposed of at whatever the market will stand, it would be well to get the temperature down as quickly as possible to that required for keeping this fruit the lower working limit being preferable. On the other hand if it is a shipment of sound fruit that is to be kept some time, one could do better to work at a higher temperature and cool the fruit more gradually, it being re- cognized, of course, that under such conditions the refrigeration can be done more economically. In both these cases, the moisture in the air in a given cold room would have a considerable bearing on the course pursued. Where certain rooms are used for commission trade with goods being taken in and out at frequent intervals, the refrigeration must be more effective than for the same class of goods stored over a long period of time. Altitude and local conditions affect the case to a REFRIGERATION 181 TABLE XXI Temperatures for Cold Storage of Products PRODUCTS DEO. F. PRODUCTS DEO. F. Apple butter 42 Apples ' 30 Asparagus 33 Bananas 45 Beans (dried) 45 Beer (bottled) 45 Berries, fresh (few days only) .... 40 Buckwheat flour 42 Butter 14 Butterine 20 Cabbage 33 Canned fruits . . 40 Canned meats 40 Cantaloupes (one to two months) 33 Cantaloupes (short carry) 40 Carrots 33 Caviar 36 Celery 32 Cheese (long carry) 35 Chestnuts 34 Chocolate dipping room 65 Cider _ 32 Cigars 42 Corn (dried) 45 Corn meal 42 Cranberries 33 Cucumbers 38 Currants (few days only) 32 Cut roses 36 Dates 55 Dried beef 40 Dried fish 40 Dried fruits 40 Eggs 30 Ferns 28 Field grown roses 32 Figs 55 Fish, fresh water (after frozen). . . 18 Fish, nt frozen (short carry) .... 28 Fish, salt water (after frozen) .... 15 Fish (to freeze) 5 Frogs legs (after frozen) 18 Fruit trees 30 Fur and fabric room 28 Furs (undressed) 35 Game (after frozen) 10 Game (short carry) 28 Game (to freeze) Ginger ale 36 Grapes 36 Hams (not brined) 20 Hogs 30 Hops 32 Huckleberries (frozen, long carry) Japanese fern balls Lard Lemons (long carry) Lemons (short carry) Lily of the valley pips Livers Maple sugar Maple syrup Meat, fresh (ten to thirty days) . Meats, fresh (few days only) Meats, salt (after curing) Mild cured pickled salmon Nursery stock Nuts in shell Oatmeal Oils Oleomargarine Onions Oranges (long carry) Oranges (short carry) , . Oxtails Oysters, iced (in tubs) Oysters (in shell) Palm seeds Parsnips Peach butter Peaches (short carry) Pears Peas (dried) Plums (one to two months) Potatoes Poultry, (after frozen) Poultry, dressed (iced). ........ Poultry (short carry) Poultry (to freeze) Raisins Ribs (not brined) Salt meat curing room Sardines (canned) Sauerkraut ... casings Scallops (after frozen) Shoulders (nt brined) Strained honey Sugar Syrup Tenderloin, etc Tobacco Tomatoes (ripe) Watermelons (short carry) Wheat flur Wines 20 31 40 38 60 29 20 45 45 30 35 43 33 30 40 42 45 20 32 34 50 30 35 43 38 32 42 50 33 45 32 34 10 30 28 55 20 33 40 38 20 16 20 45 45 45 33 42 42 40 42 50 182 REFRIGERATION certain extent and the best rule for the practical man is to study his own plant and the conditions prevailing; being careful particularly to see that his thermometers are correct so that, when he finds some unusual temperature the best for a certain article in his plant, it will not be due to error in his instrument. As a rough guide to be used where no other information for the particular plant is available, Cooper gives the temperatures shown in Table 21, which, however, should be used with caution. Other authorities give figures varying anywhere up to 10 degrees from the data in this table, but on the whole the table may be considered about the least arbitrary of all and is based in the main on figures taken from practice. INSULATION In considering this topic, the student should recall the discussion of heat in the first part of this paper, where it was shown that heat is transmitted in three ways by convection, by radiation, and by conduction the transmission taking place in all three of these ways in cold storage plants. Owing to the low temperatures, however, there is comparatviely little transmission in storage rooms by radia- tion, and practically all heat passes into the rooms by the process of conduction. Where air space insulation is used there is consider- able transmission by convection currents in the manner explained already and this is the principal reason why air space insulation is inefficient as compared with the other methods of insulating. When it is considered that from one-half to seven-eighths of the refrigera- ting work in a storage plant is required to remove the heat that leaks through the walls, the importance of good insulation is seen. The increase in cost for insulating work well done is insignificant as compared with the- resulting decrease in operating cost. On the other hand, the cheaper insulation is less permanent and demands a larger amount of coal to drive the refrigerating machinery to keep out the heat from the rooms, which could have been excluded with effective insulation. If a perfect insulation could be had there would be no need of refrigerating machinery except to cool the rooms down in the first place and to remove any heat admitted by opening doors for taking goods in and out of store. Such a condition is impossible, however, as, owing to the nature of heat, it is not possible to wholly prevent REFRIGERATION 183 an increase in the rate of vibration in a body that has contact with a hotter body in which the rate of vibration is more rapid. Differ- ent rates of vibration tend to become equalized in adjacent bodies just as naturally as water tends to run down hill. Different mater- ials have varying capacities for hindering or retarding such vibra- tion but no matter what the material or how thick the walls, some transmission will take place until finally the temperatures on the two sides of the wall will be equal. During the past cen- tury scientists have made many laboratory tests as to the heat- transmitting qualities of various insulating materials, but in most cases these results are of little value to refrigerating men on account of the fact that the experiments were mostly performed with high differences in temperature and dry-air conditions, as for the insula- tion of steam pipes where the temperature difference is at least 275 degrees. These conditions do not apply for the low temperatures and moist air met in refrigerating establishments and it is usually the case that a good insulator, for the conditions named, is a decidedly poor one under the conditions prevailing in cold storage establishments. Non=Conductors. To be a good insulator a material should have poor conducting power at low temperatures or with small tem- perature differences, and should have a high specific heat and high specific gravity. The higher the product of the two last items, the more valuable, other things being equal, is the insulation. As an example take a cubic foot of air and a cubic foot of flake charcoal used as insulation. The air weighs 0.0807 pound and since its specific heat is 0.237 it will require 0.0191 B. T. U. to increase its temperature 1 F. For charcoal, the figures for weight, specific heat, and heat required for 1 degree rise of temperature are 11.4, 0.242 and 2.758 respectively. In case, then, the machinery should be stopped for any reason, the insulating material would have to be heated up be- fore the temperature in the storage rooms could rise, the amount of heat absorbed by the insulation itself being in proportion to the pro- duct just mentioned. In other words for each degree rise in temper- ature in the rooms the cubic foot of air must absorb only 0.0191 B. T. U. while the charcoal must absorb 2.758 units. This is the reserve power of the insulation and is of considerable importance, though it may be overbalanced by the conductivity of a materal if this be high. 184 REFRIGERATION TABLE XXII Non-Conducting Power of Substances NON-CONDUCTORS ONE INCH THICK NET CUBIC IN. OF SOLID MATTER IN 100 HEAT UNITS TRANS- MITTED PER SQ. FT. PER HOUR Still air 43 Confined air 108 Confined air = 310 203 Wool = 310 4.3 36 Absorbent cotton Raw cotton Raw cotton Live-geese feathers = 310 Live-geese feathers = 310 Cat-tail seeds and hairs 2.8 2 1 5 2 2 1 36 44 48 41 50 50 Scoured hair, not felted Hair felt 9.6 8 5 52 56 Lampblack = 310 Cork ground 5.6 41 45 Cork solid 49 Cork charcoal = 310 White-pine charcoal 310 5.3 11 9 50 58 Rice-chaff 14.6 78 Cypress ( Taxodiuin) shavings 7 60 Cypress ( Taxodium) sawdust Cypress ( Taxodium} board 20.1 31.3 84 83 Cypress (Taxodium) cross-section Yellow poplar (Liriodendron) sawdust... Yellow poplar (Liriodendron) board Yellow poplar (Liriodendron) cross-sec.. "Tunera" wood, board Slag wool (Mineral wool) Carbonate of magnesium 31.8 16.2 36.4 30.4 79.4 5.7 6 2 3 145 75 76 141 156 50 50 52 "Magnesia covering," light "Magnesia covering," heavy 8.5 13.6 58 78 Fossil meal =*= 310^ 6 60 Zinc white 310 8.8 72 Ground chalk = 310 Asbestos in still air Asbestos in movable air Asbestos in movable air = 310 Dry plaster of paris = 310 Plumbago in still air Plumbago in movable air = 310 Coarse sand = 310 Water, still 25.3 3 3.6 8.1 36.8 30.6 26.1 52.0 80 56 99 210 131 134 296 264 335 345 290 251 Glycerin, Castor oil, ' Cotton-seed oil, " Lard oil, " Aniline, ' Mineral sperm oil, " Oil of Turpentine, " 197 136 129 125 122 115 95 RFFRIGFPATION 185 Ordway gives the data in Table 22 for the non-conducting power of various substances, the figures being determined from insulation tests on steam pipes where the difference in temperature on the two sides of a 1-inch thickness of the substances was 100 degrees. Where not stated in the table, the source of heat was water at about 176 F., but in some cases steam at a temperature of 310 F. was used. It will be noted in the table that still air is one of the poorest conductors of heat, but if a body of confined air is arranged to allow the set- ting up of convection currents as before mentioned, the air is ren- dered a much better conductor. It is to prevent these currents, that the air is confined in spaces small enough to keep it still, and the value of most insulators is determined by the effectiveness with which they prevent the air from moving by separating it into such small particles that its viscosity is too great to allow of movement. Experiments have been made to determine the amount of heat conduction through a vacuum, with results that tend to indicate a much smaller rate of conduction than through still air. In laboratory experiments liquid air when placed in a glass vessel surrounded by a vacuum retained its liquid form for several days, but no success- ful scheme for applying a vacuum in practical insulation work has yet been evolved. It has generally been assumed that the rate of heat transmission is in proportion to the difference of temperature on the two sides of a wall and inversely proportional to the thickness of the material; but recent experiments go to show that the rate of transmission increases w T ith increase of temperature difference and that it does not decrease exactly in inverse proportion with increase of thickness. As most coefficients of heat transmission are deter- mined with a temperature difference of 1 degree, it is obvious that they cannot be correct for much larger differences and should in fact be increased by at least 50 per cent in practical calculations. With the constant tendency toward the use of lower temperatures in cold storage and general refrigeration work, this matter becomes of first importance. In some cases the temperature difference may be as much as 90 F. Aside from the loss, incident to using poor insulating material by reason of the heat that must be removed, there are other disad- vantages that must be taken into consideration. The heat admitted through poor insulation raises the temperature of the outer parts of 186 REFRIGERATION a room near the walls so that it is impossible to keep all parts of the store at the same temperature. This is undesirable in many respects and for fear of freezing the goods near the cooling pipes or air ducts, it often happens that the temperature is carried too high for best results. On the score of conductivity, the choice of insulators is limited to vegetable and animal substances. In selecting one of these a number of practical considerations must be taken into ac- count. The material should be odorless so as not to taint the goods and, as far as possible, should be proof against moisture. In case it gets wet, it should not be of such nature as to rot easily. It should have no tendency to spontaneous conbustion and should be elastic so that it can be packed er,ough to avoid settling. Aside from these things, the material should be reasonably cheap and easy to apply in general work, and should be vermin proof. As far as pos- sible the insulation should be waterproof and fireproof, but as none of the vegetable and animal materials have these qualities, special measures must be taken to make the finished work proof against fire and water. This is done by masonry work and cement plaster. For practical purposes, the choice of an insulating material will be restricted to cork, dry shavings, mineral wool, or hair felt. Tarred papers are used on the board work used to retain the insula- ting material in place and each of the materials named may be used in a number of combinations and forms. In brick buildings it is customary to use a hollow tile course in the walls, or rather to lay such tile in the wall so as to form a moisture barrier. Two such arrangements are shown at the top of Fig. 79, which shows a number of composite insulation structures, tested by the Fred W. Wolf Co. Several other combinations arranged and tested by Madison Cooper are shown in Fig. 80. In both these illustrations the figures at the right represent the number of B. T. U. transmitted per square foot per day per degree difference of temperature. It will be noted that in all cases the air-space insulation makes a poor showing as com- pared with other forms, especially in view of the care and attention necessary to construct it properly. It is almost impossible to get workmen that will give proper attention in putting together the timber work for such insulation so that it will be tight, and much of the complaint with cold stores in the past has been due to air leaks resulting from such neglect. 3" SCRATCHED HOLLOW TILES. 4" SPACE FILLED WITH MINERAL WOOL. CEME.HT PLA 5 TER. m B.T.U 0.70 FLOOR CONSTRUCTION -FIREPROOF. -3"FRAME PLAN OF WALL. DRY CIHDER F/tLIHG. DOUBLE 5P/ICE HOLLOW TILE ARCHES. \^ CEME/1T PLASTER. BRICK WALL. IR SPACE. Va"0.&M. BOARDS. WATERPROOF- PAPER. 4-5PACE FILLED WITH MINERAL WOOL. /"AIR SPACE. 7 /eD.e.n BOARDS. SIDING. WATERPROOF PAPER. 7/s-BOARDS. Z"X6" STUDS-16" O.C. 4" SPACE FILLED WITH MINERAL WOOL. WATERPROOF PAPR. 7/a'BOARDS. ?"AIR SPACE. 0.70 1.74 2.90 DOOR 7/a "BOARDS. WATERPROOF PAPfR. 2" SPACES FILLED W/TH MINERAL WOOL. JOISTS. 7/a "BOARDS. WATERPROOF PAPER. Vt PLANK FLOORING, ^r'/a" BOARDS. /WA TERPROOF PAPERS. " ~-4"5PACe FILLED WITH ....... ...... ....^ Km*-* ..-.-^-. - ...... -i.tfc.YM. ' - ^ MINERAL WOOL. -^m^^^r^^i^mr:--^^, r "- ; , 'fe^-^^ ^"BOARDS. .':^-i .V-:v''^;-Sr.^S;^i?v--'.-.--: -v- ^Pf^^ ^"/r^" BEDDED m DRY ^v^V^'/f'v-^^^^K^-^'-V^:' -. v * , !cr- '-.^t C/HDER FILLII FILLING IS "HIGH. FLOOR CONSTRUCTION. Fig. 79. Composite Insulation Tested by Fred W. Wolf Co. E.I7 I.9E V&"D.&N. BOARDS. 14- - '/ 2 AIR SPACES WATERPROOF PAPERS. Ve'O.&M.BOAROS. ET.U 3 1 6 NO.l. j ^ i ^^^^=^*^-^^^^- '0. N0.8. ..-. ; -;- ...:...'..:. . . : N0.3. Vfr /;//? SPACES WATERPROOF PAPERS. D.&M. BOARDS. - We" D.&M. BOARDS. ' W.KPAPfR. 4"MIHERAL WOOL. W.P.PAPfR. 7/e' & &M. BOARDS. 4.27 3.46 N0.4. i" 0.$ fit. BOARDS. ^T", -W.P.PAPfR. V&'fr-4"MILl SHAVIHGS, 'gZ&L*^ W.P.PAPfR. Va'D.&M.BOARDS. Z.95 N0.8.. NO. 10. JSO.Il. 7/a'D.8.M. BOARDS. W.P. PAPfR. 3"5HEfT CORK -/"5HT5. W.P. PAPER. >/a"O.&M.BOARDS. 7/a"D.&M.BO/}RDS. W.P.PAPfR. WD.&M.BO/tRDS. W.P. PAPfR. Va"D.&M. BOARDS. W.P. PAPER. 3 "HAIRFEi. T - 1" SHEETS. - W.P. PAPER. . - WD.&M.BOffRDS. 7/e" D.8.M. BOARDS. W.P.PAPfR. I" HAIR FELT. W.P. PAPER. Va'D.SiM.BOARDS. W.P.PAPfK. I" SHEET CORK. W.P. PAPER.. 7/a ">. &M. BOARDS. "^>.&.M.BOARD5. /"AIR SPACE.. s^r W.P.PAPER. ^ % "/?. SURFACE BOARDS. 2" HAIR FELT. CORK OR MINERAL WOOL BLOCK. WATERPROOF PAPER . Va" SURFACE BOARDS. WATERPROOF PAPER BA5EMENT FLOOR "Va'iD.&M. BOARDS. WATERPROOF PAPER. 7 /e" SURFACE BOARDS. HAIR FELT. CORK OR MINERAL WOOL BLOCK. 'fVLLED JPACf. WATERPROOF COATING. DAMP COURSE. SECTION OF INSULATION FINISHED JAMB. /"CORK, HAIR FELT OR MINERAL WOOL BLOCK. WATERPROOF PAPER. 13/4." FRAME. DOOR BRICK WALL PLAN OF INSULATION Fig. 81. Cooper's Method of Insulating Buildings. 190 REFRIGERATION Various methods of applying insulation to buildings are in use. Fig. 81, illustrating the construction designed by Madison Cooper, may be considered as representative of the best modern practice for ordinary cold storage buildings. The walls are made waterproof with asphalt or similar material; the filling material, either shavings, granulated cork, or mineral wool, is placed against the wall. The sheathing and paper are arranged in courses inside as shown in the figure. An 8-inch filled space with 4 inches of sheathing etc., gives the insulation for 30 degrees. A total thickness of 13 inches is about right for 20 to 25 degrees, and for sharp freezers the filled space should be 10 inches with an additional thickness of sheet material. This form of insulation is compact and durable, the indestructible mater- ials such as waterproof paper, sheet cork, mineral wool block, etc., be- ing placed inside where the conditions are most severe. In many storage houses constructed within the last five years, sheet cork is used exclusively, being laid in cement directly on the brick walls in one or more layers as desired and finished over inside with waterproof cement after the manner already mentioned for ice storage rooms. In packing any filling material, due regard should be had to getting it compact enough to preclude the possibility of settling, but at the same time not too dense, especially in the case of those sub- stances which are fairly good conductors in the natural state. Where the building regulations of cities require fireproof construction, the problem of insulation is much complicated and it is difficult to con- struct any effective insulation at moderate cost. About the most practical construction is the use of corkboard cemented direct on the brick or tile walls and ceilings as already mentioned. Plaster-of -Paris blocks have been tried as a fireproofing over the filling material but with poor results as the blocks give way in fire and let the filling fall out. Especial care must be taken to insulate all steel I-beams and other structural metal parts in fireproof structures, as the high conducting power of the metal will work havoc with insulation other- wise well constructed when these beams and columns are neglected. This and the other difficulties met in fireproof structures make the insulation of such buildings much more expensive than for ordinary structures and it is not generally believed that this expense is justified, except in special cases, as where furs and valuable garments are carried in store. Other goods generally carried are not inflammable REFRIGERATION 191 and most fires originate outside of the storage rooms or on account of improper electric wiring. METHODS OF COOLING In olden days, natural ice was the sole reliance of cold storage people and knowledge of the laws governing air circulation and ven- tilation was so meager that little success was had in using it. Me- chanical refrigeration has now become so w r ell understood in its pro- duction and application that there is little use for ice, even in northern climes where it is produced naturally, as the expense of harvesting taken with that of delivery is greater in many cases than the cost of making artificial ice and delivering it to the customer. This, taken with the fact that refrigeration by ice is very inefficient and expensive as compared with the direct application of cold produced mechanic- ally, places ice out of consideration as a cooling medium, except for household refrigerators. Even in this application ice is being abandoned in some quarters, where owners are able to install one of the small automatic refrigerating outfits already mentioned. For applying mechanically produced refrigeration, there are a number of methods in use, some of which are now considered obso- lete, while each of the others has its advantages and disadvantages. In primitive cold stores, gravity air circulation was relied upon for mixing and cooling the air to uniform temperature throughout the rooms; but the system proved inefficient, as most of the cooling was done by direct radiation and little or no circulation of air was induced. The unsatisfactory results had thus led to a study of direct radiation. In the first cold stores, pipes containing expanding ammonia gas or cold brine were placed directly in the rooms and the cooling produced was by direct radiation of heat from the air in the rooms to these pipes. As the results were poor, various systems were devised to improve the circulation; thus leading to the indirect-radiation system, where the coils are located in a loft separate and apart from the room and above it to one side, so that the greater height gives a greater differ- ence in density between the cold and hot air. The circulation is directed as desired by false ceiling and wall shields. Modern practice considers both these radiation systems out of date, the principal objection to the indirect system aside from the fact that circulation is imperfect, being the impracticability of intro- 192 REFRIGERATION ducing fresh air into the rooms. There are in use at the present time five systems of cooling rooms, some of which are combinations of the elementary processes. Thus we have direct expansion where the refrigerant is expanded direct in the coils placed in the rooms to be cooled, the best arrangement being that with deflecting shields, etc., for directing circulation of the air in the manner just mentioned. This method can be applied successfully in large rooms where the temperature and duty to be performed is constant, such as in brew- eries, packing houses, and large cold storage rooms; or where very Fig. 82. Direct-Expansion Cold Store. low temperatures are required as in sharp freezers for fish, poultry, etc., in which work direct expansion is desirable, the efficiency being much greater with this system than with any other. Fig. 82 illustrates a large room arranged for direct expansion, where the ammonia is expanded by the valve A into the piping B, the gas be- ing returned to the compressor through the pipe C. Fig. 83 shows a fish freezing room on each side of which is arranged a series of pipe- coil shelves through which the ammonia is evaporated. Fish are 'aid in tin trays and placed on the pipe shelves until the room is REFRIGERATION 193 filled, when the room is closed and the ammonia turned on the coils as long as necessary to freeze up the fish. As the coils are both above and below the trays and close together, the application of cold is effective and only a few hours are required for freezing. In some cases, as has already been mentioned, it is desirable to use brine circulation for cooling the rooms, the arrangement for which is shown in diagrammatic form by Fig. 84, which illustrates a system using a brine-cooling tank with the brine coils set directly in the room to be cooled. This, it will be seen, is an application of direct radiation. The system may be used to better advantage with Pig. 83. Fish Freezing Room. a brine cooler connected instead of the brine-cooling tank, as the cooling with double-pipe brine coolers is more rapid and efficient than with the tank, for reasons already stated. Fig. 85 illustrates a forced-air circulation system, using direct-expansion coils in the bunker room, which arrangement is the most modern practice. Some engineers, usually of the old-time stamp, prefer to use brine coils in the bunker room; but there is no advantage in this, as a pump and brine cooler must be employed for handling the brine. Cooling is more effective with the direct-expansion coils in the bunker room. Some years ago when manufacturers were not able to put up pipe work for direct expansion, there may have been excuse for the brine- circulation system with direct radiation, but it is now altogether out 194 REFRIGERATION of date except for those who may be wedded to "their system" to such an extent that they cannot see the light of advancement and progress. If for any reason it is desired to use brine, much more effective cooling can be had by passing the brine down through the open space of the bunker room, after coming from the cooler, in thin sheets flowing over vertical walls or with other suitable arrangement. The air is forced through the brine and cooled after which it may be passed to the storage rooms. By this process, the brine purifies the air so hat the stores are kept sweet at all times, the gases and impurities taken up from the prod- ucts in the rooms being absorbed by the brine. This system has been applied with consider- able success and about the only objection is the possibility of getting too much moisture in the air going to the rooms ; which cannot oc- cur, however, if due re- gard is given to the tem- perature used in the bunker room, so that the air leaves at about the temperature of the store rooms. Where pipe coils are used in the bunker room, calcium chloride can be used to advantage. It is placed in trays over the coils in such a manner that moisture in the air will be taken up by the calcium, forming brine that drips down over the pipes and absorbs impurities. In any system of cooling, it is important that the air be circulated so as to maintain uniform temperatures in all parts of the various rooms. Also the air must be purified or renewed at suitable inter- vals if the goods are to be kept in first-class condition. There is much difference of opinion as to how often the air should be changed and the cold-storage man must use considerable judgment in this Diagram of Brine Circulation Plant. REFRIGERATION 195 matter, as much depends on the character of the goods and the length of time they have been in store. Fresh meats and vegetable products when first put in store, give off a large amount of gases and impurities which must be removed, but after having been in store for some time there is less of this action tending to contaminate the air. Ordinarily, if the entire volume of air in a room is renewed with pure fresh air once or twice a week, good results will be had. To effect this in a proper manner it is essential that some system of Fig. 85. Diagram of Air-Circulation Plant. forced-air circulation be employed; and in fact such a system is necessary, aside from the question of ventilation, if proper circulation is to be had. Although many cold-storage men are bitterly opposed to forced- air circulation, it is generally recognized by eminent authorities that such circulation is necessary if good results are to be obtained. There is a choice between the exhaust and pressure systems but the latter is so far superior that little consideration need be paid to the exhaust system of ventilating by drawing air out of the rooms. Compara- tively little power is required for the air circulation and the results obtained where the forced-air system is properly installed are much 196 REFRIGERATION superior to the results with systems now becoming obsolete. This does not mean that small fans of the type used in offices and hotel parlors should be employed, as little advantage can attach to the use of such apparatus. A properly designed fan made of light weight, corresponding to the low speed and duty required for the slow circulation of air used in refrigerating rooms, should be used and the air should be forced through bunker cooling rooms in the manner just described, fresh, purified air being drawn in as necessary. In northern climates, it has sometimes been the practice to ven- tilate the rooms in fall and winter by opening windows and doors, but there is some question as to the advisability of this practice and it should be applied with the greatest judgment and caution. Where the outside temperature is about the same as that carried in the rooms on a bright clear day, or, better still, on a clear cold night, there can be no harm in filling the rooms with Nature's pure air. There should, however, be no guess work about the matter, and measurement of the moisture in the air and its temperature should be made carefully before "opening up." Where the forced-air circulation system is used and arrangements made to draw in fresh air as needed, there is little need for opening doors and windows and in fact, such openings should not be used in storage plants where pos- sible to avoid them, owing to the difficulty of insulating them and the fact that all necessary light can be had more cheaply by using in- candescent electric lamps. There is no objection to these lamps other than the heat cast off into the rooms and this is small indeed com- pared to the heat coming through the best insulated windows, even where four or five thicknesses of glass and air spaces are employed. Some of the most successful cold-storage houses abroad have no openings or doors in the walls, entrance being had only through the top of the building. In such cases, hoists are used to elevate the goods to the top and lower them inside the building. In the large storage houses of receiving ports in England, where cargoes of fresh meats are received from steamers, houses built on this closed plan have been most successful. Where a general line of goods is carried, as for example, in the wholesale commission trade, it is imprac- ticable to operate such a house, as a certain number of doors must be had. Such doors should be of the best possible construction and it is usually better to buy one of the patent doors on the market. REFRIGERATION 197 The manufacturers, being specialists in this line of work, may be con- sidered more competent to turn out a good door than any ordinary carpenter who may be on a construction job. In nine cases out of ten the so-called "home-made" doors constructed on the premises will give poor results and be a constant source of annoyance, owing to sticking and failure to open. REFRIGERATION REQUIRED The refrigeration required depends altogether on the effective- ness of the insulation, on the character of the goods carried, on the size and shape of the rooms, the quantity of goods, and the frequency with which goods are taken in and out of store. The amount requir- ed also depends to some extent on the temperature of the goods re- ceived and to a much greater extent on the temperature at which the rooms must be kept. When all these conditions are known, Levey gives the following instructions for finding the amount of re- frigeration necessary: 1. For the room, Calculate the exact area of the exposed surface in the walls, floor, and ceiling of the rooms in square feet, and multiply the total number of square feet by the numbers given opposite the required temperature and divide by 284,000. For rooms containing less than 1,000 cubic feet; If held at zero F. multiply the exposed surface by 1,775 5 deg. 10 " 20 " 32 " 36 " 710 535 355 265 180 For rooms containing 1,000 to 10,000 cubic feet; If held at zero F. multiply the exposed surface by 1,250 " " 5 deg. " " " " " 600 " " 10 " " " " " " " 300 " " 20 " " " " " " " 190 n f 32 a a a a a 160 " " 36 " " " " " " " 125 For rooms containing over 10,000 cubic feet; If held at zero F. multiply the exposed surface by 1,100 " " 5 deg. " " " " " " 550 a a 10 a a it K a a 275 it It 2 Q II I, tl U jgQ " " 32 " " " " " " " 140 " " 36 " " " " " " " 110 198 REFRIGERATION 2. For the stores. Multiply the amount of goods (in pounds) to be stored per day by the number of degrees the temperature is to be lowered and by the specific heat of the goods, and divide by 284,000. This will give the amount of refrig- eration in tons per day necessary to hold the goods at the required temperature. Add together the results of 1 and 2 and the total will be the amount of refrigeration in tons per day which will be required to hold the goods and the room. If the goods are to be frozen, the latent heat of freezing should be added to the heat to be removed in lowering the temperature. COLD STORAGE Handling Goods. The proper handling of products stored is a matter of great importance, both from the standpoint of preservation and profit. If goods are carelessly piled in a room so that there can be little circulation of air among the packages, deterioration is the result, particularly with those packages in the middle of the pile. Also there is much danger of crushing goods in the lower tiers, where a number of cases or barrels are packed one on top of the other. Thus, for example, in storing apples in barrels several tiers high, 2 x 4-inch scantling should be placed on the floor under the ends of the first tier and similar scantlings should be placed on the barrels be- fore laying on each successive tier. In this way, the weight is taken on the heads of the barrels and not on the bilge, and danger of crushing the fruit in the lower tiers is thereby eliminated. It is important, of course, to give attention to handling the goods in and out of store with as much facility as possible, thereby saving time and trouble, but as these matters are usually looked after by warehouse foremen who do not wish to do any work that they can avoid, it is not generally up to the manager to be on the lookout in this particular. Some classes of goods can be stored more compactly than others. It matters little how close cases of butter are piled; but articles that give off moisture, such as fruits, should not be piled too close and with too many packages in a pile. With other classes of goods, as frozen fish and poultry, for example, the more compact the goods can be stored the better, as close packing tends to check the drying and evaporating action of the air in removing the coating of ice used to prevent drying out. In taking goods from store, there is likely to be trouble from sweating, as the low temperature of the goods condenses moisture present in the atmosphere. This may have a decidedly detrimental REFRIGERATION 199 effect with some classes of goods, as eggs and fruits, so^hat precau- tions should be taken to prevent the action by cooling the goods gradually. This may be done by piling them in the receiving room with a heavy wagon tarpaulin or other similar covering placed over the pile. In fall weather, if the goods are removed in this way at night they will be all right by the next morning, but in the summer season where goods are taken out of store at low temper- atures, as much as 36 to 48 hours may be necessary to get them warmed up properly. On the other hand goods taken into storage can be handled much better both from the standpoint of econ- omy and preservation of quality by lowering the temperature grad- ually. In all mechanical and engineering lines, it is a well-recognized fact that sudden changes of conditions are effected at comparatively high cost. This is particularly true of refrigerating work, where sudden temperature reductions cost much more than the same re- duction effected gradually. In storing butter, which is usually kept at about zero F., it is highly advisable to place the trucks in a com- paratively warm room before taking them into the sharp freezers. When this is done, much less cooling surface need be used for the freezers and the results are more economical and satisfactory in every way. There are many other points in handling goods in cold stores that cannot be taken up in brief space, but it should be pointed out that the large number of failures in small storage plants, usually operated in connection with ice plants, is due mostly to the fact that several products are stored in the same room at a common tempera- ture which makes impossible good results, so necessary to permanent success in storage work. Where goods are to be stored for any length of time, there are few different products that can be stored in the same room to advantage. Thus butter requires a lower temperature than chesee, while fruits are kept at a higher temperature than the cheese. If eggs and butter are kept in the same storage room with other materials, they will soon absorb the flavor of the fruits and other things in the room. Oranges, pineapples, etc., may have the most delicious flavors, but these may not be very agreeable to the palate in butter or cheese. Such prod- ucts may be stored together for a short time with some success if great care is taken with the ventilation, but it is the practice of all 200 REFRIGERATION TABLE .XXIII Rates for Cold Storage GOODS AND QUANTITY FIRST MONTH EACH SUCCEEDING MONTH IN LARGE QUANTITIES, PER MONTH SEASON RATE PER BBL. OR 100 LBS. II * Apples, per bbl Bananas, per bunch . . $0.15 15 $0 . 12*. 10 $0.12*. 10 " $0.45 May 1 Beef, mutton, pork, and fresh meats, per Ib .00| .00* OOf Beer and ale, per bbl .25 .2 " Beer and ale, per * bbl .15 .1 Beer and ale, per i or i bbl Beer, bottled, per case Beer, bottled, per bbl .10 .10 .20 .1 .1. .2. Berries, fresh, of all kinds, per qt. .'. . Berries, fresh, of all kinds, per stand. Butter and butterine, per Ib (See also butter freezing rates.) Buckwheat flour, per bbl Cabbage, per bbl Cabbage, per crate .00* .10" .OOi .15 .25 .10 .OOi "'.OOi' .10* .20 .18 .OOi "'.ooi' .10 .20 .08 .50-75 .50 Jan. 1 Oct. 1 Calves (per day), each .10 Calves, per Ib .00| .00* .OOf Canned and bottled goods, per Ib. . . Celery per case .OOi 15 .OOi 10 .OOi 10 Cheese per Ib OOJ OOi OOi 50 60 Jan 1 Cherries per quart 00* 00* OOi Cider, per bbl .25" 15* 15 Cigars, per Ib .OOi 25 .OOi 20 OOi 15 Cranberries, per case Corn meal, per bbl Dried and boneless fish, etc., per Ib. Dried corn, per bbl Dried and evaporated apples, per Ib . Dried fruit, per Ib Eggs, per case Figs per Ib .10 .15 OOi .124 .OOi .OOi .15 OOi .'12*' OOi .10 .00 A .OOi .12* OOi "'id' .00 J .10 .66i' .10 00 T V '".50" " .50 40- .50 50- .60 Nov. i Nov. i Nov. 1 Jan. 1 Fish per bbl 20 18 15 75 Oct 1 15 13 12* 50 Oct 1 (See also fish freezing rates.) Fruil s fresh per bbl 25 20 20 Fruits, fresh, per crate .10 .08 .08 Furs, undressed, hydraulic pressed, per Ib .00* .OOi .001 1 00 Oct 1 Furs, dressed, per Ib Ginger ale, bottled, per bbl Grapes, per Ib Grapes, per basket Grapes, Malaga, etc., per keg Hops per Ib . .03 .20 .00* .03 .15 OOi .02* .15" .OOi .02 .124 OOi f "02 l ...15 .OOi .01 .12} OOi 8.00 ' 2 66 Oct. 1 May V Lard per tierce . ... 25 20 20 1 00 Nov 1 Lard oil, per cask Lemons, per box Macaroni, per bbl Maple sugar, per Ib .25 .15 .20 -00i .20 .12* .15" ".OOi .20 .10 ..m -OOi 1.00 .50 :^'a Nov. 1 Nov. 1 Nov'.'l REFRIGERATION 201 TABLE XXIII Continued Rates for Cold Storage 1! S| EACH SUCCEEDING MONTH IN LARGE QUANTITIES, PER MONTH SEASON RATE PER BBL. OR 100 LBS. SEASON ENDS Maple syrup, per gallon Meats, fresh, per Ib Nuts, of all kinds, per Ib Oatmeal, per bbl Oil, per cask Oil, per hogshead Oleomargarine, per Ib Onions, per bbl Onions, per box Oranges, per box Oysters, in tubs, per gal Oysters, in shell, per bbl Peaches, per basket .01* .OOf .001 .20 .25 1.00 .00* .15 .12* .15" .05 .r,o .10 .20 .40 00* .20 .25 .001 .25 .20 .25 .15 .30 .00?, .25 .15 .25 .10 .OH .00* OOi .15 .20 .80 .00 .12i .10* .12* .04 .40 .08 .15 .30 :8 .20 .001 .20 .15 .20 .m .25" .001 .20 .10 .25 ,10 .01 .OOf 00 .12* "'66i' .10 .40-. 50 .'56-! 60 .50 Nov. i May Y ' Nov.' 1 ' Jani 1 May 1 May 1 Nov.l Nov.'l ' 6'c't! 1 .10 ' .30 .07 "'.ooi' .15 .20 .00 .20* .m .15" .10 .20 .00 J .15 .08 2.00 .60 1.20 1.00 .'GO- '.75 1.00 Pears, per box Pears, per bbl Pigs' feet, per Ib Pork, per tierce Potatoes, per bbl Preserves, jellies, jams, etc., per Ib . . Provisions, per bbl Rice flour, per bbl . , Sauerkraut, per cask Sauerkraut, per * bbl Syrup, per bbl Tobacco, per Ib Vegetables, fresh, per bbl Vegetables, fresh, per case Wine, in wood, per bbl Wine, in bottles, per case large storage establishments to have separate rooms and spaces for the different classes of goods stored. Storage Rates. All storage business is conducted for revenue and it is important that such a schedule of rates be adopted as will allow a reasonable profit for the capital, skill, and experience neces- sary to run a cold storage establishment. Rates vary with local circumstances, conditions, and with the products stored and the time they are kept in storage, so that no general rule can be laid down. Capacity for storage and the demand therefor as well as the competi- tion to be met must all be considered. As a rough guide, Siebel gives the data presented in Table 23, the figures being averages of rates prevailing in a number of large cold-storage establishments. 202 REFRIGERATION APPLICATIONS OF REFRIGERATION Breweries. Two of the most important uses of refrigeration in ice-making and cold-storage work have already been taken up at considerable length, but these industries, important as they are, do not cover the field of refrigeration applications by any means. After ice and cold-storage plants, the brewery industry is about the most important application of refrigeration. In making beer there are three distinct operations, the first being the preparation of malt from barley, the second the preparation of the wort from malt, and finally the fermentation of wort to convert it into beer. Specially prepared malt is washed or diluted with hot water to form clear wort which is boiled with hops to make the beer wort. The wort thus made is cooled and converted into beer by adding yeast, which brings about decomposition or fermentation, the process taking place in large vessels placed in rooms cooled by refrigeration. The density of wort is determined by a special instrument known as the Balling saccharometer, which is so graduated that when immersed in the liquid it indicates the percentage of solid matter mostly dextrine and saccharine that the wort contains. The specific gravity and the specific heat of wort may be taken from standard tables, and with this data the refrigeration required can be figured by the methods already explained. Cooling wort makes up the greatest part of the refrigerating work to be done in a brewery, but aside from this the machinery must remove the heat of fermentation and keep the temperature of the cellars, fermenting rooms, etc. at 34 to 38 F. As this is about the lowest temperature required, it is seen that brewery work is com- paratively light, but owing to the fact that the hot wort must be cooled quickly, it is necessary to install larger machines in breweries than would otherwise be called for. Packing Houses. Packing houses employ artificial refrigera- tion to a large extent and it is safe to say that this industry as it exists to-day would be impossible without artificial methods of cooling. There are three temperatures used respectively in the chill room, holding room, and freezing room. After the carcasses are dressed, it is impor- tant to get rid of the animal heat as rapidly as possible. This is done by suspending the carcasses in the chill room which carries a tempera- ture of about 28 degrees. Ample ventilation is provided in this room REFRIGERATION 203 to remove the gases and impurities given off from the meat in cooling. When the temperature has been reduced from blood heat about 95 degrees to 35 degrees, the meat is removed to the holding room, in which the temperature ranges from 32 to 35 degrees, but never low enough to freeze the meat. The temperature of the freezing room may be 10 degrees or under, but in freezing meat, it is neces- sary that the cooling be done gradually. If possible to avoid it, meat is never frozen; but if it must be shipped long distances, requiring several days in transit, freezing is necessary. Ample time should be allowed for the process, the tem- perature being reduced gradually, as otherwise, the meat will be seriously damaged. If the temperature is reduced suddenly, the outer portion of the meat is frozen solid before the temperature inside can be lowered and the contraction of the outer layer of frozen meat on the inner part causes rupture of the congealed cells in the meat so that, when finally thawed out, it is found that the quality of the carcass has deteriorated. In cutting into a joint of meat so treated the flesh near the bone will be found to be of a pulpy consistency. Aside from this damage to the meat, it costs more to do the freezing where the temperature is reduced rapidly, not only on account of the fact that sudden changes are always costly, but more particularly by reason of the outer layer of frozen meat having insulating qualities. So-called bone stink is nothing more than decaying marrow, which is due in most cases to rapid freezing but may be due in some measure to the condition of the animal before killing. Frozen meat may be kept for several months at a temperature of 31 degrees, but care should be taken not to let the temperature rise above this figure, for a rise even to 33 degrees may result in the meat spoiling in less than a month, although if the ventilation is good and other conditions favorable it may be kept as long as two months. Usually frozen meat is kept about six months with perfect safety. If care is taken in thawing out, the meat will be palatable and wholesome. In dis- cussing cold storage, the importance of circulation and ventilation was mentioned and the point applies with particular force to pack- ing-house work, as meat is sensitive to improper conditions and white mold spots are readily formed under such circumstances. Creameries. Creameries are in late years becoming large users of refrigeration, as it is found almost impossible to turn out good 204 REFRIGERATION dairy products without artificial cooling. From the time the milk comes from the animals until it is worked up into butter, cheese, and other products, its temperature should be regulated carefully. Like breweries, creameries require light or moderate-temperature refrigera- tion, there being two objects in using refrigeration in the industry the first, control of bacteria life in the milk; the second, regulation of temperature as required in separating the cream from the milk and in churning it. It is desirable, though not always possible, that the animal heat of the milk coming from the cows should be removed at once and if this can be done the quality is much improved. As a rule, however, the milk delivered to creameries by farmers has a tem- perature of from 65 to 70 degrees in summer and from 40 to 50 de- grees in the winter. This milk, on coming to the creamery, should be pasteurized by being heated up in a special apparatus to a tem- perature of about 180 F., thereby destroying bacteria. Not all the bacteria life is destroyed at this temperature but the milk is made immune for all practical purposes and the danger of burning that would be incurred at higher temperatures is avoided. In good separators, the cream can be removed from the milk at any temperature above 100 degrees, but 160 is the proper tempera- ture. After pasteurization and separation, the milk is cooled down by being passed over a cooler of the Baudelot type, through which well water runs, and is returned to the farmers. The cream is then cooled rapidly by being passed over a circular capillary cooler through the corrugations of which well water is circulated. On leaving this cooler it has a temperature of about 70 degrees and refrigeration is applied to reduce the temperature to 50 degrees, which gives the best results for ripening. In this latter process, the temperature rises to about 70 degrees and refrigeration must again be applied to reduce this to 48 degrees, at which temperature the cream goes to the churn. Butter is kept in cold stores at about zero, as already mentioned. Cheese must be made and stored at moderate temperatures if it is to ripen properly. The whole thing in creamery refrigeration is to control the temperatures exactly as desired, and this can be done only when refrigeration is used. Miscellaneous Applications. Aside from the leading industries discussed, refrigeration is used in a number of manufacturing and industrial processes. One of the largest applications is that for REFRIGERATION 205 drying air. A number of manufacturing processes require dry air, one of the most important being blast furnace operation. This is a comparatively new application, as until within the last few years, little was known of the extent to which moist air causes loss in steel mills. It has been found that by using a refrigerating machine to lower the temperature of the air used in blast furnaces, thereby caus- ing it to reach the dew point and precipitate practically all contained moisture, a great economy is had, the air being afterwards reheated by passing through gas stoves fed with waste gases coming from the furnaces. Sufficient coal and more is saved in the blast furnaces than is required to drive the steam plant necessary for the refrigera- ting machine, while at the same time the production of the furnace is almost doubled. Plants for this work are of large capacity ranging up into the thousands of tons. Theaters, halls, and residences are now cooled by artificial refrigeration in summer, the process generally used being a forced- air circulation where the air is driven through washing machines which remove all impurities, and then passed over cooling coils before going into the ventilating ducts. In the case of theaters, the most usual arrangement is to have the ventilating ducts pass under the lloor, the openings from the ducts being underneath the seats in all parts of the auditorium, so that ventilation is uniform without drafts and with the air at suitable conditions of temperature and humidity. Confectioners find use for refrigeration in maintaining the tem- perature of dipping rooms so that the candies are kept firm. Bakers likewise require cooling in their establishments to maintain constant temperature in the mixing rooms. Heating and cooling coils are provided so that the temperature may be raised or lowered as re- quired to keep it at a constant figure. The result of this care is bread of uniform texture from day to day, so that housekeepers can depend on getting the same kind of bread each day. This enables the pro- gressive baker to take trade from competitors. In the sporting world also refrigeration has its uses, as all large cities nowadays have their skating rinks in which large ice surfaces are formed artificially for the amusement of the public and incident- ally the profit of the owners. In laboratory experimental work ex- tremely low temperatures are frequently required and these may be had with the refrigerating machine, using special intensifying ap- 206 REFRIGERATION paratus. Medical men have long appreciated the value of ice and low temperatures in handling certain forms of disease. In fevers especially, ice is almost a necessity if the disease is to be kept under control This fact as already mentioned was largely responsible for the development of refrigerating machinery. Early machines and experiments were mostly made by physicians in the effort to afford a ready means of alleviating suffering. This use of the refrigerating machine, aside from all other applications, gives refrigeration a com- manding place among the world's greatest industries. If one stops to consider, it is seen that there is scarcely a food product or other material having to do with human existence with which refrigeration does not have to do at some time or other. Thus the importance of refrigeration as applied to-day becomes more apparent. Certainly no other scientific development has lent itself to application in a wide and varied field of usefulness in a manner that can compare in any way with mechanical refrigeration as applied at the present time, INDEX PAGE Absorber 51 Absorption system. ....... 46 absorber 51 ammonia pump 52 ammonia regulator 53 analyzer 48 binary systems 56 care and management .' 57 charging 59 condenser 50 economy of absorption machine 61 efficiency tests : 60 equalizer 50 generator 48 operation 53 power for absorption plant 53 rectifier 50 Air-machine 2 Air system, arrangement of 37 Ammonia 29 loss of 142 Ammonia condensers 94 atmospheric condenser 98 double-pipe condenser 104 oil separator or interceptor 109 submerged condenser 95 Ammonia liquor t 32 Ammonia pump .- 52 Ammonia receiver. 125 Ammonia regulator 53 Analyzer 48 Aqua ammonia 32 Atmospheric condenser 98 Auxiliary apparatus 125 ammonia receiver 125 pipes 125 pressure gauges 128 valves 128 B Binary systems 56 Brine agitators 156 Brine cooler . . 118 2 INDEX PAGE Brine tank 114 Breweries 202 C Can plant equipment. 147 Can system 146 Carbon dioxide 29 Charging 134 Cold, production of 20 Cold-air machine 36 arrangement of air system 37 commercial form of air machine 38 compressor cylinder 41 Cold storage 178, 198 goods, handling of 198 storage rates 201 Commercial form of air machine 38 Commercial machines 81 carbon dioxide machines 87 horizontal double-acting 81 Linde 83 Triumph 81 small refrigerating plants 90 vertical compressors 85 Great Lakes 86 York 85 Compression system 61 compressor piston 73 compressors 64 lubrication 78 operating principle 62 stuffing box 75 valve operation f 71 valve proportions 72 water jacket 76 Compressor cylinder 41 Compressor losses 93 Compressors 64 essentials in. . 66 piston 73 valves 67 vertical 85 Condenser .* 50 Conduction 20 Convection : 19 Cooling, methods of 191 Cooling coils and gas cooler 152 Cooling towers . 109 Crane and hoist. . . 158 INDEX 3 D PAGE Distilling apparatus 148 Double-pipe condenser 104 Dumping and filling 158 E Equalizer 50 Evaporators 113 brine cooler 118 brine tank 114 Expansion coils 154 F Filters 152 Freezing tank 154 G Generator 48 Grating and covers 156 H Heat 4 Heat measurement, units of 6 Hot skimmer and reboiler 149 I Ice, storing and selling 174 Ice cans 155 Ice-making plants 145 brine agitators 156 can plant equipment 147 can system : 146 cooling coils and gas cooler 152 crane and hoist 158 distilling apparatus 148 dumping and filling 158 expansion coils 154 filters 152 freezing tank 154 grating and covers 156 hot skimmer and reboiler 149 ice cans 155 layout 160 plate system 162 steam condenser 149 Ice-plant insulation 176 Insulation. . . 182 4 INDEX L PAGE Layout. . 160 Lubrication 78 N Non-conductors 183 O Oil separator or interceptor 109 P Packing houses 202 Pipes. . 125 Plant, operation and management of 139 ammonia, loss of 142 purging and pumping out connection 143 Plant capacity, unit of 13 Plate system 162 Preservation, conditions for 179 Pressure gauges 128 R Radiation 18 Rectifier 50 Refrigerants, tests of 33 Refrigerating plant, proportion between parts 132 Refrigerating plants (small) 90 Refrigeration 1-206 absorption system 46 air-machine 2 ammonia condensers 94 applications 202 breweries 202 miscellaneous 204 packing houses 202 auxiliary apparatus 125 charging 134 cold, production of 20 cold-air machine 36 cold storage 198 cold storage (general) 178 cooling, methods of 191 cooling towers 109 commercial machines 81 compression system 61 compressor losses 93 conduction. . . 20 INDEX 5 Refrigeration 1>AQB convection 19 definitions 3 heat 4 heat measurement, units of 6 historical 1 ice, storing and selling 174 ice-making plants 145 ice-plant insulation. 176 insulation 182 methods of 131 operation and management of plant 139 radiation 18 refrigerants, tests of 33 refrigerating plant, proportion between parts 132 required 197 systems of 36 testing % 134 unit of plant capacity 13 vacuum process 44 S Steam condenser 149 Storage rates 201 Stuffing box 75 Submerged condenser 95 Sulphur dioxide 29 T Table ammonia, solubility of in water 32 aqua ammonia, strength of 34 beer wort, specific heat and specific gravity of 13 calcium brine solution, properties of 120 cold storage, rates for 200, 201 critical data 24 freezing mixtures, composition of 21 gas, cubic feet pumped per ton 72 heat generated by absorbing ammonia 54 refrigerants, comparative values of three 27 refrigerants, qualities of principal 26 salt brine solution, properties of 121 saturated ammonia gas, properties of 31 saturated carbon dioxide, properties of 30 saturated sulphur dioxide, properties of 30 specific heat of various susbstances under constant pres- sure 12 substances, boiling point and latent heat of 25 6 INDEX Table PAOK substances, fusion and vaporization data of 14 substances, non-conducting power of 184 temperatures for cold storage of products 181 thermometer scales 10 Tank insulation 177 Testing 134 Vacuum process 44 Vacuum pump 45 Valve operation 71 Valve proportions 72 Valves 128 W Water jacket 76 The School Behind the Book THIS practical handbook is one of the representatives of the American School of Correspondence. It is the only kind of representative by which the School reaches the general public and extends its educational work. The American School of Correspondence is chartered, under the same laws as a State University, as an educational institution. Its instruction books, written especially to suit the needs of men seeking self-improvement through correspondence work, are reserved for its students and for class use in educational institu- tions; many of these texts are used in the class room work of the best resident schools in the country. However, in order that the large number of ambitious men, for whom class work and correspondence study are neither prac- tical nor advisable, may not be deprived of this valuable material, it is published by the School both in sets covering the several branches that it teaches, and in a series of single Home Study volumes treating of specialized lines of practical knowledge. This book is a sample of the make-up of the Home Study volumes and the titles and authors are shown on the following page. By this method the School broadens its field of activity; and from these sales it derives an income to use in general educational work. The School's publications are clear and practical, and will be found ideal for reference and home reading. For those, how- ever, who desire more systematic study of the subjects in which they are particularly interested, the School advises a thorough course by correspondence as the quickest and surest means of obtaining the practical knowledge desired. The School offers correspondence instruction in all branches of architecture, civil engineering, college preparatory work, account- ing and business administration, drawing and design, electrical engineering, fire prevention and insurance, American law, mechan- ical, sanitary, and steam engineering, and textile manufacturing. It adapts its courses to the needs of the individual, by starting him where his previous education stopped, and giving him only such work as is necessary to fit him for the work he wants to do. On request the School will mail to any address a Bulletin containing full information regarding its courses and methods. It employs no representative other than its own publications. AMERICAN SCHOOL OF CORRESPONDENCE CHICAGO, U. S. A. American School of Correspondence PRACTICAL HANDBOOKS FOR HOME STUDY OWING to a constant and increasing demand for low-priced single volumes covering the sub- jects treated in the courses and cyclopedias of the American School of Correspondence, a series of practical handbooks have been com- piled to be sold through the Book Stores all over the world. If any purchaser finds that his local dealer does not carry the particular title which interests him, he can order direct from the publisher, who will make shipment on receipt of price. If, after five days' exam- ination, the volume is found unsuited to his need, the purchaser may return it and his money will be promptly refunded. Partial List of Titles and Authors PRICE Alternating- Current Machinery William Esty $3.00 Architectural Drawing and Lettering Bourne-von Hoist-Brown 1.50 Bank Bookkeeping ,. Charles A. Sweetland 1.00 Boiler Accessories ' Walter S. Leland 1.00 Bridge Engineering Roof Trusses Frank O. Dufour 3.00 Building and Flying an Aeroplane Charles B. Hay ward 1.00 Building Superintendence Edward Nichols 1.50 Business Management, Part I _ James B. Griffith 1.50 Business Management, Part II Russell-Griffith 1.50 Carpentry Gilbert Townsend 1.50 Care and Operation of Automobiles Morris A. Hall 1.00 Commercial Law John A. Chamberlain 3.00 Compressed Air Lucius I. Wightman 1.00 Contracts and Specifications James C. Plant 1.00 Corporation Accounts and the Voucher System ..James B. Griffith 1.00 Cotton Spinning Charles C. Hedrick 3.00 Department Store Accounts Charles A. Sweetland ... 1.50 Descriptive Astronomy Forest Ray Moulton.- _ 1.50 Dynamo-Electric Machinery F. B. Crocker. . . .1.50 Electric Railways Henry H. Norris 1.50 The Electric Telegraph.. .. -Thorn-Collins 1.00 Partial List of Titles and Authors Continued PRICK Electric Wiring and Lighting Knox-Shaad $1.00 Estimating . Edward Nichols .. 1.00 Factory Accounts Hathaway-Griffith 1.50 Forging John Lord Bacon 1.00 Foundry Work Wm. C. Stimpson 1.00 Freehand and Perspective Drawing Everett-Lawrence 1.00 The Gasoline Automobile . Lougheed-Hall . .' 2.00 Gas Engines and Producers Marks- Wyer 1.00 Heating and Ventilation Charles L. Hubbard 1.50 Highway Construction _.Phillips-Byrne 1.00 Hydraulic Engineering Turneaure-Black 3.00 Insurance and Real Estate Accounts Charles A. Sweetland ... 1.50 Knitting .... M. A. Metcalf 3.00 Machine Design Charles L. Griffin 1.50 Machine-Shop Work Frederick W. Turner 1.50 Masonry and Reinforced Concrete Webb-Gibson 3.00 Masonry Construction Phillips-Byrne 1.00 Mechanical Drawing Ervin Kenison 1.00 Modern American Homes H. V. von Hoist 3.00 Motion Pictures David S. Hulfish 4.00 The Orders Bourne- von Hoist-Brown 3.00 Pattern Making James Ritchey 1.00 Plumbing '_ Gray-Ball J 1.50 Power Stations and Transmission Geo. C. Shaad 1.00 Practical Aeronautics Chas. B. Hayward 3.50 Practical Bookkeeping James B. Griffith 1.50 Practical Lessons in Electricity Millikan-Knox-Crocker _ 1.50 Reinforced Concrete Webb-Gibson 1.00 Railroad Engineering Walter Loring Webb 3.00 Refrigeration M. W. Arrowwood 1.00 Sewers and Drains A. Marston 1.00 Sheet Metal Work William Neubecker 3.00 Stair-Building and Steel Square Hodgson- Williams 1.00 Steam Boilers Newell-Dow 1.00 Steam Engines L. V. Ludy 1.00 Steam Turbines Walter S. Leland 1.00 Steel Construction E. A. Tucker 1.50 Strength of Materials Edward Rose Maurer ... 1.00 Surveying Alfred E. Phillips 1.50 Telephony Miller-McMeen 4.00 Textile Chemistry and Dyeing Louis A. Olney 3.00 Textile Design Fenwick Umpleby 3.00 Tool Making Edward R. Markham ___ 1.50 Valve Gears and Indicators L. V. Ludy 1.00 Water Supply Frederick E. Turneaure. . 1.00 Weaving H. William Nelson 3.00 Wireless Telegraphy and Telephony Ashley-Hay ward 1.00 Woolen and Worsted Finishing John F. Timmerman 3.00 Woolen and Worsted Spinning Miles Collins 3.00 UNIVERSITY OF CALIFORNIA LIBRARY Los Angeles This book is DUE on the last date stamped below. ?& MAY 151959., MAY 1 5 8EP 1 3 1971 SEP 7 Form L9-100m-9,'52(A3105)444 bfumrhl Libry rr w A 000803865 5 AUXILIARY SEP 73