Complete Text (Part 3)

possible. In the THE) VARISTINS, OF REFRIGERATING MACHINES—ALL HAVE THEN, perfect machine, of whatever type, as will be shown SAME EFFICIENCY WHEN PERFECT—THE COMPRESSION AND ABSORPTION MACHINES. By Geo. Ricuonp, M. E. EFRIGERATING machinery has a singular variety R in outward appearance, mode of action, and in the substances employed as agents, but as the object in each and every one is the same, namely, to remove heat, we are prepared to find that one common principle under- lies them all. An observer cannot fail to notice one characteristic common to all such machinery; and if the apparatus were entirely covered from view, it is certain that he would find high temperature heat, or the means of pro- ducing it, going in at one end,and low temperature heat, or substances cooled below the surrounding tempera- ture, coming out at the other. Whatever may be the claims as to the advantage of this or that style, and how- ever mysterious its operation may appear, we could cer- tainly predict that a certain amount of coal would have to be supplied for every ton of ice turned out. over, as we have seen, we can predict further (when we know the temperatures involved) the least possible amount of coal which will be needed, and that without considering the details of the process. This fact is of some consequence, for ingenious men can readily make complex combinations, which it would be very difficult to analyze or examine in detail, the moreso as the phys- ical properties involved may be only very vaguely known. The claim in any such case must be limited to the maximum production possible. Any refrigerating apparatus may be represented by the simple scheme, Fig. 1, in which 4 is a source (namely, the boiler or generator) from which a quantity of high temperature heat, /, is supplied, and B is a re- frigerator from which a certain quantity of low tempera- ture heat, 4, is drawn. C encloses a mechanism of some kind, by the operation of which the double flow of heat is caused to take place; or, rather, by reason of which the flow of heat from the refrigerator is brought about as a consequence of the flow of heat from the generator. The object of all refrigerating processes is to obtain the greatest amount of refrigeration with the least ex- More- ~ sCopyright by Geo. Richmond, M. E. All rights reserved. 2 “hereafter, these two quantities of heat are directly pro- portional to the temperatures at which they are supplied, and inversely proportional to the ranges through which they are used. The general character of the various machines con- stituting the compensating device C must be well known to the reader, and he will find descriptive details of nearly every class in earlier numbers of this journal, and particularly in a series of articles by Mr. A. J. Rossi, running through the first and second volumes. They Foeone scsi 5S z i 1 im an ¢ Hh i ‘ % a i t rt 1 | Fic. 1. may be conveniently classified as follows: I. Compres- sion machines. II. Absorption machines. III. Mixed. IV. Vacuum machines. V. Liquefaction machines. Compression machines may be again divided into: (a) Those using permanent gas with open circuit, or closed circuit (¢. ¢., dense air system of L. Allen). (4) Those using liquefiable gas, asammonia, sulphuric acid, car- bonic acid, water. (¢) With or without expansion cyl- inder. Air machines must and it would seem that car- bonic acid ought to have expansion cylinders. (¢) Those using wet or cold compression,and those running with superheated gas. The former is known as the Linde system, while the latter is in more general use in America. 10°". “. ICE .. AND .°. REFRIGERATION Absorption machines present an endless variety in details, but the mode of operation in all is very nearly the same, with exceptions that will be noticed in the proper place. One characteristic division is that of intermittent and continuous machines. Another is that of those using liquid absorbents and those using dry ab- sorbents. Mixed machines are those employing partly com- pression and partly absorption, such as the machine of Harrison, and, more recently, thatof Mr. Thomas Rose. Under the name ‘‘Vacuum,” two machines are known, one of which is properly a compression machine using water as an agent instead of ammonia; and the other is of the absorption type, in which water is used instead of ammonia, and sulphuric acid in place of water. The liquefaction apparatus is that employing the solu- tion of solids more generally known as freezing salts. They are generally intermittent in action, but have been designed to run continuous!: In all these machines it is not difficult to trace the compensation above referred to. It may not be so obvious in the last class, but it must be remem- bered that in order to get the salt back again in- to condition for doing more cooling it must be evapora- ted by high temperature heat. It will be sufficient for our purpose to trace the course of the two quantities of heat in question through an apparatus of the compres- sion type and one of the absorption type. , In the compression machine this is very easy; and in Fig. 2 the essential features comprising the compen- sator C, are sketched in, and are seen to consist of an engine with its condenser and a compressor with its condenser. The heat // passes into the engine, where a portion of it, IV, isconverted into work, and the re- mainder //— JV, passes into the engine condenser (which in the case of a non-condensing engine is the atmos- phere). The work J s transferred to the compressor A By) BOILER fnew —4 Steam, combewsen| e Heh TAN: compens fe fiew —t a Onn en nen fene en nee eet Fie. 2. and the heat / from the refrigerator flows through the compressor, and carries with it the work J” in the form of heat into the ammonia condenser, so that the sum of the discharged or rejected heats is /+/, in accordance with the gencral scheme, Fig. 1. We see now why the flow of high temperature heat causes the flow of low temperature heat, and also, from Fig. 3, the relationship which must obtain between these two quantities, In Fig. 3 (a) the larger rectangle represents a quantity of heat, #, the height being the absolute temperature, 7’, at which it is supplied, and the smaller rectangle the work which can be obtained from it, while ® is the fall of temperature utilized, #. ¢., the difference in tempera- ture between the boiler and engine condenser. The equal width of each rectangle is marked ¢’, and we shall in future indicate the width of any heat area by this fle iat ra oo f \ Tl a \ ' ' I ! Eh oS Fis. 3. letter. Since rectangles, having equal widths, are pro- portional to their heights, we have: Wee enh oT Ww oo yt pte Q) In Fig. 3 (4) in the same manner the quantity of heat, 4, removed from the refrigerator is represented by arectangle whose height is equal to the temperature (absolute) of the refrigerator from which it is taken, and ® is the rise in temperature through which it is lifted, ¢. ¢., the difference in temperature between the ammonia condenser and the refrigerator. As before, we have, inverting the proportion: If we multiply together the equations (1) and (2), noticing that the //” will cancel, we have: A Tr o work oe =e which proves the general statement'with which we set out, so far as the compression machine is concerned. The work done by high temperature heat is equal to the work done on the low temperature heat, and each may be written down as the product of the two sides of the respective work rectangles, that is: vou oe = O86 =-(4) If the width # represent a weight of water and ® the distance through which it can fall, then the work done would be ® # foot-pounds. Again, if ¢ represent another weight of water and ® the distance through which it is lifted the work necessarily expended is ® ¢ foot-pounds, and, if we had perfect machinery, these two quantities must be equal to enable us to lift the maximum amount of water for the least amount allowed to flow down. From these hydraulic analogies, Zeuner has termed the width of the heat area the ‘‘heat weight.” When the converter Cis an absorption machine it is more difficult to trace the course of the two quantities of heat. Stripped of all details the main features are represented in Fig. 4. There is the same general con- dition of high temperature heat supplied and of low temperature heat flowing to a higher temperature, but there is no trace of work obtained or work performed, . ICE .. JULY, 1893. Yet, while it is not recognizable, we know that the trans- fer of low temperature heat could not take place without the equivalent transfer of the high temperature heat. Moreover, in practice we find that the quantity of heat discharged into the ammonia condenser is approxi- mately the same as that discharged in the compression machine, and the heat discharged from the absorber ap- proximates to that discharged by the engine condenser. Following the agent as it travels around, the pecul- iarity of the absorption machine seems to be that it discharges the heat due from the refrigerator and the heat equivalent of the work necessary for the refrigera- tion in advance of the actual performance of the refrig- eration. Thus, as figured above, if // is the heat leav- ing the generator 4+ IV of this is discharged in the am- monia condenser and /7—A— IJ goes forward with the am- monia to the refrigerator. We may conceive that the ammonia carries with ita draft drawn by the generator on the refrigerator for the amount of heat /to cover what has already been ad- vanced on its behalf. Accordingly the refrigerator honors the draft by supplying the quantity of heat 4, and the ammonia goes forward to the absorber where it Fgewcose ' : iz a ' i ' ' hew a q CONDENSER a Hehe } ABSORBER ’ p+ H-w ' ft ’ T ' ee 2 rr a ' \ delivers the heat //—IV. The final result is the same, all the heat discharged from both the generator and the refrigerator, viz., +4, being the same as in the general scheme, Fig. 1. This, of course, is merely a mental pic- ture of what we may suppose to take place in order to comply with the necessary conditions, and it may be asked what reason we have for supposing that the same rela- tion obtains between two quantities of heat in the ab- sorption machine as obtains in the case of the compress- ion machine. In other words, is equation 3 necessarily true for the absorption machine? This is a most important matter, the more so as its denial is implied in some explanations of the absorption machine by authorities entitled to the highest consid- eration. Suppose that it is not true, and that we have two machines working with identical temperatures and ranges, but one on the compression plan and the other on the absorption, and that they both receive the same supply of high temperature heat, namely //, but that while the compression machine furnishes 4 7. U. of re- frigeration the absorption machine furnishes a larger amount, say 24. Let the refrigeration 24 be represented AND .. REFRIGERATION .. ny by acertain quantity of ice, and let us remove it from the absorption machine and place it in the refrigerator of the compression machine (supposed to have lain idle up to the present), which will now have a stock of ice representing a capacity for absorbing heat to the amount of 24. Now let the compression machine be reversed. Let the compressor be changed to an engine, and the The ammonia can be boiled in the ammonia condenser, and will pass through the engine to a compressor. ammonia engine; the refrigerator will be a surface con- denser for it until all the ice has melted or the quantity of heat 24 has been supplied. When this happens the ammonia engine will have furnished work to the steam compressor equal to 2/4, but one of these is sufficient to cause the passage of heat //— IV backward to the boiler, and being itself transformed into heat the boiler will re- ceive in all H units of heat. The position we are now in is this: We have imparted to the boiler a quantity of heat, //, and we have quantity of work IJ” left over. The heat // can be transferred to the absorp chine, where it will again produce 2/ of refrigeration, so that as a final result we have the quantity of work I” produced at each operation free of cost without the ex- penditure of any heat at all. Since we cannot admit this possibility we must believe that the absolute efh- ciency expressed by cquation 3 is the greatest that any refrigerating machinery can have, whatever the nature of its details may be. On the other hand, the temperature and ranges being the same, no reason can be assigned why any other type of machine should not have precisely the same efficiency. The compression machine was chosen as the standard simply because it is easily seen how it can be reversed, for it is evident that reversibility is the true test of our having found the correct statement of the law governing the equivalent transfer of the two quantities of heat, which law must be independent of the mechanism em- ployed. noma. [10 bE costinveD.] BOSTON paper (think of it) has made the un- A pardonable faux pas of saying that ‘ the announce- ment of a formation of an ice trust has undoubtedly sent a cold chill up the back of many a consumer." Take any shape but that. Call it red hot, a boiling flood, a~ anything but acold chill, What's the use of having an ice trust if the mere announcement is going to chill the consumer? The ice man gives it to ‘em hot, don't you know. HIE information comes from Ellensburgh, Wash., T that four years ago some citizens built an ice house on the Nanum and filled it with ice of an eacellent quality. The ice was put up as a reserve, and it has kept asa reserve, notwithstanding the roof and sides have been wrecked. There are tons of it still imbedded in the sawdust, fresh and solid as when taken from the pond. Nothing seems to be impossible ‘‘in this glorious climate” of Washington! —The business of C. G. Mayer, 744 Broadway, York, builder of ice machines, has incorporated Newark, N. J., asa stock company, to be known as the C. G, Mayer Ice Machine Co., capital, £50,000, fully paid up. John nright, Albert W. Jacobs and George W. Wicdenmayer, of Newark, and Charles G. Mayer and Julius J. Mayer, of New York are the incorporators. bee 12 «. ICE .. AND .. REFRIGERATION .°. JULY, 1893. (Reprint from unidentified EXCBANGE.| FREEZING MIXTURES. SUBSTANCES WHICH MAY BE EMPLOYED FOR LOWERING TEMPERA- TURES—SOME FAIRLY EFFECTIVE FREEZING MIXTURES MANUFACTURE OF ICE BY THEM A FAILURE. HE numerous and varied applications which ice has found in these times have greatly enhanced the im- portance of that product, and while large portions of it have annually been transported from the colder to the hotter regions of the globe, scientific ingenuity has at- tacked, energetically and successfully, the problem of producing cold by artificial means for industrial and other purposes. In a recent number of Dingler’s Polytechnisches Journal, Professor Meidinger has an in- structive paper giving an account of the progress made in recent years in the art of ice manufacture. There are three ways indicated by physics in which temperature may be lowered, and ice formed, viz., so- lution of solid substances, evaporation of liquids, and expansion of gases. The following is an abstract of that portion of Professor Meidinger’s paper relating to pro- duction of cold by solution: Heat is absorbed in bringing solids to the liquid condition; and the cold thus produced may prove suf- ficient to convert water into ice. The best known of the numerous freezing mixtures that have been hitherto described is, of course, one in- volving ice itself; it consists of three parts of ice and one part of ordinary salt. Dissolving concurrently, these two substances give a temperature of —21° C. (the freezing point of the so- lution). The melting of only a part of the mixture is sufficient to produce this temperature throughout the mass; and with constant admission of heat, and stirring, the low temperature is maintained until the whole is dissolved. The freezing apparatus of confectioners is well known: a tin pot containing cream, a wooden or metallic vessel inclosing the pot, and the interval filled with ice and salts, which is frequently stirred, that the ice may not sink to the bottom. In a Paris machine for home use the agitation of the freezing mixture is maintained by rotation of the double cylinder contain- ing it and the cream vessel round an axis at right angles to the cylinder's length. Professor Meidinger has con- structed a machine based on the observation that a so- lution of ordinary salt under o° also fuses ice, and, so long as its concentration is maintained, produces the same low temperature as the mixture of salt and ice. He provides a sieve-like vessel, containing salt, to main- tain the concentration as the ice melts. The lowering of temperature is uniform throughout the vessel, and no