NATURE 



401 



THURSDAY, JANUARY 24, 1918. 



THE ELEMENTS OF REFRIGERATION. 



The Elements of Refrigeration. A Text-book for 

 Students, Engineers, and Warehousemen. By 

 Prof. A. M. Greene, jun. Pp. vi + 472. (New 

 York : John Wiley and Sons, Inc. ; London : 

 Chapman and Hall, Ltd., 1916.) Price 185. 6d. 

 net. 



'T^HIS book is another striking example of the 

 -■- thoroughness of American (U.S.) technical 

 educational methods, as shown by many excellent 

 text-books — the scientific, the applied scientific, 

 and the practical (including cost) being combined 

 in a manner quite refreshing to British engineer- 

 ing students. 



The table of contents discloses an excellent 

 arrangement of matter, viz. : (r) Physical pheno- 

 mena ; (2) methods of refrigeration ; (3) thermo- 

 dynamics of refrigerating apparatus ; (4) types of 

 machines and apparatus ; (5) heat transfer, insula- 

 tion, and amount of heat ; (6) cold storage ; (7) ice- 

 making ; (8) other applications of refrigeration ; 



(9) costs of insulation and operating costs ; 



(10) problems. 



We think, however, this arrangement would 

 have been further improved by placing the thermo- 

 dynamic .section just before the problems, particu- 

 larly as the author is a little disconcerting in his 

 detailed methods. Thus, on p. 55, we have the 

 end of a number of formulae dealing with the air 

 machine. The last formula is numbered (62), and 

 is given as follows : — 



W, = M^p(T2-T,) + ;//(57.,+a 

 = M<rp{T2 - Tj) + ///(zjj - /, 



•^1- 



in) 



where Wc= work done in compressor. 



The author then gives an example : — "To apply 

 these formulae, it is desired to cool a room to 0°, 

 with cooling water at 60° F., and the data for 

 I ton of refrigeration is [sic] to be found. With a 

 10° rise in the water, a 10° difference between air 

 and cooler and a counter-current air-cooler, the 

 temperature of the air will be reduced to 70° F. 

 The air in the refrigerator will be —10° F." 



In this problem the temperature differences are 

 pure assumptions, but of the order generally em- 

 ployed by the practical man in his approximations. 

 It would have been much better if the author had 

 cither kept such a problem for the last chapter, 

 or taken a set of actually observed temperatures 

 and then applied them in the formula, showing — 

 and accounting for — the difference in the work 

 done, as given by the formula, and the actual ex- 

 penditure of energy as registered by the ordinary 

 practical methods. If this had been done, the 

 student would not get so hopelessly mixed between 

 the refinements of a thermodynamic equation and 

 the everyday approximations and assumptions of 

 the engineer. It would further have shown the 

 value of comparing the ideal with the actual. 



It is interesting to note that the author in his 

 NO. 2517, VOL. 100] 



tables has used the excellent material on the pro- 

 perties of NH3, CO2, and SO2 provided by the Re- 

 frigeration Research Committee of the Institution 

 of Mechanical Engineers (Sir Alfred Ewing, chair- 

 man). It is to be regretted, however, that he has 

 not mentioned the recommendations of that com- 

 mittee respecting the unit of refrigeration. 



The author states : " Refrigeration is usually 

 measured in tons of ice-melting capacity per 

 twenty-four hours. Since the latent heat of fusion 

 of ice is i43'4 B.Th.U. per pound, according to 

 the latest experiments, this unit means the removal 

 of 286,800 B.Th.U. per twenty-four hours, or 

 i99'2 B.Th.LT. per minute." 



The first of five specific recommendations of Sir 

 Alfred Ewing's committee surmounts this diffi- 

 culty of the "latest" value by suggesting "that 

 the refrigeration produced by a refrigerating 

 machine be expressed in calories per second." 

 Standard conditions of temperature are then laid 

 down in the report, and the term " rated capacity " 

 is proposed, the following explanation being 

 given : " Thus, a machine may be classed as hav- 

 ing a rated capacity of one unit if it produces a 

 refrig-eration of one calory per second (say 342,860 

 B.Th.U. per day) in steady working under the 

 standard conditions specified." 



At the present moment each country takes its 

 own unit, and as this country differs from the 

 United States in the value of the ton (2240 lb. and 

 2000 lb.), initial troubles begin. Added to this is 

 the fact that " ice-making capacity " (in addition 

 to " ice-meJting ") is often used, while no two 

 makers of refrigerating machines assume the same 

 temperature differences. 



The author should have informed his readers of 

 these differences and put them on their guard, 

 incidentally mentioning the British recommenda- 

 tions. In any case, we express the hope that this 

 unit — one calorie per second — will become a uni- 

 versal standard. It is absurd for any standard 

 or unit to be changing with the "latest " research 

 results. 



The most disappointing point in an unusually 

 good book is t*' be found in the opening words 

 of chap, vi., on "cold storage": "The purpose 

 of cold storage is to prevent the development of 

 life which would cause decay of living tissue; 

 it is also used to prevent the development of 

 living organisms." This statement is calculated 

 to make our men of pure science see that it is 

 time they took some interest in low-temperature 

 effects and their practical application in the cold- 

 storage industry. It further indicates the spade- 

 work necessary to link up science with the pre- 

 servation of foodstuffs; but, the gulf once bridged, 

 the field of research opened out will be boundless, 

 while the merchant and t"he engineer will be able 

 to get correct fundamental ideas that will be 

 of the greatest value in the development of an in- 

 dustry that is scientifically sound. 



Despite the fact that the book is based on 

 American practice, it should prove of great value 

 to students of refrigeration in this country. 



J. Wemvss Anderson. 



