NATURE 



481 



THURSDAY, FEBRUARY 21, 1918. 



HEAT-DROP TABLES. 



(1) Heat-drop Tables. Absolute Pressures. Cal- 

 culated by Herbert Moss from the Formulae 

 and Steam, Tables of Prof. H. L. Callendar. 

 Pp. 63. (London : Edward Arnold, 1917.) 

 Price 5^. net. 



(2.) Heat-drop Tables. H-P. Gauge, Pressures. 

 L.P:. Absolute Pressures.. Calculated by Herbert 

 M6ss from the Formulae and Steam. Tables 

 of Prof. H. L. Callendar. Pp, 6(3. (London : 

 Edward Arnold, 1917:.) Price 55. net,. 



(3) Correction Tables for Thermodynamic Effici- 



" ency. Calculated by C. H. Naylor. Pp. 59. 



(London: Edward Arnold, 1917-) Price 55. net. 



THESE three little manuals are- compiled at 

 the instance of the Turbine Section of the 

 British Electrical, and Allied Manufacturers' Asso- 

 ciation for a severely practical purpose. Engineers 

 dealing with designs or specifications for steam 

 turbines- will use them in framing estimates of 

 performance, and it is to enable this to be done 

 with? the least possible expenditure qf. thought and 

 time that these tables of heat-drop and certain 

 correcting factors, have been put into a handy 

 form for office use. They are founded on the 

 calculations of Prof. H. L, Callendar, who has 

 revolutionised our knowledge of the properties of 

 steam. It is satisfactory to see such clear evi- 

 dence that British engineers are alive to the prac- 

 tical value of Callendar's scientific work, and 

 ready to avail themselves of. it in their business 

 as manufacturers of steam-engines. 



For a long time it; was known that the data 

 regarding steam, which had come down from 

 Regnault and Rankine, and were quoted in all 

 engineering text-books, were erroneous as well 

 as incomplete. Not only did they fail to meet 

 the new needs that arose when superheating 

 became common, but they also contained grave 

 inconsistencies when tested by means of the 

 general thermodynamic relations that hold among 

 the properties of any fluid. In a paper published 

 in 1900 Callendar showed how a rational 

 table of the properties of steam, complete for all 

 conditions that occur in engineering practice, 

 could be deduced, by the aid of well-established 

 data, from a characteristic equation which he 

 assumed to connect the pressure, temperature, 

 and volume of water vapour in- any state.' He 

 gave various a priori' reasons for the type of equa- 

 tion which he selected, and also showed that it 

 had. this justification, that the results deduced from 

 it were in close accord with the best results of 

 experiment; Later measurements have only served 

 to confirm this conclusion. More recently Cal- 

 lendar, to the very great advantage of steam 

 engineering, has issued a complete set of steam 

 tables based on his method. The publications now 

 • under review accept Callendar's values of the pro- 

 ! parties of steam as authoritative, and give them 

 NO, 2521, VOL. 100] 



! certain specific applications, in connection espe-- 

 I cially with steam-turbine design. 

 I Like many other British initiatives, the new 

 ' departure which we owe to Callendar found its 

 I earliest practical development in Germany. To 

 Prof. Mollier, of Dresden, who is himself the 

 author of valuable contributions to technical 

 thermodynamics, belongs the credit of first* recog- 

 nising the importance of Callendar's work. He 

 turned it to. good account in the steam tables and 

 i diagram wTiich he published in 1906; and in 1910 

 j the present writer introduced (in the third edition 

 j of. his book on the steam-engine) the Callendar 

 method and MoUier's application of it to the notice 

 ' of English students of engineering. Mollier 'sex- 

 j cellent diagram of total heat and entropy, which 

 enables graphic measurement to take the place of 

 calculation, is now well known. ^ 



' The "heat-drop" with which these books are 

 I concerned is the change that occurs during adiar 

 I batic expansion in one of the properties of steam, 

 ' namely, the function E + PV to which Callendar in 

 1903 gave the now generally accepted name of 

 "total heat." It is the function which does not 

 change when the fluid is forced through a throttle- 

 valve or porous plug. In adiabatic passage 

 through an engine, on the other hand, the total 

 heat changes by an amount which directly 

 measures the- work done. Consequently the heat- 

 i drop between admission and exhaust is a measure 

 i of the utmost amount of work that can be obtained 

 from steam in. passing through a turbine or any 

 other form of engine. Hence its great importance 

 in the design of such engines. For reasons that 

 we cannot go into here the- same function in other 

 fluids is equally important in connection with prac- 

 tical problems of refrigeration. 



It may seem a far cry from the philosophical 

 abstractions of' Willard Gibbs to the everyday re- 

 quirements of the engineer. The genius of Gibbs 

 laid foundations for much subsequent building, 

 which has been sure, if slow. In this matter we 

 have another proof that science, as the handmaid 

 of industry, fulfils herself in unexpected ways. 

 For the total heat, the "drop" of which is here 

 so fully and exactly tabulated, is nothing else than 

 one of the three thermodynamic "potentials" 

 which Gibbs described in his paper of 1875, using 

 the symbols f, x> '^"d l- Of these three functions, 

 rp and ^ have been applied in the thermodynamics 

 of chemistry, and x^ — ^ stone for which the 

 chemists had apparently no use — has indeed be- 

 come a corner-stone ih the temple of the engineer, 

 who, it may be added, has lately adopted ip also, 

 but with its sign reversed; 



The tables have evidently been prepared with 

 much care? On©- cannot but- regret that the com- 

 pilers have taken the very retrograde step of using 

 the Fahrenheit scale of temperature. English 

 engineers were beginning to free themselves from 

 this vexatious burden; It is a severe and wholly 

 unnecessary handicap to national progress in 

 engineering. 



J. A. EWING. 



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