. The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world . zed, since there is alwayssome conduction and radiation of heat by thematerials of the compressing mechanism. Were it possible to compress a volume of airstrictly according to Boyles Law — , isother-mally — it is evident that when the originalpressure had been doubled, the original volumewould have been reduced exactly one half. Butin practise it is found that when the pressurehas been doubled, the volume has not been re-duced one half,
. The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world . zed, since there is alwayssome conduction and radiation of heat by thematerials of the compressing mechanism. Were it possible to compress a volume of airstrictly according to Boyles Law — , isother-mally — it is evident that when the originalpressure had been doubled, the original volumewould have been reduced exactly one half. Butin practise it is found that when the pressurehas been doubled, the volume has not been re-duced one half, and the temperature is verymuch increased. If now the process of com-pression be stopped and the temperature of theair allowed to drop to its original value, thevolume remains the same but the pressure isfound to have fallen to less than twice the origi-nal. To reach the required pressure of twicethe initial, compression must be carried Stillfurther, with another manifestation of heat. Aconsideration of these facts shows plainly thata part of the work of compression was ex-pended in producing an increased temperature COMPRESSED AIR COMPRESSED AIR INDUSTRIAL LOCOMOTIVE FOR SURFACE USE. COMPRESSED AIR which, acting momentarily according to Gay-Lussac*s Law, increased the pressure of the airvolume. But this added pressure was an un-stable quantity, disappearing as the air cooled;and it is evident that the energy applied in pro-ducing this heat increment of pressure was,for all practical purposes, wholly lost. Inother words, more power is required to producea given volume at a given pressure when the airis allowed to heat itself, than would be necessaryif the air could be kept cool throughout com-pression. In the first case, we have adiabaticcompression; in the second, isothermal. This,in brief, is an explanation of the phenomenaand the problems which have confronted the de-signers of the modern air compressor. Evidently the solution of the thermo-dynamicproblems
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectencyclo, bookyear1903
