Compressed air production; or, The theory and practice of air compression . gauge pressure at half stroke. Thedifference, 9 pounds, represents the effect of the heat of compression inincreasing the relative volume of the air. The specific heat of air under constant pressure being , wehave heat units produced by compressing one pound, or13 cubic feet, of free air into one-ialf its volume; (Joules equiva-lent)3^ 1,3 07 foot pounds. We know that 33,000 foot pounds is onehorse-power, and we see how easily about two-thirds of a horse-power inheat units may be produced a
Compressed air production; or, The theory and practice of air compression . gauge pressure at half stroke. Thedifference, 9 pounds, represents the effect of the heat of compression inincreasing the relative volume of the air. The specific heat of air under constant pressure being , wehave heat units produced by compressing one pound, or13 cubic feet, of free air into one-ialf its volume; (Joules equiva-lent)3^ 1,3 07 foot pounds. We know that 33,000 foot pounds is onehorse-power, and we see how easily about two-thirds of a horse-power inheat units may be produced and lost in compressing one pound of this same loss is suffered when compressed air does work in anengine without reheating, and is expanded down to its original other words, the heat of compression and the cold of expansion are indegree equal. Figure 1 is a sketch designed to indicate graphically the effect of heatand cold in compression and expansion of air. Rt«t ^ ft 1?& aYh.«\*\ ExpATV*T,oivii<$ Conltviwiouft H«eftvng. ?. The sketch illustrates an open cylinder, which may serve both as an aircompressor and an air engine. The piston at the point shown is sup-posed to confine a volume of free air in the cylinder and at a temperatureof 60 degrees; let it be pressed down until it reaches the point indicated COMPRESSED AIR PRODUCTION. 7 by 45 pounds, and the pressure will follow the dotted lines marked Adia-batic. This is, of course, assuming that the heat, which is invariablyproduced by compression, is suffered to remain in the air and to in-fluence the pressure. We here have a confined volume of compressed airat a pressure of 45 pounds and a temperature of 320 degrees. Let therebe no absorption of heat and the piston if released will return to thestarting point, the pressure following exactly the line indicated duringcompression and the temperature returning to 60 degrees. In such acase we assume, of course, that the piston is frictionl
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Keywords: ., bookcentury1800, bookdecade1890, bookid, booksubjectcompressedair
