. The steam-engine and other heat-motors . ly, increasing compression should produce a loss ofeconomy for the following reason. The steam-engine is a mechan-ism for the conversion of heat into work. No economy can resultby changing the expensively obtained work back into heat, sinceall changes of energy from one form into another are accompaniedby loss. As a practical result, in engines designed for economy,clearance surface is reduced to the minimum by placing the valvesin the cylinder-heads and only a moderate amount of compression,conducive to smooth running, is used. 6. The amount of conde
. The steam-engine and other heat-motors . ly, increasing compression should produce a loss ofeconomy for the following reason. The steam-engine is a mechan-ism for the conversion of heat into work. No economy can resultby changing the expensively obtained work back into heat, sinceall changes of energy from one form into another are accompaniedby loss. As a practical result, in engines designed for economy,clearance surface is reduced to the minimum by placing the valvesin the cylinder-heads and only a moderate amount of compression,conducive to smooth running, is used. 6. The amount of condensation will be affected by the sizeand proportions of the cylinder. Comparing two cylinders (the 190 THE STEAM-ENGINE AND OTHER HEAT-MOTORS. linear dimensions of one being twice that of the other), thelarger one could perform eight times the work of the smaller,but its internal exposed area would only be four times as great,hence the percentage of condensation would be for engines of the same volume, by proper choice of. Fig. 110. dimensions there would be one of minimum exposed internalsurface. 7. Other variables also affect the result. We may men-tion steam-pressure, revolutions, ratio of expansion, and jacketing. Range of Temperature.—The amount of initial condensationdepends upon the range of temperature of the cylinder walls, and MEASUREMENT OF HEAT LOSSES. 191 economy follows a reduction of this range. The range is de-creased— 1. By a late cut-off. By studying the conditions we notethat the part exposed to the initial steam was exposed to theexhaust conditions for a short time only, and more of the sur-face is at the highest temperature. 2. By the reduction of the amount of water present at cut-off. The walls part readily with their heat to a film of waterand less readily to dry steam. Therefore the lower tempera-ture is raised by reducing the amount of water to be evaporated. 3. By reducing the time of exposure. The element of timealways affects th
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