Thermal Properties of Systems Exhibiting Optimum Countercurrent Heat Exchange

Abstract

Heat flow in heat exchange systems, operating at constant pressure, is.considered in relation to the thermodynamical measure of entropy called by Keenan. the availability. The ratio of the maximum attainable mechanical work from two.systems (1) and (2) is shown to be equal to the ratio of the two availabilities or.l:1B1/l:1Bg, and this reasonably approaches unity only when the exchanger involves.countercurrent flow. The temperatures and temperature differences may be plotted against the linear dimension along the exchanger. The temperature difference will pass through one or more stationary values associated with a temperature T*. At such a pivotal point, we may define enthalpies, l:1H;, l:1H; and specific heats (c;, c;) of the two streams in which the following relations hold: