In this paper, two fundamental principles of differential Second Law analysis are set forth for heat exchanger design. The first principle defines a Second Law temperature, while the second principle defines a Second Law temperature difference. The square of the ratio of the Second Law temperature difference to the Second Law temperature is shown always to be equal to the negative of the partial derivative of the rate of entropy generation (for heat transfer) with respect to the overall conductance of the heat exchanger. For the basic design of elementary heat exchangers, each of these two Second Law quantities is shown to take the form of a simple geometric average. Nonelementary considerations result in corrected geometric averages, which relate directly to the corrected log-mean temperature difference. Both the corrected log-mean temperature difference (nonelementary considerations) and the uncorrected or just log-mean temperature difference (elementary considerations) are widely used in heat exchanger analysis. The importance of these two principles in both exergy and essergy analysis is illustrated by a unified basic treatment of the optimum design of elementary heat exchangers. This results in a single optimization expression for all flow arrangements (i.e., counterflow, parallel flow, and certain crossflow cases).
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Two Principles of Differential Second Law Heat Exchanger Design
R. B. Evans,
R. B. Evans
Georgia Institute of Technology, The George W. Woodruff School of Mechanical Engineering, Atlanta, GA 30332
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M. R. von Spakovsky
M. R. von Spakovsky
E´cole Polytechnique Fe´de´rale de Lausanne, De´partment de me´canique, Laboratoire d’e´nerge´tique industrielle, Lausanne, Switzerland
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R. B. Evans
Georgia Institute of Technology, The George W. Woodruff School of Mechanical Engineering, Atlanta, GA 30332
M. R. von Spakovsky
E´cole Polytechnique Fe´de´rale de Lausanne, De´partment de me´canique, Laboratoire d’e´nerge´tique industrielle, Lausanne, Switzerland
J. Heat Transfer. May 1991, 113(2): 329-336 (8 pages)
Published Online: May 1, 1991
Article history
Received:
April 26, 1989
Revised:
August 31, 1990
Online:
May 23, 2008
Citation
Evans, R. B., and von Spakovsky, M. R. (May 1, 1991). "Two Principles of Differential Second Law Heat Exchanger Design." ASME. J. Heat Transfer. May 1991; 113(2): 329–336. https://doi.org/10.1115/1.2910565
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