Effectiveness-NTU Relationship for a Counterflow Heat Exchanger Subjected to an External Heat Transfer

[+] Author and Article Information
Gregory F. Nellis

 University of Wisconsin, 1500 Engineering Drive, Madison WI 53706gfnellis@engr.wisc.edu

John M. Pfotenhauer

 University of Wisconsin, 1500 Engineering Drive, Madison WI 53706

J. Heat Transfer 127(9), 1071-1073 (Nov 11, 2004) (3 pages) doi:10.1115/1.2010496 History: Received August 26, 2004; Revised November 11, 2004

This paper presents the analytical solution for the effectiveness of a counterflow heat exchanger subjected to a uniformly distributed, external heat flux. The solution is verified against conventional ε-NTU relations in the limit of zero external heat flux. This situation is of interest in applications such as cryogenic and process engineering, and the analytical solution provides a convenient method for treating differential elements of a heat exchanger in a numerical model.

Copyright © 2005 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 1

(a ) Counter-flow heat exchanger with a uniform external load applied to both streams and (b ) a differential control volume for the heat exchanger

Grahic Jump Location
Figure 2

Effectiveness as a function of NTU in the limit of no external heat load for various values of Cr using the zero external heat load solution, Eq. 30, and the solution derived here, Eq. 24

Grahic Jump Location
Figure 3

Ratio of the hot-side effectiveness to the zero parasitic effectiveness as a function of NTUh for various values of parasitic heat loads (with Crh=1).



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