Effect of finite thermal conductivity of the separating wall on the performance of counterflow heat exchangers

Abstract

Axial conduction is a major source of inefficiency in a compact counterflow heat exchanger. Any attempt to reduce axial conduction by using material of low thermal conductivity for the separating wall results in increased resistance to lateral heat flow, thereby reducing the overall thermal efficiency of the heat exchanger. The governing equations including axial conduction and lateral resistance due to the separating wall have been solved and an expression, for the overall efficiency of the heat exchanger has been derived in terms of relevant nondimensional parameters. Computed results have been presented which give the optimum thermal conductivity of the wall material.