The effects of longitudinal fin conduction on multipass cross-counterflow heat exchanger performance are considered in this numerical study. The nondimensional differential equation system that describes the temperature distributions in the fluids and fins is solved in terms of normalised heat exchanger thermal resistances. Model results are presented in a series of graphs that show the regimes in which longitudinal fin conduction must be considered. The locus of points that describes optimal heat exchanger performance is presented with a simple correlation. The application of the results to heat exchanger design optimisation is discussed.

KEYWORDS: heat exchangers, cross flow heat exchangers, counterflow heat exchangers, finned tube heat exchangers, optimisation, performance, temperature distribution, fluids, conduction, thermal resistance, heat transfer coefficient