Estimating the non-uniform air velocity distribution for the optimal design of a heat exchanger

The maldistribution of flow in a heat exchanger usually has negative effects on the heat exchanger specifications such as the effectiveness, annual cost, and pressure drop. This paper examines the issue to improve the thermoeconomic performance. For this purpose, a plate-fin heat exchanger was selected and optimized by considering both the effectiveness and total annual cost as objective functions. The design parameters were the parameters of the heat exchanger and fin, as well as the non-uniform inlet flow profiles for both sides of the hot and cold streams. To generalize the results, the optimization was applied at different mass flow rates. The optimum results of the non-uniform profile were compared with those obtained with a uniform profile of the inlet flow. The optimum results reveal that thermoeconomic improvement occurred in the case of non-uniform flow compared with the case of uniform flow. For example, a 12.7% reduction for the total annual cost was found in the case of non-uniform flow in comparison to the uniform flow for a fixed effectiveness of 0.92. At low effectiveness, no significant improvement was found in the case of non-uniform flow. Nevertheless, the suggested profiles could be considered as an alternative to uniform inlet profiles.