Air side thermal and hydraulic performance assessment of skived, louver, offset honeycomb, and metal foam finned mini-channel heat exchangers

Abstract

This study presents a comparative performance evaluation of mini-channel compact heat exchangers, focusing on four distinct extended surface configurations of skived plate fin, louver fin, metal foam, and offset honeycomb. The experiments are conducted in an air tunnel, where the Re number of the airflow ranges from 100–1400, and a constant surface temperature is maintained using a water bath. To ensure a fair comparison, all four configurations are tested under identical conditions. The performance of each configuration is assessed in terms of air-side heat transfer coefficient, pressure drop, Colburn j-factor, and friction factor. In addition to these conventional performance indicators, the heat exchangers are further evaluated using the heat transfer index with respect to friction power, both with and without accounting for compactness. According to the findings, although the cell-based configurations consistently outperform the plate-fin configurations under all conditions, the metal foam and offset honeycomb each demonstrate superiority in different performance metrics. While the heat transfer coefficient reaches approximately 110 W/(m²K) for the metal foam configuration, the offset honeycomb achieves up to 100 W/(m²K) within the same flow range. When evaluated based on the heat transfer index considering compactness, the performance order shifts, with offset honeycomb and metal foam providing values of 60.08 kW/(m³K) and 56.76 kW/(m³K), respectively. Under all tested conditions, the louver configuration, although the most commonly utilized extended surface in conventional applications, falls short of achieving the performance levels demonstrated by the novel designs introduced in this study.