STATE-OF-THE-ART REVIEW ON THE INFLUENCE OF FIN GEOMETRY ON AIR-SIDE HEAT TRANSFER AND PRESSURE DROP IN COMPACT HEAT EXCHANGERS

Abstract

This review comprehensively examines the influence of fin geometry on the thermo-hydraulic performance of compact heat exchangers (CHEs), emphasizing both plate-fin heat exchangers (PFHEs) and printed circuit heat exchangers (PCHEs). The study integrates findings from experimental investigations, numerical simulations, and analytical correlations to elucidate the relationship between fin configuration, heat transfer enhancement, and pressure loss. For PFHEs, louvered fins demonstrated superior heat transfer augmentation but incurred high pressure penalties, while perforated and wavy fins provided balanced performance with moderate hydraulic losses. In PCHEs, channel topology—ranging from straight and zigzag to wavy, S-shaped, and airfoil fins—significantly influenced flow distribution and overall efficiency. Straight channels offered minimal pressure drop yet limited enhancement, whereas zigzag and wavy geometries improved convective mixing and thermal uniformity. S-shaped fins effectively mitigated reverse flow and reduced pressure loss by up to fivefold, and airfoil fins achieved optimal thermal–hydraulic synergy with superior flow stability. Empirical and semi-empirical correlations for Nusselt number, friction factor, and Colburn j-factor were reviewed and compared across various Reynolds number regimes. The findings underscore that optimal fin geometry selection is critical to balancing heat transfer augmentation with hydraulic efficiency, making advanced PCHE designs—especially wavy, S-shaped, and airfoil configurations—promising candidates for supercritical CO₂ Brayton cycles, molten-salt systems, and next-generation high-efficiency energy applications.