Numerical study of curved pin-fin cross-sections for enhanced thermal–hydraulic performance in microchannel cooling

Efficient heat dissipation is crucial for modern high-heat-flux systems, where microchannel cooling offers compactness and high surface–area density. This study numerically investigated the thermal–hydraulic performance of air-cooled microchannels equipped with curved pin-fins featuring four cross-sectional shapes: a smooth circular baseline (C1) and multi-convex profiles containing 2, 3, and 4 lobes (C2–C4). Simulations were performed for Reynolds numbers of 200–1000 under uniform heat flux applied to both the endwall and fin surfaces, and the resulting flow structures, heat-transfer behavior, and pressure losses were evaluated using local and area-averaged Nusselt numbers, friction factors, and thermal-performance factors ( TPF ). The results showed that introducing cross-sectional convexity substantially modified the internal flow by enhancing impingement, strengthening secondary vortices, and suppressing wake regions. Among the tested designs, the two-convex geometry (C2) showed the greatest heat-transfer enhancement, whereas the three-convex configuration (C3) provided the most favorable thermal–hydraulic balance and consistently yielded the highest TPF . These findings clarified the governing mechanisms associated with curvature-induced mixing and demonstrated how tailored cross-sectional shaping can improve energy efficiency in microchannel-based cooling systems. The work provided practical geometric guidelines for advanced thermal management in battery modules, compact heat exchangers, and high-power electronics.