Multi-objective optimization of heat sinks with micro variable-density pin-fins for hotspot thermal management

This study proposes a novel micro pin–fin heat sink (MPFHS) with locally concentrated pin–fin arrangement (MP-LC) to efficiently cool hotspot region under ultra-high heat flux. The MP-LC consists of two regions: One is an ultra-high heat flux hotspot region (1000 W/cm²), using cylindrical pin-fins with small diameters and pitches to enhance heat dissipation. The other is the background region (50 W/cm²), featuring pin-fins with large diameters and pitches to avoid excessive pressure drop. This study employs computational fluid dynamics (CFD) simulation to analyze the hydrothermal characteristics of the MP-LC. The results indicate that the MP-LC provides a 52.72 % higher Nusselt number and a 38.2 % lower mean absolute temperature difference than those of globally sparse pin–fin heat sink, while its friction factor is 84.08 % lower than that of globally dense pin–fin heat sink. Moreover, the thermal enhancement factors of the MP-LC are all greater than 1.2. These findings suggest that the MP-LC significantly enhances heat dissipation at the ultra-high heat flux hotspot while effectively maintaining a low increase in pressure drop. This study further optimizes different pin–fin combinations for MP-LC by applying the NSGA-II algorithm, with the dual objectives of heat transfer maximization and pressure drop minimization. The optimization procedure generates a set of Pareto front solutions and the optimal solutions are selected from them by the TOPSIS and LINMAP methods.