Thermo-hydraulic and thermodynamic performance of a diamond-based hybrid pin-fin microchannel heat sink for hotspot mitigation

With the rapid advancement and miniaturization of high-power integrated circuits, local heat fluxes can exceed 1000 W/cm 2 , posing severe challenges to thermal management. This study proposes a diamond-based hybrid pin-fin microchannel heat sink (MCHS) for localized hotspot mitigation and numerically investigates four pin-fin geometries. The thermo-hydraulic performance, entropy generation characteristics, and heat dissipation limits are systematically evaluated. The circular pin-fin configuration exhibits the best heat-transfer performance, with the lowest surface temperature and total thermal resistance; at Re =1000, its total thermal resistance is 8.2% lower than that of the triangular configuration. In contrast, the triangular pin-fin exhibits the lowest pressure drop but the highest total thermal resistance, highlighting the trade-off between thermal and hydraulic performance. Second-law analysis shows that temperature-difference-induced entropy generation dominates the total irreversibility, while the frictional contribution remains below 0.3%. The circular pin-fin also achieves the lowest augmented entropy generation number of 0.347 at Re = 1000. Under the prescribed thermal safety constraint of T max < 358.15 K, the circular pin-fin achieves the highest removable heat flux of 3200 W/cm 2 at Re = 800 and T inlet = 293.15 K, exceeding those of the diamond, square, and triangular configurations by 8.5%, 10.3%, and 14.3%, respectively. A combined assessment using COP, PEC , and entropy-based metrics further indicates that the configuration with the best thermal performance does not necessarily provide the best overall energy efficiency. These findings provide guidance for the design of hotspot-oriented microchannel cooling systems under ultra-high-heat-flux conditions.