Experimental and numerical investigations of the thermal–hydraulic characteristics of novel micropin-fin heat sinks

Micropin-fin heat sinks (MPFHSs) have great potential to dissipate heat from microelectronic equipment. However, explorations of MPFHSs with novel pin fins are still rare. By drawing on the flower of Clematis montana and the skin of Squalus acanthias, two micropin-fin structures, termed petaloid and placoid, were designed. The thermal–hydraulic characteristics of water flowing in MPFHSs were investigated with inlet temperatures of 10 and 20 °C, Reynolds number (Re) values of approximately 300–1500, and heat fluxes of 80–120 kW/m2. The heat transfer coefficient, Nusselt number (Nu), pressure drop and friction factor (f) of the MPFHS with petaloid pin fins were the largest, and those of the MPFHS with placoid pin fins were the smallest. The values increased with increasing Re except for the f, changed slightly with heat flux, and decreased with inlet temperature except for the f due to variation in physical properties. The temperature and velocity fields of MPFHSs were affected by pin fins. The water temperature was higher near the tail of the pin fins than in areas farther from the pin fins. Vortices generated by petaloid pin fins were the most plentiful and largest, while those generated by placoid pin fins were the least plentiful and smallest. For MPFHSs with different pin fins, the transition from laminar to turbulent flow was different; the transition Re was approximately 900 for petaloid and circular pin fins and larger than 1500 for placoid pin fins. The comprehensive performances of MPFHSs were evaluated by different indicators. For indicators emphasizing heat transfer, petaloid pin fins performed better than circular pin fins at small Re, and placoid pin fins performed worst in the whole Re range. For indicators emphasizing flow resistance, petaloid pin fins performed worst, and placoid pin fins performed best. New correlations of the Nu and f for MPFHSs with different pin fins were proposed with mean absolute deviations less than 2.0 and 4.5%, respectively.