Coupled effects of fin structures and nanofluids on the thermal-hydraulic characteristics of mini plate-fin heat sinks

To meet the heat dissipation requirements of high-heat-flux electronic components, miniature plate-fin heat sinks with four fin geometries, namely straight (fa), interrupted (fb), triangular corrugated (fc), and trapezoidal corrugated (fd), were designed and fabricated. Experiments were conducted using deionized water and Al 2 O 3 -water nanofluids with mass fractions of 0.1 wt% and 0.2 wt% as working fluids. The effects of heating power (30, 45, and 60 W), Reynolds number ( Re ), fin geometry, and working-fluid thermophysical properties on the thermal and flow characteristics of the heat sink were systematically investigated, including wall temperature, overall heat transfer coefficient, Nusselt number, pressure drop, friction factor and pumping power. The results show that the 0.1 wt% nanofluid provides the best cooling performance, effectively reducing the maximum local wall temperature by up to 2.13°C compared with deionized water. Among the tested structures, the trapezoidal corrugated fins (fd) combined with the 0.1 wt% nanofluid exhibit the optimal comprehensive thermal-hydraulic performance, with the Energy Efficiency Criterion (EEC) reaching up to 3.4 under high heat flux conditions. However, for the highly viscous 0.2 wt% nanofluid, the interrupted fin (fb) demonstrates a superior EEC due to its effective periodic disruption of the thickened thermal boundary layer. Although corrugated structures increase the pressure drop, the performance evaluation factor ( j / f ) and EEC results indicate that their heat transfer enhancement is more pronounced under high heat flux conditions. This improvement is attributed to the synergy between the secondary flow induced by trapezoidal corrugations and the enhanced thermal conductivity of the nanofluid, which disrupts the thermal boundary layer and improves overall performance with only a modest increase in pumping power. The results provide useful guidance for understanding the role of fin geometry and for evaluating the comprehensive performance of similar heat sinks operating with nanofluids.