The present research work examines the use of Al2O3- and CuO-water-based nanofluids in microchannel heat sinks via combined CFD simulations and experiments. The study targeted the effect of the parameters on the performance of the MCHS. The microchannel heat sinks considered in this work are rectangular channels with a width of 100 m and a height of 300 m. A 3D steady-state single-phase mixture model was used to perform heat transfer and flow simulations in these microchannels under a constant heat flux of 100 W/cm over the Reynolds number range of 400-1200 and 0-4%. The simulation results showed an enhancement by 12-41% for the Nusselt number (Nu) and heat transfer coefficient (h) relative to water, with the maximum at 2-4% AlO-water (Nu=11.9, h=35.7 kW/mK at Re=800). The thermal resistance was decreased by 24%, and the maximum temperature decreased from 68.5°C to 57.8°C. There were certain compromises on the pressure drop side, with the pressure drop reaching as much as 50% (P=11.2 kPa at Re=1200) and pumping power increasing by 39%. Nevertheless, the ratio of heat transfer coefficient to pressure drop remained favourable for Re below 800. The CFD results were compared to the reference experiments, and the agreement was within 1-5%. The elevated conductivity and micro-convection of the nanofluids were the main factors that made them effective. The best performance was realised by the working fluid of 2% AlO-water, which corresponded to a thermal improvement of 28%, but the hydrodynamic performances were still at acceptable levels. So, it seems realistic to utilise the compact cooling system for the electronics with heat fluxes exceeding 790 W/cm, which was the maximum limit when potable water was used as the cooling fluid.

CFD, Heat Sinks, MCHS, heat transfers, nano-fluids