Enhancement in thermo-hydraulic performance of ceramic-based disk heat sink with fractal micro-channels via double layering, hybrid nanofluids, and cross-sectional convergence

The focus of this paper is to further improve the thermo-hydraulic performance of a disk heat sink with fractallike microchannels by introducing four distinct modifications: incorporating convergent cross-sections in microchannels, implementing double layering, utilizing a high-conductivity material (AlN ceramic) for the heat sink, and integrating hybrid nanofluids. Hybrid nanofluids, encompassing Aluminum Oxide-Graphene, Aluminum Oxide-Copper, and Copper-Graphene, each with varying volume fractions and an overall volume fraction of 2 % and 4 %, were systematically evaluated. The cumulative impact of these modifications on the four levels fractal-like microchannel heat sink's thermo-hydraulic performance was rigorously assessed through numerical simulations. The flow rate ranges from 300 to 600 ml/min, corresponding to an inlet Reynolds number in the range of 3014 to 6018.The findings reveal that the increase around 10 % in Nusselt number can be achieved through implementing converging cross-sections at levels 3 and 4. Substituting silicon with AlN ceramic leads to a reduction in maximum temperature from 1.85 to 2.58 degree celsius, depending on the flow rate. Under a heat flux of 40 W/cm2, double layering can reduce thermal resistance by 0.2. Most effective configuration involves a doublelayered fractal microchannel with convergent cross-sections at levels 3 and 4, employing AlN ceramic as the material, and utilizing a hybrid water-based nanofluid with a volume fraction of Cu 3 %-Al2O3 1 %. This configuration achieves a notable reduction in maximum temperature by 11.1 degrees C and 17.97 degrees C under heat fluxes of 40 and 80 W/cm2, respectively, at a volumetric flow rate of 300 ml/min.