Multi-objective optimization of a hybrid nanofluid jet impinging on a microchannel heat sink with semi-airfoil ribs based on field synergy principle

With the increasing power density of electronic devices, improving the cooling performance of their heat sinks is an important aspect of heat transfer enhancement research. A novel jet impinging microchannel heat sink with semi-airfoil ribs (JIMCHS-SAR) is proposed. Hybrid Cu-Al2O3/H2O nanofluid is adopted as the coolant. Using the field synergy principle, the flow and heat-transfer characteristics of the hybrid nanofluid impinging on the JIMCHS-SAR are investigated by both single-factor analysis and multi-objective optimization. The effects of jet Reynolds number and hybrid nanoparticle concentration on the optimized JIMCHS-SAR are also evaluated. The results show that a bilateral symmetrical arrangement of the semi-airfoil ribs provides the best thermal resistance and the smallest field synergy angle. Using the optimal structural parameters of the JIMCHS-SAR obtained from multi-objective optimization can significantly improve its overall performance. The thermal resistance and pump power of the optimal JIMCHS-SAR are 1.080 K/W and 0.387 W, respectively. The maximum temperature of the JIMCHS-SAR bottom surface is 8.1 K less than that for a jet impingement microchannel flat plate heat sink. As Reynolds number increases from 6000 to 14,000 and hybrid nanofluid volume fraction increases from 0 to 2.0 %, the thermal resistance decreases from 1.185 K/W to 0.908 K/W, a decrease of 23.4 %, while the pump power increases from 0.22 W to 2.1 W, a nearly 10-fold increase.