Entropy analysis and thermal performance of Ag/MgO hybrid nanofluid in microchannel: A numerical study

• Ag-MgO/water HNF in CPU microchannel: Numerical study (φ=0-1.5%, Re=100-2000) vs MNFs. • HNF best reduces thermal resistance with rising φ/Re, outperforms MNFs across all φ. • Max CPU temperature drop: 6.32% (HNF, φ=1.5%, Re=100) vs base fluid, cutting hotspot risk. • HNF entropy generation drops at high Re: Thermal entropy decrease dominates frictional rise. • Bejan number falls with Re/φ; HNF shows lowest values (14.16%↓ at φ=1.5%, Re=2000). This study numerically examines the effect of Ag-MgO/water hybrid nanofluid (HNF) concentration (0.5-1.5 vol%) on hydrodynamics, heat transfer, and entropy generation in a heated microchannel (Dh = 0.42 mm, AR = 2.33, q'' = 60.225 kW/m²) under laminar flow (Re = 100-2000). Numerical simulations were performed using a finite volume method. The findings show that the maximum augmentation in Nusselt number was 13.33%, 6.15%, and 4.08% at concentration 1.5%, for the Ag-MgO/water, Ag/water, and MgO/water, respectively, compared to the base fluid. Hence, a maximum reduction in CPU temperature was achieved, 6.32% for HNF at Re = 100 and φ = 1.5% compared to the base fluid. Furthermore, for HNF, an increase in the Re reduces total entropy generation (a decrease in thermal entropy generation significantly outweighs the increase in frictional entropy generation) compared to mono nanofluids (MNF) and base fluids. The Bejan number (Be) for both HNF and MNF varies inversely with increasing Re and concentration. The values of thermohydraulic performance factor (THPF) enhance with increasing concentration. The highest THPF at 1.5% volume concentration and Re = 800 is 1.254 for the Ag-MgO/water hybrid nanofluid, compared to 1.229 for Ag/water MNF and 1.222 for MgO/water MNF. These improvements can lead to more compact, reliable, and energy-efficient cooling solutions for high-performance electronic devices.