Conjugate heat transfer analysis of micro-channel using novel hybrid nanofluids (Al2O3 + Ag / Water)

Laminar forced convection flow of nanofluids in a wide rectangular micro-channel has been numerically studied. The present study investigated the flow and heat transfer characteristics of Aluminium oxide (Al2O3), silver (Ag) and hybrid (Al2O3+Ag) nanofluids in a micro-channel. The conduction phenomena of the solid region show a significant effect on the heat transfer characteristics of nanofluid. Hence, the channel is considered with finite thickness on its bottom to accommodate heat source or electronic component and a uniform heat flux is applied to the three sides of the solid region. A two-dimensional conjugate heat transfer homogeneous phase model has been developed and results are reported for different Reynolds numbers. The governing equations are solved by Simplified Marker and Cell (SMAC) algorithm on non-staggered grid using finite volume method. The effects of Reynolds number, pure nanoparticles volume concentration, hybrid nanoparticles mixture volume concentrations and nanoparticles size on the flow and heat transfer characteristics are reported. The results show that the average convective heat transfer coefficient increases with increase in nanoparticles volume concentration and Reynolds number. The nanofluids obtained by dispersing nanoparticles such as Al2O3, Ag and hybrid (Al2O3+Ag) in the base fluid shows a significant enhancement of average convective heat transfer coefficient in comparison with pure water. It is also observed that 3 vol.% hybrid nanofluid (0.6 vol.% Al2O3+2.4 vol.% Ag) shows higher average convective heat transfer coefficient than that of pure water, pure oxide (Al2O3) and pure metallic (Ag) nanofluids. The study presents that hybrid nanofluids are the new class of working fluids with less volume concentration of metallic (Ag) nanoparticles. Moreover, use of hybrid nanofluids at high volume concentration reduces the cost of the working fluid and enhances the heat transfer characteristics in comparison with that of metallic nanofluids. The interface temperature between solid and fluid regions are reported for different nanofluids. The size of the nanoparticle shows significant effect on heat transfer characteristics. The present results are matching with the numerical and experimental results available in the literature