Local thermal non-equilibrium analysis of conjugate free convection within a porous enclosure occupied with Ag-MgO hybrid nanofluid

Current investigation aims to analyze the conjugate free convection inside a porous square cavity occupied with Ag-MgO hybrid nanofluid using the local thermal non-equilibrium(LTNE) model. Hybrid nanofluids are a novel kind of enhanced working fluids, engineered with enhanced thermo-physical and chemical properties. Two solid walls located between the horizontal bounds in two sides of cavity play the role of a conductive interface between the hot and cold walls, and moreover, the top and bottom bounds have been insulated. The governing differential equations are obtained by Darcy model and then for better representation of the results, converted into a dimensionless form. The finite element method is utilized to solve the governing equations. To evaluate the correctness and accuracy of the results, comparisons have been performed between the outcomes of this work and the previously published results. The results indicate that using the hybrid nanoparticles decreases the flow strength and the heat transfer rate. The heat transfer rate augments when R-k rises and the flow strength augments when Ra grows. Enhancing the porosity increases strongly the size and strength of the vortex composed inside the porous medium. When K-r is low, the heat transfer rate is low and by increasing K-r, thermal fields become closer to each other. The effect of hybrid nanoparticles on thermal fields with the thinner solid walls is more than that the thicker ones. An increment in H eventuates the enhancement of heat transfer and hence, the thermal boundary layer thickness. By increasing the volume fraction of the hybrid nanoparticles, Nu(hnf) and Nu(s) decrease in constant Ra. Besides, increase in Ra enhances the Nu(hnf) and Nu(s). For a certain d, the reduction of Nu(s) due to using the hybrid nanoparticles is more than that for Nu(hnf). The increment of d lessens Nu(hnf) for all values of K-r and has not specific trends for Nu(s). Utilizing hybrid nanoparticles decreases Nu(s) (except d=0.4), rises Nu(s) when K-r<18, while it can increase Nu(s) for K-r>42. In constant d, increment of H, respectively, decreases and boosts Nu(hnf) and Nu(s). For all values of d, increment of epsilon declines Nu(hnf). In low value of d, the increase in epsilon reduces Nu(s), whereas at higher values, Nu(s) has continuously enhancing trend. For different values of d, the increase in epsilon scrimps Nu(hnf). The increment of d and also epsilon, and H are, respectively, decreases and increases the heat transfer rate.