Natural convection–thermal radiation interaction in a non-Newtonian nanofluid-filled square cavity with a conductive baffle

Abstract

This research aims to investigate the combination of natural convection and surface and volumetric radiation in water-aluminum oxide nanofluid with non-Newtonian effects in a square cavity with a conductive baffle on its hot wall. The left wall is hot while the right one is cold. Moreover, the horizontal walls are insulated, and the internal walls are radiatively active. The mass, momentum, and energy conservation equations are solved numerically using the control-volume-based finite difference method and the SIMPLE algorithm considering the surface radiation for the interior surfaces of the cavity and volumetric radiation for the non-Newtonian nanofluid. The volumetric radiation term in the energy equation is approximated using the Rosseland method. The effect of the Rayleigh number (Ra), the power-law index, and the volumetric radiation parameter on the flow field and the heat transfer rate are investigated using the numerical analysis results. Based on the results, an increase in Ra and a decrease in the power-law index lead to a rise in the heat transfer rate at a constant radiation parameter. As the Ra rises in the range, the average Nusselt number increases to 10 times at n = 0.8. Moreover, a rise in the volumetric radiation parameter increases the radiative Nusselt number and decreases the convective Nusselt number in both shear thickening and shear thinning fluids, although it increases the overall Nu. Increasing the volumetric radiation parameter from 0 to 2 enhances the average Nusselt number by more than 2.5 times at Ra = 103 and less than 2 times at Ra = 105.