Numerical investigation of natural convection of a non-Newtonian nanofluid in an F-shaped porous cavity

This study numerically investigates the free convective heat transfer of a non-Newtonian nanofluid through an F-shaped porous cavity. The thermal conditions of the walls of the cavity are assigned as T-C and T-H for the cold right wall and the hot left wall, respectively, and the remaining walls of the cavity are assigned as insulated walls. The model for this investigation is designed, implemented, and analyzed by COMSOL Multiphysics. The Galerkin finite element method is used to model and solve the governing equations of the flow and heat transfer process inside the porous media. Physical parameters are presented in the following order: 6 x 10(-2) >= phi >= 0.0,0.4 >= AR >= 0.1,10(-1) >= Da >= 10(-3),1.4 >= n >= 0.6, and 10 >= Ra >= 10(6). The goal of this study is to study the influence of geometry configuration (F shape) and the above parameters on the flow structure, isotherms, and heat transfer. These parameters have been taken into account to investigate their effects on this kind of heat transfer mechanism. Results show that the addition of nanoparticles plays a significant role in changing heat transfer rates. In addition, an increase in the aspect ratio (AR) leads to create narrow areas, which promotes the stagnation zones, thus decreasing the distance between cold and hot walls. This, in turn, enhances the flow uniformity. Moreover, it has been generally concluded that the Nusselt number and velocity rates are directly proportional to the AR, Darcy number (Da), and Rayleigh number (Ra), and negatively proportional to the power-law index (n); however, there are some exceptions and unusual behaviors noticed and explained through the paper.