THE EFFECT OF AL2O3 NANOPARTICLES SPHERICITY ON HEAT TRANSFER BY FREE CONVECTION IN AN ANNULAR METAL-BASED POROUS SPACE BETWEEN VERTICAL CYLINDERS SUBMITTED TO A DISCRETE HEAT FLUX

In the present study, the transferred thermal heat by the phenomenon of free convection flow in an annular metal-base porous space inside two vertical concentric cylinders saturated by a (AL(2)O(3)-water) nanofluid with different shapes of nanoparticles (NPs) has been numerically investigated. The finite difference method is used to solve the governing system of equations. The outer cylinder is kept at constant temperature, and the discrete heat flux and the unheated adiabatic sections are placed on the inner cylinder. The base walls are insulated and impermeable. The obtained results of the numerical simulation are presented to exhibit the consequences of various parameters, such as the Rayleigh number (Ra-Th), Darcy number (Da), porosity (epsilon), solid NPs volume fraction (phi), and the shape of NPs as well as the conductivity ratio of porous media (lambda). It is observed that the transferred thermal flux increases as the conductivity ratio of porous media increases. The results obtained also show an improvement of the rate of heat transfer with the increase in Darcy number, Rayleigh number, and NPs volume fraction. Furthermore, a significant improvement in the overall heat transfer has been found with oblate and prolate alumina (Al2O3) spheroid NPs.