A numerical study on natural convection and entropy generation in a porous enclosure with heat sources

Abstract

In this paper, fluid flow and thermal characteristics associated with natural convection heat transfer in a porous enclosure containing high temperature heat sources placed on top and bottom walls are studied. For this purpose, two-dimensional, time-dependent Navier–Stokes equations with Darcy–Brinkman–Forchheimer terms are solved in a Cartesian framework by using Streamline Upwind Petrov–Galerkin (SUPG) based finite element method. The effect of heat sources on flow pattern, entropy generation and temperature distribution are studied for different Darcy numbers, porosities and Rayleigh numbers. The results show that maximum entropy generation due to heat transfer irreversibility is observed in the vicinity of heat sources due to the presence of high thermal gradient. The global entropy generation due to fluid friction is found to increase in convection dominated regime. It is also observed that with increasing Darcy number, porosity and Rayleigh number the surface averaged Nusselt number for both top and bottom heat sources is increased.