NUMERICAL SIMULATION OF FREE CONVECTION IN A PARTLY POROUS CAVITY

In the present paper, the effect of effective thermal conductivity on natural convection heat transfer in threelayer porous cavity are analyzed using a collocated control volume formulation and a SIMPLT algorithm for pressure-velocity coupling. Identical porous layers are attached to the vertical walls, and the walls are held at constant temperature. The horizontal walls of the enclosure are assumed to be adiabatic. The problem is studied using a modified form of the Navier-Stokes equation by addition of a Darcy-Forchheimer terms. The aspect ratio of the cavity is equal to five and the saturated fluid is air ( 707 . 0 Pr = ). The analysis is performed for Rayleigh number 4 10 to 6 10 , porosity of 0.8 and for different Darcy numbers. It is shown that the main effect of the introduction of porous layers is to produce a large decrease of the effective thermal conductivity when the Darcy number is reduced. Moreover, the higher the Rayleigh number is the increase of effective thermal conductivity. So the main effect of porous layers is to reduce the upwind flow and then to decrease the natural convection heat transfer and effective thermal conductivity.