Effects of a random porosity model on heat transfer performance of porous media

Abstract

Due to the non-uniform distribution and fractural structure of the beads inside a porous medium, the porosity distributed in the porous medium is random for most realistic situations. Therefore, the effects of the porosity distributed casually inside a porous block mounted on a heated region with a laminar slot impinging jet on flow and thermal fields are investigated numerically. A numerical method of SIMPLEC is adopted to solve governing equations, as for the energy equation, a one-equation thermal model with Van Driest's wall function is adopted. AU the non-Darcian effects including the solid boundary and inertial effects are considered and three different porosity models of constant, variable and random are examined. The results indicate that the relationship between the local Nusselt number Nu(x) and the near wall local porosity epsilon(x) is a negative correlation. Consequently, in order to enhance the thermal performance of the porous medium, the porosity near the solid plate should be smaller to make the conductive heat transfer to be dominant. (C) 1998 Elsevier Science Ltd. All rights reserved.