EFFECT OF ANISOTROPY IN PERMEABILITY AND EFFECTIVE THERMAL CONDUCTIVITY ON THERMAL PERFORMANCE OF AN ALUMINUM FOAM HEAT SINK

Abstract

A numerical study has been carried out to investigate the thermal characteristics of an aluminum foam heat sink. An aluminum foam heat sink horizontally placed in a channel is modeled as a hydraulically and thermally anisotropic porous medium. A uniform heat flux is given from the bottom of the heat sink. Cold air is supplied from the top opening of the channel and exhausts to the channel outlet. Comprehensive numerical solutions are acquired to the governing Navier-Stokes and energy equations, using the Brinkman-Forchheimer extended Darcy model for the region of heat sink. It is assumed that the solid is in the local thermal equilibrium with the fluid. Details of flow and thermal fields are examined over wide ranges of the principal parameters: the Darcy number Da, the anisotropic permeability ratio K*(=K ₂/K ₁), and the anisotropic effective thermal conductivity ratio k*(=k ₂/k ₁). The results indicate that the anisotropy in permeability and effective thermal conductivity yields a significant change in the heat transfer rate. The same numerical approach that involves the anisotropic porous medium model is also applied to the thermal analysis of a conventional pin-fin heat sink.