A numerical study has been carried out to optimize the thermal performance of a pin-fin heat sink. A pin-fin heat sink placed horizontally in a channel is modeled as a hydraulically and thermally anisotropic porous medium. A uniform heat flux is prescribed at 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 derived from the governing Navier-Stokes and energy equations, using the Brinkman-Forchheimer extended Darcy model and the local thermal non-equilibrium (LTNE) model for the region of heat sink. Results from this study indicate that the anisotropy in permeability and solid-phase effective thermal conductivity changes substantially with the variation of porosity. The pin-fin heat sinks considered in the present study show an optimum porosity of 0.75<εopt<0.95 for maximum thermal dissipation depending on the flow and geometric conditions. Generally, a thick pin-fin displays a lower optimum porosity.

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