Abstract
The present work analyzes heat transfer inside pin fins with cores filled with porous media. Two different systems are considered: a typical fin-porous-medium system (type A) and a joint fin-porous-medium system (type B). The coupled energy equations are solved numerically by an implicit, iterative finite difference scheme. Comparisons between numerical and analytical solutions are performed, and very good agreement is obtained. A new criterion for the validity of local thermal equilibrium assumptions inside the pin fin cores is identified. The numerical results are presented graphically in terms of Darcy number, porosity, thermal conductivity ratio, Biot numbers, relative radii ratio, Peclet number, and aspect ratio. It is found that thermal efficiencies of these systems can be increased significantly by introducing highly convective flows inside the porous cores. However, factors causing increases in external convections are found to decrease the thermal efficiency. Yet the decrease is expected to be higher for ordinary fins. Moreover, thermal efficiencies of type B systems are found to be highly responsive to internal convections, while those of type A systems are less sensitive to internal convections. Finally, the obtained results demonstrate that fins-porous-media systems can be efficient in transferring heat, which can be at no additional cost if the pressure difference across the joined reservoirs is large.