Effective permeability of a layered porous cavity

The feasibility of using a lumped system approach in the heat transfer anal ysis of a layered porous cavity is numerically investigated in this paper. Two layered cavities are considered; in one case the sublayers are perpendi cular to the imposed temperature gradient while in the other case they are parallel to the imposed temperature gradient. Numerical calculation have co vered a wide range of parameters (i.e., 10 less than or equal to Ra(1)less than or equal to 1000, 0.01 less than or equal toK(1)/K(2)less than or equa l to 100, and L-1/L(H-1/H) =0.25, 0.5 and 0.75). The results are presented in terms of the effective Rayleigh number which is defined based on the eff ective permeability; one is arithmetic average and the other is harmonic av erage. The results show that the lumped system approach can provide a fairl y accurate prediction in heat transfer if the permeability is correctly cha racterized. Also found is that the effective permeability of a layered poro us cavity is strongly dependent on the orientation of the sublayers and the primary heat flow direction.