摘要
Natural convection heat transfer in a horizontal enclosure filled with anisotropic porous media,being isothermally heated at bettom and cooled at top while the vertical walls being adiabatic, is numerically studied by applying the Brinkman model-a modified form of Darcy model giving consideration to the viscous effect. The results show that:(1)a larger permeability ratio (K*) causes a lower flow intensity in the enclosure and a smaller Nusselt number, all Nusselt numbers approach unity in the limit of K* → ∞;a larger thermal conductivity ratio (λ*) causes a stranger distortion of isotherms in the enclosure and a higher flow velocity near the walls, all the Nusselt numbers approach unity in the limit of λ*→0; the permeability and thermal conductivity ratios generally have opposing effects on the Nusselt number. (2) an increasing Darcy number decreases the flow intensity and heat transfer rates,which is more significant at a lower permeability ratio. In particular, with K*0.25, the Nusselt number for Da=10-3 would differ from that of Darcy flow up to an amount of 30%, an analysis neglecting the non-Darican effect will inevitably be of considerable error.
