Natural convection in porous media bounded by short concentric vertical cylinders

Free-convective heat transfer in short cylindrical annuli filled with saturated porous media has been studied numerically and experimentally. For an annulus whose inner wall is heated at constant temperature and outer wall is isothermally cooled, the top and bottom being insulated, heat transfer results have been obtained numerically for 0.9 ≥ A ≥ 0.3, 1 < k ≤ 11 and Rayleigh number, Ra^* upto 10⁴, where A is the aspect (height-to-gap width) ratio and k is the radius ratio. Introduction of curvature effects diminishes the multicellular flow behavior observed in the case of shallow cavity, and hence, the higher the radius ratio, the lower is the aspect ratio required for multicellular flow to exist. Heat transfer rates for isothermal heating have also been determined experimentally for A = l and k = 5.338, using water and glass beads (3 and 6 mm dia) as the porous media. The experimental values of Nusselt number agree well with the numerical predictions for Ra^* up to 4000. Agreement between the measured temperatures at various locations and the numerically established temperature field is also quite reasonable.