BUOYANCY-DRIVEN CHANNELING FLOW IN VERTICAL POROUS LAYER

The porosity of the near-wall region is higher than that of the core region in a porous insulating layer. Then the buoyancy-driven flow will be channelled along the wall of the layer. Considering such an inhomogeneous porous multilayer consisting of a thin fluid layer and a homogeneous porous layer, and proposing an extension of the Beavers-Joseph condition, a theoretical analysis is made on the buoyant channelling flow to clarify the effect of flow and thermal resistance near the wall on heat transfer characteristics. It is shown that heat transfer is generally enhanced by enthalpy transport due to the channelling flow; however, in the weak convection region it is reduced by the thermal resistance near the wall. Discussion is also focused on the critical thickness of the effective fluid layer to eliminate the effect of the enthalpy transport.