Natural convection in enclosures containing an insulation with a permeable fluid-porous interface

A numerical study was performed to analyze steady-state natural convective heat transfer in rectangular enclosures vertically divided into a fluid-filled region and a fluid saturated porous region. The interface between the two regions was permeable, allowing the fluid to flow from one region to the other. The vertical boundaries of the enclosures were isothermal and the horizontal boundaries were adiabatic. The flow in the porous region was modeled using the Brinkman-extended Darcy's law to account for no-slip at the walls and the interface. Numerical experiments were performed for different enclosure aspect ratios, Rayleigh numbers, Darcy numbers, thermal conductivity ratios and thicknesses of the porous region. The effects of the governing parameters on heat transfer were established. It was found that, when compared to the case where the fluid and porous regions were separated by an impermeable partition, heat transfer across the enclosure was higher. Also, for certain values of the governing parameters, heat transfer across the enclosure could be minimized by filling the enclosure partially with a porous material instead of filling it entirely.