Buoyant Convection in Superposed Metal Foam and Water Layers

Heat transfer measurements for natural convection in superposed metal foam and water layers are reported. Two systems heated at the lower boundary are considered: a water-filled cavity with a foam layer on the heated surface and a water-filled cavity with foam layers on the upper and lower surfaces. The present experiments use open cell copper foams with a nominal porosity of 92%, and the relative thicknesses of the water and foam layers are varied. Steady state Nusselt numbers show that the presence of foam on the boundaries enhances overall heat transfer coefficients over that for the water-only layer. Enhancement of overall Nusselt numbers varies from 12% to 60% depending on Rayleigh number. Sublayer configurations with foam on both heat transfer surfaces are more effective for enhancement than a configuration with foam only on the heated surface.