Natural convection in water-saturated metal foam

Natural convection in water-saturated copper foam is measured for 2.5 × 10−4 < Da < 1.2 × 10−5, 10 < Ram < 210, and 7.5 × 105 < Raf < 2.5 × 108. Experiments are reported for foam with 92% porosity and 10 and 20 pores per inch. The primary finding is that the Nusselt numbers do not follow the published heat transfer correlations with Rayleigh number for a packed bed of spheres and are 27–42% less than that predicted by these correlations at the maximum Rayleigh numbers encountered for Da ∼ 10−5. A single heat transfer correlation of Nusselt number is obtained in terms of Rayleigh and a modified Prandtl number equal to PrmDa-1/2Cf-1. In comparison to natural convection in a water layer, enhancement of heat transfer is primarily via conduction. Enhancement of the advective component of heat transfer is obtained only for Raf ∼ 108 and 1.2 × 10−5 ⩽ Da ⩽ 2.4 × 10−5.