Array Jet Impingement on High Porosity Thin Metal Foams: Effect of Foam Height, Pore-Density, and Spent Air Crossflow Scheme on Flow Distribution and Heat Transfer

Experimental investigation was carried out to study heat transfer and fluid flow in high porosity (93%) thin metal foams (MFs) subjected to array jet impingement, under maximum and intermediate crossflow exit schemes. Separate effects of pore-density (pores per inch: PPI) and jet-to-target spacing (z/d) have been studied. To this end, for a fixed pore-density of 40 PPI foams, three different jet-to-target spacings (z/d = 1, 2, 6) were investigated, and for a fixed jet-to-target spacing (z/d) of 6, three different pore-density of 5, 20, and 40 PPI were investigated. The jet diameter-based Reynolds number was varied between 3000 and 12,000. Both flow and heat transfer experiments were carried out to characterize the flow distribution, crossflow mass flux accumulation, and local Nusselt numbers for different jet impingement configurations. The heat transfer results were obtained through steady-state experiments. Local flow measurements show that, as jet-to-target distance decreases, the mass flux distributions were increasingly skewed with higher mass flux distributed toward the exit(s). It was observed that Nusselt number increased with increasing pore density at a fixed jet-to-target spacing and reduced with increase in jet to target spacing at a fixed pore density. Intermediate crossflow had higher heat transfer than maximum crossflow with significantly lower pumping power. For a fixed pumping power, z/d = 2, 40 ppi foam provided an average heat transfer enhancement of 35% over the corresponding baseline configuration for intermediate crossflow scheme and was found to be the optimum configuration.