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

Abstract

Abstract An experimental investigation was carried out to study heat transfer and fluid flow in high porosity (93%) thin metal foams subjected to array jet impingement, under maximum and intermediate crossflow exit schemes. Separate effects of pore-density and jet-to-target spacing (z/d) have been studied. To this end, for a fixed pore-density of 40PPI foams, three different jet-to-target spacing (z/d=1, 2, 6) were investigated, and for a fixed z/d of 6, three different pore-density of 5, 20 and 40PPI were investigated. The jet diameter-based Reynolds number was varied between 3,000-12,000. Experiments were carried out to characterize local flow distribution and Nusselt numbers for different jet impingement configurations. The heat transfer results were obtained through steady-state experiments. Local flow measurements show that, as z/d decreases, the mass flux distributions are increasingly skewed with higher mass flow rates near the exits. Heat transfer enhancement has been calculated and the optimum foam configuration has been deduced from the pumping power. It was observed that Nusselt number increases with increasing pore density at a fixed z/d and reduces with increase in z/d at constant pore density. Intermediate crossflow had higher heat transfer than maximum crossflow with significantly lower pumping power. Under a constant pumping power condition, z/d = 2, 40ppi foam provided an average enhancement of 35% over the corresponding baseline configuration for intermediate crossflow scheme and was found to be the most optimum configuration.