Air-Based Cooling in High Porosity, Aluminum Foams for Compact Electronics Cooling

Abstract

An experimental study was carried out to evaluate heat transfer and pressure drop performance of high porosity (93%) aluminum foams with pore densities 5 pores per inch (PPI), 20 PPI and 40 PPI. Tests were run with air as the working fluid in a rectangular channel of aspect ratio 8:3. The metal foam samples were 50.8 mm ( $W$ ), 20 mm ( $H$ ) and 254 mm ( $L$ ). A smooth channel without metal foam was tested to establish baseline performance curves. Studies were undertaken to investigate the distribution of local Nusselt number along the streamwise direction as a function of metal foam pore density. All foam samples exhibited short thermal developing length of $x/D_{h}\sim 4.2$ after which the heat transfer converged to almost constant value. As expected, heat transfer performance improved with increase in foam pore density, however, accompanied by higher pressure drop. For a given pumping power, the 40 PPI foam sample showed the highest heat transfer performance. Heat transfer with the 40 PPI foam was found to be 27.5 higher than the baseline smooth surface. Metal foams showed excellent promise in high heat flux cooling applications like electronics cooling.