Metal foams as compact high performance heat exchangers

Open-cell metal foams with an average cell diameter of 2.3 mm were manufactured from 6101-T6 aluminum alloy and were compressed and fashioned into compact heat exchangers measuring 40.0 mm × 40.0 mm × 2.0 mm high, possessing a surface area to volume ratio on the order of 10,000 m²/m³. They were placed into a forced convection arrangement using water as the coolant. Heat fluxes measured from the heater-foam interface ranged up to 688 kW m^?2, which corresponded to Nusselt numbers up to 134 when calculated based on the heater-foam interface area of 1600 mm² and a Darcian coolant flow velocity of approximately 1.4 m/s. These experiments performed with water were scaled to estimate the heat exchangers’ performance when used with a 50% water–ethylene glycol solution, and were then compared to the performance of commercially available heat exchangers which were designed for the same heat transfer application. The heat exchangers were compared on the basis of required pumping power versus thermal resistance. The compressed open-cell aluminum foam heat exchangers generated thermal resistances that were two to three times lower than the best commercially available heat exchanger tested, while requiring the same pumping power.