Aluminum foams vs conventional extended surfaces for air cooled condensers

Metal foams are a class of cellular structured materials with low density and novel thermal and mechanical properties. Open cell metal foams have high specific surface area, relative high thermal conductivity and present tortuous flow path to promote mixing. Recently, aluminum foams have been suggested as a highly compact replacement for conventional fins for brazed aluminum heat exchangers. This paper presents a study on possible application of aluminum foams in compact air cooled condensers to be inserted in a mini vapour cycle system (VCS) for electronics cooling in aeronautical application. Present authors have experimentally measured the heat transfer coefficients and pressure drops during air forced convection in several aluminum foams with different pore densities and porosities. The effects of the pore density on the heat transfer and fluid flow performance of the aluminium foams are highlighted by varying the number of pores per inch from 5 to 40. Starting from the experimental campaigns, the performance of air cooled condensers, especially designed for aeronautical applications which implement these new enhanced surfaces, are simulated using a numerical code. Finally, the simulated solutions with aluminum foams are compared with a reference air cooled condenser with traditional finned surface.