Measurement and interpretation of the heat transfer coefficients of metal foams

The heat transfer characteristics of FeCrAlY (an iron-based alloy with a melting point of 1510°C sintered foams are presented. The foams have open cells and hollow cell ligaments. The foam samples had a range of cell sizes (1-3 mm) and relative densities (4.6-12.5 percent). Foam cores sandwiched between two conductive substrates were subjected to forced air convection with a constant input heat flux. The volumetric heat transfer coefficient is shown to depend on the effective porosity. Heat transfer is predominantly due to the increased flow mixing that the foam structure promotes. With higher-conductivity materials, the foam also acts to increase the heat transfer by providing an extended surface area, but this is not a strong effect in FeCrAlY foams owing to the low thermal conductivity of 16 W/m K. The FeCrAlY foam is compared with copper foam, and the latter effect is more significant.