Numerical Convection Heat Transfer in Metal Foam Using Unit Cell Geometry

Open-cell metal foam is a class of modern porous media that possesses high thermal conductivity, large accessible surface area per unit volume and high porosities (often greater than 90%). The high porosity means very low weight. The internal structure of the foam is web-like. Internal flow inside the foam is complex and includes flow reversal, destruction of boundary layers and vigorous mixing. All of these attributes make metal foam a very attractive heat transfer core for many applications. The rather complex and intrinsically random architecture of the foam is virtually impossible to capture exactly. In this paper, we present a unit cell geometrical model that was used to represent the foam structure for numerical analysis purposes. In particular, the unit cell is used to numerically study forced convection heat transfer between aluminum foam and air. The Navier-Stokes and the governing energy equation are solved directly and the temperature fields are obtained using COMSOL. The details of the modeling process are given in this paper. The results are encouraging and lend confidence to the modeling approach, which paves the way for other investigations of the foam, as well as optimization work based on the structure of the foam.