THE EFFECT OF POROSITY ON REPRESENTATIVE VOLUME ELEMENT FOR PRESSURE DROP IN OPEN-CELL FOAMS

Heat transfer can be enhanced by employing open-cell metal foams which are cellular materials where a fluid passes through a highly conductive solid matrix. They enhance convective heat transfer because of their mixing capability and high specific surface area. The foams complex geometry requires large computational power and makes the accurate numerical simulation of their thermal performance a challenging task. Difficulties are overcome by carrying out computations on a Representative Volume Element (RVE) of the foam, defined as the cubic sub-volume having the same characteristics as those of the whole foam. The effects of porosity on RVE for pressure drop in open-cell foams, for different velocities of the fluid, are analyzed in this paper. Foam geometries are reconstructed with Computed Tomography (CT) scans of real aluminum foams manufactured by ERG Aerospace (Oakland, CA). The numerical grid is then built up by employing the MATLAB tool iso2mesh. Finally, mass and momentum equations are solved numerically by means of the finite-element commercial code COMSOL Multiphysics. Pressure drop, permeability, and inertial factor, for different porosities and inlet flow velocities, are presented; from these results, it is possible to obtain the minimum RVE size. The minimum RVE size can provide guidance to reduce computational needs.