IMPACT OF ANISOTROPY ON GEOMETRICAL AND THERMAL CONDUCTIVITY OF METALLIC FOAM STRUCTURES
Résumé
The thermo-physical properties of open cell metal foams depend on their microscopic structure. Various virtual ideal periodic isotropic foam samples having circular, square, hexagon, diamond, and star strut cross sections with various orientations are realized in the porosity range from 60 to 95%. The anisotropy of the original foam sample is then realized by elongating in one direction by a factor Omega, while a factor of 1/root Omega is applied along the two perpendicular directions to conserve the porosity of the original sample. A generalized analytical model of geometrical parameters has been proposed and all results are fully compared with the original measured data. Three-dimensional heat conduction numerical simulations at the pore scale have been performed, which allow determining the macroscale physical properties, such as the effective thermal conductivity, using the volume averaging technique. Two analytical models are derived simultaneously in order to predict the intrinsic solid phase conductivity (lambda(s)) and effective thermal conductivity (lambda(eff)). A modified correlation term (F) is introduced in the analytical resistor model to take into account the thermal conductivities of constituent phases and a modified Lemlich model is derived. The analytical results of the effective thermal conductivity are compared with the numerical data and excellent agreement is observed.