Homogeneous phase and multi-phase approaches for modeling radiative transfer in foams

The aim of the present study is to investigate the suitability of two different continuum-based approaches for the modeling of the radiative transfer in two types of foams lying in the geometric optic regime: open cell metal foams and closed cell polymer foams. The two approaches are the commonly used Homogeneous Phase Approach (HPA) and the Multi-Phase Approach (MPA) which is rather new in the field of radiative transfer. For both approaches, the radiative properties involved in their respective frameworks are determined using newly developed Ray-Tracing methods applied to 3-D meshes representing the porous structures of open cell or closed cell foams. The 3-D meshes have been obtained from X-Ray Tomography applied to real metal and polymer foams. The radiative properties determined are used to compute the transmittances and reflectances of one-dimensional slabs of foams by the two approaches. They are compared with the results of a baseline Monte Carlo simulation in order to evaluate, for the two types of foams, the suitability of each method. It appears that both approaches are globally appropriate for predicting the radiative transfer in open cell metal foams although they are not able to match exactly the directional distribution of the transmittances and reflectances. For polymer foams, the accuracy of the HPA is demonstrated whereas the MPA provides significant differences with the reference MC simulations.