Radiative heat transfer analysis in pure scattering layers to be used in vacuum insulation panels

Radiative heat transfer in the pure scattering layers in vacuum insulation panels is analyzed using Monte Carlo method for two cases; for isotropic scattering and the other for pure backward scattering. The result for isotropically-scattering medium agrees well with the diffusion solution within 1% error. This, indeed, shows that the diffusion approximation can be used as a good approximation in the tested cases. The results also suggest that the radiative heat transfer in the vacuum insulation panels can be effectively reduced by increasing the optical thickness of the core material and/or decreasing the surface emissivity by inserting more radiation shields. When the pure backward scattering is applied, significant reduction is found in the radiative heat transfer rate compared with the isotropic scattering case. It is shown that radiative thermal conductivity of the scattering layer is decreased to nearly half for the backward scattering medium when the optical thickness is large and the wall emissivity is high. Thus, the materials with highly backward scattering are recommended to be used as the core or insertion material between the radiation shields to enhance the performance of the vacuum insulation panels.