Ray-Tracing Method for Radiative Heat Transfer in a Two-Layer Anisotropic Scattering Medium

Abstract

Transient radiation heat transfer in a two-layer anisotropic scattering medium is investigated. Each layer of the medium can have different thermal and radiative properties. The two surfaces are assumed to be semitransparent or opaque, and the interface between the two layers is assumed to be semitransparent. Specular reflection is considered at the surfaces and the interface. A general criterion for total reflection at the surfaces and the interface is proposed to overcome the integral singularity problem above the critical angle. A fully implicit control-volume method is used to solve the transient energy equation of coupled radiation and conduction, and a ray-tracing/nodal-analyzing method is applied in the solution of the radiative transfer. Effects of emissivities of the surfaces, extinction coefficients, and optical boundary conditions on transient radiative heat transfer are examined. Results show that for the medium layer having a larger refractive index, its average temperature level may be higher, mainly due to the contribution of total reflection at the interface facing the layer, even if its absorption coefficient is relatively small compared to the medium layer having a larger absorption coefficient and a smaller refractive index.