Refractive index effects on heat transfer in multilayer scattering composite

By the use of the ray tracing method, in combination with Hottel and Sarofim's zonal method and spectral model, transient coupled radiative and conductive heat transfer in a multilayer absorbing, isotropically scattering composite with semitransparent and specular surfaces and interfaces is investigated. The specular reflectivities of all of the surfaces and interfaces are determined by Fresnel's reflective law and Snell's refractive law. For the ray tracing method, the complex total reflection problem of the multilayer composite is properly solved, and the radiative transfer coefficients (RTCs) of the multilayer composite are derived. The RTCs are used to calculate a radiative source term, and the transient energy equation is solved by the fully universal implicit discrete control volume method. Combined with extinction coefficient, conduction-radiation parameter, scattering albedo, layer thickness, and number of layers, the effects of refractive index on pure radiative and coupled radiative and conductive heat transfer are investigated. The analysis shows that, if the refractive indexes of the layers are arranged according to a specified periodical behavior along the thickness, and the other corresponding parameters of each layer are kept the same, then the temperature distribution within the composite shows a similar complex periodical behavior as well.