Radiative Heat Transfer And The Apparent Emission Characteristics For A 2-D Spatially Variable Refractive Index Medium

The typical variable refractive index materials conclude the Graded Index and multi-layers materials, which is widely employed in the nature and practical engineering, such as processing modeling of photonic crystals, light transmission in the atmosphere and seawater and manufacturing of optical instruments, etc. Because of the light's transfering along a curved path and the existing of total reflection within the Graded Index(GRIN) media, the distribution of radiation energy in the GRIN media is totally different from that of the media with constant refractive index, and so there must be some special characteristics and phenomenon of radiative heat transfer. Because of the different refractive indices between two sub-layers who close to each other, there is much complex condition of reflection and refraction on the interface, which can lead to important thermo-optical effect.According to the two dimensional arbitrary multi-layers and gradient refractive index distribution, emitting, absorbing and scattering gray media, this thesis use the Monte Carlo Method(MCM) to study the radiative heat transfer on the condition of the specular interfaces between the sub-layers and the specular or diffuse wall surfaces. Also we get the distribution of temperature and radiative heat flux and the apparent emissivity of north wall surface.The main contents of this thesis include:(1) The MCM is extended to solve the radiative heat transfer within the 2D arbitrary multi-layers media, and we develop a numerical model for the coupled radiative and conductive heat transfer in this 2D media, on the basis of the model for radiative heat transfer in the homogeneous media. Correctness of coupled radiative and conductive heat transfer model for 2D multi-layers media is validated by comparison with literature data. Then the effects of the distribution of refractive index and scattering albedo on the coupled heat transfer is investigated.(2) On the basis of coupled heat transfer model in the 2D multi-layers medium, we develop a numerical model of coupled heat transfer model in a GRIN medium, according to the principal of multi-layers approximation. The comparison with the benchmark solutions of the literature in the 2D GRIN media validates the correctness and accuracy of this thesis's results. On the conditions of the four side wall surface all being semitransparent and being opaque, the coupled heat transfer in the GRIN media and the influences of distribution of refractive index, optical length, scattering albedo and phase functions, the emissivity of four opaque surface are studied.(3) The thermal emission of GRIN and multi-layers media in 2D rectangular composite is investigated by the methods of multi-layers approximation and MC discretized curved ray tracing method, combination of the backward MCM which is developed on the basis of directional radiative distribution factors. The thermal emission model is also validated by comparison with the literature data. The influences of refractive index and scattering albedo, the black environmental radiation and the different methods to set the temperature field of 2D media, are calculated and analysed in details.