Research On Inversion Of Radiation Characteristics And Optical Constants Within One-dimensional Plate

As a basic heat transfer way in nature,radiation heat transfer is widely used in daily life and various technosphere,such as in defense,solar energy,energy-efficient buildings,and etc.Radiation characteristics are the important indicator of materials' optical properties.For the convenience of calculations,it is usually assumed that the reflectance characteristics of the real walls is similar to diffuse or specular surfaces' in traditional radiative heat transfer analysis,and the bidirectional reflection distribution function(BRDF)can describe the real walls' radiation more accurately,which can make the radiative heat transfer analysis results more reliable.The main work in this thesis is listed as follows:In the visible and near infrared bands,the effect of surface roughness can not be neglected because the surface roughness and the incident wavelength of the material are equal to the grain size of the crystal.In order to obtain accurate radiative properties of the medium,this study considers the effects of the BRDF surface,and build an inverse method to simultaneously obtain the internal medium and surface radiative properties within a onedimensional plate using hemispherical reflectance,hemispherical transmittance,normal spectral reflectance and normal spectral transmittance.The Distributions of Ratios of Energy Scattered or Reflected(DRESOR)method is utilized to solve the direct radiative transfer problem within the one-dimensional plate,and both the internal medium and surface radiative properties are retrieved using the particle size distribution(PSO)method.Moreover,the method is applied to cases of absorbing and scattering medium,highly absorbing medium,and highly scattering medium,respectively.Obtained results demonstrate a reasonable agreement between the optimal results and the given original values.Therefore,this method is available for inversing internal medium and surface radiative properties.In the far-infrared band,the influence of the roughness of the surface of the materials is negligible compared to the wavelength of the incident light.Hence,we can calculate the optical constants using the measured hemispherical reflectance.This study calculates the optical constants of polycrystalline Al2O3 using Lorentz model and Kramers-Kronig relationships to verify the validity of the method.At last,the optical constants of Al2O3 and SiC with different crystal structure are calculated by Lorentz model.Due to the differences in crystal structure,the optical properties vary widely.