Spectral Transmission and Reflection Properties of High Temperature Insulation Materials and their Relation to Radiative Heat Flow
This paper describes two approaches for a determination of radiative properties of high temperature insulations: a) Experimental: calorimetric measurements of total thermal conductivity and optical transmission and reflection studies are applied for determination of extinction coefficients and for verification of the increase of radiative transfer in cases of forward scattering media; b) Theoretical: application of rigorous Mie scattering theory, Monte Carlo simulations of both calorimetric and optical measurements, and five-flux formulas obtained from the method of discrete ordinates. The findings from both approaches establish the wavelengths resolved extinction coefficient and the first order term of the scattering phase function series expansion to be indispensible parameters for an optimization of the insulation properties of anisotropically scattering media. The paper demonstrates the validity of the diffusion approximation for radiative transfer also in these cases.
KeywordsOptical Thickness Total Thermal Conductivity Scatter Phase Function Anisotropic Scattering Specific Extinction Coefficient
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