Theoretical Modeling of the Radiative Properties and Effective Thermal Conductivity of the Opadfied Silica Aerogel

摘要

In this paper, we investigate the radiative properties and the effective thermal conductivity (ETC) of the opacified silica aerogel by theoretical method. The radiative properties of the opacified silica aerogel are obtained by the modified Mie Scattering Theory that is used for particle scattering in absorbing medium. The modified gamma distribution is used to take account of the non-uniformity of the particle size. The solid thermal conductivity of the composite material is obtained by considering the scale effect of the particles. Based on these calculated thermophysical properties the coupled heat conduction and radiation through the evacuated opacified aerogel are solved by the finite volume method. And the radiation flux is computed by the P-l approximation combined with the gray-band model. Results show that, the calculated thermophysical properties of the TiO_2-doped silica aerogel are close to the experimental data. The optimal mean radius for the largest radiation extinction of the SiC particles is about 1 jum. The presented data of optimal doping amount of the SiC particles at different temperature conditions for the evacuated silica aerogel is very useful for thermal insulation material design.