Study on theoretical model for the effective thermal conductivity of silica aerogel composite insulating materials

In this paper, the effective thermal conductivity model of silica aerogel composite insulating materials was established. A fractal-intersecting sphere model was proposed for the nano-porous silica aerogel in which the scale effect on gas conduction and solid-matrix conduction were both considered. While for composite insulating materials, Rossland approximation were used to account for the radiative thermal conductivity. The radiative properties of additives (opacifier particles and fibers), which are needed for calculating the radiative conductivity in Rossland equation, were determined by Mie theory. The established theoretical model was compared with several experimental results of thermal conductivities of insulating materials, including nano-porous silica aerogel as well as kinds of aerogel composite materials. The comparisons show the effectiveness of the theoretical model in predicting effective thermal conductivity of aerogel composite insulating materials.