Numerical study of radiative properties of nanoporous silica aerogel

• Absorption and scattering is modeled with Generalized Multiparticle Mie-solution.
• Nanoscale effects from porosity and particle size are studied.
• Extinction coefficient and temperature is modified with the Monte Carlo method.
• Optimal temperature-dependent density is obtained for insulating capability.

Silica aerogel as a super-insulating material has a large application potential in many engineering fields. This article aims at studying the radiative properties of silica aerogel in three aspects including nanoscale effect, radiative thermal conductivity and optimal temperature-dependent density. Firstly, radiative properties of three-dimensional silica aerogel made up of chain-like equal-sized nanospheres are investigated by considering the dependent scattering. The results indicate that the effect of nanostructure is limited on radiation insulating performance of silica aerogel. Secondly, we simulate the radiative transfer in bulk silica aerogel, and the parameter errors of extinction coefficient and mean temperature in Rosseland equation are discussed. The modified extinction coefficient is given and more accurate radiative thermal conductivity is observed. Finally, by evaluating the effective thermal conductivity from the total contributions of solid phase, gas phase and radiation as a function of temperature and density, we obtain the optimal temperature-dependent density at which the heat transfer in silica aerogel can be mostly suppressed.