Gas-solid coupling in a randomly distributed ceramic nanofibrous aerogel

Ceramic nanofibrous aerogel (CNA) has received tremendous interest recently due to its advantageous properties and potential applications. However, modeling its gas-contributed thermal conductivity is quite difficult due to the intricate gas-solid coupling heat transfer mechanism and complex structure. Herein, based on an equivalent method used for a gas in free space, a model for predicting gas-contributed thermal conductivity in its nanopores is built to provide a straightforward solution to the above-mentioned issues. We study both gas and gas-solid coupling effects on the effective thermal conductivity of the randomly distributed Al₂O₃-carbon core-shell nanofiber aerogel. The coupled term demonstrates low gas-contributed and effective thermal conductivity of 0.022 and 0.065 W m⁻¹ K⁻¹ at 1500 K, respectively. It is shown that the coupling effect of gas-solid interaction is noticeable and should not be ignored when the gas pressure p_g ≤ 0.1 bar. The predicted effective thermal conductivity demonstrates good consistency with available experimental data, which could provide direction for quick and accurate design and optimization of high-temperature thermal insulation materials.