Theoretical study and parameter correlation analysis of thermal conductivity of silica aerogels based on the parallel aligned spherical pore model

With the advancement of technology, aerogels have transitioned from military to civilian applications, leading to an increase in their variety. Consequently, research on highly applicable and accurate thermal conductivity calculation formulas has become increasingly important. Due to their complex internal structure, which includes both nanoscale and microscale pores, accurately calculating their thermal conductivity is challenging. Previous heat transfer models have primarily relied on spherical particles. This paper introduces a novel dual-scale pore model, the Parallel Aligned Spherical Pore Model (PASPM), which is based on spherical pores and offers a fresh perspective. Using gas molecular dynamics theory and heat transfer principles, we derived a thermal conductivity calculation formula. Comparing the results from experimental data and the Wei model, the PASPM showed superior performance in calculating the thermal conductivity of powdered silica aerogels. The PASPM had a minimum average deviation of 5.37 %, a maximum average deviation of 24.31 %, and a minimum deviation of just 0.61 %. For granular silica aerogels, the PASPM had a minimum average deviation of 22.53 % and a maximum average deviation of 28.93 %, both outperforming the Wei model. The increased deviation at higher pressures was attributed to the impact of pressure on the mean free path of gas molecules. Correlation analysis using SPSS, combined with the formulas for particle size and pore size, revealed that thermal conductivity is significantly influenced by temperature, pressure, and average particle size. Moreover, average particle size shows significant correlations with parameters such as density, porosity, specific surface area, and average pore size. To streamline future calculations of aerogel thermal conductivity, it is possible to simplify the formula by consolidating the parameters and retaining only particle size as the primary structural variable, making the equation more concise.