Design and thermal insulation performance analysis of endothermic opacifiers doped silica aerogels

摘要

In order to reduce the thermal radiation and further deter the heat transfer in silica aerogel thermal insulation materials, the endothermic opacifier is designed with the shell of SiC and the core of phase change material (PCM) in this paper. Then the transient heat transfer characteristics of the endothermic opacifiers doped silica aerogel (EOSA) are numerically investigated and its short-term thermal insulation performance is estimated with a modified lattice Boltzmann method (LBM) model. The modified LBM scheme is established with a new source term to remedy the effect of the variation in the volumetric heat capacity of the specimen, and this scheme is fully validated based on the analytical results and available experimental data. The results demonstrate that adding the endothermic opacifier to silica aerogels results in a significant heat transfer delay and an improvement in short-term thermal insulation performance by suppressing radiation heat transfer and solid-liquid phase change heat absorption. With the same doping amount, the endothermic opacifiers doped silica aerogel exhibits more excellent short-term thermal insulation performance and a lower density than that of SiC opacifiers doped silica aerogels (SOSA). It indicates that the EOSA possesses great potential to be a candidate as the lightweight and efficient thermal insulation material at high temperature. Besides, exhaustively parametric studies based on the EOSA, including doping amount, latent heat of PCM, phase change temperature and endothermic opacifier particle size are conducted, and several design rules are established. This analysis could serve as a framework to develop and design silica aerogel composites with low-density and excellent short-term thermal insulation performance.