Heat transfer with nano/micro-scale specialties in silica aerogel will affect its macroscopical thermophysical properties. The paper is to study the heat transfer mechanism in silica aerogel and further to provide the theoretical directions for thermal design and application of compound insulating materials. A heat transfer model of solid matrix unit obtained from the structure of silica aerogel is developed. According to the kinetic theory and with the consideration of the different limitations of phonon mean free paths, the influencing factors on thermal conductivity of solid matrix unit in silica aerogel are analyzed. According to the microstructure of silica aerogels, nanopore model is built. The apparent conductivity in several conditions is calculated. This paper also studied the effect of the physical parameters of silica aerogels on the apparent conductivity, then compared the apparent conductivity in several nanopore models, and finally compared with the experimental values.%以SiO2气凝胶为研究对象,对其气相和固相导热机理进行了研究,进而为SiO2气凝胶材料传热设计提供理论指导.建立了SiO2气凝胶固相结构单元导热模型,在考虑对声子平均自由程的各种限制条件基础上,运用动力学理论分析了影响SiO2气凝胶固相结构单元热导率的影响因素.根据SiO2气凝胶微观结构特点,建立了几种纳米孔隙模型,计算了各种条件下SiO2气凝胶的当量热导率,研究了SiO2气凝胶各物性参数对其当量热导率的影响,并对比了几种纳米孔隙模型下SiO2气凝胶的当量热导率,并与实验值做了比较.
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