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本文基于二氧化硅气凝胶的微观结构特点,运用小球构成的立方阵列单元体纳米孔隙模型,结合固相导热和气相传热的尺度效应,计算得到了一定尺寸范围内材料的等效热导率,分析了材料密度、颗粒接触面积、材料比表面积等因素对材料等效热导率的影响。结果表明:存在使气凝胶等效热导率取最小值的最佳密度;在一定的密度范围内,孔隙率一定时,材料的等效热导率随比表面积的增大而减小;颗粒间接触界面直径与固相颗粒直径的比值越大,等效热导率越低,在该比值一定时,气孔的尺寸和分布成为影响模型等效热导率的关键因素。
Based on the microstructural characteristics of silica aerogels and using the nano-pore model of cubic array unit composed of small spheres, the equivalent heat of material in a certain size range was calculated by combining the scale effects of solid-state heat transfer and gas-phase heat transfer Conductivity, the material density, particle contact area, material surface area and other factors on the material thermal conductivity. The results show that there is an optimum density for taking the minimum value of the equivalent thermal conductivity of the airgel. When the porosity is constant, the equivalent thermal conductivity of the material decreases with the increase of the specific surface area. The larger the ratio of the interfacial contact interface diameter to the solid particle diameter is, the lower the equivalent thermal conductivity is. When the ratio is fixed, the size and distribution of the pores become the key factors that affect the equivalent thermal conductivity of the model.