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基于分形理论,描述了玻璃纤维多孔介质材料微尺度空间结构,建立分形等效单元体模型,分析了影响其真空下有效导热系数关键因素为固体基质导热系数、空隙率、纤维丝空间结构、分形直径、残余气体压力及导热系数、玻璃纤维材料厚度、使用环境等,并导出了气相、固相热传导计算公式和热辐射等效导热系数计算公式及材料总有效导热系数计算公式。研究表明,玻璃纤维有效导热系数随着分形直径、分形维数、残余气体压力的增大而增大,随着空隙率的增大而减小。同时,模型计算值与实验测量值比较,具有较好的一致性。文章的分析方法对新型真空绝热材料的研制和绝热性能的提高具有实用价值。
Based on the fractal theory, the micro-scale spatial structure of glass fiber porous media was described and the fractal equivalent element model was established. The key factors affecting the effective thermal conductivity under vacuum were analyzed as thermal conductivity of solid matrix, porosity, spatial structure of fiber, fractal Diameter, residual gas pressure and thermal conductivity, thickness of glass fiber material, environment of use, etc. The calculation formulas of gas phase, solid phase heat conduction and thermal radiation equivalent thermal conductivity and the formula of total effective thermal conductivity of material are deduced. The results show that the effective thermal conductivity of glass fiber increases with fractal diameter, fractal dimension and residual gas pressure, and decreases with the increase of void fraction. At the same time, the calculated values of the model are in good agreement with the experimental ones. The analysis method of the article is of practical value for the development of a new vacuum insulation material and the improvement of the adiabatic performance.