The open cell polyurethane foam is a typical kind of porous material. Based on the fractal theory, the geometric structure inside the foam was illustrated and one simplified cell model was made. According to the model, the method of the equivalent thermal conductivity for the foam was described and the fractal dimension was calculated. The mathematic formulas for the fractal equivalent thermal conductivity combined with gas phase and solid phase, for heat radiation equivalent thermal conductivity and for the total thermal conductivity. The calculated results had better agreement with the experimental data. And the main influence factors were summarized. The study is useful for the foam's adiabatic performance enhancement and new material development.%开孔聚氨酯泡沫保温材料是一种典型的多孔介质.采用分形理论描述开孔聚氨酯泡沫材料的微尺度空间结构,建立了简化单元体模型,提出了计算其有效导热系数的分形模型,并导出了气相和固相热传导计算公式、热辐射等效导热系数计算公式、材料总有效导热系数计算公式.模型计算值与实验测量值比较具有较好的一致性,同时总结了多孔介质材料绝热性能的主要影响因素.该分析方法对新型绝热材料的研制和绝热性能的提高具有实用价值.
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