The existing structural characterization methods of building materials as well as thermal conductivity calculation models can not be directly applied when considering fibrous building thermal insulation materials with intricate skeletons. In this study, rock wool is considered the research object, and the X-ray tomography method is used to characterize the pore structure and extract structural parameters. Based on the actual pore morphology of the material, the pores in the representative elementary volume (REV) are reasonably assumed to be cubic. Additionally, considering the contact thermal resistance of fibers and the randomness of pore distribution, the curved pattern of heat conduction pathway with the ever-changing diameter is reasonably simplified into a series-parallel form of the curved heat chain with the same diameter. On this basis, the fractal models of effective thermal conductivity are established in horizontal and vertical directions. Finally, a modified formula for the effective thermal conductivity calculation of fiber thermal insulation materials is proposed, taking into account the influence of fiber orientation on the material thermal conductivity. It was shown that the relative deviation between the calculated correction value and the experimental value of the effective thermal conductivity is all less than 16.13%.

中文翻译：

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基于X射线断层扫描的纤维建筑保温材料孔结构表征及有效导热系数建模

现有的建筑材料结构表征方法以及导热系数计算模型在考虑骨架复杂的纤维建筑保温材料时不能直接应用。本研究以岩棉为研究对象，采用X射线断层扫描方法表征其孔隙结构并提取结构参数。根据材料的实际孔隙形态，代表性单元体积（REV）中的孔隙被合理地假设为立方体。另外，考虑到纤维的接触热阻和孔隙分布的随机性，将不断变化直径的弯曲热传导路径模式合理简化为同直径弯曲热链的串并联形式。在此基础上，建立了水平和垂直方向有效导热系数的分形模型。最后，考虑纤维取向对材料导热系数的影响，提出了纤维隔热材料有效导热系数计算的修正公式。结果表明，有效导热系数计算修正值与实验值的相对偏差均小于16.13%。