Solid and gas thermal conductivity models improvement and validation in various porous insulation materials
Solid and gas thermal conductivity models improvement and validation in various porous insulation materials
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DOI：
10.1016/j.ijthermalsci.2023.108164
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发表时间：
2023-05
影响因子：
4.5
通讯作者：
S. Shrestha;Janak Tiwari;A. Rai;D. Hun;D. Howard;A. Desjarlais;M. Francoeur;Tianli Feng
中科院分区：
文献类型：
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作者：
S. Shrestha;Janak Tiwari;A. Rai;D. Hun;D. Howard;A. Desjarlais;M. Francoeur;Tianli Feng
在过去的几十年里，人们在提高对隔热材料热传输机制的理论理解并推动导热系数的下限方面做出了巨大的努力。然而，大多数工作都只关注特定类型的材料，并且用于热导率预测的模型多种多样 - 适合一种材料的模型可能不适合其他材料。在这里，我们改进并统一了多孔材料的气体和固体导热率模型。通过对几种不同材料的实验表征以及其他材料的文献数据，这些模型得到了验证。我们还发现，大多数材料的压力相关气体导热率可以通过使用一种或两种孔径来很好地拟合，而不需要使用复杂的孔径分布。通过改进的模型，我们将几种隔热材料的有效导热系数分解为气体、固体和辐射贡献。对于多孔（聚苯乙烯和聚氨酯）泡沫，空气、固体和辐射的相对贡献分别为 58-75%、3-11%、16-38%。对于粒状多孔材料（本文中为聚氨酯和二氧化硅），空气、固体和辐射的贡献分别为 45-66%、34-46% 和 0-8%。这项工作预计将为下一代隔热材料的设计和优化提供指导，例如通过努力减少泡沫中的气体传导和辐射以及抑制气凝胶中的气体和固体传导。
In the past few decades, significant efforts have been made to improve the theoretical understanding of thermal transport mechanisms in thermal insulation materials and push the thermal conductivity's lower limits. However, most works focused singularly on specific types of materials, and the models used for thermal conductivity predictions are diverse - a model that fits one material might not fit others. Here, we improve and unify the gas and solid thermal conductivity models for porous materials. Through experimental characterization of several different materials as well as literature data for other materials, these models are validated. We have also found that the pressure-dependent gas thermal conductivity of most materials can be well fitted by using one or two pore sizes without using a complex pore size distribution. With the refined models, we decompose the effective thermal conductivity of several thermal insulation materials into gas, solid, and radiation contributions. For cellular (polystyrene and polyurethane) foams, the relative contributions from air, solid, and radiation are 58–75%, 3–11%, 16–38%, respectively. For granular porous materials (polyurethane and silica in this work), the contributions from air, solid, and radiation are 45–66%, 34–46%, and 0–8%, respectively. This work is expected to provide guidance on the design and optimization of the next generation of thermal insulation materials, for example, through the effort of reducing gas conduction and radiation in foams and suppressing gas and solid conduction in aerogels.