Due to their special combination of nanostructure and high porosity, aerogels are key materials for high performance thermal insulation. However, measuring reliable thermal conductivity values, which are essential for material’s optimization and as product parameter, is a challenging task in the case of aerogels. Experimentally derived thermal conductivity values for aerogels are so far more or less influenced by the experimental set-up and the experimental conditions and have to be carefully discussed. Here we present results of an intercomparison on thermal conductivity measurements performed for a polyurethane aerogel produced on a pilot scale as stiff panels by BASF. Prior to the intercomparison, the material was checked for reproducibility in production and homogeneity. The dependence of thermal conductivity on atmospheric pressure and temperature was also determined. We discuss the results submitted by 12 participants with respect to the different experimental techniques applied and identify experimental parameters with severe impact on the resulting thermal conductivities. The derived mean values for the thermal conductivity at 20 °C, 40 °C and 60 °C were related with relative uncertainties in the range from 0.6 % to 0.9 %. The dependence of the derived thermal conductivity values on the geographical location of the participating laboratory and the atmospheric weather conditions could be clearly observed and the precision of the results could be significantly improved by correcting for these effects. The values had to be partly corrected up to 2.5 %.

中文翻译：

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纳米多孔有机气凝胶热导率测量的比对

由于纳米结构和高孔隙率的特殊组合，气凝胶是高性能隔热的关键材料。然而，对于气凝胶而言，测量可靠的热导率值对于材料的优化和产品参数至关重要，这是一项具有挑战性的任务。迄今为止，气凝胶的实验得出的热导率值或多或少受实验设置和实验条件的影响，必须仔细讨论。在这里，我们展示了对由 BASF 以中试规模生产的作为刚性面板的聚氨酯气凝胶进行的热导率测量的相互比较结果。在比对之前，检查材料的生产再现性和均匀性。还确定了热导率对大气压力和温度的依赖性。我们讨论了 12 位参与者提交的关于所应用的不同实验技术的结果，并确定了对所得热导率有严重影响的实验参数。在 20 °C、40 °C 和 60 °C 下得出的热导率平均值与 0.6 % 至 0.9 % 范围内的相对不确定性相关。可以清楚地观察到导出的热导率值对参与实验室的地理位置和大气天气条件的依赖性，并且可以通过校正这些影响来显着提高结果的精度。这些值必须部分修正至 2.5%。我们讨论了 12 位参与者提交的关于所应用的不同实验技术的结果，并确定了对所得热导率有严重影响的实验参数。在 20 °C、40 °C 和 60 °C 下得出的热导率平均值与 0.6 % 至 0.9 % 范围内的相对不确定性相关。可以清楚地观察到导出的热导率值对参与实验室的地理位置和大气天气条件的依赖性，并且可以通过校正这些影响来显着提高结果的精度。这些值必须部分修正至 2.5%。我们讨论了 12 位参与者提交的关于所应用的不同实验技术的结果，并确定了对所得热导率有严重影响的实验参数。在 20 °C、40 °C 和 60 °C 下得出的热导率平均值与 0.6 % 至 0.9 % 范围内的相对不确定性相关。可以清楚地观察到导出的热导率值对参与实验室的地理位置和大气天气条件的依赖性，并且可以通过校正这些影响来显着提高结果的精度。这些值必须部分修正至 2.5%。