Uncertainty in measuring the thermal conductivity coefficient of thermal insulation materials with internal inhomogeneity using the reference standard method

Results of assessing the total standard uncertainty of experimental measurements of the thermal conductivity coefficient of thermal insulation materials with significant internal heterogeneity are presented. The measurements are carried out using the reference standard method and a virtual test bench. The distinctive feature of this measurement method is the application of a constant thermal load to two reference objects with high thermal conductivity: one of them is shielded from the surrounding environment by a sample of the material under study, while the other is in the surrounding environment. Based on the difference in heating rates of two reference objects, the thermal conductivity coefficient of the material under study is determined using the calibration characteristic of the experimental setup, which is obtained by means of a virtual copy of the setup in a CAE program. To improve the accuracy of the method, a dimensionless difference in the heating rates of the two reference objects is used, which required the application of the results of experimental and virtual studies of a third reference sample with a known thermal conductivity coefficient. A methodology for assessing the total standard uncertainty of measuring the thermal conductivity coefficient of a thermal insulation material using the method of etalons is developed, and the optimal method for processing the results of experimental and virtual studies is selected. According to the calculations, the total standard uncertainty in measuring the thermal conductivity coefficient using the reference standard method is ±0.0136 W/(m·K).

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