稳态法测试保温材料导热系数的系统性误差

Systematic Errors in Steady-state Measurements on the Thermal Conductivities of Insulation Materials

导热系数是保温材料最重要的热物理性能,对其进行准确的测试具有十分重要的意义。测试过程会受到方法及一些不可控因素的影响,因此测试结果的准确性需要被对比验证。本文以热流计法和防护热板法为例,对常用保温材料膨胀聚苯乙烯板(expanded polystyrene,EPS)的导热系数进行测定。实验采用不同厚度的试件进行测试。实验结果表明试件的热阻随试件的厚度的增加而线性增大;而导热系数作为材料的固有属性,也随厚度增加呈现上升趋势,说明了对测试结果进行修正的必要性。分析结果显示修正后材料的导热系数与试件厚度无关,通过2种方法得到的导热系数差异为2%,准确性较高。热流计法和防护热板法得到的测试导热系数与修正导热系数的最大差异分别为16%和25%,证明了测试中的系统性误差需要被考虑和修正。

Thermal conductivity is the most important thermal property of insulation materials. It is of great significance to carry out accurate measurements on it. Due to different test principles and uncontrollable factors during the testing process,the accuracy of test results needs to be compared and validated. In this paper,the thermal conductivity of expanded polystyrene（ EPS）,a kind of common insulation material,was measured using the heat flow meter method and the guarded hot-plate method. Specimens of different thickness were tested. The results indicate that the thermal resistance of specimens increases linearly with thickness. As an intrinsic property of the material,thermal conductivity also showed an increasing trend with specimen thickness,indicating the necessity to correct results. Analysis shows that the corrected thermal conductivity is irrelevant with specimen thickness,and the difference between corrected thermal conductivity obtained by the two methods is 2%,which is reliable.Compared with the corrected thermal conductivity,the maximum deviations for uncorrected values are 16% and25% for the heat flow meter method and the guarded hot plate test method,respectively. This demonstrates that the systematic errors of the tests need to be considered and corrected.