边界热损失对TPS平板法测量物质热导率的影响

摘要

假想热源法是基于瞬态平面热源(transient plane source,TPS)法测量平板样品导热系数的理论基础,但是其没有考虑测量过程中背景材料本身的有限热阻所导致的边界热损失,从而直接影响导热系数的测量精度.该文基于假想热源法和热探测深度理论,建立一种可实现边界热损失补偿的数学模型.该数学模型揭示探头尺寸、样品厚度以及背景材料的导热系数和热扩散率对边界热损失的影响.为验证该数学模型的有效性,通过变换背景材料和探头尺寸对不锈钢、铅、45钢、Q235A.F钢、黄铜、6061铝合金、纯铝以及紫铜的导热系数进行测量.结果表明:该数学模型能够对不同的探头尺寸、平板样品以及背景材料进行有效的热损失补偿,使导热系数的测量误差从热损失补偿前的2.14%~3.49%减小到补偿后的-1.39%~0.80%,显著提高平板样品导热系数的测量精度.%Image source method is the theoretical basis for measurement of the thermal conductivity of slab samples based on the transient plane source (TPS) method. However, this theory neglects the boundary heat loss caused by the limited thermal resistance of the background materials during measurement, which directly influences the measurement accuracy of the thermal conductivity. Based on image source method and thermal probing depth theory, a mathematical model which could effectively compensate the boundary heat loss was built. The model revealed the influence of probe size, sample thickness and thermal conductivity and thermal diffusivity of background materials on boundary heat loss. In order to verify the effectiveness of the model, the thermal conductivity of stainless steel, lead, 45 steel, Q235A.F steel, brass and 6061 alloy, pure aluminium and red copper was measured by changing probes and background materials. The results show that the model can be applied to different probes, slab materials and background materials for effective heat loss compensation and the measurement error of the thermal conductivity can be decreased from 2.14%-3.49%(before heat loss compensation) to -1.39%-0.80%(after heat loss compensation), which significantly improves the measurement accuracy of the thermal conductivity of plane samples.