瞬态平面热源法加厚探头的数值模拟研究

Numerical simulation of thickening probe based on transient plane source method

瞬态平面热源法(TPS)的理论假设限制了该方法的使用场景,为此该文研究了加厚探头的导热系数测量精度并提出热容修正模型。利用COMSOL Multiphysics软件建立5501型探头的三维模型和增加镍丝厚度形成的加厚探头模型,根据模拟得出的温度历史数据绘制探头温升曲线,结合无量纲时间函数,迭代拟合得出待测样品的导热系数,并探讨加热功率及加热时间对加厚探头测量精度的影响。结果表明:由加厚模型得出的导热系数相对误差显著增大;随着加热功率的提高,材料导热系数测量误差减小;热容修正模型在测量不同材料时的修正幅度,与探头比热容相对待测材料比热容的大小呈正相关;使用热容修正模型后探头测量导热系数的相对误差在1.5%以内。研究证明提出的加厚探头结构及修正模型能够满足TPS法对导热系数测量精度的要求,同时提高探头强度使其适应较为复杂的使用环境。

Extensive use of transient plane source(TPS)method is limited due to its theoretical assumptions.Therefore,the thermal conductivity measurement accuracy of the thickening probe and its heat capacity correction model,namely reducing the error caused by thickness change,are necessary to be developed.The three-dimensional model of standard 5501 probe and the thickened probe model,formed by increasing the thickness of nickel wire,are esrablished by COMSOL Multiphysics software.Combining with temperature rise curve of nickel wire,drawn according to the temperature history data derived from software,and dimensionless time function,can get the thermal conductivity of the measured sample through iterative fitting procedure.In this paper,the priority given to research lies in the influence of heating time and power to the accuracy of measurement using thickening probe based on TPS method.The results of simulation show that the relative error of thermal conductivity obtained by the thickening model have a significant increase.When increasing heating power,along with the measurement error of thermal conductivity decreasing.The performance of the heat capacity correction model has a positive relationship to the comparison between heat capacity of the probe and that of measured materials.At last,the measurement error of thickening probe is strictly controlled within 1.5%,in which temperature curve is modified by the heat capacity correction model.It is proved that the proposed thickening probe structure and heat capacity correction model can satisfy the requirements of measurement accuracy of TPS method,which improving applicability of the probe to fit the more complex usage scenario.