Abstract

Coaxial thermocouples have been widely used for transient heat transfer measurements in high-enthalpy shock tunnels. The one-dimensional semi-infinite heat conduction theory is typically used for temperature data processing. However, due to the material difference between the two electrodes and the junction, lateral heat transfer occurs, causing a deviation in the heat flux measurement from the prediction results of the one-dimensional semi-infinite heat conduction theory. Thus, the lateral heat transfer effect has to be investigated to improve the accuracy and reliability of heat flux measurements. In this article, the heat transfer in E-type (chromel-constantan) coaxial thermocouples was analyzed by numerically solving the two-dimensional axisymmetric heat conduction equation with the Du Fort-Frankel scheme. During the heating process, the maximum temperature point on the surface of the coaxial thermocouples moved to the positive electrode over time. The numerical simulation indicated that the surface temperature of the coaxial thermocouples and the derived heat flux were larger than the theoretical value. The heat flux measurement error of the coaxial thermocouples can be reduced by increasing the width of the positive electrode. The results of this study can provide a reference for the design and manufacture of coaxial thermocouples.

摘要

同轴热电偶已广泛用于高焓激波隧道中的瞬态传热测量。一维半无限热传导理论通常用于温度数据处理。然而，由于两个电极和结之间的材料差异，会发生横向传热，导致热通量测量与一维半无限热传导理论的预测结果存在偏差。因此，必须研究横向传热效应以提高热通量测量的准确性和可靠性。本文采用 Du Fort-Frankel 格式对二维轴对称热传导方程进行数值求解，分析了 E 型（铬镍-康铜）同轴热电偶的传热。在加热过程中，随着时间的推移，同轴热电偶表面的最高温度点移至正极。数值模拟表明同轴热电偶的表面温度和导出的热通量均大于理论值。通过增加正极的宽度可以减小同轴热电偶的热通量测量误差。本研究结果可为同轴热电偶的设计和制造提供参考。通过增加正极的宽度可以减小同轴热电偶的热通量测量误差。本研究结果可为同轴热电偶的设计和制造提供参考。通过增加正极的宽度可以减小同轴热电偶的热通量测量误差。本研究结果可为同轴热电偶的设计和制造提供参考。