Study on the Improvement of Accuracy for the Measurement of Thermophysical Properties at High Temperature by a Singgle Rectangular Pulse Heating Method

工业的各个领域都需要新材料的热物理性质信息。作者提出了一种简便的单次矩形脉冲加热导热系数和比热的测量方法。该方法考虑了有限圆盘试样在真空高温炉中的所有表面的热辐射损失。在各表面发射率相同的情况下，随着环境温度的升高，流散热损失增大，随着试样的热扩散率和比热的增大而减小。因此，如果对陶瓷等热效率较低的材料在高温范围内进行测量，辐射损失会很大。因此，由于发射率的不确定性造成的误差似乎是不可避免的。本研究的目的是研究在高达1600k的高温下涂层对样品发射率的温度依赖性，并提高测量的准确性。发射率测量技术是基于比较样品和保持相同温度的黑体炉的辐射。对四种耐热涂层进行了试验。结果表明，在800 ~ 1600 k范围内，涂层与试样之间没有分离现象，温度依赖性较弱。然后，采用单矩形脉冲加热技术测量了SiC喷涂镍镁砖的导热系数和比热。认识到目前的测量方法与以前使用炭黑涂层的测量方法存在一些差异，并对测量精度进行了改进。

The information on thermophysical properties of new materials are required in vatious fields of industry. One of the authers presented a convenient measuring method of thermal conductivity and specific heat by a single rectanguar pulse heating. In this method, the thermal rdiation losses from all the surfaces of a finite disk specimen which is set in a vacuum high temperature furmace are taken into account. If the eemissivities are same on the all surfaces of the specimen, the rafiation heat loss increases with ambient temperature increase and decreases with thermal diffusivity and specific heat of the specimen increase. Therefore, if the measurement on a material having low thermal vonfuctivity as ceramics was carried out at high temerature tange, the rdiation loss will be large. So, the errors caused by uncertainty of the emissivity seem to be unavoidable. The obhjective of this study is to investigate the temperature dependence of the emissivity of the coatings on the specimen at high temperature up to 1600 k, and to improve the accuracy of the measurement.The technique of the emissivity measurement is based on comparing radiance from the specimen and a blackbody furnace keeping the same temperature. Four kinds of heat resisting coats were examined. It was found that no separation of coating from the specimen appeared and the temperature dependence was rather fiat in the 800-1600 k for SiC spray coating. Then, the thermal diffusivity and specific heat were measured on nickel and magnesia brick with SiC spray coating by the single rectangular pulse heating rechnigue. It was recognised that there were some differences between the present measuremeent recognized that there were some differences between the present measuremeent and the former one using carbon black coating, and improvement of the accuracy.