Effect of Thermocouple Sheaths on Temperature Response in Thermal Property Measurement

Isothermal curves within a cylindrical specimen in which thermocouples were inserted with sheaths and whose surface was heated continuously or sinusoidally were calculated by the finite element method. The measurement error of thermal diffusivity was estimated as a function of the thermal property and the location of the probe (thermocouple and sheath). A thermal diffusivity of the probe higher than that of the specimen intensely affects the temperature field around it. The error increases with the ratio of the thermal diffusivity of the probe to that of the specimen. The preferred position of the porbe is found to be away from the specimen surface.