Investigation and Optimization of the Hot Disk Method for Thermal Conductivity Measurements up to 750 °C

The Hot Disk method is a transient measurement method for the determination of thermal properties like the thermal conductivity, which is characterized by advantages such as a short measurement time or a low effort for the sample preparation. However, some difficulties related to measurements at elevated temperatures, which could be attributed to inaccuracies of the Temperature Coefficients of Resistance (TCRs), have been pointed out in the past. This paper presents a detailed investigation of the Hot Disk method for the determination of the thermal conductivity and contributes to a further improvement of its measurement accuracy. Subsequent to an extensive literature review of available reference materials for the thermal conductivity, measurements up to 750 °C were carried out with a Hot Disk TPS 2500 S with various Kapton and Mica sensors using three reference materials (Silcal 1100, Pyroceram 9606, Inconel 600). While room-temperature measurements confirmed the suitability of the reference samples as well as the independence of the measured thermal conductivity from the sensor, temperature-dependent measurements allowed the verification of the accuracy of the given TCRs. A set of optimized TCRs is proposed, with which the thermal conductivity of all three reference materials could be determined with an accuracy of 2 %. Furthermore, the measurement uncertainty of ± 5 % specified by the manufacturer could be confirmed. Hence, with the newly suggested TCRs, the Hot Disk method enables the determination of the thermal properties of a variety of materials even at high temperatures with high accuracy.