Step-wise transient method for analysis of thermal properties of materials Part 2. Experimental investigations

Abstract

The subject of the paper which is a continuation of part 1 are issues related to the implementation of the stepwise transient plane source method. Both the measuring device and the testing methodology were developed. Measurements of thermophysical properties k, a and cp of selected materials from the group of thermal insulating foams (polyurethanes, polystyrenes), organic glass polymers and metals, including high thermal conductivity ones, i.e. duralumin at one measurement, were carried out. The measurement time was on the order of a few to several hundred seconds. Procedures for calculating thermal effusivity b and thermal diffusivity a were illustrated. Parameters of the thin-layer heater used in the measurement system were studied, i.e. measurements of the resistance change of the heater in the function of the voltage of the power supply and examination of the heater homogeneity were performed using a thermal imaging camera. The method requires that the thermocouples should be mounted on the faces of the samples. According to authors, this is an advantage of the method, because it allows to limit the applied pressure of the measuring stack on the accuracy of materials thermophysical properties measurements, especially metals. The measurements confirmed the suitability of the method for testing the thermophysical parameters of different groups of materials. The obtained experimentally accuracy of thermophysical parameters of testing materials in relation to reference values did not exceed 10%. The usefulness of the analytical solution of 2D transient heat conduction problem in the considered measuring stack has been confirmed by the results of numerical simulation, which includes heat transfer in a sample and in a flexible thin layer Kapton-nichrome heater.