The characterization of thermophysical properties by thermal impedance measurements taken under random stimuli taking sensor-induced disturbance into account

Abstract

The characterization of thermal systems can be performed by using thermal impedance measurements. Experimentally, this method requires simultaneous measurements of the variations in heat flux and the temperature of the measuring surface. The sensor, placed on the system to be characterized, induces a disturbance. For a slow change in thermal characteristics and for low frequencies, the disturbance due to the sensor is negligible. The low-frequency case has been studied in several works, but we show here that it is possible to extend the method to higher frequencies by taking the sensor disturbance into account. A model accounting for sensitivity to parameters shows that in a zone called `the middle frequency zone' the disturbance is limited to a resistive effect. This zone is studied in this work and concrete was tested under these conditions. Several tests were carried out on the same sample. The contact resistance was modified for each test and the method used led to a stable value of material effusivity.