Determination of the thermophysical properties of media with the help of a needle probe

Needle probes with linear heater inside are often used for determining the thermophysical characteristics of loose rocks. The main issue of contact methods of the measurements of the thermal characteristics of different media consists in the establishment of a thermal contact resistance at the boundary (line) between the source and the medium. This contact resistance should be taken into account while measuring the thermal diffusivity of the medium. The paper describes a mathematical model of the heating of a long needle probe in the medium under study that takes into account the size and thermal characteristics of the needle probe and an imperfect thermal contact between the probe and the studied medium. On the basis of this model, we pose and solve the inverse problem of finding the thermal diffusivity of the medium and the thermal contact resistance at the boundary between the probe and the medium. The aim of this research is to develop a new method for determining the thermal properties of various media in the field.