Generalised hot wire method for thermal conductivity measurements

The hot wire method for the measurement of thermal conductivity is generalised to the configuration where the wire separates the half-spaces of homogeneous materials, having different thermal conductivities and diffusion constants. This configuration has several advantages since it enables the construction of a measuring probe which simplifies measurements considerably. The expression for the temperature variation at the contact plane is derived. It is shown that the long-term behaviour depends in a simple way solely on thermal conductivities. Corresponding formulae for anisotropic materials are presented. The technical application is also discussed.