A new non-contact optical method for determining the thermal conductivity of metals and carbides at their melting/freezing temperatures

摘要

It is now recognized that the contact methods to measure a thermal conductivity of metals and carbides in liquid/solid phase transition are facing some difficulties. On the other side, the normal spectral emissivity for these materials at melting/freezing points can be measured with high degree of accuracy. Therefore, it is of considerable interest to develop a method that makes it possible to determine the thermal conductivity through the measured value of the normal spectral emissivity. A new optical non-contact method to determine the thermal conductivity of metals and carbides at their melting/freezing points is proposed. This method is based on the use of the Drude model, the Hagen-Rubens relation, and the Wiedemann-Franz law. To define the thermal conductivity of materials at melting/freezing points, the experimental measurements of the normal spectral emissivity in a specific far-infrared range are needed. The proposed method does not require to model the power balance of heat transport for calculating the thermal conductivity. The applicability of the proposed method was demonstrated on cobalt, nickel, and zirconium carbide. A good agreement with experimental data published in the literature is obtained. The gap between the thermal conductivity of the materials under study in the solid and liquid phases at their melting/freezing temperatures is calculated. The temperature dependence of the thermal conductivity of the "ideal" solar power emitter is obtained.