A high-precision instrumentation of measuring thermal contact resistance using reversible heat flux

During measuring the thermal contact resistance (TCR) of solids by using traditional steady-state test methods, it is observed that the measured results are unavoidable to be impacted by the direction of exerting heat flux between dissimilar and similar metals. Such a directional effect has also been found for the cases between two solids of identical material with the same surface properties. Uncertainty analysis shows that the directional effect between two solids may result from the additive errors. In order to improve the measurement precision, we propose a method by using harmonic mean value of TCR in two directions of exerting heat flux to diminish the effect. Meanwhile, a modified experimental apparatus has been designed and established to high-precisely measure TCR between two solids of the identical material. To verify the accuracy of the method, the TCRs of samples of 99.999% standard pure copper and Elkonite copper-tungsten alloy 30W3 are measured and discussed in detail. The results show that the present method has high precision and can be used in a relatively wide range of TCR measurement for identical solids and the characterization of thermal interface materials.