摘要
The main target of the paper is to present the problems in measuring the thermal properties of natural stones and evaluating the influence of cavities at the interface of non-planar surfaces of samples. Air voids present between the surfaces of the sample set induce anomalous heat transfer behaviour in the rocks by increasing the thermal contact resistance. The Slab model derived for the Pulse Transient Technique supports data evaluation by introducing two additional parameters in the experiment i.e. the heat capacity of the heat source (C) and the heat transfer coefficient between the heat source and specimen (α) that is related with the specimen planarity, surface roughness and the air gaps at the interfaces. The experiment was performed under two different states of thermal contact at the sample - heat source interfaces to show the influence of the decreased thermal contact resistance by filling the air voids with a thermally conductive paste made of bentonite powder mixed with water. Temperature response during measurement of thermal properties of the samples has clearly shown the effect of poor thermal contact at the untreated interfaces compared to the case when thermal contact at the interface has been improved by application of thermally conductive bentonite paste. Moreover, measurements using the bentonite paste as the heat contact agent exhibited reduced scattering in data calculated using the Slab model."