ABSTRACT
To investigate temperature effects on the thermal transport properties of several typical rocks, thermal conductivity, thermal diffusivity and specific heat capacity or volumetric heat capacity of dry granite, gabbro, marble and sandstone samples and a fused silica sample were measured under high ambient temperature conditions from room temperature up to 160°C and under atmospheric pressure condition. For this purpose, we developed a new measurement system for the three thermal transport properties of dry rock samples under high ambient temperatures up to 180°C. The results of our experiments conducted in this study clearly showed that the thermal properties of dry rocks change with ambient temperature changes, in addition, the thermal property change patterns were different for different rock types. For example, the thermal conductivities of granite, marble and sandstone decreased with temperature, however that of gabbro kept almost constant.
Thermal transport properties are necessary for understanding heat flow and temperature structure in the crust. Usually, thermal properties of rock formations are measured by using rock core samples retrieved from a great depth where temperature is higher than on the ground. To exactly evaluate thermal transport properties of a rock sample retrieved from a deep borehole at its original in-situ conditions, the high temperature effects must be taken into consideration. To realize this purpose, we developed a simple new measurement system for the three thermal transport properties including thermal conductivity, thermal diffusivity and volumetric heat capacity and/or specific heat capacity of rock specimens under high ambient temperatures. This system consists of a commercial thermal constants analyzer TPS 1500 (Hot Disk, Gothenburg, Sweden), a high temperature chamber in which the rock samples and the sensor of thermal property measurements were installed. The highest temperature limit of the measurement system is 180°C. In this study, we used this new system and examined the effects of high temperature on thermal conductivity, thermal diffusivity and specific heat capacity for dry samples of four terrestrial rock types and an artificial material of fused silica.
