Development of Specific Heat Measuring Apparatus of Geothermal Related Rocks and Their Measurement

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Specific heat of rocks was measured by two different methods, direct method and indirect method. In the direct method, a differential scanning calorimeter was used. In the indirect method, the specific heat was calculated by measuring the thermal conductivity and the thermal diffusivity by using the hot wire method.In the direct method, the bad repeatability was the most significant problem. As for the countermeasure of this problem the specimen with smaller particle size and the vessels, weight of them lie in a certain range, were used. The stability of the baseline was a little bit improved by these measures, but the repeatability was not sufficient.In the indirect method, the thermal conductivity was successfully measured between room temperature and 400 - 600^ﾟC. The measured rocks were granite, andesite, sandstone , shale and coals. In the measurement of the thermal diffusivity, the contact between the rock specimen and the hot wire was found to be the most important , which would deviate the measured temperature from the theoretical one at the time of the initial heating. The specific heat at the room temperature was obtained with a reasonable value.