抄録
The practical use of rock cavern storage for liquefied fuel (liquefied natural gas, liquid hydrogen, and DME) requires a heat conduction analysis for predicting the temperature distribution in rock mass near the cavern. This analysis is performed by using values for the thermophysical properties (thermal conductivity, thermal diffusivity, and specific heat) of rock mass containing ice. In our research, we attempted to measure the thermal diffusivity of frozen-state wet rock (water-saturated rock) using an optional heating method, which is an unsteady method for measuring thermal diffusivity, and verified the usefulness of this method. Next we investigated the impact of cooling on rock's thermal diffusivity by measuring the thermal diffusivity of rock samples with different porosities. Our results revealed the following observations. Measurements for Ogino tuff, Kimachi sandstone, and Himekami granite showed that the frozen rock's thermal diffusivity at -20℃was 0.51 mm2/s for the tuff, 0.66 mm2/s for the sandstone, and 1.51 mm2/s for the granite. The optional heating method can be used to measure the thermal diffusivity with an uncertainty of approximately ± 5％ (based on measuring the rock sample three times). Furthermore, a comparison between frozen rock and wet rock revealed that the freezing of pore water caused the thermal diffusivity of sandstone and granite to increase by a factor of 1.4. On the other hand, no variations were observed in the thermal diffusivity of tuff due to the freezing of pore water.
