Thermophysical properties of coal measure strata under high temperature

Thermophysical properties (such as specific heat capacity, thermal conductivity, and thermal diffusivity) of coal measure strata at a wide range of temperatures are important to coal in situ gasification with environmental treatments. These thermophysical properties have been investigated for different rocks but few are available for the rocks from coal measure strata. This study experimentally investigated the specific heat capacity and the thermal conductivity of six types of rock samples from coal measure strata, including sandy mudstone 1 and 2, mudstone, siltstone, coarse sandstone, and fine sandstone when the testing temperature varies from 100 to 1000 degrees C. Two critical temperatures, 500 degrees C for sandy mudstone 1 and 400 degrees C for the other five types of rock samples, were observed. The test results show that both the specific heat capacity and the thermal conductivity decrease with the increase of temperature when the testing temperature is below the critical temperature. When the testing temperature is over the critical temperature, the specific heat capacity is almost constant and the thermal conductivity still continues decreasing. These test results further show that the classical physics theory can well predict the experimental data for both specific heat capacity and thermal conductivity of six rocks.