Experimental study on heat transfer characteristics of bituminous coal with different metamorphic degrees

To investigate the development tendency of coal fires, the long-flame coal, gas coal, coking coal, and meager-mean coal from Daliuta Coal Mine, Xinglongzhuang Coal Mine, Dingji Coal Mine, and Wangjialing Coal Mine were selected, and the laser-flash apparatus FLA 457 was adopted to analyze the change of specific heat capacity, thermal diffusivity, and thermal conductivity of each coal under air atmosphere from 30 ℃ to 300 ℃. The grey correlation method was used to master the relation between basic parameters（moisture, ash, volatiles, and fixed carbon） and thermophysical parameters （thermal diffusivity, specific heat capacity, and thermal conductivity）. Results indicated that as temperature increased, the thermal diffusivity decreased and then increased, specific heat capacity rose and then tended to be steady, and thermal conductivity increased and then rapidly increased. Furthermore, the thermal diffusivity and thermal conductivity of long-flame coal from Daliuta Coal Mine were the smallest, but those of coking coal from Dingji Coal Mine were the largest, this phenomenon can be explained that the volatiles, ash, and fixed carbon in coal contribute greatly to the change of coal thermophysical parameters.