Numerical simulation of thermal-fluid-solid coupling of the flow dominance ofcoal under different temperature conditions

The temperature of the coal seam continues to rise due to the increase of coal seam mining depth, and the fluid in the pores and cracks of the coal body has different flow directions and flow advantages parameters under different temperature conditions, and it is of great significance to study the dominance of gas flow in pores and crackss of coal seams at different temperatures to prevent coal and gas outburst disasters. In this paper, finite element software COMSOL Multiphysics was used to establish a thermal-fluid-solid coupling numerical model gas-containing coal, and based on the Monte-Carlo method, the coal seam crack was simulated. The flow characteristics of gas in partially connected fractures and fully connected fractures were studied at four different temperatures. The results show that under the condition of constant model boundary load, the boundary seepage gas pressure difference is constant, and the coal body temperature is the same everywhere. The higher the coal temperature is, the greater the gas pressure and the gas pressure gradient and the range of gas pressure field are. The greater the change in coal temperature difference, the greater the gas flow velocity, gas seepage velocity field in the pores and fissures of the coal, and the permeability of the pores and fissures of the coal. The results show that: the gas pressure, gas pressure gradient and gas pressure field range of the full-through fracture is larger than that of other fractures. Compared with other pores and fractures, the gas seepage velocity, gas seepage velocity field range and the permeability of coal pores and fissures are larger in all-through fractures. Therefore, under four kinds of test temperature conditions, the higher the temperature and the greater the difference in temperature, the greater the advantage of gas flow in the full-through fractures of the coal body, and the easier it is for gas to seep along the full-through fractures.