Numerical Simulation On Heat And Mass Coupling In On-saturated Loose Coal Mass With Internal Heat Source

One of the main threats to the safety production of coal mine is the spontaneous combustion of the loose coal in the open pit,the mined out area and the high caving area.Because of the large area of open pit coal seam,underground mining area and working face,loose coal stacking patterns,the time and position of spontaneous combustion are random,studying the rule of the coupling of heat and mass in loose coal,which is helpful to prevent the spontaneous combustion of loose coal in the coal mining area.In this paper,a mathematical model of coupled heat and mass transfer in porous media is established based on the physical model of loose coal with internal heat source.By using the algebraic method in the body fitted coordinate system,the grid is divided into an irregular trapezoid physical solution domain,and the physical solution and grid node data are transformed into a rectangular computational domain.Grid generation algorithm and Simple algorithm were written by using the C sharp software,which used to solve the mathematical model.According to the numerical solution,study on changes of internal coal temperature and humidity,analyzed coal pore gas phase in the internal heat source under flow conditions,as well as in the heat under the loose coal pore in unsaturated liquid water evaporation with time and the gas phase natural convection et al.According to the analysis that numerical solution of mathematical model the results show that loose coal containing unsaturated liquid water that under the action of internal heat source,the internal temperature and vapor volume fraction of the loose coal with the heat source as the center are elliptical,that is,the longitudinal temperature change and water vapor phase volume fraction are faster than that in the transverse direction.This phenomenon is not obvious when the internal heat source control temperature is low,but it will become more significant with the increase of the internal heat source control temperature.In the process of changing the internal heat source temperature from 50 ℃ to 350 ℃,the maximum temperature difference between longitudinal 0.4m and transverse 0.3m of the heat source is more than 10℃,and the maximum value of the gas flow velocity in the vicinity of the heat source has reached the order of 10-3m/s,there is obvious natural convection near the heat source.At the same time,the numerical results are compared with those obtained by fluent software.Based on the comprehensive analysis of the heat source in the loose coal,with the influence of the evaporation of liquid water,the mass diffusion and thermal diffusion of the gas phase,it is found that the temperature distribution of the loose coal in the vicinity of the heat source is elliptical,and the variation of ellipse shape with time and heat source temperature,which provides some guidance for the control of the height of the loose coal pile and the monitoring of the internal temperature in the open coal seam,the goaf and the high caving area.