水分相变下松散煤体导热系数的数值模拟研究

Simulation study of water phase transition effects on thermal conductivity of loose coal

煤自燃过程中水分的相变与迁移对松散煤体所处的导热和蓄热环境具有重要影响,而导热系数的变化可直观表征水分相变对松散煤体导热能力的改变。考虑到水分相变对松散煤体自燃过程中热湿迁移的实际作用,建立了含水松散煤体的简化物理模型,运用有限元数值模拟的方法,求解了二维稳态条件下,水分发生相变时含水松散煤体的温度场和热流密度分布,分析了水分相变对松散煤体内部各处导热能力的改变,并计算得到了相应的导热系数。研究结果表明:水分相变的发生直接影响了含水松散煤体内部温度及热流的分布,最终表现为含水松散煤体导热能力的整体变化;基于水分相变的影响,随着液相饱和度的增大,含水松散煤体的导热系数基本呈线性增加,增加趋势随着温度的升高逐渐变缓;100℃时水分相变下导热系数与液相饱和度满足关系:λe=0.130 1+0.132 8S,通过与对比数据的误差分析,验证了模拟的可靠性。

Phase transition and migration of moisture during coal spontaneous combustion have a significant influence on the environment of heat conductivity and the accumulation of loose coal,at the same time,the changes of thermal conduction properties of loose coal can be directly expressed by heat conductivity coefficient.As water transition has practical effect on the humid-warm transition during the spontaneous combustion of loose coal,this paper built a simplified physical model of moisture loose coal,using finite element simulation to calculate the temperature and heat flux distribution during phase transition,analyzed the change of thermal conductivity of moisture loose coal with phase transition and then obtained its relevant heat conductivity coefficient.The results show：The water phase transition directly affects the internal distribution of temperature and heat flow in moisture loose coal,and finally brings the overall change of the thermal conductivity;Based on the influence of the water phase transition,the thermal conductivity of moisture loose coal increases linearly along with the saturation-degree of liquid phase,and the increasing trend gradually slows down with the increase of temperature;The relationship between the thermal conductivity and the liquid saturation at 100 ℃ is as follows：λe =O.130 1 ＋0.132 8S,the reliability of the simulation is verified by the error analysis of the results and the comparison data.