Study on the influence range of liquid nitrogen cold impact on gas extraction borehole

In order to study the influence range of the gas extraction borehole under the cold impact of liquid nitrogen, using theoretical analysis and based on heat transfer theory, the mathematical and physical equation of coal temperature distribution around the borehole under the cold impact of liquid nitrogen was established, and the influence of water content in coal and the latent heat of phase change was fully considered. The analytical solution of the influence range of gas extraction borehole by liquid nitrogen cold impact was obtained. The influences of the original temperature, thermal conductivity and water content of coal seam on the cold impact of liquid nitrogen on gas extraction borehole were analyzed. The results show that the influence range of liquid nitrogen cold impact is most obviously controlled by the original temperature of the coal seam, followed by thermal conductivity of the coal seam and coal water content.