Numerical calculation on heat-moisture coupling and phase change process of the soil around buried pipeline

A natural convection heat exchange model for a porous media phase change is established based on finite volume method. Taking the pipeline in the permafrost saturated area as an example and by utilizing SIMPLER algorithm to calculate the heat transfer process of buried pipeline, it gives the law of temperature field of the permafrost around pipe and the moving interface of soil and ice and moisture transfer in different seasons. The study shows that the temperature field varies sharply with the periodical ground temperature change. A natural convection eddy is formulated when moisture transfer from top to bottom of the pipeline centerline due to temperature gradient and gravity. The pattern and intensity of the natural convection changes with the variation of ground temperature, which shows the moisture transfer is greatly affected by the temperature gradient.