饱和含水土壤埋地原油管道冬季停输温降

建立了饱和含水土壤埋地原油管道在低于冰点环境温度下的停输流动和传热模型，该模型不仅考虑土壤水分结冰和管内原油凝固相变过程与初始温度场和流场的影响，而且考虑了水分在土壤多孔介质中和管内原油的自然对流。通过数值模拟，获得了停输期间温度场、流场以及土壤水分结冰界面和管道中原油凝固界面的分布情况。结果表明，停输期间越靠近管壁正上方的土壤，其温度梯度越大；受温度分布的影响，土壤水分和管内原油产生沿y轴对称线自下而上的自然对流；土壤水分结冰界面和管道中原油凝固界面随停输时间向埋深方向推进，管道顶部土壤中的结冰界面推进速度较远离管道土壤中的结冰界面缓慢，管内原油凝固界面也向埋深方向偏移。

Temperature decrease of crude oil pipeline buried in soil saturated with water during shutdown in winter

A flow and heat transfer model for a crude oil pipeline buried in soil saturated with water during shutdown where ambient temperature is below the freezing point of water has been established.The phase changes involving water freezing in the soil and crude oil solidifying in the pipeline and the influence of initial temperature and flow field were taken into consideration,and the natural convection of water in soil and crude oil in the pipeline were also taken into account.Temperature and flow fields,and interfaces of water freezing in soil and crude oil solidifying in the pipeline were obtained through numerical simulation.Numerical results show that the temperature gradient in the soil is greater near the top of pipeline than in other places,and that natural convection of water and oil occurs from bottom to top along a vertical symmetrical line in both soil and pipeline due to the temperature distribution.The freezing interface of water in soil and solidification interface of oil in the pipeline advance to greater depth with increasing time of shutdown.The rate of increase in the depth of the freezing interface is slower in the soil near the top of the pipeline than in that far from the pipeline and the solidification interface of oil in the pipeline also shifts to greater depth.