饱和含水冻土区埋地管道水热耦合数值模拟

Numerical simulation of water-thermal coupling of porous frozen-soil around buried pipeline in saturated water frozen-soil area

通过对冻土区管道运行研究,提出针对管道安全运行的措施.采用有限容积法,得到多年冻土多孔介质水热耦合数学模型,地表面温度采用随年周期性变化条件,应用SIMPLER算法对模型进行数值求解.通过对无保温层和有相同厚度两种保温材质的管道在春季、夏季和冬季的土壤温度场进行数值模拟,显示在地表温度波动的条件下,热流密度随土壤温度波动呈现周期性变化.在长期运行管道中,无保温措施的管道周围冻土融化剧烈,管壁热流密度大且振幅波动大.使用厚度为40mm的两种保温材料中,40 mm聚氨酯保温效果较好.冻土区运行管道应加敷导热系数较小的保温材料,可极大降低融化深度,保护管道安全运行.

When the crude oil pipeline crosses frozen soil area,the thawing of the frozen soil results in the heterogeneous deformation of the pipeline foundation and influences the pipeline security.The water-thermal coupling model for porous frozen-soil media was established by finite volume method,and SIMPLER algorithm is used to solve this model.In the model,the surface temperature varies periodically in every year.The temperature fields in the soil around crude oil pipelines without any thermal insulation layer and with two kinds of thermal insulation layers of the same thickness of different materials in spring,summer and winter are simulated.The results show that the heat flux density in the frozen soil also varies periodically with the fluctuation of soil temperature.In the running process of the pipeline,the frozen soil around the pipeline without thermal insulation layer thaws dramatically,in which there is a great heat flux density with great amplitude fluctuation.Among two kinds of thermal insulation material layers of 40 mm thickness,polyurethane foam insulation layer has preferable thermal insulation performance.Therefore,the crude oil pipeline in the permafrost region should overlay with the thermal insulation material of small thermal conductivity coefficient,which can greatly reduce the thawing depth and ensure the security of pipeline running.