回填土质对埋地热油管道传热影响的研究

The Study on Unsteady-State Heat Transfer of Buried Hot Oil Pipelines with Different Backfill Soil

针对不同导热系数的土样回填管沟,忽略管道轴向温降建立二维非稳态传热模型,环境温度采用周期性边界条件。利用有限容积法,对方程进行离散,数值模拟了管道投产第一年内正常运行非稳态传热过程,同时应用"焓-多孔度"技术,并考虑原油凝固潜热对温降的影响,数值模拟了管道停输非稳态温降过程。结果表明:采用导热系数相对较小的土质回填管沟,管壁及保温层外壁热流密度明显减小,而且回填区温度较高散热较慢,由计算的安全停输时间可知,回填土质导热系数越小安全停输时间越长,模拟结果符合实际。

A two-dimensional unsteady-state heat transfer model ignoring the axial temperature drop of pipelines was established for backfilling trench with soil samples of different thermal conductivity coefficient,with ambient temperature based on periodic boundary conditions.The unsteady-state heat transfer process of pipeline which has been put into operation in the first year was simulated with finite volume method discreting the equations.At the same time,considering the impact of latent heat and solidification of crude oil on temperature drop,the unsteady-state temperature drop process of pipeline shutdown was simulated with the ＂Enthalpy-Porosity＂ technology.The results showed that the heat flux density of pipe wall and outside wall of insulation layer was significantly reduced with the trench backfilled with soil sample of the relatively low thermal conductivity,and the backfill area had high temperature and slow heat loss.According to the calculated time of the safe shutdown,the smaller the thermal conductivity coefficient of backfill soil is,the longer the time of safe shutdown will be.Therefore the simulation suits practice.