Three-Dimensional CFD Modeling on the Thermal Characteristics of Buried Oil Pipeline Involving the Heat Transfer of Wax Layer

It is common to have a wax layer on the inner wall of waxy crude oil pipeline. However, the study of the wax layer on the heat transfer of buried pipeline systems is inadequate due to its instability of composition and properties; it may lead to the inaccurate prediction of the pipeline temperature field. Based on the finite element simulation technology, a three-dimensional heat transfer model of buried crude oil pipeline involving wax layer was proposed and solved. The thermal effect of the wax layer on pipeline system was analyzed quantitatively. Numerical results show that the average deviation of soil temperature near the pipeline reach 1.42 K when there is a 4 mm wax layer. Among different thermal conductivity models of heterogeneous materials, the EMT model plays best in predicting the conductivity of a waxy layer. By setting different working conditions, the influence mechanisms of several thermal influencing factors are discussed. The results show that the thermal influence range of heated pipe is positively associated with oil temperature and velocity. The core thermal response zone is about 12 m along the X-axis. Beyond 8 m depth from ground surface, the temperature fluctuation of soil is almost unaffected by the oil pipeline.