Numerical Study on the Optimal Thermally Affected Region of a Buried Oil Pipeline

Crude oil pipeline transportation is usually a closed process under a certain depth of burial, and the condition of oil in the pipeline changes with the continuous decline of temperature during the transportation process. The safety and energy consumption of pipeline transportation are closely related to the accurate prediction of oil temperature. It is a popular technique to use the thermally affected region to overcome the problem of an unclosed calculation domain caused by the semi-infinite soil around the pipeline. However, there is no clear and unified guidance on the thermally affected region at present, and improper region size may lead to a loss of the accuracy of the pipeline system. Therefore, our study answers two questions about the optimal form of the thermally affected region and its economic scope of application. The coupled solution of heat transfer and flow in a tridimensional numerical model is carried out, and the thermodynamic influences of the geometric shape and range of the thermally affected region on the buried pipeline system are investigated. The results show that the rectangular region is more suitable for the modeling of buried oil pipelines, and a region with 16 m width and 9 m height is recommended for the conventional case.