Transient thermal characteristics of the buried crude oil pipeline system during the reverse pipelining

Abstract

Mathematical models and numerical approaches are applied to the thermal system coupling by the crude oil, pipeline and soil during the reverse pipelining of pipeline. On the basis of the above, five simulation cases are carried out to investigate the transient thermal characteristics of the thermal system. It can be concluded that the time evolution of crude oil temperature can be divided into three stages; among them, thermal performance in each stage is different due to the different dominating mechanisms. Based on the variation of the temperature profile along the pipeline, the crude oil pipeline can be divided into three regions. Among them, the temperature profile characteristics in each region are different due to the different dominating mechanisms. Further, the detailed evolution characteristics of thermal performance along the pipeline during the reverse pipelining are presented. So as to investigate the heat transfer mechanism of the thermal process, the temperature profile of soil around the pipeline is also presented. It can be concluded that the temperature of soil around the pipeline has the similar thermal characteristics as crude oil except the thermal hysteresis phenomena are presented. In addition, there exist two thermal influence regions around the pipeline during the reverse pipelining. One region is influenced by the reverse pipelining process. And another region is much larger and influenced by the crude oil pipeline. Furthermore, the effects of the outlet temperature and flow rate as well as the atmospheric temperature and pipeline diameter on the thermal characteristics of the pipeline system are also analyzed.