Numerical simulation for the heat transfer behavior of oil pipeline during the shutdown and restart process

Mathematical models for the heat transfer behavior of the oil pipeline during shutdown and restart are established. And the finite difference and finite volume method are used to disperse the mathematical models to investigate the heat transfer characteristics of the thermal system. Five simulation cases are executed to obtain some findings. During restart, the pipeline can be divided into three regions with each region has a certain temperature changing trait. And the increasing of temperature on certain position has two stages and each stage has a different temperature evolution due to the movement of remain cold oil and entering of hot oil. The surrounding soil has the analogical temperature evolution in contrast to the crude oil except some thermal hysteresis exists. And a thermal influence region is also found around the pipeline. The influence of restart flow and temperature on the oil pipeline is also investigated. There is a worthy of note that in case that the restart flow is lower than a certain value, there may be appears a period of time that the oil temperature continues to decrease although the pipeline has been restarted. This condition increases the risk of oil gelatinization.