Research on heat transfer characteristic of waxy crude oil after oil pipeline shutdown

By means of additional specific heat capacity and momentum source term methods, the heat transfer characteristic of waxy crude oil after pipeline shutdown is investigated by the numerical simulation. Comparing to the previous research, some new findings are obtained. New division method for the cooling process according to the heat transfer behavior of oil is proposed. Special concern is taken on the gelation process of waxy crude oil. The gelled crude oil first appears on the bottom of the pipe. And then the gelation interface gradually changes from ellipse shape into the concentric circle shape. The evolution of heat transfer coefficient of the inner wall is different during the cooling process. Therefore, the forecast of heat transfer coefficient should follow different mathematical formulation. Heat conduction is the driving force for the movement of gelation interface and the determinant for the temperature gradient in the pipe. The smooth temperature gradient brings about the integral gelation of waxy crude oil. On this condition, the gelled crude oil has more powerful structural strength. The variation of oil viscosity has the limited effect on the cooling rate of oil. As the cooling process proceeds, heat convection continues to weakening. Thus, the effect of oil viscosity on the heat transfer gradually decreases.