Solving the waxy crude-oil pipeline-flow-restart problem numerically in nonisothermal condition from the perspective of engineering

For maintenance, emergency, or other reasons, pipeline flow can stop. In the development of startup models, the heat diffusion between oil and the surrounding region has not always been considered. Here we establish a numerical restart model for buried pipelines consisting of a new simplified oil heat-transfer model and a cold oil-displacement-flow model considering oil heat diffusion to low-temperature soil and temperature gradients in the axial direction. In addition, we present our studies on the effects of axial-mesh size, timestep, different boundary conditions of the pipe wall, and shutdown in different seasons.