Thermal characteristics of waxy crude oil during its static cooling in an overhead pipeline

Abstract

By means of additional specific heat capacity and momentum source term methods, the thermal characteristics of waxy crude oil during its static cooling in an overhead pipeline after shutdown are investigated by the numerical simulation. According to the different thermal performances, the cooling can be divided into three stages. In the first stage, the temperature distribution of stratification, the flow pattern of cold oil sinking and hot oil rising is the main performance. In the second stage, the isotherm in the pipeline changes from parallel line into ellipse shape, which implies that the natural convection is gradually replaced by heat conduction. During this stage, the gelled oil generates first at the bottom of the pipeline. And then it extends upward along the pipeline wall. In the last stage, the isotherm gradually becomes a concentric circular shape reflecting the characteristics of heat conduction. In this stage, the jelled boundary is approximately round shape, and the gelled structure is gradually pushed from the pipe wall to the center of the pipe. Furthermore, the detailed evolution characteristics of the temperature and convective heat transfer coefficient along the pipe wall are presented which are significantly influenced by the transition of the heat transfer mechanism.