Abstract
Oil–water annular flow is an efficient method of heavy oil transportation for energy-saving. To deeply study the influencing factors of the energy savings of oil–water annular flow, this paper compares the interface fluctuation and energy-saving situation of oil–water annular flow under different pipe structures (such as straight pipe, sudden-contraction pipe, and elbow pipe), flow parameters, and fluid properties. In the straight pipe, the flow parameters can impact the oil–water annular flow pattern and the energy savings, and the interface fluctuation is consistent with the energy savings. The stable oil–water core annular flow has slight interface fluctuation and significant energy savings. At the same time, the influences of pipe structure and fluid properties on energy saving are also analyzed. In the sudden-contraction pipe, the oil–water interface fluctuates, largely due to the sharp changes in flow cross-section, which leads to reduced energy savings. In the elbow, the oil–water interface fluctuates greatly due to the influence of centrifugal force caused by flow direction variation, and also leads to a decline in energy savings. The effects of oil property or annulus liquid property on the interface fluctuates, and the energy savings are analyzed; reducing surface tension is an effective measure to provide an energy-saving effect. These results can provide a reference for the design of heavy-oil-transportation pipelines, the analysis of interface fluctuation, and the energy-saving evaluation of oil–water annular flow.
Highlights
Heavy oil–water annular flow is a potential method for heavy oil transportation, whose center is heavy oil, and the annulus is water film
Charles et al studied oil–water annular flow, the parts of which were of equal density and different viscosity, and a theoretical model was proposed to obtain the reduction in pressure loss and energy [5]
(coupled LS with VOF), and found that Coupled LS and VOF (CLSVOF) combines the advantages of VOF and LS [38], so the CLSVOF approach is adopted for tracking the oil–water interface, which involves the N-S (Navier–Stokes) equations and LS and
Summary
Heavy oil–water annular flow is a potential method for heavy oil transportation, whose center is heavy oil, and the annulus is water film. Charles et al studied oil–water annular flow, the parts of which were of equal density and different viscosity, and a theoretical model was proposed to obtain the reduction in pressure loss and energy [5]. Bentwich studied the interface shape and its influencing factors (interfacial tension, capillary forces, and so on), and found that core–annular flow could reduce the pressure by 50% if the viscosity ratio of oil to water was 20 [7]. Brauner analyzed the energy factor of core–annular flow, which is a function of the viscosity ratio of oil and water They found that the energy factor increases with the decrease in the density difference between the two fluids [33]. Investigating the energy-saving situation of oil–water annular flow can provide supporting data for the design of parameters for heavy oil transportation, and it is worth continuing. The influence factor of energy saving will be investigated, and these results will provide a basis for optimizing the operation and geometric parameters for the pipelines design of heavy oil transportation
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