Modelagem e simulação de escoamento anular de água-óleo pesado-ar em dutos horizontais.

Abstract

In this work numerical simulation was employed to study the fluid dynamic behavior of a three-phase flow system comprised by water-heavy oil- air. The focus was on the transport of heavy oils and ultraviscous in horizontal pipelines, using the technique "core annular flow" in isothermal and non -isothermal system. The mathematical model used was non-homogeneous and Eulerian-Eulerian structure was employed to derive the governing equations. Two models were considered in order to couple the terms of the interfacial transfer of momentum: a mixture model in continuous phase (water-heavy oil) and a particle model, for dispersed and continuous phases (air- heavy oil). Through these models the influence of superficial velocity, volume fraction, roughness of the pipeline, fluid thermophysical properties, flow pattern and pressure drop were then investigated. The results obtained were compared with experimental data and showed that the core-flow technique proved to be efficient for the transport of three-phase flows. Findings showed that the fluids moved with same velocity (in situ), behaving as a mixture. It was observed higher pressure gradients in the entrance region of the duct. However, when the flow became fully developed (i.e. stable), the pressure gradients became constant. Thus, this may allow estimates in pressure drops in pipes of greater length. Findings showed that core oil eccentricity was caused by buoyancy. This buoyancy was balanced by pressure gradient caused by duct wall in the vertical direction. The volumetric flow of air and heavy fuel oil, and the surface roughness of the pipe, exerted a strong influence on the behavior of the flow and pressure drop. Conclusively, the mathematical approach was adequate for the physical representation of the of three-phase flow water- heavy oil -air, as well it was able to predict pressure drops along the flow, velocity profiles and the influences of temperature and duct roughness on the system.