Abstract
This study investigates the effects of elbow on the transition and development of multiphase flow using computational fluid dynamics modelling techniques. The Eulerian - Multifluid VOF model coupled with an Interfacial Area Transport Equation has been employed to simulate air-water two-phase flow in a pipe with two standard 90 degree elbows mounted in series. Turbulence effects were accounted for by the RNG k-ε model. The effects of separation distance on two-phase flow development have been studied for initial slug and churn flow regimes. Computational fluid dynamics simulation results of phase distribution and time series of void fraction fluctuations were obtained and they showed good agreement with available experimental data. The results show that for initial slug flow regime, there is no flow regime transformation upstream and downstream of the two elbows. While at initial churn flow regime, flow regime transformation occurs at different sections of the flow domain before and after the two elbows. It was noticed that irrespective of the flow regime, the amplitudes and frequencies of void fraction fluctuation become smaller as the fluid flows along the pipe. Changes in the separation distance between the two elbows have larger effects on the flow at churn flow regime.
Highlights
Two-phase gas-liquid flow occurs in many industries such as chemical, petroleum, food and drink, processing and manufacturing
Two-phase flow is characterised by differences in the interface between phases leading to different two-phase flow regimes
Computational Fluid Dynamics (CFD) has been used to simulate air-water two-phase flow with the use of the Eulerian-Multifluid Volume of Fluid (VOF) with RNG k À turbulence model in a pipe with two standard 90 degree elbows mounted in series in upward verticalhorizontal-downward vertical configuration
Summary
Two-phase gas-liquid flow occurs in many industries such as chemical, petroleum, food and drink, processing and manufacturing. Two-phase flow is characterised by differences in the interface between phases leading to different two-phase flow regimes. Due to the availability of space and economics of design, there is a need for using complex piping systems such as multiple bends pipe, and U-bend to transport fluids. The knowledge of two-phase flow phenomenon in bends and its development downstream of bends is important in many industrial applications. In addition to oil-gas processing platforms where two-phase flow undergoes several changes of directions due to bends under limited space, Zhao et al.[2] have shown two specific examples of two-phase flow at multiple bends (i) fire reboiler with serpentine tubing and (ii) a novel combined bend/T-junction phase separator
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