Chemical Engineering Research & Design, Vol.153, 201-211, 2020
Experiments and CFD modelling for two phase flow in a vertical annulus
Simulations of two-phase (air and water) flow in a pipe are among the widely discussed topics; however, with the increased understanding of multiphase flow in pipes, the application of computational fluid dynamics (CFD) in other complex flow geometries involved in oilfield operations is becoming more common. This study is aimed to investigate and better understand two-phase flow characteristics in the annulus using computational fluid dynamics and experimental approaches. The experimental study included two sets of five tests with increasing superficial gas velocity (9.2-47.2 m/s) at a constant liquid flow rate. Experiments were conducted in concentric annulus test Section (35 mm x 82.5 mm) that had an overall length of 5.5 m.'Ilmo flow patterns (churn and annular) were observed during the experiment. Using CFD simulation, pressure drop, void fraction, and flow regime are determined. The VOF multiphase model and two turbulence models (realizable k-epsilon and SST k-omega models) were implemented, and comparative study was conducted to understand the relevance of each method in high gas velocity scenarios for flow in the annulus. The simulated macroscopic behavior of the flow shows consistent pressure gradient patterns and mimics the void fraction behavior. Probability density functions were implemented on time series evolution of void fraction to identify the flow regime for the CFD results. The simulation results show a reasonable agreement with the experimental data within a mean error of 20%. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Keywords:Two-phase flow in annulus;Annular and churn flow regimes;CFD simulation;Void fraction;Pressure gradient;Probability density function