Dynamics of flow transitions from bubbly to churn flow in high viscosity oils and large diameter columns

Mohammed, Shara K.; Hasan, Abbas H.; Ibrahim, Abubakr; Dimitrakis, Georgios; Azzopardi, Barry J.

Abstract

The dynamic behaviour of the gas-liquid two phase flows and in particular the flow pattern stability and transition between the flow regimes are influenced significantly by both the properties of the liquid and gas as well as the pipe diameter. The majority of the studies reported in the literature on the dynamics of gas-liquid flow transitions focus only on low viscosity liquids (e.g. water) and small diameter pipes. In the present work a series of experiments were carried out to study the dynamics of flow transitions (bubbly to slug and slug to churn) of gas rising through very viscous oils (330 Pa s and 360 Pa s) in two large diameter columns (290 and 240 mm, respectively), using Electrical Capacitance Tomography (ECT) and pressure sensors. The experiments aimed to imitate a number of realistic flow conditions that might be encountered, for examples, in; bitumen, crude oil, viscous liquids in food processing and volcanic magmatic flows. Observation and quantification of bubbly to slug and slug to churn flow transitions for gas-high viscous liquids in large pipe diameters are presented for the first time. Flow parameters and characteristics including; void fraction, pressure gradient, Probability Density Function, structure velocity, lengths of large/Taylor bubbles and liquid slugs and the effect of liquid temperature on the void fraction and Taylor bubble lengths, were measured and analysed. It was found that transition to slug and churn flow occurs gradually. Transition to slug flow occurs at a gas superficial velocity of 0.011 m/s–0.016 m/s, while transition to churn appears in the range of 0.127–0.243 m/s in both columns.

Citation

Mohammed, S. K., Hasan, A. H., Ibrahim, A., Dimitrakis, G., & Azzopardi, B. J. (2019). Dynamics of flow transitions from bubbly to churn flow in high viscosity oils and large diameter columns. International Journal of Multiphase Flow, 120, https://doi.org/10.1016/j.ijmultiphaseflow.2019.103095

• Journal Article Type: Article
• Acceptance Date: Aug 15, 2019
• Online Publication Date: Aug 16, 2019
• Publication Date: 2019-11
• Deposit Date: Sep 4, 2019
• Publicly Available Date: Aug 17, 2020
• Journal: International Journal of Multiphase Flow
• Print ISSN: 0301-9322
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 120
• Article Number: 103095
• DOI: https://doi.org/10.1016/j.ijmultiphaseflow.2019.103095
• Keywords: High viscosity liquids; Flow transitions; Large diameter; Taylor bubbles; Churn flow; Electrical Capacitance Tomography
• Public URL: https://nottingham-repository.worktribe.com/output/2561072
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0301932219302794
• Additional Information: This article is maintained by: Elsevier; Article Title: Dynamics of flow transitions from bubbly to churn flow in high viscosity oils and large diameter columns; Journal Title: International Journal of Multiphase Flow; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.ijmultiphaseflow.2019.103095; Content Type: article; Copyright: © 2019 Elsevier Ltd. All rights reserved.