International Society for Industrial Process Tomography

Investigation of Venturi Constriction Charateristics in Multiphase Flow using High Speed Gamma-Ray Tomography

S. H. Stavland^1*, S-A. Tjugum², A. Hallanger³, R. Maad¹ and B. T. Hjertaker¹

¹ Dept. of Physics and Technology, University of Bergen, P.O. Box 7803, NO-5020 Bergen, Norway

² Roxar Emerson Process Management AS, Kokstadveien 23, NO-5257 Kokstad, Norway

³ Christian Michelsen Research AS, P.O. Box 6031, NO-5892, Bergen, Norway

^*Email:stian.stavland@uib.no

ABSTRACT

The Venturi flow measurement principle has proven to be robust in multiphase flow applications, and is an integral part of several commercial multiphase flow meters. Due to the increased drive by regulators and industry to improve multiphase flow measurement accuracy, there is a need for better understanding of the multiphase flow behavior through the Venturi constriction.

The presented work examines the multiphase hydrocarbon flow behaviour under different flow conditions through a vertical-mounted Venturi constriction using the high-speed gamma-ray tomograph developed at the University of Bergen, Norway. The experimental results are compared with Computational Fluid Dynamics (CFD) simulations using models with corresponding pipe geometry, fluids and flow rates. The cross-sectional distribution of the different flow components is of special interest, as both radially symmetric and non-symmetric distribution may affect the accuracy of multiphase flow measurements. The experiments are based on the high-speed gamma-ray tomograph (GRT) and are performed in the multiphase flow facility at Christian Michelsen Research in Bergen, Norway. The GRT facilitates tomographic measurements with a temporal resolution as low as 10 ms, and is based on five 241Am gamma-ray sources mounted symmetrically around the pipe section. For each gamma-ray source there is a detector array of 17 CdZnTe semiconductor detector elements mounted on the opposite side of the pipe. The CFD simulations were performed using the OpenFOAM CFD software with the multiphaseEulerFoam solver. The simulations includes both dispersed and separated flow within similar geometry and transient flow regimes like churn and slug flow.

Keywords Computational fluid dynamics, high-speed gamma-ray tomography, multiphase flow, Venturi constriction flow characteristics

Industrial ApplicationOil and gas, and General