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Multiphase Science and Technology

A Quarterly

ISSN for PRINT: 0276-1459

Institutional price:	$694.00
Issues per year:	4

Best Paper Award Selection - Editorial Board Site

2005, Volume17

190 pages

DOI: 10.1615/MultScienTechn.v17.i1-2

Issue price - $280.00

EXPERIMENTAL AND ANALYTICAL STUDIES OF GAS ENTRAINMENT PHENOMENA IN SLUG FLOW IN HORIZONTAL AND NEAR HORIZONTAL PIPES

C. P. Hale
Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK

Geoffrey Hewitt
Department of Chemical Engineering & Chemical Technology, Imperial College of Science, Technology & Medicine, Prince Consort Road, London SW7 2BY UK

I. G. Manolis
Dept. of Chemical Engineering, Imperial College, London, UK

M. A. Mendes
Department of Chemical Engineering and Chemical Technology, Imperial College London, South Kensington Campus, London SW72AZ, UK

S. M. Richardson
Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK

W. L. Wong
EPTG Pipelines Team, BP Exploration, Sunbury-on-Thames, TW16 7LN, UK

ABSTRACT

For analysing cases of slug flow in which the slug body contains gas bubbles, a common assumption is that the liquid and gas enter the slug to form a homogeneous mixture which passes through the slug and discharges at the tail. The liquid holdup in the slug calculated by this assumption is simply the ratio of the liquid volume flowrate entering the slug divided by the sum of the gas and liquid flowrates entering the slug.
In this paper the validity of the homogeneous assumption in the prediction of the liquid holdup within the slug body has been examined by conducting several campaigns of experiments in horizontal and 1° upwardly inclined test-sections. A special ("push-in") experiment is also described which allows an objective measurement of the gas entrainment rate.
Comparisons between the predictions of the homogeneous "unit cell" model and the experimental data showed good agreement at superficial mixture velocities above 6 ms¹. However, the model under-predicts the experimental holdup values at lower superficial mixture velocities. Gamma tomographic measurements of gas content distributions in the liquid slugs show that the gas tends to separate towards the top of the tube at lower flowrate. A two-fluid type model for the slug body is described for a stratified flow consisting of a bubbly layer at the top of the tube flowing over a pure liquid layer at the bottom. This appears to match the experimental observations.