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Multiphase Flows

Modeling the Onset of Gas Entrainment in a Reduced T-Junction With Co-Current Stratified Gas-Liquid Flow

[+] Author and Article Information
Robert C. Bowden

Department of Mechanical and Industrial Engineering,  Concordia University, Montreal, QC, H3G 2W1, Canada

Ibrahim G. Hassan

Department of Mechanical and Industrial Engineering,  Concordia University, Montreal, QC, H3G 2W1, CanadaIbrahimH@alcor.concordia.ca

J. Fluids Eng 134(8), 081303 (Aug 08, 2012) (12 pages) doi:10.1115/1.4003854 History: Received March 29, 2010; Revised March 02, 2011; Published August 08, 2012; Online August 08, 2012

A model was developed to predict the onset of gas entrainment in a single downward oriented branch. The branch was installed on a horizontal square cross-sectional channel having a smooth stratified co-currently flowing gas-liquid regime in the inlet region. The branch flow was simulated as a three-dimensional point-sink while the run flow was treated as a uniform velocity at the critical dip. Experiments were performed to determine the critical liquid flow distribution between the run and the branch. A correlation was developed relating the branch Froude number to the ratio of the superficial liquid mass fluxes in the run and the branch. The correlation was used as a boundary condition in the model. A methodology was developed using digital imaging to record the coordinates of the critical dip at the onset of as entrainment. The dip angle was found to range between 40 to 60 degrees and constant dip angles of 40, 50 and 60 degrees were selected as boundary conditions. The critical height was predicted to within 50% of experiments with the error attributed to differences in the modeled and experimental geometries. A semi-empirical analysis using the experimental geometry yielded a critical height prediction to within 20% of experimental results.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Problem description

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Figure 3

Schematic of the experimental facility (elevation view)

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Figure 4

Image analysis procedures showing (a) calibration using a static interface and the (b) dip profile measurement

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Figure 5

Comparison between imaging and transducer measurements under smooth-stratified conditions

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Figure 6

Two-phase flow structure (a) just prior to gas entrainment and (b) at transient dip breakup with subsequent gas entrainment

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Figure 7

Critical liquid flow distribution between run and branch

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Figure 8

Critical interface profiles obtained from (a) imaging measurements and (b) transducer measurements

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Figure 9

Experimental dip characteristics demonstrating (a) dip angle and (b) dip velocity

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Figure 10

Dip prediction showing (a) the critical dip height accompanied by the (b) acceleration field for Frd  = 15 and 50 degree dip angle

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Figure 11

(a) The predicted dip height compared with experiments and (b) the predicted crossflow Froude number at the dip

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Figure 12

Comparing the dip kinetic energy obtained from Bernoulli’s equation and the potential function for (a) the inlet velocity defined as a function of the inlet height and (b) the inlet velocity defined explicitly as ULA  = 0.24 m/s

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Figure 13

(a) The inlet average velocity accompanied by (b) the inlet crossflow Froude number (c) inlet critical height prediction compared with experiments and (d) comparison of inlet critical height using a square and circular channel

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