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Research Papers: Multiphase Flows

Transition of Bubbly Flow in Vertical Tubes: New Criteria Through CFD Simulation

[+] Author and Article Information
A. K. Das

Department of Mechanical Engineering, IIT Kharagpur, 721302, Indiaarup@mech.iitkgp.ernet.in

P. K. Das1

Department of Mechanical Engineering, IIT Kharagpur, 721302, Indiapkd@mech.iitkgp.ernet.in

J. R. Thome

LCTM, EPFL, Lausanne CH-1015, Switzerlandjohn.thome@epfl.ch

1

Corresponding author.

J. Fluids Eng 131(9), 091303 (Aug 18, 2009) (12 pages) doi:10.1115/1.3203205 History: Received January 13, 2009; Revised July 04, 2009; Published August 18, 2009

The two fluid model is used to simulate upward gas-liquid bubbly flow through a vertical conduit. Coalescence and breakup of bubbles have been accounted for by embedding the population balance technique in the two fluid model. The simulation enables one to track the axial development of the voidage pattern and the distribution of the bubbles. Thereby it has been possible to propose a new criterion for the transition from bubbly to slug flow regime. The transition criteria depend on (i) the breakage and coalescence frequency, (ii) the bubble volume count below and above the bubble size introduced at the inlet, and (iii) the bubble count histogram. The prediction based on the present criteria exhibits excellent agreement with the experimental data. It has also been possible to simulate the transition from bubbly to dispersed bubbly flow at a high liquid flow rate using the same model.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

Steps of the breakage and coalescence process

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Figure 3

Solution methodology of the proposed model

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Figure 4

Effect of radial mesh refinement on void distribution

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Figure 5

Comparison of void fraction of present model and experimental data of Serizawa (50)

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Figure 6

Comparison of void fraction with the present model and experimental data of Ohnuki and Akimoto (51)

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Figure 7

Radial distribution of volume averaged bubble diameter; a comparison between present model and experimental data of Ohnuki and Akimoto (51) at high flow rates

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Figure 8

Comparison of the computed bubble Sauter diameter along a radial plane with the experimental result of Shen (52); low gas superficial velocity

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Figure 9

Comparison of the computed bubble Sauter diameter along a radial plane with the experimental result of Shen (52); high gas superficial velocity

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Figure 10

Radial bubble count histogram at an axial distance of 10D for low flow rates

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Figure 11

Radial bubble count histogram at an axial distance of 30D for low flow rates

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Figure 12

Radial bubble count histogram at an axial distance of 60D for low flow rates

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Figure 13

Radial bubble count histogram at an axial distance of 10D for high flow rates

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Figure 14

Radial bubble count histogram at an axial distance of 20D for high flow rates

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Figure 15

Radial bubble count histogram at an axial distance of 30D for high flow rates

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Figure 16

Volume of bubbles above tenth subgroup (size at inlet) as a function of axial length; low superficial velocities

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Figure 17

Evolution of breakage and coalescence with axial location at lower flow rates

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Figure 18

Evolution of breakage and coalescence with axial location at higher flow rates

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Figure 19

Volume of bubbles above the tenth subgroup (size at inlet) as a function of axial length; high superficial velocities

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Figure 20

Change of maximum bubble diameter along axial length for air water two phase flow

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Figure 21

Transition of bubbly flow; present simulation and experimental results of Olmos (27) and Mercadier (62)

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Figure 22

Radial bubble count histogram for the high liquid flow rate showing dispersed bubbly flow

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Figure 23

Indication of different flow regimes by the bubble volume histogram obtained with a variation in liquid velocity for a fixed gas flow rate

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Figure 1

Schematic representation of bubbly flow

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