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Research Papers: Multiphase Flows

Annular Gap Bubble Column: Experimental Investigation and Computational Fluid Dynamics Modeling

[+] Author and Article Information
Giorgio Besagni

Department of Energy,
Politecnico di Milano,
Via Lambruschini 4,
Milan 20156, Italy
e-mail: giorgio.besagni@polimi.it

Gaël Raymond Guédon

Department of Energy,
Politecnico di Milano,
Via Lambruschini 4,
Milan 20156, Italy
e-mail: gaelraymond.guedon@polimi.it

Fabio Inzoli

Department of Energy,
Politecnico di Milano,
Via Lambruschini 4,
Milan 20156, Italy
e-mail: fabio.inzoli@polimi.it

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 24, 2015; final manuscript received June 26, 2015; published online August 10, 2015. Assoc. Editor: Riccardo Mereu.

J. Fluids Eng 138(1), 011302 (Aug 10, 2015) (15 pages) Paper No: FE-15-1126; doi: 10.1115/1.4031002 History: Received February 24, 2015

This paper investigates the countercurrent gas–liquid flow in an annular gap bubble column with a 0.24 m inner diameter by using experimental and numerical investigations. The two-phase flow is studied experimentally using flow visualizations, gas holdup measurements, and double fiber optical probes in the following range of operating conditions: superficial air velocities up to 0.23 m/s and superficial water velocities up to −0.11 m/s, corresponding to gas holdups up to 29%. The flow visualizations were used to observe the flow patterns and to obtain the bubble size distribution (BSD). The gas holdup measurements were used for investigating the flow regime transitions, and the double fiber optical probes were used to study the local flow phenomena. A computational fluid dynamics (CFD) Eulerian two-fluid modeling of the column operating in the bubbly flow regime is proposed using the commercial software ansys fluent. The three-dimensional (3D) transient simulations have been performed considering a set of nondrag forces and polydispersity. It is shown that the errors in the global holdup and in the local properties are below 7% and 16%, respectively, in the range considered.

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References

Figures

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Fig. 1

Experimental facility details: (a) experimental facility, (b) air distributor, and (c) photo of the facility

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Fig. 2

The optical probe and its position within the pipe cross section

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Fig. 3

Image processing: (a) bubble sampling and (b) sampling area (top view of the column)

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Fig. 4

Photographs of the air–water flow at h=2.8 m—influence of the superficial gas velocity: JL = 0 m/s and (a) JG = 0.0087 m/s, (b) JG = 0.0220 m/s, (c) JG = 0.0313 m/s, (d) JG = 0.0408 m/s, (e) JG = 0.1192 m/s, and (f) JG = 0.1986 m/s

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Fig. 5

Photographs of the air–water flow at h=2.8 m—influence of the superficial liquid velocity: JG = 0.220 m/s and (a) JL = 0 m/s; (b) JL = −0.08 m/s

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Fig. 6

Image analysis results (JG = 0.0087 m/s and JL = 0 m/s): (a) BSD and (b) relation between aspect ratio and equivalent diameter

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Fig. 8

(a) Swarm velocity and (b) transitions velocity

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Fig. 9

Holdup measurements (JL = 0 m/s): (a) comparison with literature correlations and (b) comparison with data from the literature (Table 3)

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Fig. 10

Proposed correlation for the gas holdup

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Fig. 11

Optical probe measurements: (a) local void fraction, (b) bubble velocity, (c) bubble Sauter mean diameter, and (d) interfacial area

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Fig. 12

Bubble chord distributions

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Fig. 13

Cross-sectional contour of time-averaged air volume fraction at various vertical positions for case A (values of the area-averaged air volume fraction are also displayed)

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Fig. 14

Cross-sectional contour of time-averaged air volume fraction at various vertical positions for case B (values of the area-averaged air volume fraction are also displayed)

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Fig. 15

Cross-sectional contour of time-averaged volume fraction at the horizontal plane h = 2.3 m (the black dot indicates the probe location for local measurements): (a) case A and (b) case B

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