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Research Papers: Multiphase Flows

The Effects of Inlet Geometry and Gas-Liquid Mixing on Two-Phase Flow in Microchannels

[+] Author and Article Information
M. Kawaji1

Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, ON, M5S 3E5, Canada

K. Mori

Department of Mechanical Engineering, Osaka Electro-Communication University, 18-8 Hatsu-cho, Neyagawa, Osaka, Japan 572-8530

D. Bolintineanu

Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, ON, M5S 3E5, Canada

1

Corresponding author.

J. Fluids Eng 131(4), 041302 (Mar 11, 2009) (7 pages) doi:10.1115/1.3089543 History: Received October 08, 2007; Revised January 19, 2009; Published March 11, 2009

The effects of gas-liquid inlet geometry and mixing method on adiabatic gas-liquid two-phase flow in a microchannel of 100μm diameter have been investigated using a T-junction inlet with the same internal diameter as the microchannel. Two-phase flow patterns, void fraction, and friction pressure drop data obtained with the T-junction inlet were found to be significantly different from those obtained previously with a reducer inlet. For the T-junction inlet, the two-phase flow patterns in the microchannel were predominantly intermittent flows with short gas and liquid plugs/slugs flowing with nearly equal velocities. The void fraction data then conformed nearly to that of a homogeneous flow model, and the two-phase friction multiplier data could be described by the Lockhart–Martinelli correlation applicable to larger channels. However, when a reducer inlet was used previously and the diameter of the inlet section was much larger than that of the microchannel, an intermittent flow of long gas slugs separated by long liquid slugs became prevalent and the void fraction decreased to values far below the homogeneous void fraction. The differences in the two-phase flow characteristics between a T-junction inlet and reducer inlet were attributed to the differences in the gas bubble/slug generation mechanisms.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Experimental apparatus

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Figure 2

Gas-liquid mixing at the microchannel inlet

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Figure 3

Reducer inlet and mixer used by Kawahara (7) and Chung and Kawaji (8)

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Figure 4

Two-phase flow patterns observed in a microchannel with a micro-T-junction inlet

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Figure 5

Two-phase flow pattern maps for a micro-T-junction inlet (a) ConFig. 1 and (b) ConFig. 2, and (c) a reducer inlet used by Kawahara (7) (an open circle indicates the occasional appearance of a ring-film flow pattern)

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Figure 6

Sequence of images showing gas plug generation at a micro-T-junction (from Ref. 24)

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Figure 7

Formation of a long gas slug from a bubble in a reducer inlet (not to scale)

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Figure 8

Comparison of flow pattern transition boundaries

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Figure 9

Void fraction data for Configuration 1 of the T-junction inlet; (– – –) homogeneous model (ε=β), (——) Armand correlation (ε=0.833β), and (----) Eq. 1)

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Figure 10

Void fraction data for Configuration 2 of the T-junction inlet; (– – –) homogeneous model (ε=β), (——) Armand correlation (ε=0.833β), (----) (Eq. 1)

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Figure 11

Two-phase friction multiplier data for (a) ConFig. 1 and (b) ConFig. 2 of the T-Junction Inlet

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