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Research Papers

Gas–Liquid Flow Dispersion in Micro-Orifices and Bubble Coalescence With High Flow Rates

[+] Author and Article Information
A. Tollkötter

Laboratory of Equipment Design,
Department of Biochemical and
Chemical Engineering,
TU Dortmund University,
Emil-Figge-Straße 68,
Dortmund 44227, Germany
e-mail: alexander.tollkoetter@bci.tu-dortmund.de

F. Reichmann

Laboratory of Equipment Design,
Department of Biochemical and
Chemical Engineering,
TU Dortmund University,
Emil-Figge-Straße 68,
Dortmund 44227, Germany
e-mail: felix.reichmann@bci.tu-dortmund.de

F. Schirmbeck

Laboratory of Equipment Design,
Department of Biochemical and
Chemical Engineering,
TU Dortmund University,
Emil-Figge-Straße 68,
Dortmund 44227, Germany
e-mail: fschirmbeck@web.de

J. Wesholowski

Laboratory of Solids Process Engineering,
Department of Biochemical and
Chemical Engineering,
TU Dortmund University,
Emil-Figge-Straße 68,
Dortmund 44227, Germany
e-mail: jens.wesholowski@bci.tu-dortmund.de

N. Kockmann

Laboratory of Equipment Design,
Department of Biochemical and
Chemical Engineering,
TU Dortmund University,
Emil-Figge-Straße 68,
Dortmund 44227, Germany
e-mail: norbert.kockmann@bci.tu-dortmund.de

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received October 1, 2015; final manuscript received January 2, 2016; published online March 10, 2016. Assoc. Editor: Toru Ikeda.

J. Electron. Packag 138(1), 010905 (Mar 10, 2016) (8 pages) Paper No: EP-15-1105; doi: 10.1115/1.4032557 History: Received October 01, 2015; Revised January 02, 2016

The flow of microbubbles in millichannels with typical dimensions in the range of few millimeters offers a reduced pressure loss with simultaneous large specific contact surface. The transformation of pressure into kinetic energy creates secondary flow in micro-orifices, which results in continuous bubble dispersion. In this work, bubble flow through different orifices and channel modules with widths up to 7 mm are experimentally and numerically studied. The effect of the orifice dimensions on bubble sizes is evaluated for hydraulic diameters of 0.25–0.5 mm with different aspect ratios. To provide larger residence times of the generated dispersions in the reactor, several channel structures are analyzed to offer less coalescence. Volume flow rates of 10–250 mL/min are studied with various phase ratios. Bubble diameters are generated in the range of less than 0.1–0.7 mm with narrow size distributions depending on the entire flow rate. Opening angles of the orifices above 6 deg resulted in flow detachments and recirculation zones around the effluent jet. The first break-up point is shifted closer to the orifice outlet with increasing velocity and hydraulic diameter. The entire break-up region stays nearly constant for each orifice indicating stronger velocity oscillations acting on the bubble surface. Linear relation of smaller bubble diameters with larger energy input was identified independent from Reynolds number. Flow detachment and coalescence in bends were avoided by an additional bend within the curve based on systematically varied geometrical dimensions.

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References

Figures

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Fig. 1

Schematic flow through orifices. Dissipation volume VDiss is marked gray (modified from Refs. [20] and [24]).

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Fig. 2

Reactor concept with various modules (left) and a single inlet module (right top). The close-up (right bottom) shows significant dimensions and relevant geometrical parameters of the orifices in mm according to Ref. [16].

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Fig. 3

Particle tracking procedure by GIMP

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Fig. 4

Drawing of a middle module of the reactor concept with an optimized channel structure. Detailed view of the elbow with varied ranges of its geometrical parameters.

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Fig. 5

Influence of the orifice outlet angle on flow detachment and recirculation zones

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Fig. 6

Particle tracks for sizing of turbulent regions in structures A and B

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Fig. 12

Top: simulated velocity distribution and bubble tracks in an optimized channel structure with an additional bend. Bottom: simulated velocity distribution and bubble tracks in an optimized channel structure regarding the maximum area and residence time.

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Fig. 11

Velocity distributions of simulated channel structures with enlarged cross (a) and (b) sections and inserts (c)

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Fig. 10

Comparison of theoretically calculated and experimentally determined Sauter diameters for different orifices (a) and the corresponding constants cD (b)

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Fig. 9

Bubble size distributions of two-phase flow in structures A and E for different total flow rates and ϕg  = 0.1

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Fig. 8

Bubble break-up points in structures A and C for different Reynolds numbers and ϕg  = 0.1

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Fig. 7

Pressure loss and energy dissipation rates of the structures A–E for different GCs. Standard deviations are excluded regarding their small values less than 1%.

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