Research Papers: Two-Phase Flow and Heat Transfer

Impact of Flow Dynamics on the Heat Transfer of Bubbly Flow in a Microchannel

[+] Author and Article Information
Farzad Houshmand

e-mail: farzad.houshmand@gmail.com

Yoav Peles

e-mail: pelesy@rpi.edu
Department of Mechanical,
Aerospace, and Nuclear Engineering,
Rensselaer Polytechnic Institute,
110 8th Street,
Troy, NY 12180

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received October 24, 2012; final manuscript received August 13, 2013; published online November 7, 2013. Assoc. Editor: Ali Ebadian.

J. Heat Transfer 136(2), 022902 (Nov 07, 2013) (8 pages) Paper No: HT-12-1589; doi: 10.1115/1.4025435 History: Received October 24, 2012; Revised August 13, 2013

During nucleate flow boiling, the bubble dynamics affect the liquid flow field and the corresponding heat transfer process through several distinct mechanisms. At the microscale, this effect is different than at the macro scale partly because the bubble dimensions are comparable to the characteristic length scale of the channel. Since the process involves several mechanisms, an attempt to isolate and study them independently from one another is desired in order to extend knowledge. To remove the evaporation effect from the heat transfer process, noncondensable gas bubbles were introduced upstream of a 1 mm × 1 mm heater into a 220 μm deep and a 1.5 mm wide microchannel and the heat transfer coefficient was measured and compared to single-phase liquid flow. High speed imaging and micro particle image velocimetry (μ-PIV) measurements were used to elucidate the bubble dynamics and the liquid velocity field. This, in turn, revealed mechanisms controlling the heat transfer process. Acceleration and deceleration of the liquid flow due to the presence of bubbles were found to be the main parameters controlling the heat transfer process.

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Fig. 1

Micro device's schematics

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Fig. 2

Micro device's package

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Fig. 3

Schematics of experimental setup

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Fig. 4

Bubbles before detachment at different flow rates

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Fig. 5

Sequence of high speed images from bubble growth and detachment at 6300 fps; jl = 0.95, jg = 0.25 (m/s)

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Fig. 6

Bubble frequency (Orifice I)

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Fig. 7

Bubble frequency (Orifice II)

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Fig. 8

Average Nusselt number for single-phase water flow

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Fig. 9

Temperature change during the bubble injection (Orifice I); jl = 1.24, jg = 0.30 (m/s)

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Fig. 10

Effect of bubbles on the heat transfer (orifice I)

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Fig. 11

Velocity field around the bubbles injected from Orifice I

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Fig. 12

Velocity field around developing bubbles injected from Orifice I; jl = 0.95, jg = 0.25 (m/s)

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Fig. 13

effect of bubbles on heat transfer (Orifice II)

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Fig. 14

Velocity field around the bubbles injected from Orifice II




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