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Research Papers: Evaporation, Boiling, and Condensation

Modeling of Dry-Out Incipience for Flow Boiling in a Circular Microchannel at a Uniform Heat Flux

[+] Author and Article Information
Amen Younes

Department of Mechanical
and Industrial Engineering,
Concordia University,
455 de Maisonneuve Bouelvard W,
Montreal, QC H3G 1M8, Canada
e-mail: amyounes2001@gmail.com

Ibrahim Hassan

Department of Mechanical
and Industrial Engineering,
Concordia University,
455 de Maisonneuve Bouelvard W,
Montreal, QC H3G 1M8, Canada
Mechanical Engineering Department,
Texas A&M University at Qatar,
P.O. Box 23874, Doha, Qatar
e-mail: ibrahimh@alcor.concordia.ca

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received May 1, 2013; final manuscript received October 19, 2014; published online November 25, 2014. Assoc. Editor: Wei Tong.

J. Heat Transfer 137(2), 021502 (Feb 01, 2015) (12 pages) Paper No: HT-13-1224; doi: 10.1115/1.4029019 History: Received May 01, 2013; Revised October 19, 2014; Online November 25, 2014

Dry-out is an essential phenomenon that has been observed experimentally in both slug and annular flow regimes for flow boiling in mini and microchannels. The dry-out leads to a drastic drop in heat transfer coefficient, reversible flow and may cause a serious damage to the microchannel. Consequently, the study and prediction of this phenomenon is an essential objective for flow boiling in microchannels. The aim of this work is to develop an analytical model to predict the critical heat flux (CHF) based on the prediction of liquid film variation in annular flow regime for flow boiling in a horizontal uniformly heated circular microtube. The model is developed by applying one-dimensional (1D) separated flow model for a control volume in annular flow regime for steady, and sable saturated flow boiling. The influence of interfacial shear and inertia force on the liquid film thickness is taken into account. The effects of operating conditions, channel sizes, and working fluids on the CHF have been investigated. The model was compared with 110 CHF data points for flow boiling of various working fluids, (water, LN2, FC-72, and R134a) in single and multiple micro/minichannels with diameter ranges of (0.38Dh3.04 mm) and heated-length to diameter ratios in the range of (117.7 (117.7Lh/D470)470). Additionally, three CHF correlations developed for saturated flow boiling in a single microtube have been employed for the model validation. The model showed a good agreement with the experimental CHF data with mean absolute error (MAE) = 19.81%.

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References

Figures

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Fig. 1

(a) schematic diagram of an annular flow pattern, (b) a symmetric sketch of the chosen control volume for applying mass balance, (c) a symmetric sketch shows the forces applied on the control volume

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Fig. 2

Flow chart shows the procedure of calculations for the present model

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Fig. 3

Comparison of the present CHF model with CHF data obtained by Qu and Mudawar [4] for flow boiling of water in multiple channels heat sink

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Fig. 4

Comparison of the present CHF model with CHF data obtained by Roday and Jensen [35] for flow boiling of water in a single microtube with diameter of 0.427 mm

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Fig. 5

Comparison of the present CHF model with CHF data of Wojtan et al. [8] for flow boiling of R134a in a single microtube for internal diameters 0.50 mm and 0.80 mm

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Fig. 6

Comparison of the present CHF model with CHF data of Ong and Thome [16] for flow boiling of R134a in a single microtube for internal diameters 1.03, 2.20, and 3.04 mm

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Fig. 7

Comparison of the present CHF model with CHF data of Fan and Hassan [36] for flow boiling of FC-72 in a single microtube with internal diameter of 0.889 mm

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Fig. 8

Comparison of the present CHF model with CHF data of Qi et al. [6] for flow boiling of LN2 in mini and microtubes with internal diameters 0.531, 0.834, 1.042, and 1.931 mm

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Fig. 9

Comparison of experimental CHF data for flow boiling of R134a, LN2, FC72, and water in mini and microchannels with that predicted by the present CHF model

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Fig. 10

Comparison of experimental CHF data for flow boiling of R134a, LN2, FC72, and water in mini and microchannels with that predicted the CHF correlation of Wojtan et al. [8]

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Fig. 11

Comparison of experimental CHF data for flow boiling of R134a, LN2, FC72, and water in mini and microchannels with that predicted by Ong and Thome [16] correlation

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Fig. 12

Comparison of experimental CHF data for flow boiling of R134a, LN2, FC72, and water in mini and microchannels with that predicted the CHF correlation of Qi et al. [6]

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Fig. 13

Comparison of the experimental CHF data in terms of the exit vapor quality predicted by the current model for flow boiling of R134a through a 0.8 mm inner diameter microtube with those measured by Wojtan et al. [8]

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