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Research Papers

A Statistical Model of Bubble Coalescence and Its Application to Boiling Heat Flux Prediction—Part II: Experimental Validation

[+] Author and Article Information
Wen Wu1

Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801wen.wu@gat.com

Barclay G. Jones2

Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801bgjones@uiuc.edu

Ty A. Newell3

Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801tynewell@uiuc.edu

1

Corresponding author. Present address: General Atomics, P.O. Box 85608, San Diego, CA.

2

Present address: University of Illinois at Urbana-Champaign, Department of Nuclear, Plasma, and Radiological Engineering, 214 Nuclear Engineering Laboratory, 103 South Goodwin Avenue, Urbana, IL 61801-2984.

3

Present address: University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, 2115 Mechanical Engineering Laboratory, 1206 West Green Street, Urbana, IL 61801.

J. Heat Transfer 131(12), 121014 (Oct 15, 2009) (11 pages) doi:10.1115/1.4000025 History: Received January 29, 2009; Revised July 16, 2009; Published October 15, 2009

A mechanistic model for the boiling heat flux prediction proposed in Part I of this two-part paper (2009, “A Statistical Model of Bubble Coalescence and Its Application to Boiling Heat Flux Prediction—Part I: Model Development,” ASME J. Heat Transfer, 131, p. 121013) is verified in this part. In the first step, the model is examined by experiments conducted using R134a covering a range of pressures, inlet subcoolings, and flow velocities. The density of the active nucleation sites is measured and correlated with critical diameter Dc and static contact angle θ. Underlying submodels on bubble growth and bubble departure/lift-off radii are validated. Predictions of heat flux are compared with the experimental data with an overall good agreement observed. This model achieves an average error of ±25% for the prediction of R134a boiling curves, with the predicted maximum surface heat flux staying within ±20% of the experimentally measured critical heat flux. In the second step, the model is applied to water data measured by McAdams (1949, “Heat Transfer at High Rates to Water With Surface Boiling,” Ind. Eng. Chem., 41(9), pp. 1945–1953) in vertical circular tubes. The consistency suggests that the application of this mechanistic model can be extended to other flow conditions if the underlying submodels are appropriately chosen and the assumptions made during model development remain valid.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic diagram of apparatus for flow visualization experiments

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Figure 2

Structural design of the test section: (a) assembly view of the flow channel, the test section, and heaters; and (b) thermocouple locations in the test section

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Figure 3

Image processing flowchart for measuring the active nucleation site density

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Figure 4

Measured active nucleation site density

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Figure 5

Flow visualization of bubbles originating from a nucleation site

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Figure 6

Image processing flowchart for measuring bubble size

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Figure 7

Measured bubble growth at 300 kPa

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Figure 8

Measured bubble growth at 400 kPa (5)

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Figure 9

Bubble departure radius rd with varying flow velocity

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Figure 10

Comparison between predicted and measured bubble departure radii

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Figure 11

Bubble departure radius distribution

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Figure 12

Bubble sliding velocity distribution

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Figure 13

Bubble lift-off radius rl with varying flow velocity

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Figure 14

Bubble lift-off radius distribution

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Figure 15

Comparison between predicted and measured bubble lift-off radii

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Figure 16

Measured boiling curves under different experimental conditions

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Figure 17

Predicted R134a boiling curves at 400 kPa

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Figure 18

Comparison of the predicted heat flux with R134a data at 400 kPa

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Figure 19

Bubble lift-off radius distribution at 400 kPa. (The sudden increase in pit for ΔTsat=10°C at rb=rl10=0.084 mm is governed by the model of Thorncroft (7), which predicts that all bubbles surviving from bubble interactions should lift off at rl. This also explains the similar behavior of pit in Fig. 2.)

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Figure 20

Fractional contribution of heat flux at 400 kPa

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Figure 21

Comparison of the predicted heat flux with R134a data at higher pressures

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Figure 22

Bubble lift-off radius distribution at higher pressures

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Figure 23

Variation in critical diameter Dc with pressure

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Figure 24

Fractional contributions of heat flux at higher pressures

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Figure 25

Comparison of the predicted critical heat flux with R134a data

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Figure 26

Boiling curve comparison with the data by McAdams (8)

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Figure 27

Boiling curve comparison with the data by McAdams (8)

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