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Research Papers: Evaporation, Boiling, and Condensation

Observations of the Critical Heat Flux Process During Pool Boiling of FC-72

[+] Author and Article Information
J. Jung

Korea Advanced Institute of Science and Technology,
Department of Mechanical Engineering,
Daejeon 305-701, Korea
e-mail: dongwhy@kaist.ac.kr

S. J. Kim

Korea Advanced Institute of Science and Technology,
Department of Mechanical Engineering,
Daejeon 305-701, Korea
e-mail: sungjinkim@kaist.ac.kr

J. Kim

University of Maryland,
Department of Mechanical Engineering,
College Park, MD 20742
e-mail: kimjh@umd.edu

A movie of the heat flux and temperature distribution as the surface transitions though CHF can be viewed at http://heattransfer.asmedigitalcollection.asme.org/article.aspx?articleID=1760213 on the ASME.org Digital Collection by clicking the tab “Supplemental Material.” Text files of the time-resolved local temperature and heat flux distributions at selected heat flux values from which the reader can rederive many of the results given below can be obtained by contacting the corresponding author.

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received April 6, 2013; final manuscript received July 31, 2013; published online January 24, 2014. Assoc. Editor: Patrick E. Phelan.

J. Heat Transfer 136(4), 041501 (Jan 24, 2014) (12 pages) Paper No: HT-13-1189; doi: 10.1115/1.4025697 History: Received April 06, 2013; Revised July 31, 2013

Experimental work was undertaken to investigate the process by which pool-boiling critical heat flux (CHF) occurs using an IR camera to measure the local temperature and heat transfer coefficients on a heated silicon surface. The wetted area fraction (WF), the contact line length density (CLD), the frequency between dryout events, the lifetime of the dry patches, the speed of the advancing and receding contact lines, the dry patch size distribution on the surface, and the heat transfer from the liquid-covered areas were measured throughout the boiling curve. Quantitative analysis of this data at high heat flux and transition through CHF revealed that the boiling curve can simply be obtained by weighting the heat flux from the liquid-covered areas by WF. CHF mechanisms proposed in the literature were evaluated against the observations.

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References

Figures

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Fig. 1

Pool-boiling experimental facility

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Fig. 2

Test heater construction

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Fig. 3

Experimental setup for validation (not to scale)

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Fig. 4

Boiling curves from experiments at saturation temperature (P = 1 atm) obtained as the heat flux was increased

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Fig. 5

Sample IR images of boiling on a silicon heater at q″ = 15.7 W/cm2 (P = 1 atm)

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Fig. 6

Local temperature and heat flux from a typical point on the surface at q″ = 15.7 W/cm2 (P = 1 atm): (a) Local temperature and (b) local heat flux

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Fig. 7

Temperature and heat flux distribution at q″ = 15.7 W/cm2 for two successive frames

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Fig. 8

The evolution of temperature and heat flux at q″ = 15.7 W/cm2 as the heater transitions through CHF

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Fig. 9

Sketch of the microregion at the contact line

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Fig. 10

Example illustrating the algorithm to determine contact line location: (a) Heat flux and (b) Contact line location. The white line in (b) indicates the location of the contact line. The black and gray areas indicate the dry and wetted areas, respectively.

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Fig. 11

Contact line movement between successive frames taken at 383 Hz. Examples of the various heat transfer regions are shown.

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Fig. 12

Two methods for estimating contact line speed

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Fig. 13

(a) Evolution of WF and CLD with time at different heat fluxes. (b) Evolution of area averaged heat flux, area averaged temperature, CLD, and WF with time at 15.0 W/cm2.

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Fig. 14

Regional contribution to the wall heat transfer at various heat fluxes

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Fig. 15

Relation with heat flux from the surface and the wetted area

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Fig. 16

The speed of advancing and receding contact line determined using the two methods

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Fig. 17

The change of advancing and receding area with heat fluxes at Tbulk = 56 °C: (a) Contact line length and (b) percentage of the total area associated with advancing and receding areas

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Fig. 18

(a) Dryout function at various heat fluxes at center of heater. “0” and “1” indicate liquid and vapor on the surface, respectively. (b) Average duration of dry patch and frequency of bubble events with heat flux. (c) Dryout function and temperature history at the center of the heater during transition through CHF.

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Fig. 19

Distribution of individual dry patch size with heat flux

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