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Research Papers

Transient Critical Heat Fluxes of Subcooled Water Flow Boiling in SUS304-Circular Tubes With Various Twisted-Tape Inserts (Influence of Twist Ratio)

[+] Author and Article Information
Koichi Hata

Institute of Advanced Energy,
Kyoto University,
Gokasho, Uji, Kyoto 611-0011, Japan
e-mail: hata@iae.kyoto-u.ac.jp

Katsuya Fukuda

Department of Marine Engineering,
Kobe University,
5-1-1, Fukaeminami,
Higashinada, Kobe 658-0022, Japan
e-mail: fukuda@maritime.kobe-u.ac.jp

Suguru Masuzaki

National Institute for Fusion Science,
Oroshi-cho, Toki, Gifu 509-5292, Japan
e-mail: masuzaki@LHD.nifs.ac.jp

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received October 21, 2013; final manuscript received December 25, 2013; published online March 17, 2014. Assoc. Editor: Jovica R. Riznic.

J. Thermal Sci. Eng. Appl 6(3), 031010 (Mar 17, 2014) (14 pages) Paper No: TSEA-13-1176; doi: 10.1115/1.4026491 History: Received October 21, 2013; Revised December 25, 2013

The transient critical heat fluxes (transient CHFs) in SUS304-circular tubes with various twisted-tape inserts are systematically measured for mass velocities (G = 3988–13,620 kg/m2s), inlet liquid temperatures (Tin = 287.55–313.14 K), outlet pressures (Pout = 805.11–870.23 kPa) and exponentially increasing heat inputs (Q = Q0 exp(t/τ), exponential periods, τ, of 28.39 ms to 8.43 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-circular tube of inner diameter (d = 6 mm), heated length (L = 59.4 mm), effective length (Leff = 49.4 mm), L/d (=9.9), Leff/d (=8.23), and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) is used in this work. The SUS304 twisted-tapes with twist ratios, y [H/d = (pitch of 180 deg rotation)/d], of 2.40 and 4.45 are used. The transient critical heat fluxes for SUS304-circular tubes with the twisted-tapes of y = 2.40 and 4.45 are compared with authors' transient CHF data for the empty SUS304-circular tube and a SUS304-circular tube with the twisted-tape of y = 3.37, and the values calculated by authors' transient CHF correlations for the empty circular tube and the circular tube with twisted-tape insert. The influences of heating rate, twist ratio and swirl velocity on the transient CHF are investigated into details and the widely and precisely predictable correlations of the transient CHF against inlet and outlet subcoolings for the circular tubes with various twisted-tape inserts are given based on the experimental data. The correlations can describe the transient CHFs for SUS304-circular tubes with various twisted-tapes of twist ratios (y = 2.40, 3.37, and 4.45) in the wide experimental ranges of exponential periods (τ = 28.39 ms to 8.43 s) and swirl velocities (usw = 5.04–20.72 m/s) obtained in this work within −26.19% to 14.03% difference. The mechanism of the subcooled flow boiling critical heat flux in a circular tube with twisted-tape insert is discussed.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Prototype of the helical divertor plate for LHD located in NIFS (http://www.lhdnifs.ac.jp/en/lhd/LHD_info/heldiv.html)

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Fig. 2

Schematic diagram of experimental water loop

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Fig. 3

Vertical cross-sectional view of 6 mm inner diameter test section with the twisted-tape insert

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Fig. 4

Photograph of the SUS304 twisted-tape coated with alumina thermal spraying

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Fig. 5

SEM photograph for the SUS304 test tube of d = 6 mm with the rough finished inner surface

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Fig. 6

Measurement and data processing system

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Fig. 7

qcr,sub,st versus ΔTsub,in for SUS304 test tube of d = 6 mm and L = 59.4 mm with the twisted-tape of y = 2.40 at Pin = 838.83–994.07 kPa (green symbols)

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Fig. 8

qcr,sub,st versus ΔTsub,in for SUS304 test tube of d = 6 mm and L = 59.4 mm with the twisted-tape of y = 4.45 at Pin = 834.97–927.71 kPa (orange symbols)

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Fig. 9

Ratio of CHF data for SUS304 test tubes of d = 6 mm and L = 59.4 mm with the twisted-tapes of y = 2.40, 3.37, and 4.45 to the values derived from the inlet CHF correlation for the test tube with various twisted-tape inserts versus ΔTsub,in at Pin = 834.97–994.07 kPa

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Fig. 10

qcr,sub,st versus ΔTsub,out for SUS304 test tube of d = 6 mm and L = 59.4 mm with the twisted-tape of y = 2.40 at Pout ≅ 800 kPa (green symbols)

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Fig. 11

qcr,sub,st versus ΔTsub,out for SUS304 test tube of d = 6 mm and L = 59.4 mm with the twisted-tape of y = 4.45 at Pout ≅ 800 kPa (orange symbols)

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Fig. 12

Ratio of CHF data for SUS304 test tubes of d = 6 mm and L = 59.5 mm with the twisted-tapes of y = 2.40, 3.37, and 4.45 to the values derived from the outlet CHF correlation for the test tube with various twisted-tape inserts versus ΔTsub,out at Pout ≅ 800 kPa

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Fig. 13

The qcr,sub for SUS304 test tube of d = 6 mm with the twisted-tape of y = 2.40 with exponentially increasing heat input of τ = 28.39 ms to 8.43 s at ΔTsub,in = 150 K

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Fig. 14

The qcr,sub for SUS304 test tube of d = 6 mm with the twisted-tape of y = 4.45 with exponentially increasing heat input of τ = 28.39 ms to 8.43 s at ΔTsub,in = 150 K

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Fig. 15

Typical photograph for SUS304 test tubes of d = 6 mm and L = 59.4 mm with the twisted-tapes of y = 2.40, 3.37, and 4.45 burned out in transient CHF experiments

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Fig. 16

(qcr,sub − qcr,sub,st)/qcr,sub,st versus p* for SUS304 test tubes of d = 6 mm with the twisted-tapes of y = 2.40, 3.37, and 4.45 with exponentially increasing heat input

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Fig. 17

Ratios of qcr,sub for SUS304 test tube of d = 6 mm with the twisted-tape of y = 2.40 with exponentially increasing heat input (91 points) to values calculated by Eq. (23) versus p*

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Fig. 18

Ratios of qcr,sub for SUS304 test tube of d = 6 mm with the twisted-tape of y = 4.45 with exponentially increasing heat input (46 points) to values calculated by Eq. (23) versus p*

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Fig. 19

Ratios of qcr,sub for SUS304 test tubes of d = 6 mm with the twisted-tapes of y = 2.40, 3.37, and 4.45 with exponentially increasing heat input (186 points) to values calculated by Eq. (1) versus p*

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Fig. 20

Ratios of qcr,sub for SUS304 test tube of d = 6 mm with the twisted-tape of y = 2.40 with exponentially increasing heat input (91 points) to values calculated by Eq. (24) versus p*

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Fig. 21

Ratios of qcr,sub for SUS304 test tube of d = 6 mm with the twisted-tape of y = 4.45 with exponentially increasing heat input (46 points) to values calculated by Eq. (24) versus p*

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Fig. 22

Ratios of qcr,sub for SUS304 test tubes of d = 6 mm with the twisted-tapes of y = 2.40, 3.37, and 4.45 with exponentially increasing heat input (186 points) to values calculated by Eq. (2) versus p*

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Fig. 23

qcr,sub versus usw for SUS304 test tube of d = 6 mm with the twisted-tape of y = 2.40 with exponentially increasing heat inputs of τ = 40 ms, 165 ms, and 8 s at ΔTsub,in = 150 K

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Fig. 24

qcr,sub versus y for SUS304 test tubes of d = 6 mm with the twisted-tapes of y = 2.40, 3.37, and 4.45 with exponentially increasing heat inputs of τ = 40 ms, 165 ms, and 8 s at ΔTsub,in = 150 K

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Fig. 25

Typical heat transfer processes for the SUS304 test tube of d = 6 mm and Leff = 49.4 mm with the twisted-tape of y = 3.37 at usw ranging from 5.37 to 17.97 m/s on τ ranging from 0.083 to 8.42 s

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