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Technical Briefs

Flow Boiling Heat Transfer of Liquid Nitrogen in Heated U-Tubes

[+] Author and Article Information
D. Deng

e-mail: D.Deng@sjtu.edu.cn

S. W. Xie

e-mail: xiesiwei143@163.com

School of Mechanical Engineering,
Shanghai Jiaotong University,
800 Dongchuan Road,
Shanghai 200240, China

X. D. Li

School of Aerospace, Mechanical,
and Manufacturing Engineering,
RMIT University,
P. O. Box 71, Bundoora VIC 3083, Australia
e-mail: xiangdong.li@rmit.edu.au

R. S. Wang

School of Mechanical Engineering,
Shanghai Jiaotong University,
800 Dongchuan Road,
Shanghai 200240, China
e-mail: rswang@sjtu.edu.cn

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received October 15, 2012; final manuscript received September 20, 2013; published online November 7, 2013. Assoc. Editor: Wei Tong.

J. Heat Transfer 136(2), 024501 (Nov 07, 2013) (9 pages) Paper No: HT-12-1563; doi: 10.1115/1.4025542 History: Received October 15, 2012; Revised September 20, 2013

The flow boiling heat transfer characteristics of liquid nitrogen in three U-tubes with different curvature ratios were investigated experimentally. The effects of inlet pressure, heat flux, and curvature ratio on heat transfer characteristic are analyzed. The results indicate that the local heat transfer characteristics change obviously as fluid flows through the return bend, especially in the case of high heat flux. The drying out occurs near the inner wall of the return bend under high heat flux. A parameter Rh (down/up), which is defined as the ratio of heat transfer coefficient between the downstream and upstream section of U-bend, is proposed to evaluate the contributions of the curvature ratio to the heat transfer. It is found that the Rh (down/up) increases with the decrease of the curvature ratios. Furthermore, the experiments results of the average heat transfer coefficient are compared with the calculated results of the empirical correlations.

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References

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Figures

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Fig. 1

Schematic of experiment device

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Fig. 2

Test section schemes

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Fig. 3

Test section structure schemes

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Fig. 4

The samples and the averaged value of gas volume of case 1

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Fig. 5

The schemes of the thermocouple distribution

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Fig. 6

Local heat transfer coefficient of UD6R20 (3#) at Pin = 202.8 kPa, G = 255.2 kg/m2s, q = 5734.5 W/m2

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Fig. 7

Local heat transfer characteristic of UD6R20 (3#) at Pin = 185.0 kPa, G = 102.7 kg/m2s, q = 22.4 kW/m2

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Fig. 8

Influence of inlet pressure on local heat transfer characteristic of 3# pipe when q = 15,385 W/m2

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Fig. 9

Influence of heat flux on local heat transfer characteristic of 2# pipe when Pin = 216 kPa

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Fig. 11

Comparison of average heat transfer coefficient with predictions of three correlations: Edelstein, Shah, and Kandlikar

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Fig. 10

The Rh (down/up) versus x

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