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Research Papers: Natural and Mixed Convection

Experiment of Heat Transfer to Supercritical Water Flowing in Vertical Annular Channels

[+] Author and Article Information
Qincheng Bi

e-mail: qcbi@mail.xjtu.edu.cn

Richa Hu

State Key Laboratory of Multiphase Flow
in Power Engineering,
Xi'an Jiaotong University,
Xi'an, 710049, China

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received February 22, 2012; final manuscript received November 27, 2012; published online March 20, 2013. Assoc. Editor: W. Q. Tao.

J. Heat Transfer 135(4), 042504 (Mar 20, 2013) (9 pages) Paper No: HT-12-1066; doi: 10.1115/1.4023224 History: Received February 22, 2012; Revised November 27, 2012

An experimental study of heat transfer to supercritical water has been performed at Xi'an Jiaotong University with a vertical annular tube. The annular test sections were constructed with an annular gap of 2 mm and an internal heater of 8 mm outer diameter. Experimental parameter covered pressures of 23 and 25 MPa, mass fluxes of 700 and 1000 kg/m2s, and heat fluxes of 200–1000 kW/m2. Experimental data were acquired from downward flow and upward flow, respectively. There were differences of heat-transfer characteristics between the two flow directions. Compared to upward flow, the heat-transfer coefficient increased at downward flow. A strong effect of spacer on heat transfer is observed at locations downstream of the device in the annuli regardless of flow direction. The spacer effect impaired the buoyancy effect at low heat flux, but not for large heat flux. Complex of forced convection and mixed convection in supercritical water is due to various thermophysical properties and the gravity. The affected zone of the spacer effect depends on the flow conditions. The buoyancy effect was analyzed qualitatively in this study and the criterion Gr¯/Re2.7<10-5 for negligible heat-transfer impairment was discussed. Four correlations were compared with the experimental data; the Swenson correlation predicted nearly the experimental data but overpredicted slightly the heat-transfer coefficients.

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Figures

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Fig. 1

Schematic diagram of the high pressure water loop system

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Fig. 2

(a) and (b) Flange structures, (c) upward test section geometry, and (d) downward test section geometry

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Fig. 3

(a) Spacer structure and (b) spacer structure

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Fig. 4

(a) Comparison of wall temperatures at different heat fluxes (upward flow), (b) comparison of heat-transfer coefficients at different heat fluxes (upward flow)

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Fig. 5

(a) Comparison of wall temperatures at different heat fluxes (downward flow), (b) comparison of heat-transfer coefficients at different heat fluxes (downward flow)

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Fig. 6

(a) Comparison of wall temperatures in different flow directions, (b) comparison of heat-transfer coefficients in different flow directions

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Fig. 7

(a) Comparison of wall temperatures at different measuring positions (high mass fluxes), (b) comparison of heat-transfer coefficients at different measuring positions (high mass fluxes)

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Fig. 8

(a) Comparison of wall temperatures at different measuring positions (low mass fluxes), (b) comparison of heat-transfer coefficients at different measuring positions (low mass fluxes)

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Fig. 9

Comparison of wall temperature at different measuring positions and flow directions (low mass fluxes)

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Fig. 10

(a) Comparison of wall temperature at different measuring positions and flow directions (high mass fluxes), (b) comparison of heat-transfer coefficients at different measuring positions and flow directions (high mass fluxes)

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Fig. 11

Effects of heat flux on the Nusselt number in upward flow

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Fig. 12

Comparison of Gr¯/Re2.7 in different flow directions

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Fig. 13

Comparison of experimental values with those calculated through different correlations (low ratio of q/G)

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Fig. 14

Comparison of experimental values with those calculated through different correlations (high ratio of q/G)

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