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RESEARCH PAPERS: Natural and Mixed Convection

# Effect of Buoyancy on Heat Transfer in Supercritical Water Flow in a Horizontal Round Tube

[+] Author and Article Information
Majid Bazargan

University of Tehran, Iran

Daniel Fraser

Department of Mechanical and Manufacturing Engineering, University of Manitobafraserdw@cc.umanitoba.ca

Vijay Chatoorgan

Department of Mechanical and Manufacturing Engineering, University of Manitobachatoorg@cc.umanitoba.ca

J. Heat Transfer 127(8), 897-902 (Mar 22, 2005) (6 pages) doi:10.1115/1.1929787 History: Received October 02, 2003; Revised March 22, 2005

## Abstract

Heat transfer to supercritical water and buoyancy∕natural convection effects are becoming increasingly important areas of research due to current trends in nuclear reactor design and supercritical water oxidation facilities. A pilot-scale supercritical water oxidation loop was constructed at the University of British Columbia. For this work, the facility was used to study the relative importance of buoyancy effects on supercritical water flowing in a horizontal pipe. Local heat transfer coefficients at the top and bottom surfaces of the horizontal test section were systematically measured over a wide range of conditions at supercritical pressures between 23 to 27 MPa, uniform heat fluxes were up to $310kW∕m2$, and the mass flux ranged from 330 to $1230kg∕m2s$. It was found that neglecting buoyancy effects could cause large discrepancies between the predictions of available empirical correlations and the experimental data. The data was used to assess available criteria for the buoyancy-free region during horizontal supercritical fluid flows. The criterion of Petukhov and Polyakov, which, for the range of parameters in this study, was found to be accurate in predicting the onset of buoyancy effects. The experimental investigation is confined to supercritical flows with heat addition only. Hence, no heat loss conditions at supercritical temperatures were investigated.

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## Figures

Figure 11

Variations of Grq∕Grth with bulk enthalpy for cases C and D

Figure 10

Variations of Grq∕Grth and wall temperature with bulk enthalpy for case A

Figure 9

Variations of Gr∕Re2 along the test section for various mass flows (q″≈300kW∕m2)

Figure 8

Wall and bulk temperature variations along the test section P=25.2MPa, G=964kg∕m2s, q″=307kW∕m2, case D

Figure 7

Variation of water density with temperature at P=24.4MPa (IAPWS)

Figure 6

Differences of heat transfer coefficients at top and bottom surfaces P=24.4MPa, G=340kg∕m2s, q″=300kW∕m2, case A

Figure 5

Wall and bulk temperature variations with bulk enthalpy (critical and postcritical regions), P=24.4MPa, G=340kg∕m2s, q″=300kW∕m2, case A

Figure 4

Wall and bulk temperature variations with bulk enthalpy (precritical and critical regions), P=24.4MPa, G=340kg∕m2s, q″=297kW∕m2, case A

Figure 3

Schematic of UBC test facility

Figure 2

Comparison of predictions of empirical correlations with UBC experiment P=25.2MPa, G=964kg∕m2s, D=6.3mm, q″=307kW∕m2

Figure 1

Variations of properties of supercritical water with temperature at P=235MPa

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