Nuclear Energy for New Europe 2009

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No: 210

Conference: Nuclear Energy for New Europe 2009

Title: Development of a Supercritical Water Heat-Transfer Correlation for Vertical Bare Tubes

Theme: Thermal Hydraulics

Author(s): Sarah Mokry, Amjad Farah, Krysten King, Sahil Gupta, Igor Pioro, P. Kirillov

Contact : Igor Pioro

E-mail: Igor.Pioro@uoit.ca

Address: Faculty of Energy Systems and Nuclear Science University of Ontario Institute of Technology
Oshawa ON L1K 2S8

Country: Canada

This paper presents an analysis of heat transfer to supercritical water in bare vertical tubes. A large set of experimental data, obtained in Russia, was analyzed and a new heat-transfer correlation for supercritical water was developed. This experimental dataset was obtained within conditions similar to those for proposed SuperCritical Water-cooled nuclear Reactor (SCWR) concepts. Thus, the new correlation presented in this paper can be used for preliminary heat-transfer calculations in SCWR fuel channels.
The experimental dataset was obtained for supercritical water flowing upward in a 4-m-long vertical bare tube. The data was collected at pressures of about 24 MPa for several combinations of wall and bulk-fluid temperatures that were below, at, or above the pseudocritical temperature. The values for mass flux ranged from 200–1500 kg/m2s, for heat flux up to 1250 kW/m2 and inlet temperatures from 320 to 350°C.
Previous studies have confirmed that there are three heat-transfer regimes for forced convective heat transfer to water flowing inside tubes at supercritical pressures: (1) Normal heat-transfer regime; (2) Deteriorated heat-transfer regime, characterized by lower than expected heat transfer coefficients (HTCs) (i.e., higher than expected wall temperatures) than in the normal heat-transfer regime; and (3) Improved heat-transfer regime with higher-than-expected HTC values, and thus lower values of wall temperature within some part of a test section compared to those of the normal heat-transfer regime.
Also, the previous studies have shown that the HTC values calculated with the Dittus-Boelter and Bishop et al. correlations deviate quite substantially from those obtained experimentally. In particular, the Dittus-Boelter correlation overpredicts significantly the experimental data within the pseudocritical range.
A new heat-transfer correlation for forced convective heat transfer in the normal heat-transfer regime to supercritical water in a bare vertical tube is presented in this paper. It has demonstrated a relatively good fit (±25%) for the analyzed dataset. This correlation can be used for future comparisons with other independent datasets, with bundle data, for the verification of computer codes for SCWR core thermalhydraulics and for the verification of scaling parameters between water and modeling fluids.

No:	210
Conference:	Nuclear Energy for New Europe 2009
Title:	Development of a Supercritical Water Heat-Transfer Correlation for Vertical Bare Tubes
Theme:	Thermal Hydraulics
Author(s):	Sarah Mokry, Amjad Farah, Krysten King, Sahil Gupta, Igor Pioro, P. Kirillov
Contact :	Igor Pioro
E-mail:	Igor.Pioro@uoit.ca
Address:	Faculty of Energy Systems and Nuclear Science University of Ontario Institute of Technology Oshawa ON L1K 2S8
Country:	Canada

This paper presents an analysis of heat transfer to supercritical water in bare vertical tubes. A large set of experimental data, obtained in Russia, was analyzed and a new heat-transfer correlation for supercritical water was developed. This experimental dataset was obtained within conditions similar to those for proposed SuperCritical Water-cooled nuclear Reactor (SCWR) concepts. Thus, the new correlation presented in this paper can be used for preliminary heat-transfer calculations in SCWR fuel channels. The experimental dataset was obtained for supercritical water flowing upward in a 4-m-long vertical bare tube. The data was collected at pressures of about 24 MPa for several combinations of wall and bulk-fluid temperatures that were below, at, or above the pseudocritical temperature. The values for mass flux ranged from 200–1500 kg/m2s, for heat flux up to 1250 kW/m2 and inlet temperatures from 320 to 350°C. Previous studies have confirmed that there are three heat-transfer regimes for forced convective heat transfer to water flowing inside tubes at supercritical pressures: (1) Normal heat-transfer regime; (2) Deteriorated heat-transfer regime, characterized by lower than expected heat transfer coefficients (HTCs) (i.e., higher than expected wall temperatures) than in the normal heat-transfer regime; and (3) Improved heat-transfer regime with higher-than-expected HTC values, and thus lower values of wall temperature within some part of a test section compared to those of the normal heat-transfer regime. Also, the previous studies have shown that the HTC values calculated with the Dittus-Boelter and Bishop et al. correlations deviate quite substantially from those obtained experimentally. In particular, the Dittus-Boelter correlation overpredicts significantly the experimental data within the pseudocritical range. A new heat-transfer correlation for forced convective heat transfer in the normal heat-transfer regime to supercritical water in a bare vertical tube is presented in this paper. It has demonstrated a relatively good fit (±25%) for the analyzed dataset. This correlation can be used for future comparisons with other independent datasets, with bundle data, for the verification of computer codes for SCWR core thermalhydraulics and for the verification of scaling parameters between water and modeling fluids.