Proceedings of ICONE19 19th International Conference on Nuclear Engineering May 16-19, 2011, Chiba, Japan 1 Copyright © 2011 by JSME ICONE19-43644 TEMPERATURE PROFILES OF A VERTICAL BARE 7-ELEMENT BUNDLE COOLED WITH SUPERCRITICAL FREON-12 G. Richards University of Ontario Institute of Technology 2000 Simcoe St. Oshawa Ontario, Canada Email: Graham.Richards@uoit.ca A.S. Shelegov Obninsk State Technical University (IATE) Obninsk, Russia P.L. Kirillov Institute of Physics and Power Engineering, Obninsk, Russia I.L.Pioro University of Ontario Institute of Technology 2000 Simcoe St. Oshawa, Ontario, Canada Phone : 905.721.8668 Email: Igor.Pioro@uoit.ca G. Harvel University of Ontario Institute of Technology 2000 Simcoe St. Oshawa, Ontario, Canada Phone : 905.721.8668 Email: Glenn.Harvel@uoit.ca Keywords: Heat Transfer, Fluid Properties, Supercritical Pressures, Freon-12, Temperature Profiles ABSTRACT Experimental data on SuperCritical-Water (SCW) cooled bundles are very limited. Major problems with performing such experiments are: 1) small number of operating SCW experimental setups and 2) difficulties in testing and experimental costs at very high pressures, temperatures and heat fluxes. However, SuperCritical Water-cooled nuclear Reactors (SCWRs) cannot be designed without such data. Therefore, as a preliminary approach experiments in SCW- cooled bare tubes and in bundles cooled with SC modeling fluids can be used. One of the SC modeling fluids typically used is Freon-12 (R-12) where the critical pressure is 4.136 MPa and the critical temperature is 111.97ºC. These conditions correspond to a critical pressure of 22.064 MPa and critical temperature of 373.95ºC in water. A set of experimental data obtained in R-12 cooled vertical bare bundle at the Institute of Physics and Power Engineering (IPPE, Obninsk, Russia) was analyzed. This set consisted of 20 cases of a vertically oriented 7-element bundle installed in a hexagonal flow channel. Data was collected at pressures of about 4.65 MPa for several different combinations of wall and bulk-fluid temperatures that were below, at, or above the pseudocritical temperature. The values for mass flow rate ranged from approximately 10 kg/s to 30 kg/s and inlet temperatures from 72ºC to 120ºC. The test section consisted of fuel elements that were 9.5 mm in diameter with the total heated length of 1 m. Bulk-fluid and wall temperature profiles were recorded using a combination of 8 different thermocouples. The data was analyzed with respect to temperature profiles along the heated length of the test section. In a previous study [1] it was confirmed that there is the existence of three distinct regimes for forced convention with supercritical fluids. (1) Normal heat transfer; (2) Deteriorated heat transfer, characterized by higher than expected temperatures; and (3) Enhanced heat transfer, characterized by lower than expected temperatures. These regions were observed for the 7 rod bundle experiments. This work compares the wall and bulk fluid temperature data of the experiments to predictions based upon current correlations for heat transfer in super critical fluids where the 1-D correlations are based upon tube data under supercritical water conditions. The results indicate that the correlations produce reasonable predictions of the experimental data considering that three dimensional effects are not included. 1. Introduction Generation-IV nuclear-reactor technology is increasing in popularity worldwide. One of the six Generation-IV reactor options is a SuperCritical Water-cooled nuclear Reactor (SCWR). The main objective of SCWRs is increasing thermal efficiency of SCW Nuclear Power Plants (NNPs). This reactor type is being developed based on concepts of Light Water Reactors (LWRs), direct-cycle Boiling Water Reactors (BWRs) and supercritical fossil- fuel-fired thermal power plants, especially, their supercritical-pressure turbines’ technology. SCWRs are similar to LWRs, but operate at a significantly higher pressure and temperature. [2] As an alternative to using SuperCritical Water (SCW) as a nuclear-reactor coolant, modeling fluids, for example, such as Freon-12, can be tested as a preliminary approach. The critical parameters of Freon-12 are the following: pressure of 4.1361 MPa and temperature of 111.97ºC, which are The Japan Society of Mechanical Engineers NII-Electronic Library Service