ICONE19-43644 TEMPERATURE PROFILES OF A VERTICAL BARE 7-ELEMENT BUNDLE COOLED WITH SUPERCRITICAL FREON-12

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 SCWcooled 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 111.97℃. These conditions correspond to a critical pressure of 22.064 MPa and critical temperature of 373.95℃ 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 72℃ to 120℃. 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 it was confirmed that there is the 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.