International Scientific Journal


The aim of this work is to investigate experimentally the increase of mixing phenomenon in a coolant flow in order to improve the heat transfer, the economical operation and the structural integrity of Light Water Reactors-Pressurized Water Reactors (LWRs-PWRs). Thus the parameters related to the heat transfer process in the system will be investigated. Data from a set of experiments, obtained by using high precision measurement techniques, Particle Image Velocimetry and Planar Laser-Induced Fluorescence (PIV and PLIF, respectively) are to improve the basic understanding of turbulent mixing phenomenon and to provide data for CFD code validation. The coolant mixing phenomenon in the head part of a fuel assembly which includes spacer grids has been investigated (the fuel simulator has half-length of a VVER 440 reactor fuel). The two-dimensional velocity vector and temperature fields in the area of interest are obtained by PIV and PLIF technique, respectively. The measurements of the turbulent flow in the regular tube channel around the thermocouple proved that there is rotation and asymmetry in the coolant flow caused by the mixing grid and the geometrical asymmetry of the fuel bundle. Both PIV and PLIF results showed that at the level of the core exit thermocouple the coolant is homogeneous. The discrepancies that could exist between the outlet average temperature of the coolant and the temperature at in-core thermocouple were clarified. Results of the applied techniques showed that both of them can be used as good provider for data base and to validate CFD results.
PAPER REVISED: 2014-02-26
PAPER ACCEPTED: 2014-03-27
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THERMAL SCIENCE YEAR 2015, VOLUME 19, ISSUE Issue 3, PAGES [989 - 1004]
  1. Jacopo B., Lin WH., Nano-Fluid Heat Transfer Enhancement For Nuclear Reactor Applications, Proceedings of the ASME, 2nd Micro/Nanoscale Heat & Mass Transfer International Conference, Shanghai, China, (2009)
  2. Larisza Sz., Capacity Upgrade at Paks Nuclear Power Plant,
  3. Bezrukov Yu. A., et al., Investigation of the Mixing of Coolant Flows in a VVER Vessel, Atomic Energy, 96 (2004), pp. 391 -398
  4. Rehme K. Pressure Drop Correlations For Fuel Element Spacers, Nuclear Technology, 17 (1973), pp. 15-23
  5. Chun T. H., Oh D. S., A Pressure Drop Model for Spacer Grids with and without Flow Mixing Vanes, Journal of Nuclear Science and Technology, 35 (1998), pp. 508-510
  6. Shen Y. F., Cao Z. D., Lu Q. G., An Investigation of Cross Flow Mixing Effect Caused by Grid Spacer With Mixing Blates in a Rod Bundle, Nuclear Engineering and Design, 125 (1991), pp. 111-119
  7. Holloway M. V. et al., The Effect of Support Grid Features on Local, Single-Phase Heat Transfer Measurements in Rod Bundles, Journal of Heat Transfer, 126 (2004), pp. 43-53
  8. Kobzarv L.L. , Oleksyuk D.A., Experiments on Simulation of Coolant Mixing in Fuel Assembly Head and Core Exit Channel of VVER-440 Reactor, 16th Symposium of AER on VVER Reactor Physics and Reactor Safety, Slovac Republic, (2006)
  9. Karoutas Z., Gu C., Sholin B., 3D Flow Analyses for Design of Nuclear Fuel Spacer, Proceedings of the 7th International Meeting on Nuclear Reactor Thermal-hydraulics NURETH-7, New York, USA, (1995), pp. 3153-3174
  10. Imaizumi al., Development of CFD Method to Evaluate 3D Flow Characteristics for PWR Fuel Assembly, Transactions of the 13th International Conference on Structural Mechanics in Reactor Technology SMIRT 13, Porto Alegre, Brazil (1995), pp. 3-14
  11. Ikeda K., Hoshi M., Development of Mitsubishi high thermal performance grid, JSME International Journal, series B, 45 (2002), pp. 586-591
  12. Ikeno T., Kajishima T., Decay of Swirling Turbulent Flow in Rod-Bundle, Journal of Fluid Science and Technology, 1 (2006), pp. 36-47
  13. Caraghiaur D., Anglart H., Measurements and CFD Predictions of Velocity, Turbulence Intensity and Pressure Development in BWR Fuel Rod Assembly with Spacers, Proceedings of the 12th International Meeting on Nuclear Reactor Thermal Hydraulics (NURETH12), Pittsburgh, Pennsylvania (2007)
  14. Sándor T., Attila A., CFD Study on Coolant Mixing in VVER-440 Fuel Assembly Head, Proceedings of ICAPP ‘08 Anaheim, CA, USA (2008), pp. 1813-1823
  15. Shakir H. et al., CNPP Fuel Rod Vibration Analysis Using Finite Element Method, Technical Journal, University of Engineering and Technology Taxila, Vibration analysis issue (2012), pp. 24-34
  16. Gerard C. et al., Fluid flow Fundamentals, Oilfield Review Schlumberger's flagship technology journal, Winter, 8 (1996), pp. 61-64
  17. Philip J. W., Donald R.W., Turbulent Diffusion, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia, pp. 1-42
  18. Toppila T., Lestinen V., CFD Simulation of Coolant Mixing Inside the Fuel Assembly Top Nozzle and Core Exit Channel of a VVER-440 Reactor, 14th Symposium of AER on VVER Reactor Physics and Reactor Safety, Espoo, Finland & Baltic Sea Cruise to Stockholm, (2004)
  19. Khudheyer S. Mushatet, Simulation of Turbulent Flow and Heat Transfer over a Backward Facing Step with Ribs Turbulators, Thermal Science, 15 (2011), pp. 245-255
  20. Agrawal A., Prasad A., Measurements within Vortex Cores in a Turbulent Jet, Journal of Fluids Engineering, Transaction of the ASME, 125 (2003), pp. 561-568
  21. Raffel M. et al., Particle Image Velocimetry: a Practical Guide Berlin Heidelberg New York, Springer 978-3-54072307-3, (2007)
  22. DantecDynamics, FlowManager Software and Introduction to PIV Instrumentation Software User´s guide, Dantec Dynamics A/S, (2000)
  23. Elvis E. D. et al., Experimental Benchmark Data for PWR Rod Bundle with Spacer-Grids, Proceedings of the CFD for Nuclear Reactor Safety Applications (CFD4NRS-3) Workshop, Bethesda North Marriott Hotel & Conference Centre, Bethesda, MD, USA, (2010)

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