The influence of density differences on the mixing of the primary loop inventory and the emergency core cooling (ECC) water in the cold leg and downcomer of a pressurized water reactor (PWR) was analyzed at the Rossendorf coolant mixing (ROCOM) test facility. This paper presents a matrix of ROCOM experiments in which water with the same or higher density was injected into a cold leg of the reactor model with already established natural circulation conditions at different low mass flow rates. Wire-mesh sensors measuring the concentration of a tracer in the injected water were installed in the cold leg, upper and lower part of the downcomer. A transition matrix from momentum to buoyancy-driven flow experiments was selected for validation of the computational fluid dynamics software ANSYS CFX. A hybrid mesh with elements was used for the calculations. The turbulence models usually applied in such cases assume that turbulence is isotropic, whilst buoyancy actually induces anisotropy. Thus, in this paper, higher order turbulence models have been developed and implemented, which take into account that anisotropy. Buoyancy generated source and dissipation terms were proposed and introduced into the balance equations for the turbulent kinetic energy. The results of the experiments and of the numerical calculations show that mixing strongly depends on buoyancy effects: At higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this circumferential propagation with lower mass flow rates and/or higher density differences. The ECC water falls in an almost vertical path and reaches the lower downcomer sensor directly below the inlet nozzle. Therefore, density effects play an important role during natural convection with the ECC injection in PWR and should be also considered in pressurized thermal shock scenarios. ANSYS CFX was able to predict the observed flow patterns and mixing phenomena quite well.
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January 2009
Research Papers
Experimental and Numerical Modeling of Transition Matrix From Momentum to Buoyancy-Driven Flow in a Pressurized Water Reactor
Thomas Höhne,
Thomas Höhne
Forschungszentrum Dresden-Rossendorf (FZD),
e-mail: t.hoehne@fzd.de
Institute of Safety Research
, P.O. Box 510119, D-01314 Dresden, Germany
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Sören Kliem,
Sören Kliem
Forschungszentrum Dresden-Rossendorf (FZD),
Institute of Safety Research
, P.O. Box 510119, D-01314 Dresden, Germany
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Roman Vaibar
Roman Vaibar
Forschungszentrum Dresden-Rossendorf (FZD),
Institute of Safety Research
, P.O. Box 510119, D-01314 Dresden, Germany
Search for other works by this author on:
Thomas Höhne
Forschungszentrum Dresden-Rossendorf (FZD),
Institute of Safety Research
, P.O. Box 510119, D-01314 Dresden, Germanye-mail: t.hoehne@fzd.de
Sören Kliem
Forschungszentrum Dresden-Rossendorf (FZD),
Institute of Safety Research
, P.O. Box 510119, D-01314 Dresden, Germany
Roman Vaibar
Forschungszentrum Dresden-Rossendorf (FZD),
Institute of Safety Research
, P.O. Box 510119, D-01314 Dresden, GermanyJ. Eng. Gas Turbines Power. Jan 2009, 131(1): 012906 (10 pages)
Published Online: October 2, 2008
Article history
Received:
July 21, 2008
Revised:
July 23, 2008
Published:
October 2, 2008
Citation
Höhne, T., Kliem, S., and Vaibar, R. (October 2, 2008). "Experimental and Numerical Modeling of Transition Matrix From Momentum to Buoyancy-Driven Flow in a Pressurized Water Reactor." ASME. J. Eng. Gas Turbines Power. January 2009; 131(1): 012906. https://doi.org/10.1115/1.2983137
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