Nuclear Energy for New Europe 2009

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No: 204

Conference: Nuclear Energy for New Europe 2009

Title: Influence Of Air Entrainment On The Liquid Flow Field Caused By A Plunging Jet

Theme: Thermal Hydraulics

Author(s): Eckhard Krepper, Sören Alt, Stefan Renger

Contact : Eckhard Krepper

E-mail: e.krepper@fzd.de

Address: Forschungszentrum Dresden-Rossendorf
D-01328 Dresden

Country: Germany

Plunging jets play an important role in nuclear reactor safety research. In the actual paper the case of the strainer clogging issue is considered. During a LOCA insulation debris might be released near the break. Fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems. The jet-induced flow into the sump will sensitively influence the fibre transport.
In the University of Applied Science in Zittau experiments in a plexiglass tank having dimensions of about 1*1*1 m were performed. High-speed video was used as measurement technique, which enables the determination of the bubble entrainment plume.
In the presented investigations air entrainment is given as an inlet boundary condition according published correlations. The point of interest is here the influence of the entrained gas on the liquid flow field. Using the CFD-code ANSYS/CFX-11 the influence of entrained air on the liquid flow field could be shown. The simulated gas penetration depth and the shape of the bubble entrainment plume were compared to the experiments.
To check the validity of the simulations at the beginning of some tests the bottom of the tank was covered by a fibre layer. Influenced by the jet these fibres were redistributed. The redistributed deposition picture influenced by entrained air could be shown both in the experiments and in the calculations. During further tests the influence of the entrained air on the temperature distribution in the tank volume was investigated for the case of a lower temperature of the jet. The temperature mixing procedure influenced by entrained air was investigated both in the experiments and in the simulations.
In a larger volume having a length of 6 m, a width of 1 m and a water height of maximum 3 m the single phase water flow and the influence of the air entrainment on fibre deposition pattern on the bottom were observed and simulated by the CFD model.
The calculations show that CFD is able to calculate the main flow characteristics. The preferred regions of fibre accumulation dependent on the flow situation can be identified. The application of such models to real sump geometries enables at least qualitative statements.

No:	204
Conference:	Nuclear Energy for New Europe 2009
Title:	Influence Of Air Entrainment On The Liquid Flow Field Caused By A Plunging Jet
Theme:	Thermal Hydraulics
Author(s):	Eckhard Krepper, Sören Alt, Stefan Renger
Contact :	Eckhard Krepper
E-mail:	e.krepper@fzd.de
Address:	Forschungszentrum Dresden-Rossendorf D-01328 Dresden
Country:	Germany

Plunging jets play an important role in nuclear reactor safety research. In the actual paper the case of the strainer clogging issue is considered. During a LOCA insulation debris might be released near the break. Fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems. The jet-induced flow into the sump will sensitively influence the fibre transport. In the University of Applied Science in Zittau experiments in a plexiglass tank having dimensions of about 111 m were performed. High-speed video was used as measurement technique, which enables the determination of the bubble entrainment plume. In the presented investigations air entrainment is given as an inlet boundary condition according published correlations. The point of interest is here the influence of the entrained gas on the liquid flow field. Using the CFD-code ANSYS/CFX-11 the influence of entrained air on the liquid flow field could be shown. The simulated gas penetration depth and the shape of the bubble entrainment plume were compared to the experiments. To check the validity of the simulations at the beginning of some tests the bottom of the tank was covered by a fibre layer. Influenced by the jet these fibres were redistributed. The redistributed deposition picture influenced by entrained air could be shown both in the experiments and in the calculations. During further tests the influence of the entrained air on the temperature distribution in the tank volume was investigated for the case of a lower temperature of the jet. The temperature mixing procedure influenced by entrained air was investigated both in the experiments and in the simulations. In a larger volume having a length of 6 m, a width of 1 m and a water height of maximum 3 m the single phase water flow and the influence of the air entrainment on fibre deposition pattern on the bottom were observed and simulated by the CFD model. The calculations show that CFD is able to calculate the main flow characteristics. The preferred regions of fibre accumulation dependent on the flow situation can be identified. The application of such models to real sump geometries enables at least qualitative statements.