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 Detailed pressure drop measurements in single- and two-phase adiabatic air-water turbulent flows in realistic BWR fuel assembly geometry with spacer grids
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
KTH, Superseded Departments, Energy Technology.
KTH, Superseded Departments, Mechanics.
2004 (English)In: The 6th International Conference on Nuclear Thermal Hydraulics, Operations and Safety (NUTHOS-6) Nara, Japan, October 4-8, 2004, 2004Conference paper (Refereed)
Abstract [en]

In recent years, advanced numerical simulation tools based on CFD methods have been increasingly used in various multi-phase flow applications. One of these is two-phase flow in fuel assemblies of Boiling Water Reactors. The important and often missing aspect of this development is the validation of CFD codes against proper experimental data. The purpose of the current paper is to present detailed pressure measurements over a spacer grid in adiabatic single- and two-phase flow, which will be used to validate and further develop a CFD code for BWR fuel bundle analysis. The experiments have been carried out in an asymmetric 24-rod sub-bundle, representing ¼ of Westinghouse SVEA-96 nuclear reactor fuel assembly. Single-phase measurements have been performed at superficial velocities comprised between jliq: 0.90 – 4.50 m/s and in the two-phase, which was simulated by air-water mixture, measurements have been performed at void fractions ranging from 4 to 12% and liquid superficial velocity jliq : 4.50 m/s. In order to increase the number of the measured points, five pressure taps were drilled in one of the rods, which was easily moved vertically by a traverse system, covering most of the points in axial direction. The possibility to substitute any of the rods in the fuel bundle by the pressure sensing rod and the possibility to change the pressure taps facing-angle provides more measuring points inside the subchannels. A detailed pressure distribution comparison between single- and two-phase flows for different subchannel positions and different flow conditions was performed over one of the spacers.  In addition, single-phase pressure drop measurements on the upper part of the test section comprising two spacer grids has been carried out.

Place, publisher, year, edition, pages
Keyword [en]
Pressure drop, pressure distribution, fuel bundle, spacer grid, air-water mixture, pressure sensing rod
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-9904OAI: diva2:158031
The 6th International Conference on Nuclear Thermal Hydraulics, Operations and Safety (NUTHOS-6) Nara, Japan, October 4-8, 2004
QC 20101007Available from: 2009-02-18 Created: 2009-01-29 Last updated: 2010-10-07Bibliographically approved
In thesis
1. Experimental Study and Modelling of Spacer Grid Influence on Flow in Nuclear Fuel Assemblies
Open this publication in new window or tab >>Experimental Study and Modelling of Spacer Grid Influence on Flow in Nuclear Fuel Assemblies
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The work is focused on experimental study and modelling of spacer grid influence on single- and two-phase flow. In the experimental study a mock-up of a realistic fuel bundle with five spacer grids of thin plate spring construction was investigated. A special pressure measuring technique was used to measure pressure distribution inside the spacer. Five pressure taps were drilled in one of the rods, which could exchange position with other rods, in this way providing a large degree of freedom. Laser Doppler Velocimetry was used to measure mean local axial velocity and its fluctuating component upstream and downstream of the spacer in several subchannels with differing spacer part. The experimental study revealed an interesting behaviour. Subchannels from the interior part of the bundle display a different effect on the flow downstream of the spacer compared to subchannels close to the box wall, even if the spacer part is the same. This behaviour is not reflected in modern correlations. The modelling part, first, consisted in comparing the present experimental data to Computational Fluid Dynamics calculations. It was shown that stand-alone subchannel models could predict the local velocity, but are unreliable in prediction of turbulence enhancement due to spacer. The second part of the modelling consisted in developing a deposition model for increase due to spacer. In this study Lagrangian Particle Tracking (LPT) coupled to Discrete Random Walk (DRW) technique was used to model droplet movements through turbulent flow. The LPT technique has an advantage to model the influence of turbulence structure effect on droplet deposition, in this way presenting a generalized model in view of spacer geometry change. The verification of the applicability of LPT DRW method to model deposition in annular flow at Boiling Water Reactor conditions proved that the method is unreliable in its present state. The model calculations compare reasonably well to air-water deposition data, but display a wrong trend if the fluids have a different density ratio than air-water.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2009. 40 p.
Trita-FYS, ISSN 0280-316X ; 2009:02
spacer grid influence, annular flow, deposition, Lagrangian Particle Tracking
National Category
Physical Sciences
urn:nbn:se:kth:diva-9983 (URN)978-91-7415-229-6 (ISBN)
2009-02-26, FA31, Roslagstullsbacken 21, Albanova University Centre, 10:00 (English)
Available from: 2009-02-18 Created: 2009-02-18 Last updated: 2012-11-26Bibliographically approved

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