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Annular Flow Deposition Model with Obstacle Effect
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.ORCID iD: 0000-0001-5595-1952
2007 (English)In: Proceedings of the 6th International Conference on Multiphase Flow, ICMF 2007, July 9-13, Leipzig, Germany, 2007Conference paper (Refereed)
Abstract [en]

Lagrangian particle simulations were performed in round, square and subchannel-type ducts with obstacle in order to study the influence of the obstacle and the shape of the conduit on deposition. The deposition mass transfer coeffient calculated from these simulations was correlated to the averaged square root of turbulent kinetic energy in the channel upstream and downstream of the obstacle, thus to obtain a new deposition model to be included into a thermal-hydraulic subchannel code for the prediction of CHF phenomenon. The deposition results calculated by the new model were compared to Govan correlation, with the conclusion that round duct data compare good to the correlation, but not the other geometries. Since the correlation itself was developed from round duct experimental data, it can be stated that the new deposition model is able to predict the deposition rate fairly good for this case. The results from other geometries would have to be compared to experimental data to be able to conclude that the model is valid.

Place, publisher, year, edition, pages
Keyword [en]
annular flow, deposition model, obstacle effect, particle tracking
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-9907OAI: diva2:158043
The 6th International Conference on Multiphase Flow, ICMF 2007, Leipzig, Germany, July 9-13, 2007
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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