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Drop deposition in annular two-phase flow calculated with Lagrangian Particle Tracking
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.ORCID iD: 0000-0001-5595-1952
2013 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 265, 856-866 p.Article in journal (Refereed) Published
Abstract [en]

Lagrangian Particle Tracking is tested for its capability to predict deposition rates in pipes and pipes with obstacle. The drop size is one of the input parameters, which defines in its major part the deposition process. A new correlation is proposed to estimate the drop size, following a systematic analysis of the experimental drop sizes in annular twophase flow. The Lagrangian Particle Tracking model showed good capability of prediction in the cases where the drop size is known; however, when the drop size is estimated the inaccuracy in calculated deposition rate is high. If the drop size is known at the inlet of the channel, Lagrangian Particle Tracking shows good capability of predicting the deposition increase downstream of the obstacle for steam-water flows of 5, 10 and 15 bar pressure.

Place, publisher, year, edition, pages
Elsevier, 2013. Vol. 265, 856-866 p.
Keyword [en]
drops, deposition, Lagrangian Particle Tracking, annular two-phase flow, obstacle
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-106798DOI: 10.1016/j.nucengdes.2013.06.026ISI: 000330085500086ScopusID: 2-s2.0-84887048282OAI: diva2:574081

QC 20140121.  Updated from submitted to published.

Available from: 2012-12-06 Created: 2012-12-04 Last updated: 2014-02-21Bibliographically approved
In thesis
1. On drops and turbulence in nuclear fuel assemblies of Boiling Water Reactors
Open this publication in new window or tab >>On drops and turbulence in nuclear fuel assemblies of Boiling Water Reactors
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The study aims to develop the understanding of the mechanistic-type approach to quantify drop deposition in nuclear fuel assemblies of Boiling Water Reactors. This includes the effect of spacers. Spacers have a complex geometry to serve their purposes, but optimization of them alone can improve the thermal limit parameters in nuclear fuel assemblies. Thus, a mechanistic model might prove useful to increase the safety of the reactor as well as economic competitiveness of the nuclear power plant.

In this thesis, measurement techniques, such as mobile pressure rod and Laser Doppler Velocimetry are developed and tested to provide local data of the flow around spacers. It is shown experimentally that the effect of spacer on the flow differs depending on the placement of the subchannel in the rod bundle. Partly, because the spacer part differs, but also due to a global velocity profile development. Very few studies in the literature indicate this effect. It is shown that single subchannel models using Computational Fluid Dynamics (CFD) can predict the average velocity increase downstream of the spacer; however, they are not capable of calculating the spacer effect on turbulence parameters. The single subchannel CFD model has limited capability to predict the pressure development inside the spacer part, mainly because cross-flows are not taken into consideration.

The deposition of drops in annular two-phase flow is still a scientific challenge. Only empirical correlations are used nowadays to quantify this process. Empirical coefficients are needed for each spacer type to calculate the deposition increase due to obstacle. The discussion about the deposition starts with the phenomenological description. The important input parameter, namely drop size, is carefully analysed, and a new correlation is proposed to calculate the mean drop diameter. The correlation is constructed on a larger experimental data base. Lagrangian Particle Tracking model is tested in its capability to calculate deposition. Additionally, a Eulerian-type model is developed and tested. Turbulent parameters of drops are tightly related to the turbulence of the gas phase and the inertia of the drops. Several approaches are discussed about how to calculate the root-mean-square fluctuating velocities of drops. Both, Lagrangian Particle Tracking and the Eulerian-type of models show good capability in calculating the obstacle effect on deposition, providing improvements are made in prediction of drop size. The effect of increased drop concentration plays a large role and it must be taken into consideration if good quantitative approaches are envisaged.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xi, 45 p.
Trita-FYS, ISSN 0280-316X ; 2012:85
National Category
Energy Engineering
urn:nbn:se:kth:diva-107115 (URN)978-91-7501-572-9 (ISBN)
Public defence
2012-12-14, FD5, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:30 (English)
EU, European Research Council

QC 20121207

Available from: 2012-12-07 Created: 2012-12-06 Last updated: 2012-12-07Bibliographically approved

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