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Measuring liquid film thickness in annular two-phase flows by cold neutron imaging

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Abstract

An overview of a measurement method for liquid film thickness in annular flows based on cold neutron imaging is given here. Neutron imaging being a non-intrusive, contactless method is attractive option for two-phase flow investigations offering an excellent contrast. It can provide with information at a high spatial resolution on the flow structure, like the thickness of the liquid film in annular flows. The method has been optimized, and its performance, regarding bias, statistical accuracy, upper and lower detection limits, has been thoroughly quantified using computational tools and measurement results. The technique has been developed based on nuclear fuel bundle models; however, it is applicable practically to annular flows in any arbitrary flow channel geometry of interest.

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Abbreviations

cps:

Counts per second

CCD:

Charge coupled device

CNR:

Contrast-to-noise ratio

FBP:

Filtered back projections

FOV:

Field of view

LFT:

Liquid film thickness

LFS:

Liquid film sensor

LSF:

Line spread function

MC:

Monte Carlo simulation

SNR:

Signal-to-noise ratio

PSF:

Point spread function

ROI:

Region of interest

var:

Variance

A :

Area

D :

Dose or diameter

Gd:

Gadolinium

I :

Intensity

J :

Superficial velocity

L :

Length

Li:

Lithium

V :

Volume

p :

Pixel gray value

pr:

Projection

R :

Radon transform

t :

Distance

β :

Gas volume flow fraction

ε :

Liquid holdup

σ :

Standard deviation

ϕ :

Polar angle

θ :

Projection angle

Σ:

Macroscopic neutron interaction cross-section

emp:

Empty

g :

Gas

l :

Liquid

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Acknowledgments

The authors are very grateful to Dr. Anders Kaestner and to Dr. Eberhard Lehmann of the neutron imaging group of PSI for the opportunity to use the ICON beam line, for their help at performing the measurements and for the useful discussions on the results.

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Authors and Affiliations

  1. Laboratory for Thermal-hydraulics, Nuclear Energy and Safety Department, Paul Scherrer Institute, 5232, Villigen, Switzerland

    R. Zboray & H.-M. Prasser

  2. Laboratory for Nuclear Energy Systems, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092, Zurich, Switzerland

    H.-M. Prasser

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  1. R. Zboray
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  2. H.-M. Prasser
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Correspondence to R. Zboray.

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Zboray, R., Prasser, HM. Measuring liquid film thickness in annular two-phase flows by cold neutron imaging. Exp Fluids 54, 1596 (2013). https://doi.org/10.1007/s00348-013-1596-1

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  • DOI: https://doi.org/10.1007/s00348-013-1596-1

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