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

Zboray, Robert; Prasser, Horst-Michael

doi:10.1007/s00348-013-1596-1

Cited by 22 publications

(11 citation statements)

References 35 publications

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“…They have been used to study two-phase flows in pipes and nuclear fuel bundle models [10,11] and liquid-metal two-phase flows and steam explosions [12]. Cold neutron tomography has also been extensively used and validated by one of the co-authors to study thin (few 100 of microns) liquid films in annular flows in nuclear fuel bundles [13]. This has given the impetus to use it also here to validate the infrared technique.…”

Section: Cold Neutron Imagingmentioning

confidence: 99%

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Infrared film thickness measurement: comparison with cold neutron imaging

Dupont

Mignot²,

Zboray³

et al. 2016

Journal of Nuclear Science and Technology

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Near InfraRed FILM thickness PROfile (NIR-FILMPRO) is an optical technique for non-intrusive measurement of water film thickness. The technique is based on absorption of NIR light. A passband filter centered at 1612 nm was selected to measure isothermal gravity-driven films flowing on a vertical wall with sand blasted surface. Non-intrusive 2D mapping of the film thickness was acquired at 200 fps, with an image size of 320 × 256 pixels and a spatial resolution of 0.677 mm. Theoretical developments were brought to consider multiple reflections of light in the liquid film providing a more accurate model to compute the film thickness. Further improvements were made regarding the calibration procedure and the image processing. The measurements were compared against cold neutron imaging, an established technique which provides images of the time averaged thickness. An excellent correspondence between the two methods was found. The root mean square of the deviation between the two techniques taken over a region covered by a wavy film was found to be 2.3% of the measurement with film thicknesses fluctuating between approximately 100 and 500 μm. The spatial comparison with cold neutron imaging complements the previous comparisons and validates the application of the technique.

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Section: Cold Neutron Imagingmentioning

confidence: 99%

“…The pixel resolution of the images is estimated using an optical mask to be 97.56 μm/pixel. The raw images have been spot cleaned (necessary due to presence of gammas) and compensated for the dark current of the camera [13]. The liquid film thickness (LFT) is determined using the Beer-Lambert law as…”

Section: Cold Neutron Imagingmentioning

confidence: 99%

Infrared film thickness measurement: comparison with cold neutron imaging

Dupont

Mignot²,

Zboray³

et al. 2016

Journal of Nuclear Science and Technology

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“…For the latter flow regime in limited geometries (partial bundle), cold-and thermal-neutron imaging have been shown to be very useful (e.g. [2]). However for other flow patterns with a higher water content and/or for larger (full) bundle geometries, cold and thermal neutrons are not penetrating enough to be applicable.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved Fast Neutron Radiography of Air-water Two-phase Flows

Zboray

Dangendorf

Mor³

et al. 2015

Physics Procedia

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Neutron imaging, in general, is a useful technique for visualizing low-Z materials (such as water or plastics) obscured by high-Z materials. However, when significant amounts of both materials are present and full-bodied samples have to be examined, cold and thermal neutrons rapidly reach their applicability limit as the samples become opaque. In such cases one can benefit from the high penetrating power of fast neutrons. In this work we demonstrate the feasibility of time-resolved, fast neutron radiography of generic air-water two-phase flows in a 1.5 cm thick flow channel with Aluminum walls and rectangular cross section. The experiments have been carried out at the high-intensity, white-beam facility of the Physikalisch-Technische Bundesanstalt, Germany. Exposure times down to 3.33 ms have been achieved at reasonable image quality and acceptable motion artifacts. Different two-phase flow regimes such as bubbly slug and churn flows have been examined. Two-phase flow parameters like the volumetric gas fraction, bubble size and bubble velocities have been measured.

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“…0 i s y y i t c i t t (13) Then, the spatial thickness distribution can be expanded using Eq. (14) and (15 (15) At t =t0, the thickness at the transducer array location (y = y0) is the thickness at t =t0 in time series. The thickness at the ith spatial position is defined as the thickness at t =t0 -i t in time series, where i ts/ t. Thus, the spatial thickness distribution in the wave zone at t = t0 can be established.…”

Section: Spatial Expansion Of Temporal Thickness Fluctuationmentioning

confidence: 99%

“…Over the years, various experimental techniques have been developed to measure thin liquid film flows [10][11][12][13][14][15][16]. Among these techniques, fluorescence imaging based, stereoscopic imaging based, density based, and structured light projection techniques are most frequently used.…”

Section: Introductionmentioning

confidence: 99%