A Void Fraction Characterisation by Low Frequency Acoustic Velocity Measurements in Microbubble Clouds

Cavaro, Matthieu

doi:10.1016/j.phpro.2015.08.294

Cited by 6 publications

(7 citation statements)

References 5 publications

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“…For sodium applications, high-temperature ultrasonic transducers [20] called TUSHT are being developed by the CEA. The possibility of using such specific transducers for void fraction measurements has already been studied by Cavaro [19].…”

Section: Resultsmentioning

confidence: 99%

“…It is worth pointing out that this camera underestimated the number of bubbles with a radius due to the optics used. Figure 14 shows the void fraction obtained by this optical procedure compared with the one obtained by low-frequency velocity measurements, following the procedure described in another study [19]. The void fraction was modified by switching off a bubble injector at and then switching it on again at .…”

Section: Optical Measurementsmentioning

confidence: 99%

“…This equation can be solved using a least-square algorithm. Moreover, if the void fraction can be estimated separately, for example through Wood's model using low-frequency acoustic velocity measurements [19], this value can be introduced into the set of constraints. Figure 3: Typical L-curve obtained using the scripts by Hansen [18] In order to obtain a good estimation of the bubble size distributions, the regularisation parameter was adjusted using the L-curve method described by Hansen [17].…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…Void fraction estimated by the optical set-up and using sound speed measurements at low-frequency[19] …”

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confidence: 99%

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Acoustical characterisation and monitoring of microbubble clouds

et al. 2019

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Argon microbubbles will exist in the primary sodium of the next generation of sodium-cooled fast reactors (SFR). Due to its opacity, acoustic methods will be used for the in-service inspection in these reactors, but the presence of such bubbles will greatly affect ultrasonic wave propagation. Moreover, these bubbles can lead to the formation of gas pockets in the reactor and impact cavitation and boiling phenomena. It is therefore necessary to characterise what is called the 'microbubble cloud' by providing the volume fraction and the bubble size distribution. Safety requirements in this field call for robust inspection methods based on very few assumptions about the bubble populations. The objective of this study is to assess the performance of spectroscopic methods in the presence of bubbles with high polydispersity and to monitor an evolving cloud of microbubbles. The histogram and void fractions were estimated according to the regularised inversion of the complex wave number's integral equation. To reduce the need for prior information on the bubble cloud, a specific procedure was used to estimate the maximum radius of the population. The results are presented on the basis of the experimental data obtained and then compared with optical measurements.

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Section: Resultsmentioning

confidence: 99%

Section: Optical Measurementsmentioning

confidence: 99%

Section: Theoretical Backgroundmentioning

confidence: 99%

“…Void fraction estimated by the optical set-up and using sound speed measurements at low-frequency[19] …”

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confidence: 99%

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Acoustical characterisation and monitoring of microbubble clouds

et al. 2019

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“…Al-lababidi et al [14] applied this method to measure void fraction in gas-liquid slug flow and proposed their correlation for the void fraction calculation. To determine void fraction, Cavaro [15] used the results of low frequency acoustic velocity measurements in air microbubble clouds generated in water. The measurements covered quite a narrow range of void fraction in a flow without boiling.…”

Section: Introductionmentioning

confidence: 99%

Novel Twofold Use of Photographic Technique for Simultaneous Flow Boiling Image Recording and Void Fraction Computation in a Mini-Channel Experiment

Płaczkowski¹,

Grabowski

Poniewski

2021

Energies

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The paper presents a novel twofold use of the photographic technique for flow boiling heat transfer investigation in the horizontal mini-channel. The dedicated measurement system was constructed to record basic thermal and flow parameters, i.e., boiling liquid inlet and outlet temperatures and pressures, and also temperatures inside the heating block to calculate heat flux going into the liquid. A high-speed video camera equipped with synchronous movement system was applied to combine the recording of two-phase flow images with simultaneous local void fraction measurements both based on the same photographic data set. The data were collected, managed, and refined with the scripts developed in the MathWorks Matlab 2019b environment. The synchronous use of two intelligent techniques in the scripts, i.e., the background subtraction technique and the statistical analysis of individual pictures allowed obtaining reliable experimental results. The proposed method of the void fraction determination ensures high measurement accuracy.

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