Multi-needle capacitance probe for non-conductive two-phase flows

Monrós-Andreu, G.; Martínez‐Cuenca, Raúl; Torró, S.; Escrig, Josep; Hewakandamby, Buddhika N.; Chiva, S.

doi:10.1088/0957-0233/27/7/074004

Cited by 10 publications

(8 citation statements)

References 23 publications

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“…The probe will be invalid since the bubbles cannot penetrate the needle. Meanwhile, in high void fraction regions such as annular and churn turbulent regions, the flow dynamics is dominated by coalescence processes and the shapes of bubbles may become highly distorted [11]. Therefore, it is hard to calibrate using image processing and the dual needlecontact capacitance method may cause large errors.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, this method can be used to measure void fractions not only in transparent pipes at low pressure, but also in metal pipes at high pressure. However, conductance probes can only identify multiphase mixtures where phase conductivities differ in several orders of magnitude [11]. In addition, the fluid salinity and temperature also directly affect the output signal.…”

Section: Introductionmentioning

confidence: 99%

“…Meanwhile, electrical needle sensors based on conductance and capacitance can also be subdivided depending on the number of electrodes [11]. Single-tip probes enable voidfraction measurements at the location of the tip.…”

Section: Introductionmentioning

confidence: 99%

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Local Void Fractions and Bubble Velocity in Vertical Air-Water Two-Phase Flows Measured by Needle-Contact Capacitance Probe

Huang

Zong

et al. 2018

Science and Technology of Nuclear Installations

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Multiphase flow measurements have become increasingly important in a wide range of industrial fields. In the present study, a dual needle-contact capacitance probe was newly designed to measure local void fractions and bubble velocity in a vertical channel, which was verified by digital high-speed camera system. The theoretical analyses and experiments show that the needle-contact capacitance probe can reliably measure void fractions with the readings almost independent of temperature and salinity for the experimental conditions. In addition, the trigger-level method was chosen as the signal processing method for the void fraction measurement, with a minimum relative error of −4.59%. The bubble velocity was accurately measured within a relative error of 10%. Meanwhile, dynamic response of the dual needle-contact capacitance probe was analyzed in detail. The probe was then used to obtain raw signals for vertical pipe flow regimes, including plug flow, slug flow, churn flow, and bubbly flow. Further experiments indicate that the time series of the output signals vary as the different flow regimes and are consistent with each flow structure.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Local Void Fractions and Bubble Velocity in Vertical Air-Water Two-Phase Flows Measured by Needle-Contact Capacitance Probe

Huang

Zong

et al. 2018

Science and Technology of Nuclear Installations

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“…The ability of mass transfer in a gas–liquid system is indexed by the gas holdup and the bubble diameter; these two together determine the interfacial area. For Newtonian fluids, studies to obtain gas holdup , and the bubble diameter − and propose correlations for their prediction have been a subject of interest for several investigations. A few data and correlations have been reported for studies with non-Newtonian fluids .…”

Section: Introductionmentioning

confidence: 99%

Comparison of Different Impellers for Gas Dispersion in Power-Law Fluids

2021

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The 3D multiphase computational fluid dynamic (CFD) models have been developed for gas−liquid systems in a standard baffled stirred tank reactor (diameter 0.3 m) for non-Newtonian power-law fluids. The standard k-ε model has been used to model the turbulence, and drag has been modeled with the Grace drag model with Brucato modifications. CFD simulations have been carried out for three impellers, namely, the Rushton turbine, pitched blade turbine, and hydrofoil impeller. The effects of impeller design, power input per unit volume of the fluid (P/V) (1200− 5200 W/m 3 ), fluid rheology (K = 0−0.1561 Pa•s n , n = 0.687−1.000), and superficial gas velocity (7.1−28.3 mm/s) have been analyzed. The CFD model has been validated with the local distribution of axial, radial, and tangential velocities and overall gas holdup data reported in the literature. The CFD model has been used to predict the regime transition from flooding to loading and complete dispersion. A good agreement was observed for the prediction of regime transition for the Rushton turbine when compared with the experimental data. The average value of absolute error for the prediction of the gas holdup is 20%, which indicates that the developed CFD model can be successfully used to predict the gas holdup and regime transition in stirred tank reactors. Among the impellers studied, the hydrofoil impeller shows the highest gas holdup and uniform gas distribution in the vessel at low power consumption.

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“…in slug flows, but are invasive and mostly dependent on the electrical conductivity of at least one phase. Newer developments are based on the measurement of electrical conductivity or capacity but these are either dependent on the presence of electrical conductivity [11,12] or they are invasive [13]. Further non-invasive methods are acoustic detection [14], Lorentz force velocimetry (LFV) [15] or ultrasound techniques [16].…”

Section: Introductionmentioning

confidence: 99%

Detection and characterization of elongated bubbles and drops in two-phase flow using magnetic fields

Wiederhold

Boeck

Resagk

2017

Meas. Sci. Technol.

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We report a method to detect and to measure the size and velocity of elongated bubbles or drops in a dispersed two-phase flow. The difference of the magnetic susceptibilities between two phases causes a force on the interface between both phases when it is exposed to an external magnetic field. The force is measured with a state-of-the-art electromagnetic compensation balance. While the front and the back of the bubble pass the magnetic field, two peaks in the force signal appear, which can be used to calculate the velocity and geometry parameters of the bubble. We achieve a substantial advantage over other bubble detection techniques because this technique is contactless, non-invasive, independent of the electrical conductivity and can be applied to opaque or aggressive fluids. The measurements are performed in an inclined channel with air bubbles and paraffin oil drops in water. The bubble length is in the range of 0.1–0.25 m and the bubble velocity lies between 0.02–0.22 m s−1. Furthermore we show that it is possible to apply this measurement principle for nondestructive testing (NDT) of diamagnetic and paramagnetic materials like metal, plastics or glass, provided that defects are in the range of 10‒2 m. This technique opens up new possibilities in industrial applications to measure two-phase flow parameters and in material testing.

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Multi-needle capacitance probe for non-conductive two-phase flows

Cited by 10 publications

References 23 publications

Local Void Fractions and Bubble Velocity in Vertical Air-Water Two-Phase Flows Measured by Needle-Contact Capacitance Probe

Local Void Fractions and Bubble Velocity in Vertical Air-Water Two-Phase Flows Measured by Needle-Contact Capacitance Probe

Comparison of Different Impellers for Gas Dispersion in Power-Law Fluids

Detection and characterization of elongated bubbles and drops in two-phase flow using magnetic fields

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