Void fraction measurements in gas - liquid flows using capacitance sensors

Elkow, K.J.; Rezkallah, K.S.

doi:10.1088/0957-0233/7/8/011

Cited by 81 publications

(47 citation statements)

References 11 publications

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“…Aluminum was selected for its machinability, high corrosion resistance and relatively low cost. The two cylindrical probes were made to have equal lengths to eliminate non-uniformity in the sensing electric field [Elkow and Rezkallah, 1996]. The length and the diameter of the two cylindrical probes were selected to minimise three-dimensional effects.…”

Section: Description Of the Two-cylinder Capacitance Ice Sensormentioning

confidence: 99%

Capacitive probe for ice detection and accretion rate measurement: Proof of concept

2013

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Ice accretion on wind turbines is a major problem in cold climates that reduces power generation and fatigues turbine components. Effective anti-icing and de-icing strategies to manage ice accretion require reliable local assessment of icing conditions and a measure of ice accretion rate on structures. Such sensors could be located on meteorological towers near wind farms or the nacelle of wind turbines. A new concept for the estimation of atmospheric ice accretion based on the measurement of capacitance and resistance change between two charged cylinders as ice accretes on the cylinders is introduced in this study. Numerical simulation of the electric field between the charged cylinders is used to investigate the dependence of the sensitivity of capacitance to the distance between the cylindrical probes and location of ice deposits. The numerical results are validated experimentally using aluminum probes and a set of acrylic cylindrical sleeves that fit over the probes to simulate icing with accurate geometries. A charged cylindrical probes system constructed based on the numerical results is described and evaluated under controlled rime and glaze icing conditions in the University of Manitoba Icing Wind Tunnel. Test results indicate ice builds up on the cylindrical probes and the measured capacitance increases while the resistance decreases. The change in measured capacitance change correlates well with the increase in the ice mass. Rime and glaze ice are distinguishable based on the rate of change of resistance with ice accretion. The numerical and experimental results provide a proof of concept of the charged cylindrical probes ice accretion measurement concept.iii ACKNOWLEDGMENTS

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Section: Description Of the Two-cylinder Capacitance Ice Sensormentioning

confidence: 99%

Capacitive probe for ice detection and accretion rate measurement: Proof of concept

2013

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“…Capacitance sensors for instantaneous void fraction in air-oil, two-phase flow were developed [74][75][76]. This method could effectively identify the different flow regimes although it was not effective while there was high water loading.…”

Section: Advanced Void Fraction Measurement Techniquesmentioning

confidence: 99%

A Critical Review of Advanced Experimental Techniques to Measure Two- Phase Gas/Liquid Flow

Rahman¹,

Heidrick²,

Fleck³

2009

TOEFJ

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Gas assisted atomization is becoming increasingly important in many industrial applications such as physical, chemical and petroleum processes. In order to achieve proper atomization it is crucial to have proper mixing of gas (air) and liquid (water) in the feeding conduit before it enters into the nozzle. The flow regime, as well as the flow pattern and structure of the flow, are some of the important parameters that describe two-phase gas/liquid flows, and identify twophase gas/liquid flow regimes. It is also desirable to know under what conditions there is a transition among the different flow regimes (dispersed, stratified, annular, annular-dispersed, slug, wavy-slug, mist-annular). Due to the existence of relative movement in the interfaces and variable interactions between two phases, two-phase gas/liquid flow is a complex transport phenomenon compared to single-phase flow. Still, there is no effective technique to identify the two-phase gas/liquid flow regimes and it is even difficult to capture the accurate flow structures in smaller conduits in turbulent flow cases. Lack of solid and comprehensive theories for predicting and calculating the pressure and void fraction variations in two-phase air/water flow situations has left engineers without essential information for proper design of two-phase flow systems. This review is an effort to explore the state of the present advanced measurement techniques in this field of research. Subsequently, some of the advanced void fraction, photonics and pressure measurement techniques and correlations for identification of two-phase gas/liquid flow regimes and bubble sizes are investigated.

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“…Helical electrodes were found to have low sensitivity, non-linear response and poor shielding [11]. On the other hand, ring and concave type electrodes have linear relationship between void fraction and capacitance value [10].…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, ring and concave type electrodes have linear relationship between void fraction and capacitance value [10]. It was also found that concave electrodes have higher sensitivity than both the ring and helical [11][12]. There are several capacitance measuring techniques which can be used to measure the capacitance sensor.…”

Section: Introductionmentioning

confidence: 99%

Oscillating Frequency Approach for Void Fraction Measurements in Two-Phase Flow

Elsaftawy¹,

Potts²,

Chapman-Brown³

et al. 2018

Proceedings of the 5th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'18)

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-In this paper, a high resolution capacitance sensor system was developed for two-phase flow void fraction measurements and flow pattern identification. The circuit uses the LC approach whose oscillation frequency changes as the capacitance sensor value fluctuates. This change in frequency is measured and converted in to a capacitance value. The electrodes' excitation frequency is high enough to overcome the errors involved when conductive fluids are used. A LabView program was designed to interface the circuit and to record the data collected. The capacitance sensor was built with four concave electrodes and was shielded with a copper cage. The system was tested on a vertical air-water two phase flow pipe with 1.5 inch outer diameter and 1.25 inch inner diameter.

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Void fraction measurements in gas - liquid flows using capacitance sensors

Cited by 81 publications

References 11 publications

Capacitive probe for ice detection and accretion rate measurement: Proof of concept

Capacitive probe for ice detection and accretion rate measurement: Proof of concept

A Critical Review of Advanced Experimental Techniques to Measure Two- Phase Gas/Liquid Flow

Oscillating Frequency Approach for Void Fraction Measurements in Two-Phase Flow

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