Design of a capacitance sensor for void fraction measurement in annular flows through a vertical pipe

Ko, Min Seok; Yun, Byong-Jo; Kim, Kyung Youn; Kim, Sin

doi:10.1088/0957-0233/23/10/105301

Cited by 14 publications

(1 citation statement)

References 19 publications

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“…The impedance method is another widely used method that has been studied until the present. Depending on the measurement system and fluid medium, the instantaneous impedance response of the phase distribution will be governed by conductance [10][11][12][13][14] or capacitance [11,[15][16][17]. Based on impedance technology, the tomography method [18,19] has been well developed, too.…”

Section: Measurement Science and Technologymentioning

confidence: 99%

Void fraction measurement using an imaging and phase isolation method in horizontal annular flow

Niu

Wang

Yang

et al. 2019

Meas. Sci. Technol.

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A new imaging method was proposed to measure the void fraction of annular flow based on phase isolation technology in a horizontal circular tube. As the gas–liquid mixture passes through the phase isolation device, which is arranged upstream, a strong swirl flow is created due to centrifugal effect. The liquid phase is pushed to the tube wall and forms a uniform liquid film, while the gas phase is concentrated to the tube center and forms a gas core. This rectified core-annular flow has a more smooth and clear phase interface than that of natural annular flow, which makes the accurate measurement of some inherent flow parameters of gas–liquid two-phase flow possible and much easier to perform. A backlight-collimated illumination and high-resolution CCD camera were employed to capture the gas core and liquid film. A calibration experiment was conducted to acquire an accurate edge detection criterion for recognition of the phase interface. The morphological image characteristics of the core-annular flow and the beam path diagram of imaging procedure were analyzed in detail and a corresponding image processing algorithm was developed. The working fluids were air and water and the ranges of void fraction covered in the sexperiment were 0.736–0.978(Usg = 4.35 m s−1–39.12 m s−1, Usl = 0.016 m s−1–0.504 m s−1). For each experiment condition, about 800 raw images were processed to obtain an average result. Comparisons to a representative model of void fraction of natural annular flow showed that the void fraction of the core-annular flow rectified by the phase isolation device remains well consistent with that of natural annular flow in the range of low-gas volume fraction, while the void fraction of core-annular flow becomes a little lower than that of natural annular flow as the gas volume becomes very high.

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