Abstract
In this study, a new and improved electrical conductance sensor is proposed for application not only to a horizontal pipe, but also an inclined one. The conductance sensor was designed to have a dual layer, each consisting of a three-electrode set to obtain two instantaneous conductance signals in turns, so that the area-averaged void fraction and structure velocity could be measured simultaneously. The optimum configuration of the electrodes was determined through numerical analysis, and the calibration curves for stratified and annular flow were obtained through a series of static experiments. The fabricated conductance sensor was applied to a 45 mm inner diameter U-shaped downward inclined pipe with an inclination angle of 3° under adiabatic air-water flow conditions. In the tests, the superficial velocities ranged from 0.1 to 3.0 m/s for water and from 0.1 to 18 m/s for air. The obtained mean void fraction and the structure velocity from the conductance sensor were validated against the measurement by the wire-mesh sensor and the cross-correlation technique for the visualized images, respectively. The results of the flow regime classification and the corresponding time series of the void fraction at a variety of flow velocities were also discussed.
Highlights
Measurement techniques for gas-liquid two-phase flows are a challenging issue in a variety of industrial applications due to their irregular flow behavior as a result of the flow regime and complicated interactions between phases
Based on the validation works for the proposed conductance sensor, the cross-sectionally averaged time series of the void fraction in the inclined pipe were plotted in Figures 12 and 13
In the measurement results from the dynamic tests, the intermittent flow was velocity was lower than the mixture velocity; a few exceptions were noted when both of the gas and observed in more broad ranges of the flow conditions than the domain defined in the flow pattern liquid superficial velocities were low since the liquid flow was accelerated by an inclination
Summary
Measurement techniques for gas-liquid two-phase flows are a challenging issue in a variety of industrial applications due to their irregular flow behavior as a result of the flow regime and complicated interactions between phases. The void fraction is a crucial variable used in predicting the transition of flow regimes and heat transfer and pressure drop of two-phase flows, especially by means of an empirical approach. For this reason, versatile measurement techniques have been developed and applied to two-phase flow: including electrical [1,2,3,4,5,6,7,8,9,10,11], optical [12,13], ultrasonic [14] and radiation attenuation methods [15,16] and so on. ItIt takes takes into into account account the the difference difference in in the the flow flow structures structures such such the whole circumference of the sensor will be in contact with a conductive liquid film in the annular that the whole circumference of the sensor will be in contact with a conductive liquid film in that the whole circumference of the sensor will be in contact with a conductive liquid film in the the flow, while the continuous liquid will wet partially the opposite electrode pair (electrodes A and B)
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