Electrical impedance method for flow regime identification in vertical upward gas-liquid two-phase flow

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Abstract
A new method using an indigenously developed electronic circuit for identifying all the flow regime transitions in a vertical upward gas-liquid two-phase flow is reported. The circuit basically converts the void fraction signal of the two-phase mixture into a series of square pulses of varying width. The probability density function of the pulse width spectra is analysed for detection of bubble-to-slug flow transition. Slug-to-churn flow transition is detected on the basis of liquid slug length measurements. Churn to annular flow transition is identified on the basis of the number of liquid bridging. Experimental analysis shows that, in bubble flow through narrow tubes, bubbles bigger than a critical size cannot exist without forming Taylor bubbles. The technique has potential to minimize substantially the adverse effects of electrode polarization, stray impedance and varying conductance of the liquid medium. The sampling time and sampling frequency can be varied independently. The circuit can be used for measurement of both conducting and dielectric fluids.