Equivalent water layer height (EWLH) measurement by a single-wire capacitance probe in gas–liquid flows

The objective of this study was to measure EWLH in horizontal pipes by a single-wire capacitance probe. The capacitance measured by the probe is linearly proportional to EWLH with a high sensitivity of 1.52 pF/mm. The measurements are independent of water salinity, phase distribution, and wire shape. The static performance of the probe was validated theoretically and experimentally. In dynamic process, the parameters relevant to fluids and wire influence the measuring accuracy of EWLH, but the errors are constant and small. For the given wire and fluids, the accuracy decreases as bubble size decreases or interfacial velocity increases, which is mainly relevant to flow patterns.Time traces of EWLH in all the flow patterns were obtained, from which the flow parameters were estimated such as interfacial velocities, phase distributions, void fractions, and flow patterns. The measuring accuracy is high in stratified and intermittent flows, but low in bubbly and annular flows. However, the time traces can reflect the flow characteristics in all the flow patterns, and the statistical parameters of the time traces were different from each other.