Single-layer wire-mesh sensor to simultaneously measure the size and rise velocity of micro-to-millimeter sized bubbles in a gas-liquid two-phase flow

Abstract

In this work, we propose a conductivity-based single-layer wire-mesh sensor (WMS) system to simultaneously measure the planar bubble distribution, equivalent diameter, and rise velocity of micro-to-millimeter sized bubbles in a gas-liquid two-phase flow. Compared with the conventionally available WMS system, the proposed system is capable of simultaneously measuring the bubble size and velocity using a single-layer sensor by establishing the correlation between the effective time taken for the bubble to pass through the sensor wires and its rise velocity, which is validated for micro-to-millimeter sized bubbles. Using this correlation, we have improved the recursive bubble identification method to develop a nonlinear model for bubble size, making it possible to selectively measure and distinguish between the bubbles in micro-to-millimeter scales (previous sensors were validated for large bubbles only). To accomplish this, we also investigated the differences in the dynamics of bubble-wire contact in detail. In a vertical upward bubbly flow, the present sensor was employed for a wide range of bubble sizes (200μm to 3.5 mm on average) and liquid velocity of 0−0.5 m/s; the measured data were in good agreement with those measured with a high-speed shadowgraphy. Finally, we discuss some issues of the proposed system, which requires a further attention.