Gas holdup measurement for horizontal gas-liquid intermittent flow based on novel ultrasonic attenuation model

Horizontal gas-liquid intermittent flow widely exists petroleum, nuclear, chemical and other important industrial production processes, such as plug flow and slug flow. The gas-liquid intermittent flow presents pseudo-periodic motion alternating between the film region and the slug region. The water in the slug region is a continuous phase, which is filled with dispersed air bubbles. Gas holdup in the slug flow is the key flow parameter of gas-liquid intermittent flow. In this paper, a transmission ultrasonic sensor system was designed and a horizontal gas-liquid two-phase flow dynamic experiment in a small-caliber horizontal pipe was carried out to obtain the measurement response of ultrasonic sensor and Wire-Mesh sensor to gas-liquid intermittent flow. The attenuation characteristics of ultrasonic transmission waves under intermittent flow conditions are analyzed. Based on the flow visualizations of the Wire-Mesh sensor, bubble radii were extracted by the bubble labeling algorithm on a 2D plane, and the relationship between average bubble size and instantaneous gas holdup was studied. According to this, the McClements model and BLBL model are modified, and a novel physical model is proposed which takes into account the bubble size, absorption and scattering attenuation at gas-liquid interface, and finally achieves the measurement of the gas holdup of horizontal gas-liquid intermittent flow. The results show that the ultrasound attenuation physical model in this paper presents good performance in measuring the gas holdup in intermittent flows.