Gas holdup measurement of horizontal gas-liquid two-phase flows by using a novel combined ultrasonic-conductance sensor

Horizontal gas-liquid two-phase flows widely exist in petroleum, chemical, and other important industrial fields. The flow structures forming during gas-liquid flows can be complex. The transition between flow patterns greatly depends on many factors, such as the fluid properties and the flow rate. Notably, there are multi-scale flow structures even in the same flow pattern. Therefore, it is a great challenge to accurately measure the gas holdup in the horizontal gas-liquid flows by single-mode sensor technology. In this study, we designed a novel combined ultrasonic-conductance sensor (CUCS) consisting of a multi-electrode conductance sensor (MCS) and a transmission ultrasonic sensor (TUS). A flow pattern map of the horizontal gas-liquid flow was obtained in the experiment, and the responses of the CUCS under different flow patterns were collected. The stratified smooth (ST) flow, stratified wavy (SW) flow, and Taylor bubbles in intermittent flow were visualized by the MCS, and the corresponding measurement model of the gas holdup was presented. For the slug region (SR) in intermittent flow, a physical model for measuring the gas holdup was established based on the attenuation characteristics of the transmitted ultrasonic wave. The result indicates that the CUCS has a higher measurement accuracy for the gas holdup of the horizontal gas-liquid flows with different flow patterns.