Measurement of interfacial wave velocity in swirling annular flow using array conductance sensor

Swirling annular flow is widely employed in chemical processes, such as cyclone separators and intensified heat exchangers, to enhance transport phenomena. In these systems, the three-dimensional interfacial wave velocity directly governs the transfer efficiency, yet its measurement presents a significant challenge. To address this, this paper introduces a non-intrusive array conductance sensor capable of synchronously measuring the circumferential liquid film distribution at two cross-sections. Based on this sensor, a cross-correlation algorithm is proposed to decouple the axial and circumferential components of the interfacial wave velocity. Experiments are conducted in a vertical upward swirling annular flow facility to investigate the influence of different gas and liquid superficial velocities on the wave velocity components and the helix angle. The results reveal that both axial and circumferential wave velocities increase with rising superficial velocities, while the helix angle of the interfacial wave decreases. This indicates that the wave propagation path becomes more aligned with the axial direction at higher superficial velocities. Finally, a semi-theoretical model, complemented by an empirical correlation, is developed to predict the interfacial wave velocity. This model establishes separate predictive correlations for the axial and circumferential velocities, achieving Mean Absolute Percentage Errors (MAPE) of 5.63% and 9.70% for the respective predictions.