A new method for liquid film thickness measurement based on ultrasonic echo resonance technique in gas-liquid flow

Liquid film thickness is an important parameter for gas-liquid two phase flow, and the measurement methods are significant for studying heat and mass transfer characteristics. Among many liquid film thickness measurement methods, the ultrasonic method is more suitable for actual working conditions and has a good application prospect. But the common ultrasonic pulse echo method can't measure thin thickness and thin film resonance method is affected by multiple echoes and noise. To overcome above defects, a new method called ultrasonic echo resonance main frequency (UERMF) method is proposed and a measuring system is designed to measure liquid film thickness. In static experiment, the relative error of particle image method and UERMF method is within +/- 2.7%. In flowing experiment, good agreement is found between conductance probe method and UERMF method, and the error is less than +/- 10%. The results show the UERMF method can accurately measure micrometer-size liquid film thickness. (C) 2019 Elsevier Ltd. All rights reserved.