Measurement of steam flow rate using clamp-on ultrasonic flowmeter

Clamp-on type ultrasonic flowmeter has a potential to measure steam flow rate. However, the steam wetness fraction increases with the heat loss, and the liquid film and the droplets may disturb the ultrasonic propagation. In this study, ultrasonic propagation experiments were carried out in air-water two-phase and wet steam flows. Two ultrasonic sensors located at up- and down-stream positions were used for the measuring ultrasonic time-of-flight that depends on the flow rate. It was shown that the accuracy of the flow rate measurement strongly depended on the flow regime. In wavy flow, the time-difference of ultrasonic propagation were good agreement with the reference values. However, the signals were time-dependent in annular mist flow resulting in the difficulty of the flow rate measurement.