Determination of interfacial parameters of horizontal two-phase plug flow using a high speed pulse-echo ultrasonic technique

This paper presents a high-speed, multiple-transducers, pulse-echo ultrasonic technique for the measurement of interfacial parameters of horizontal two-phase intermittent flow regimes. The ultrasonic system consisted of an ultrasonic driver, a multiplexer with 4 transducers, and a microcomputer equipped with a data acquisition card, a motion controller card and the Winspect Data Acquisition software. Two transducers were mounted on the top of a 2.1 cm inner diameter circular pipe, while the other two transducers were mounted on the bottom of the pipe. Using instantaneous liquid level measurements from multiple transducers, two-phase flow interfacial parameters in plug were determined, such as the lengths and the velocities of liquid plugs and bubbles, the shape of the gas-liquid interface, and hence instantaneous and cross sectional averaged void fraction and interfacial area. The results showed that the liquid plug velocities as well as the elongated bubble velocity increases with increasing superficial liquid and gas velocities. An experimental correlation for liquid plug velocity was proposed based on the present results. The results also showed that the time and cross-sectional averaged void fraction in the plug flow regime was only slightly influenced by the superficial gas velocity but was not influenced by the superficial liquid velocity.