Characteristics of Gas-Liquid Slug Flow in Microchannel by Instantaneous Liquid Film Thickness Measurement

This paper seeks to decipher the exact relationship between the liquid film thickness and the hydrodynamics of gas-liquid slug flows. An instantaneous measurement system is developed by integrating the laser focus displacement meter (LFDM) and high-speed camera to characterize the temporal evolution of the liquid film and the dynamic characteristics of continuous slug flows. A glass tube with internal diameter of 0.75 mm is used and the tested ranges of superficial gas and liquid velocities are 0.01-1.2 m/s and 0.01-0.09 m/s respectively. The non-zero signals of LFDM representing the bubble slug flows changed from regular periodic intervals to chaotic fluctuations when slug-annular flow pattern appears. The dominant frequencies of the periodic intermittent slug flows increased from about 0.5-2 HZ to nearly 10-20 HZ as the superficial gas velocity rised from 0.025 to 0.78 m/s. The bubble and liquid slug lengths calculated by the time interval of liquid film thickness and bubble velocity correlated well with the empirical model. Meantime, the average value of void fraction derived from the calculation of transient liquid film thickness shows a linear growth with the gas holdup ratio.