Investigation of Film Bubbles in Annular Flow Based on Planar Laser-induced Fluorescence

The bubbles in the liquid film are important to improve the chemical reaction rate and the efficiency of heat and mass transfer. However, bubbles in annular flow have not been studied intensively like waves on film surface or droplets. Planar Laser-induced Fluorescence (PLIF) was employed to investigate the film bubbles in vertical upward annular flow. The subject of this paper is to study the correlation between the area, the gas holdup of bubbles in the liquid film and gas-liquid superficial velocity. The results show that the above parameters decrease with the increase of the gas superficial velocity, however, with the increase of liquid superficial velocity they are not always increasing. The variation of these parameters with the liquid superficial velocity is also diverse under different gas superficial velocity. The statistical characteristics of bubble area are studied and it can reveal how the mean bubble area decreases as the flow conditions change.