Separation Characteristics of Air-Water Bubbly Flow Around a Perforated Tube

In order to apply the characteristic of high void fraction in wake region of cylinder to gas-liquid separation, the flow and separation process of air-water bubbly flow around a perforated tube is investigated experimentally. The effects of inlet liquid flow rate and void fraction on the separation performance are analyzed. The results indicate that depending on inlet void fraction, the process can be divided to two stages including dispersed bubble flow stage and transitional stage of dispersed bubble flow to slug flow. In the dispersed bubbly flow stage, to the region of perforated tube, a lot of bubbles recirculate and coalescence or break up alternately. In the transitional stage, when the elongated bubble flows around the cylinder, an air pocket is formed in the wake region and the gas-liquid interface undergoes a complicated process including expansion, reaching the maximum, pinch-off and shedding, and contraction. With the increase of inlet void fraction the air separation efficiency presents a tendency of increasing firstly, then moderately stable and then decreasing. The inlet liquid flow rate has a more significant influence on pressure drop than the inlet void fraction.