Experimental study of bubble formation process on the micro-orifice in mini channels

A visualized experimental system is designed and constructed to study the bubble behaviors on the micro-orifice in liquid layer. The test section is performed in a rectangular duct of 0.27 m x 0.006 m x 0.012 m, and the air is injected from an orifice with 0.49 mm in diameter. The gas flow rate is in the range of 0.3-60 ml/min, while the corresponding Reynolds number is ranged from 0.87 to 173.18. The effect of gas flow rate on bubble behaviors and bubble coalescence characteristics are investigated systematically. The results state that the bubble height, the radius of curvature at the apex and the bubble detachment volume show little variation with the gas flow rate when the gas flow rate is less than 24 ml/min. While the bubble contact line diameter increases firstly and then decreases. During the multi-bubble regimes stage, the detachment volume of both leading bubbles and trailing bubbles increase with the Weber number. The time interval between two adjacent bubbles or coalescence cycles is almost 0 when Weber number is above 18.27.