Experimental and theoretical analysis of bubble departure behavior in narrow rectangular channel

• We visually study bubble departure behavior in a narrow rectangular channel.
• An analysis of force balance on a growing bubble was performed to predict the bubble departure diameter.
• The effect of bubble interface parameters on prediction of departure diameters is obtained.
• The predicted model agreed with the experimental data within the maximum relative deviation of 25%.
• The main forces controlling the bubble departure are buoyancy, surface tension force and quasi-steady drag force.

Visual experimental study focusing on bubble growth and departure behaviors in a narrow rectangular channel was carried out in this paper. Deionized water was used as working fluid, and the experiment was performed at atmospheric pressure. The cross section of the narrow rectangular channel is 2 mm × 8 mm. A high speed digital camera was applied to capture the behaviors of bubble growth and bubble departure from the nucleation site. The bubble departure diameter, bubble inclination angle, upstream contact angle, downstream contact angle and bubble contact diameter were obtained according to the observation. An analysis of force balance on a growing bubble was performed to predict the bubble departure diameter in the narrow channel, and the effect of bubble interface parameters on the prediction of bubble departure diameters was discussed in this paper. The result of predicted model agrees well with the experimental result with a maximum relative deviation less than 25%. According to the study proposed in this paper, the mechanism of bubble departure from a nucleation site can be explained based on the force balance analysis of a growing bubble, and the major forces dominating the bubble departure are the buoyancy force, surface tension force and quasi-steady drag force.