A modified bubble dynamics model for predicting bubble departure diameter on micro-pin-finned surfaces under microgravity

The micro-pin-finned structure can effectively enhance the boiling heat transfer both in terrestrial gravity on earth and microgravity environments in space, while the mechanism of boiling heat transfer is very complex. By the observation of the bubble behaviors such as growth, coalescence and departure, the dynamic process is analyzed. For the smooth surface, the traditional bubble dynamics model could accurately predict the bubble departure diameter; while for the micro-pin-finned structure surface under microgravity environment, there was a relatively large deviation for this model. The reason is that the traditional bubble dynamics model for the smooth surface was originally established with the perspective of force balance analysis of single bubble, which did not consider the strong interaction among the bubbles on the micro-pin-finned surfaces. According to the experimental phenomena under microgravity environment, there are several small bubbles sitting under a primary bubble on the micro-pin-finned surface. The interaction between the small bubbles and the primary bubble prevents the departure of the primary bubble. A modified bubble dynamics model based on force balance is proposed to predict bubble departure diameter well on the micro-pin-finned surface, which considers the role of drag force of small bubbles beneath the primary bubble.