Observation and modelling of bubble dynamics in isolated bubble regime in subcooled flow boiling

Experiments of subcooled flow boiling in isolated bubble regime were conducted to understand the dynamics of individual bubbles. The test fluid was water, the flow direction was vertical upward, and the pressure was slightly higher than the atmospheric pressure. In the present experiments, the bubbles produced at nucleation sites were commonly lifted off the vertical heated surface. They were then propelled into the subcooled bulk liquid to disappear due to heat transfer with subcooled liquid. It was frequently observed that the bubbles were suddenly accelerated in the lateral direction before the disappearance. Using the present observation results, new correlations were developed for the bubble lift-off velocity and the bubble acceleration phenomenon after the lift-off. It was shown that the bubble trajectories and the time-variation of bubble size calculated using the present correlations are in fairly good agreement with the experimental results.