Experimental and Numerical Investigation of the Dynamics of Moving Vapor Bubbles

Jet flows have been observed flowing from the tops of vapor bubbles during nucleate boiling in a variety of situations. This paper analyzes the physical mechanisms that cause jet flows to emanate from the tops of bubbles moving along microwires. The flows were analyzed by numerically solving the governing differential equations for the 3-D velocity and temperature distributions around the bubble and the heated wire as the bubble moves along the wire. The results show that the flow is most likely driven by the temperature difference from the front to the back of the bubble resulting from the bubble motion which would cause Marangoni flow. The Marangoni flow provides thrust to push the bubble forward. Comparisons with experimental observations suggests that the condensation heat transfer at the bubble interface must be restricted by noncondensable gases would increase the surface temperature gradient which would in turn increase the resulting Marangoni flow.