A study of bubble dynamics in reduced gravity forced-convection boiling

Experiments are reported in which a single vapor bubble was nucleated and grown in a flow field of FC-72 on a flat surface in terrestrial gravity and microgravity. A thin gold film semi-transparent heater was designed and used to generate single bubbles. Bubble nucleation, growth, and departure in microgravity with different flow rates were observed by a CCD camera. It was found that the transient bubble diameters during growth are proportional to the parameter of (Re−1/3t∗1/3), where Re is the Reynolds number and t∗ is the dimensionless time. The forced-convection would affect the downstream edge of a bubble significantly in microgravity, while the upstream coordinate of a bubble seems to be independent of the flow rate. It was observed that the high flow rate would offset the buoyancy effects. As a result, the bubble generation frequency, Weber number, and bubble shape tend to be similar with those in normal gravity.