Bubble growth on an impulsively powered microheater

The dynamics of single vapor bubbles in FC-72 generated by a transient heat pulse applied to a square 260 × 260 μm2 microheater are investigated for different heat fluxes between 3 and 44 MW/m2. It is found that in all cases the growth consists of two steps, a first relatively violent one, followed by a shrinking of the vapor mass and a subsequent slower expansion. At the higher heat fluxes, the initial growth takes the form of a thin vapor layer, and it is only at the end of the second phase that the bubble acquires a significant size in the direction normal to the heater. At low heat fluxes, on the other hand, the three-dimensional character is apparent from the very beginning. The air dissolved in the liquid diffuses into the bubble during its growth and significantly slows down its shrinking after the end of the heating phase.