RÉSUMÉ

The present work explores experimentally the bubble dynamics in single silicon-based, converging and diverging rectangular microchannels with their width varied linearly from 180 μm to 20 μm resulting a converging or diverging angle of 0.183°. The fabrication of the microchannel employs silicon bulk micromachining technologies, such as deep ion etching and direct writing of excimer laser, and anodic bonding process. The flow visualization is made possible by employing a high speed digital camera. The results of the present study reveal that the diverging channel, with a narrow inlet, does constrain the occurrence of reversed flow and make the two-phase flow more stable than that in the converging one, though the diverging angle is relatively small. Bubbles typically grow with a constant rate, from 30 to 1600 μm/s, similar to those for bubble growth in microchannels with uniform cross section. Moreover, the bubble growth rate and bubble departure frequency in the diverging microchannel are larger than that in the converging one, possibly due to more stable two-phase flow in the diverging channel. On the other hand, the bubble departure radius at the site of onset of nucleate boiling in the converging channel is larger than that in the diverging one.