A study on mechanism of microbubble emission boiling

Abstract

Microbubble emission boiling (MEB) is an interesting phenomenon because of extremely high heat flux over the CHF. However, the mechanism of occurrence and the heat transfer characteristics are still unknown. We carried out the experimental observation of bubble behaviors on the heating surface by using a platinum wire and a planar copper surface. The MEB was not observed in the subcooled boiling on the wire, but we found the similar behavior to the MEB on the planar surface. In the experiment, the huge coalesced bubbles were observed intermittently on the planar heat transfer surface, showing higher heat flux than the CHF. Because such large bubble was not formed on the fine wire, we are considering that the formation of the large coalesced bubbles has an important role on the occurrence of MEB. We also applied the prediction of heat transfer by the microlayer model and we have a good agreement with experiments for nucleate boiling before the MEB.