Microbubble Formation in Collapsing Process of a Single Vapor Bubble Injected in Subcooled Pool

Abstract

‘Microbubble emission boiling,’ known as MEB, is a phenomenon that emerges in a narrow range of subcooled condition with a higher heat flux than critical heat flux (CHF) accompanying with microbubble emission from the heated surface. The authors focus on the condensing process of vapor bubbles in order to comprehend the mechanism of the microbubble formation and emitting processes. In order to simplify a surely complex boiling process, the authors try to extract an interaction between the vapor bubble and the subcooled bulk in a boiling phenomenon, that is, growing and collapsing processes of a vapor bubble ejected to subcooled liquid bath. Vapor bubble is produced by vapor generate system, and ejected to a bulk of saturated distilled water at a designated degree of subcooling. The degree of subcooling is varied from 0 to 50 K. The growing/collapsing of vapor bubble behavior is detected by employing a high-speed camera at frame rates up to 50,000 fps with a back-lighting system. In the present study, the process of microbubble emission as well as the process of the irrupting vapor bubbles to the subcooled bulk is compared to that in a MEB on a thin wire.