Session: 10-01 Interactive Presentations

Paper Number: 99167

99167 - Simultaneous High-Speed Visual and Infrared Measurements for Tracking Dryspots During Boiling Crisis 

Boiling offers an effective means of high heat flux dissipation for thermal management of electronics, power plants, and nuclear reactors. System performance and efficiencies in many of these applications are often limited by thermal management, and there is a particular need to dissipate high heat fluxes while maintaining low surface temperatures. Boiling crisis, a phenomenon wherein vapor blankets the heater surface causing a catastrophic temperature spike, poses an upper limit on the heat input called the critical heat flux (CHF). To extend the efficient nucleate boiling regime up to greater heat fluxes requires an understanding of the mechanisms of vapor blanket formation so as to devise strategies to further delay it. Since the first characterization of critical heat flux by Nukiyama almost a century ago, several mechanisms such as hydrodynamic instabilities, bubble interactions, and irreversible dry spot expansion have all been proposed to explain dryout. However, the current understanding still lacks an underlying theory for the trigger mechanisms during boiling crisis. In the present work, we perform both infrared and high-speed visual measurements of a surface from below to collect the phase distribution on the surface during the boiling crisis. At high heat fluxes near CHF, dryspots appear underneath bubbles creating thermal hot spots. At CHF, these hot spots expand irreversibly triggering the boiling crisis. Through analysis of the dryspots, the present work reveals the mechanism of its irreversible expansion and provides a framework to develop a theoretical understanding of the phenomena involved in triggering boiling crisis.

Presenting Author: Manohar Bongarala Purdue University