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On Bubble Dynamics in Subcooled Nucleate Boiling on a Platinum Wire

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Original languageEnglish
Pages (from-to)1-12
JournalInternational Journal of Thermal Sciences
Volume137
Early online date22 Nov 2018
DOIs
Publication statusE-pub ahead of print - 22 Nov 2018

Abstract

While much attention has been given to the phenomenon of boiling, the underlying physics and mechanisms are still not fully understood due to its complicated and illusive nature. In this study, an experimental investigation of subcooled pool boiling of de-ionized (DI) water, at a bulk temperature of 30°C and atmospheric pressure, was performed on a platinum wire with a diameter of 250 µm, starting from the onset of nucleate boiling (ONB) and rising to higher heat fluxes. A high speed camera system was utilized for visualization. Images of bubble growth, migration, coalescence, leaping and detachment were recorded. Each of these events was investigated separately, and a comprehensive discussion undertaken. High speed camera images were analyzed by taking the most important parameters, such as surface tension, bubble-bubble interactions, nucleation site-bubble interactions, Marangoni convection and accumulation of non-condensable gases inside the bubbles. Lower applied heat fluxes led to bubble nucleation from the nucleation sites and slow growth of bubbles to a certain diameter, which were ready to migrate along the wire. Increasing the heat flux made the bubbles grow faster and favored coalescence, leaping and detaching that could be observed one after another due to an increase in the temperature gradient and perturbation of the temperature field near the nucleation sites. Another important mechanism considered was the momentum of the non-condensable gases inside the bubbles, especially while the bubble tail disappeared and the bubble shrank whilst stopping near an immobile bubble or near the nucleation sites.

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