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Dynamics of Vapour Bubbles in Nucleate BoilingWe consider the behaviour of a vapour bubble formed at a nucleation site on a heated horizontal wall. There is no forced convection of an ambient liquid, and the bubble is presumably separated from the wall by a thin liquid microlayer. The energy conservation law results in a variational equation for the mechanical energy of the whole system consisting of the bubble and liquid. It leads to a set of two strongly nonlinear equations which govern bubble expansion and motion of its centre of mass. A supplementary equation to find out the vapour temperature follows from consideration of heat transfer to the bubble, both from the bulk of surrounding liquid and through the microlayer. The average thickness of the microlayer is shown to increase monotonously with time as the bubble meniscus spreads along the wall. Bubble expansion is driven by the pressure head between vapour inside and liquid far away from the bubble, with due allowance for surface tension and gravity effects. It is resisted by inertia of liquid being placed into motion as the bubble grows. The inertia originates also a force that presses the bubble to the wall. This force is counteracted by the buoyancy and an effective surface tension force that tends to transform the bubble into a sphere. The analysis brings about quite a new formulation of the familiar problem of bubble growth and detachment under conditions of nucleate pool boiling.
Document ID
20020016394
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Buyevich, Yu A.
(NASA Ames Research Center Moffett Field, CA United States)
Webbon, Bruce W.
(NASA Ames Research Center Moffett Field, CA United States)
Callaway, Robert
Date Acquired
August 20, 2013
Publication Date
January 1, 1995
Subject Category
Fluid Mechanics And Thermodynamics
Funding Number(s)
PROJECT: RTOP 199-61-62
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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