Wed May 25th 2011
16:00
ZH286
Seminar Inertia effects in boiling
Cees van der Geld

Details:

Bubble growth in forced convective boiling under various circumstances is measured. Dedicated pool boiling measurements serve as reference experiments. Experimental conditions have been created such that most of the forces can be assessed from measured bubble shapes. Two force balances are analyzed, one an extension of the Rayleigh-Plesset equation and the other governs motion of the bubble centre away from the plane, hot wall. More than two governing equations can be analyzed in case the bubble deforms severely. Each of these equations yields an estimate of the histories of the unknown pressure drop between bubble content and the liquid at the wall, p. This p is unknown since it results of heat transfer which is not directly measured. Differences between the p’s of the two governing equations analyzed are typically less than 10 to 30 %.
It is shown that only a small deformation near the bubble foot suffices to compensate fluctuations in gravity, as with g-jitter, or to overcome inertia. Inertia is contributing both in microgravity and in case the bubble deforms strongly at terrestrial gravity. For the latter case, the Jacob and bubble Reynolds numbers need to be high and experiments have been designed to achieve this.
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