Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Year 2006

M. Barthes
Université de Provence, Marseille, France

C. Reynard
Université de Provence, Marseille, France

R. Santini
Université de Provence, Marseille, France

Lounes Tadrist
I.U.S.T.I

The objective of this work is to experimentally investigate heat and mass transfer and liquid convective instability during a single vapour bubble growth. The bubble was created on an artificial nucleation site located on a downward facing heating element maintained at constant heating power. The liquid bulk (FC-72) was maintained at constant temperature. For a degassed liquid, the influence, on heat exchanges, of the level of liquid subcooling and of the heating power applied on the nucleation surface were systematically tested and analysed. For each operating condition, the temporal evolution of geometric parameters (e.g. diameter, height, volume and shape) was measured with the help of image processing. The evaporative heat flux due to phase change (evaporation and condensation) was calculated from volume variations. This local flux was compared to the total heat flux measured on the whole nucleation surface. The evaporative and total heat fluxes decreased in the same order of magnitude when the level of subcooling was increased. On the other hand, the total heat flux increased with the heating power whereas the evaporative heat flux varied in a non-significant way. It was found that the total heat flux depends on the bubble departure period. Moreover, for a non-degassed liquid, convective instabilities were observed using a shadowgraphy method. During the vapour bubble growth, stationary and oscillatory modes were observed with the help of shadowgraphy method and tracer particles. It was found that non-condensable presence has an influence on the onset of the instability: with a degassed liquid, the oscillatory mode of the instability did not occur.

MPH-09 pages DOI: 10.1615/IHTC13.p12.90 Download article

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