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ISSN Online: 2377-424X

ISBN Print: 0-89116-130-9

International Heat Transfer Conference 6
August, 7-11, 1978, Toronto, Canada

THE BOILING MECHANISM DURING BURNOUT PHENOMENA IN SUBCOOLED TWO-PHASE WATER FLOWS

Get access (open in a dialog) DOI: 10.1615/IHTC6.750
pages 381-385

Sinopsis

The development of a bubble boundary layer and vapour slugs along the surface of a heating element in low pressure two-phase water flows (1−2.5 m/sec) accompanying the boiling crisis have been investigated by means of high speed photography and high speed film techniques.
The results give rise to a model describing the occurrence of burnout in terms of the coalescence of small hemispherical bubbles growing on the surface forming whether a bubble layer or a vapour slug isolating a thin liquid layer from the subcooled bulk liquid flow. This thin liquid layer can be evaporated in few milliseconds. The passage time of a vapour slug of the order of 0.1 sec. or the residence time of 0.1 sec. of a bubble layer gives rise to dry area and wall temperature increase sufficient to exceed the Leidenfrost temperature, to prevent rewetting and to trigger burnout.