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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

BOILING SURFACE TOPOGRAPHY

Get access (open in a dialog) DOI: 10.1615/IHTC6.3740
pages 157-161

要約

Recently there have been renewed attempts to unravel the problems posed by the nucleate boiling process. One important area requiring clarification is the mechanism determining the relation-Ship between the active site density na and the surface temperature difference ΔТ.
The first part of this study is essentially an experimental confirmation that the boiling component of the heat flux is directly proportional to both na and ΔТ in the low heat flux or discrete bubble region. The second part is devoted to an attempt to physically account for the variation of na with ΔТ. A new parameter termed the seeded proportion, s, is defined as the ratio of the density of the seeded or activated cavities of a particular mouth radius to the density of total available sites of the same mouth radius. The seeded proportion is postulated to be a function of the cavity mean depth and the volume of gas required to initiate boiling at the cavity. This allows the possibility of expressing the na − ΔТ variation for pool boiling in general terms.
For the particular experimental conditions used, allocation of reasonable values to the parameters concerned leads to a theoretical relationship of the form
na α ΔT4 which is similar to the experimentally determined variation where the power index was found to be 4.5