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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

POOL BOILING HEAT TRANSFER AND SIZE OF ACTIVE NUCLEATION CENTERS FOR HORIZONTAL PLATES WITH DIFFERENT SURFACE ROUGHNESS

Get access (open in a dialog) DOI: 10.1615/IHTC6.3730
pages 151-156

Abstract

The heat transfer from horizontal copper plates with different surface finish to boiling refrigerants Rll (CFCl3) and Rll5(C2F5Cl) was measured at saturation pressures between 0.4 and 91 percent of the critical pressure pc. Although the relative pressure dependence of the heat transfer coefficient α is similar for the plates with different surface treatment, a detailed comparison of the experimental results shows that the influence of the different surface conditions achieved by mechanical and chemical treatment on the absolute value of α cannot be correlated by a single roughness parameter within the whole range of pressures investigated.
Applying the Mikic-Rohsenow-model for the bubble population the distribution function N(r) for the size of stable vapor bubbles in active nucleation sites is evaluated from the measured relationship between α and heat flux q. For each of the surfaces the functions N(r) derived from α (q)-measurements at different saturation pressures show little differences. The distribution functions N(r) obtained in this way are in relatively good agreement with direct results for the number density of bubbles available in literature.