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ISSN Online: 2377-424X

ISBN Print: 0-89116-909-1

International Heat Transfer Conference 9
August, 19-24, 1990 , Jerusalem, Israel

LIQUID-SOLID CONTACT AND EFFECTS OF SURFACE ROUGHNESS AND WETTABILITY IN FILM AND TRANSITION BOILING ON A HORIZONTAL LARGE SURFACE

Get access (open in a dialog) DOI: 10.1615/IHTC9.230
pages 135-140

Resumo

To get insight into the mechanism of transition and film boiling heat transfer, experiments of saturated pool boiling of water on a horizontal copper surface , 100 mm in diameter, are made at atmospheric pressure for four different surface roughness levels and for contact angle levels from 27° to 80° ,with special attention to liquid-solid contact. In general, data show that increased roughness or contact angle decreases the heat flux in transition boiling. Such influence of contact angle carries over to the stage of minimum heat flux and film boiling where liquid-solid contact is possible. It is also found that stable film boiling can exist at lower surface temperatures when the contact angle becomes large. The area fraction of the heat transfer surface wetted by water is measured by an electric probe as well as a micro thermocouple, and the measured values are compared with the value predicted from the boiling curve by Kalinin's hypothesis about transition boiling heat transfer.