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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Boiling on an Isolated Nucleation Site Close to CHF Conditions

Get access (open in a dialog) DOI: 10.1615/IHTC15.pbl.008856
pages 6317-6331

Resumo

Experimental results of saturated nucleate boiling of HFE7000 at ambient pressure on an isolated artificial cavity are presented. A wide range of Jakob number, Ja, has been studied from onset of nucleate boiling (Ja ? 1) up to a critical heat flux for the cavity (Ja ? 50). Bubble growth has been studied relatively to the effects of Ja number. It is shown that the quasi-static or slow growth regime gives a good approximation of bubble contour even at large Ja as long as detachment phase is not concerned. The apparent contact angle during growth can be computed from the static equilibrium bubble contour. The value obtained is of the same order of magnitude as the prediction of macroscopic contact angle found from the model of Stephan and Busse of evaporation of an adsorbed liquid micro-layer. Deviation from the quasi-static growth can be evidenced and related to the effect of liquid dynamical pressure force acting on the bubble. When local CHF on the isolated site is approached, the contact angle has values close to 90 degrees.