TED-AJ03-515 NUCLEATION SITE INTERACTION IN POOL BOILING : EXPERIMENTAL STUDY BY EMPLOYING ARTIFICIAL SURFACE

概要

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The present work aims at studying the physical mechanisms of nucleation site interaction in pool boiling. A series of boiling experiments in water was conducted on the heated silicon surface with the cylindrical artificial cavities. The vicinity of the manufactured cavities was heated by laser irradiation from the bottom of the silicon plate. The temperature fluctuations beneath and around the cavities were measured by the radiation thermometer. The bubbling behaviors were captured by the high-speed video camera to measure the bubble departure frequency and size (Fig.A-1) and to observe the different kinds of bubble coalescences. In order to investigate the nucleation site interaction, the spacing between two cavities was varied from 1mm to 8mm, which corresponds to S/D_b^^- (the ratio of the cavity spacing to the average bubble departure diameter) from 0.3 to 3.3. Based on the comprehensive observation and analysis, three significant effect factors of nucleation site interaction are found out : 'H'-hydrodynamic interaction between bubbles; 'T'-thermal interaction between nucleation sites;'C'-horizontal and declining bubble coalescence. The intensity, competition and dominance relations of these three factors determine four interaction regions (Fig.A-2 and Table A-1) : 'I'region (S/D_b^^->3), 'H'region (2<S/D_b^^-≤3), 'H+T'region (1.5<S/D_b^^-≤2) and 'H+T+C' region (S/D_b^^-≤1.5).[figure][table]