Observation of Bubble Dynamical Behavior during Subcooled Ethanol Nucleate Boiling on Fine Heating Wires

摘要

Experimental investigations were conducted to explore the characteristics of bubble dynamics during subcooled nucleate boiling of ethanol on very thin wires (d=0.18mm), and an emphasis was addressed to observe bubble slipping phenomena. At small heat fluxes ((0.3~1.6)x 10~5W/m~2), most bubbles slipped along the heated wire instead of detaching from the wire, and moved at a uniform speed corresponding to the bubble diameter. The experimental measurements indicate that the bubble slipping velocity was closely dependent upon the applied heat flux and wire inclination (horizontal, vertical and an angle of 45° to the horizontal). Normally, bubbles slipped faster as increasing heat flux and inclination angle. For horizontal wires, a bigger bubble slipped more quickly. A special attention was paid to the effect of the buoyancy on the bubble slipping velocity.