SLIDING AND STICKING VAPOR BUBBLES UNDER INCLINED PLANE AND CURVED SURFACES

In flow boiling heat is transferred by the combined effects of nucleat e boiling, with local generation of bubbles, and evaporative and conve ctive cooling by the passage of bubbles generated elsewhere, In this s tudy, nucleate boiling was eliminated by measuring the heat transfer n ear injected steam bubbles sliding under an inclined plate heated to l ow superheats, using liquid crystal thermography combined with high sp eed video recording and computerised image analysis. Heat was transfer red by evaporation of the thin liquid film between the bubble and the wall and by enhanced convection in a wake region wider than the bubble and many bubble diameters long, Evaporation was the dominant mechanis m for large, easily deformed, slow-moving bubbles. For small, faster-m oving bubbles the reduction in evaporation was offset by an improvemen t in convection. (C) 1998 Published by Elsevier Science Ltd and IIR.