Sliding and sticking vapour bubbles under inclined plane and curved surfaces

In flow boiling heat is transferred by the combined effects of nucleate boiling, with local generation of bubbles, and evaporative and convective cooling by the passage of bubbles generated elsewhere, In this study, nucleate boiling was eliminated by measuring the heat transfer near injected steam bubbles sliding under an inclined plate heated to low superheats, using liquid crystal thermography combined with high speed video recording and computerised image analysis. Heat was transferred 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 mechanism for large, easily deformed, slow-moving bubbles. For small, faster-moving bubbles the reduction in evaporation was offset by an improvement in convection. (C) 1998 Published by Elsevier Science Ltd and IIR.