Heat transfer mechanisms in isolated bubble boiling of water observed with MEMS sensor

Heat transfer characteristics of isolated bubble saturated pool boiling of water were investigated by local wall temperature measurement using an original micro-electro-mechanical systems (MEMS) sensor and a wall heat transfer evaluation. The measured temperature clearly indicated dynamic heat transfer phenomena below an isolated bubble including microlayer evaporation, dry-out of the microlayer, and rewetting of the dry-out region. Local heat removal due to microlayer evaporation exceeded 1 MW/m2. Microlayer evaporation was found to have a central role in the wall heat transfer. The contribution of microlayer evaporation to bubble growth was about 50%, and did not vary significantly with wall superheat. The remaining 50% of the latent heat in the bubble was transferred from the superheated liquid surrounding the bubble. Finally, the spatial distribution of the initial microlayer thickness was calculated from the local heat flux of the wall.