Contribution of Microlayer Evaporation During Flow Boiling Inside Microchannels

Flow boiling through microchannels is characterized by nucleation and growth of vapor bubbles that fills the entire channel cross-sectional area. As the bubble nucleates and grows inside the microchannel, a thin film of liquid or a microlayer gets trapped between the bubble and the channel walls. The heat transfer mechanism present at the channel walls during flow boiling is studied numerically. These mechanisms are compared to the heat transfer mechanisms present during nucleate boiling and in a moving evaporating meniscus. It is shown that the thermal and the flow fields present inside the microchannels around the bubbles are fundamentally different compared to nucleate boiling or in a moving evaporating meniscus. It is explained that how thin film evaporation is responsible for creating an apparent nucleate boiling heat transfer mechanism inside the microchannels.