When vaporization occurs through a blanketing gas film, the phenomenon is referred to as ___________________ boiling?
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Answer: D. Film
Explanation
Film boiling occurs when a continuous vapor blanket forms over a very hot heating surface. This vapor film acts as a high-resistance thermal insulator, severely reducing heat transfer rates. Radiative heat transfer across the vapor blanket becomes significant at extremely high surface temperatures. Boiling regimes progress from natural convection to nucleate boiling, transition, and finally film boiling. Leidenfrost effect is a classic demonstration of liquid droplets levitating on their own vapor film. Critical heat flux marks the dangerous transition point from nucleate boiling to unstable film boiling.
Nuclear reactor safety analyses evaluate film boiling to prevent catastrophic fuel rod burnout. Quenching metal parts in hot baths must avoid stable film boiling to ensure uniform hardening. Boilers operating in film boiling regimes suffer from reduced efficiency and overheated metal walls. Pool boiling describes boiling in a large stagnant pool without forced liquid circulation. Nucleate boiling features isolated vapor bubbles forming and detaching rapidly from active sites. Transition boiling is an unstable intermediate regime between nucleate and full film boiling.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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