Which region is characterized by dry-out of the heated surface and the formation of a stable vapor film?

Which region is characterized by dry-out of the heated surface and the formation of a stable vapor film?

• A. Transition Boiling
• B. Nucleate Boiling
• C. Film Boiling
• D. Convective Boiling

Answer: (C)

Dry-out of the heated surface with formation of a stable vapor film defines the film boiling regime. When the surface becomes very hot, a continuous layer of vapor forms between the surface and the liquid, preventing direct liquid contact. This vapor film insulates the surface, so heat transfer drops compared to boiling without a film, and the surface temperature rises. Nucleate boiling involves liquid contacting the hot surface with active bubble nucleation, giving high heat transfer, while transition boiling features unstable, partial dry-out; but the hallmark of film boiling is the continuous vapor layer that keeps the surface dry.

Dry-out of the heated surface with formation of a stable vapor film defines the film boiling regime. When the surface becomes very hot, a continuous layer of vapor forms between the surface and the liquid, preventing direct liquid contact. This vapor film insulates the surface, so heat transfer drops compared to boiling without a film, and the surface temperature rises. Nucleate boiling involves liquid contacting the hot surface with active bubble nucleation, giving high heat transfer, while transition boiling features unstable, partial dry-out; but the hallmark of film boiling is the continuous vapor layer that keeps the surface dry.