Which term stands for the threshold where nucleate boiling ends and heat transfer becomes limited by a vapor layer?

Which term stands for the threshold where nucleate boiling ends and heat transfer becomes limited by a vapor layer?

• A. Departure from Nucleate Boiling
• B. Critical Heat Flux
• C. Nucleate Boiling
• D. Film Boiling

Answer: (A)

When boiling on a heated surface reaches a point where nucleate boiling can no longer be sustained, a continuous vapor layer begins to form and blanket the surface. This surplus of vapor insulates the surface and makes heat transfer rely on the film of vapor rather than active bubble nucleation, so the heat transfer capability drops and the surface heats up more rapidly. The moment this regime shift occurs is called Departure from Nucleate Boiling. It marks the end of efficient nucleate boiling and the onset of a heat transfer limitation imposed by the vapor layer. In practice, the temperature and heat flux at this transition are often associated with the Critical Heat Flux, which is the maximum heat flux at which nucleate boiling can be maintained, but the name of the threshold described in the question is Departure from Nucleate Boiling.

When boiling on a heated surface reaches a point where nucleate boiling can no longer be sustained, a continuous vapor layer begins to form and blanket the surface. This surplus of vapor insulates the surface and makes heat transfer rely on the film of vapor rather than active bubble nucleation, so the heat transfer capability drops and the surface heats up more rapidly. The moment this regime shift occurs is called Departure from Nucleate Boiling. It marks the end of efficient nucleate boiling and the onset of a heat transfer limitation imposed by the vapor layer. In practice, the temperature and heat flux at this transition are often associated with the Critical Heat Flux, which is the maximum heat flux at which nucleate boiling can be maintained, but the name of the threshold described in the question is Departure from Nucleate Boiling.