Question

Difference between nucleate boiling and film boiling

Answer 1

Nucleate boiling:
It is actually the type of boiling in which the surface temperature is more than the generally saturated fluid temperature . This happen in the condition when the critical heat flux remain higher then the heat flux . The surface temperature only greater by certain amount.

Film boiling: 
In this type of boiling the surface temperature remain much higher even the  wall are not be able to  contact with the liquid instead covered with the help of vapor. This is why it also have the low heat transfer capacity. 

Answer 2

Film boiling is a post critical heat flux (CHF) regime with a high surface temperature. The surface temperature is so high that the wall cannot be in contact with the liquid, but is covered by the vapor. Therefore, it has relatively low heat transfer efficiency due to poor heat conductivity of the vapor.

Nucleate boiling is a type of boiling which occurs when the surface temperature is hotter than the saturated fluid temperature by a certain amount. In this type of boiling, the heat flux is below the critical heat flux.

The heat transfer from surface to liquid is greater in nucleate boiling method than in film boiling method.