As the CT outer wall temperature ([T.sub.w]) increases in Figure 5, the boundary condition models are switched such as liquid convective, nucleate boiling, transition boiling, and film boiling. In Table 1, the models are listed with references.
In the transition region between the critical heat flux and the film boiling, or [T.sub.CHF] < [T.sub.w] < [T.sub.WET], Bjornard and Griffith  suggest a simple model of interpolation with the temperature ratio, [lambda] = [([T.sub.WET] - [T.sub.w]).sup.2]/[([T.sub.WET] - [T.sub.CHF]).sup.2]:
The heat increases about 40 times at the critical heat flux more than that at the boiling temperature, decreasing in the transitional boiling, and increases slowly in the film boiling.
However, the augmentation of the power influenced on a rapid boost of steam generation, and as a sequence, on the formation of dry out (film boiling or the second boiling crisis) [4-7].
Film boiling heat transfer on spherical, cylindrical and plane geometries.
Since the plate temperature is equal to the gas temperature, it can be classified into a transition boiling region at gas temperature of 250[degrees]C and 300[degrees]C, and a film boiling region at gas temperature of 350[degrees]C .
However, in the condition of the film boiling region where the gas temperature is 350[degrees]C, the vapor phase rapidly forms at the solid-liquid interface, so that the liquid film does not adhere and the plate temperature hardly decreases.
However when CHF is exceeded, film boiling occurs leading to the sudden drop of the heat transfer rate and metal temperature rise.
It occurs in three characteristic stages, which are nucleate, transition and film boiling. Boiling itself is not an issue, and some authors recommend it because the use of boiling in engine cooling systems offers higher heat transfer.
The 2012 Heat Transfer Division Best Paper Award was presented for "Modeling Sub-cooled Flow Film Boiling
in a Vertical Tube" to Meamer El Nakla, D.C.
A new Fluid Film Boiling
capability is an industry-first and it enables simulation of liquid films coming in contact with very hot surfaces.
Heat transferred to the coolant must be maintained below the critical heat flux (CHF), which is the maximum heat flux before transitioning to the film boiling