Abstract
The heat transfer regime just above the quench front during the reflood phase in PWR-LOCAs is the film boiling. A two-region model is developed for the description of saturated film boiling in this region. It is considered that the violent two-phase flow surrounds the vapor film and promotes the transition of laminar to turbulent vapor film in the reflood phase. In the model, the vapor film surrounded with the two-phase mixture core is treated with the turbulent boundary layer theory. The higher void fraction of the mixture core gives the lower heat transfer in the model. The results obtained by the model are compared with the data of the Slab Core Reflood Tests which cannot be explained with the previous laminar vapor film theory.
The data fall between the curves predicted by the models assuming zero interfacial shear stress (τi=0) and zero interfacial velocity (υi=0) at the different elevations in the core, different core inlet velocities and different system pressures. These show the applicability of the two-region model for the reflood phase.
