ISSN Online: 2377-424X
International Heat Transfer Conference 12
Numerical predictions of the critical heat flux for inverted geometries with different heated area size
Résumé
The cooling of the nuclear reactor vessel lower head during a hypothetical severe accident would be
limited under the critical heat flux conditions. The critical heat flux is determined by the formation and removal
of vapour blanket on the inverted spherical wall and depletion of liquid micro layer at the wall surface. The CHF
occurs when the vapour blanket residence time exceeds the micro layer depletion time. The vapour blanket
removal is driven by the buoyancy forces and depends on the macroscopic coolant flow structure in the vicinity
of the heated surface. The numerical investigation of the vapour blanket formation, rise and depletion at the
inverted surface is investigated. The influence of the surrounding macroscopic liquid structure on the vapour
blanket removal is predicted. The obtained results give support to the understanding of the boiling crises at the
inverted curved heated wall, and shows the confidence in CFD methods application to the prediction of boiling
crises at curved inverted heated walls of various curvatures and geometry.