The mechanism and prediction of critical heat flux in inverted geometries

Recent interest in a severe accident management scheme known as 'In-Yessel Retention' has created the need to establish the coolability limits of larg e, inverted geometries. In this paper, full-scale simulations conducted at UCSB's ULPU facility are examined at the microscopic level. Because of the peculiar geometry, it has become possible to directly visualize the boiling transition phenomenon, and with the help of microthermocouples to quantita tively identify the mechanism of dryout. Altogether, a new boiling transiti on regime was identified, with a significant coupling between overall syste ms dynamics and the microphenomena. This leads the way to the a priori pred iction of critical heat flux and factors that may influence it. (C) 2000 El sevier Science S.A. All rights reserved.