Rewetting of a hot vertical surface by liquid sprays

Hot surfaces rewetting interests several technological fields. A very important application is in nuclear reactors technology, where it governs the cooling of overheated fuel elements during hypothesized loss of coolant accidents (LOCAs). This phenomenon is also important in many normal processes and accidental situations taking place in conventional processes. For example when the integrity of metallic containers, filled by toxic or dangerous substances, is endangered by a hypothetical fire. The rewetting consists in the re-establishment of coolant in contact with metallic surfaces become dried due to high temperature. To this end cold liquid is injected on these surfaces via sprays or other means. The knowledge of the heat transfer phenomenology between the metallic wall and cooling fluid is very important for safe accident management and containment. Recently, about this topic, at the Institute of Energetic Thermal-Fluid Dynamics of ENEA (the Italian National research body for Energy and Ambient, at Casaccia), experimental tests on the cooling of a hot vertical surface have been carried out, by using spraying devices of various configuration, to supply subcooled water at the top. The reference situation was a tank surface subjected to a fire. In the framework of a research collaboration between the Department of Nuclear Engineering (DIN) of the University of Palermo and the above mentioned Institute, a model set up at DIN has been tested as regards its capability to describe the ENEA experimental data. The results of this activity seem quite satisfactory, as we'll show in the present paper. (C) 2005 Elsevier Inc. All rights reserved.