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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Heat Transfer Characterization During Transient Boiling

Get access (open in a dialog) DOI: 10.1615/IHTC15.evp.008637
pages 2471-2485

Résumé

Postulating reactivity initiated accidents in a core of a nuclear reactor, a power excursion occurs on some fuel rods. The consequent rapid boiling is a matter of study by the Institut de Radioprotection et de Sˆuret´e Nucl´eaire (IRSN) for the nuclear power plants safety evaluation, because of the risk for rod clad failure induced by large clad temperature. In order to better understand the influence of power excursions and to characterize the phases of the rapid boiling phenomenon, an experimental set-up has been built at the Institut de M´ecanique des Fluides de Toulouse (IMFT). The channel of the test section is a semi annulus. The inner half cylinder is made of a stainless steel foil, heated by Joule effect. Its temperature is measured by an infrared camera filming the backside of the foil, coupled with a high speed camera for the visualization of the phenomena. In this paper, heat transfer is experimentally studied during the different phases of the heating, which are all transient: forced convection, nucleate boiling and film boiling. From this experimental study of the transient forced convection, coupled with numerical simulations, we propose to model the onset of boiling, and more precisely the increase of the wall temperature at the onset of boiling with the supplied power. During the transient nucleate boiling, it is observed that heat flux increases with the heating rate and is higher than the steady-state boiling. Over the critical heat flux, we observe transient film boiling and visualizations show a Kelvin-Helmoltz instability.