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Article Dans Une Revue Nuclear Engineering and Design Année : 2020

Mechanistic modeling of the thermal-hydraulics in polydispersed flow film boiling in LOCA conditions

Résumé

Much effort has been devoted by the nuclear community to develop mechanistic models to predict the heatdissipation of fuel rods during a loss of coolant accident (LOCA). However, there is still the challenge to findcorrelations that accurately predict the rates of heat transfer corresponding to each involved phenomena andgather them all in a single physical model. Looking for improving thermal-hydraulics calculations in LOCAconditions, this work introduces a novel mechanistic model implemented in a new code named NECTAR tocalculate heat and mass transfer phenomena and droplets dynamics in a polydispersed flow film boiling. Thesimulation results are compared with experimental measurements using three different geometries that representthe cladding ballooning at sub-channel scale. NECTAR can predict with great accuracy the heat dissipation bythe internal steam-droplets flow with less than 8% mean deviation for all the test cases. The droplets characteristicsdownstream of the heated tube are also well predicted by NECTAR. In a detailed analysis of each heattransfer process, we found that wall-to-steam convection plays the major role in the internal heat dissipation,followed by the heat removed by the droplets impact onto the wall in spite of the very low volume fraction ofdroplets. Moreover, droplets impact and steam-to-droplets convection are also the main responsible for thedroplets evaporation. Finally, considering the droplets diameter polydispersed distribution into thermal-hydraulicscalculations (instead of a single mean diameter) has an effect only for higher volume fractions ofdroplets.
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Dates et versions

hal-02433846 , version 1 (28-10-2020)

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Paternité - Pas d'utilisation commerciale - Pas de modification

Identifiants

Citer

A.V.S. Oliveira, J.D. Peña Carrillo, Alexandre Labergue, T. Glantz, Michel Gradeck. Mechanistic modeling of the thermal-hydraulics in polydispersed flow film boiling in LOCA conditions. Nuclear Engineering and Design, 2020, 357, pp.110388. ⟨10.1016/j.nucengdes.2019.110388⟩. ⟨hal-02433846⟩
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