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- W657250293 abstract "In the case of PWR severe accident (Loss of Coolant Accident, LOCA), the inner containment ambient properties such as temperature, pressure and gas species concentrations due to the released steam condensation are the main factors that determine the risk. For this reason, their distributions should be known accurately, but the complexity of the geometry and the computational costs are strong limitations to conduct full three-dimensional numerical simulations. An alternative approach is presented in this thesis, namely, the coupling between a lumped-parameter model and a CFD. The coupling is based on the introduction of a transfer function between both models and it is expected that large decreases in the CPU-costs may be achieved. First of all, wall condensation models, such as the Uchida or the Chilton-Colburn models which are implemented in the code CAST3M/TONUS, are investigated. They are examined through steady-state calculations by using the code TONUS-0D, based on lumpedparameter models. The temperature and the pressure within the inner containment are compared with those reported in the archival literature. In order to build the transfer function, natural convection heat transfer is then studied by using the code CAST3M for a partitioned cavity which represents a simplified geometry of the reactor containment. At a first step, two-dimensional natural convection heat transfer without condensation is investigated only. Either the incompressible-Boussinesq fluid flow model or the asymptotic low Mach model are considered for solving the time dependent conservation equations. The SUPG finite element method and the implicit scheme are applied for the numerical discretization. The computed results are qualified by the second-order Richardson extrapolation method which allows obtaining the so-called Exact values, i. E. Grid size independent values. The computations are also validated through non-partitioned cavity case studies. The discussion is focused on heat transfer characteristics such as the variations of the average Nusselt number (Nu) versus the dimensionless thickness of the partition (0. 01 ≤ γ ≤ 0. 2) and conductivity ratio of the partition wall to the fluid (1 ≤ σ ≤ 10 [puissance] 5 ). Finally, a transfer function is suggested based upon the thermal resistance of the partition wall. The validity of the model is assessed thanks to comparisons with ’half-cavity’ simulations" @default.
- W657250293 created "2016-06-24" @default.
- W657250293 creator A5054234244 @default.
- W657250293 date "2005-01-01" @default.
- W657250293 modified "2023-09-27" @default.
- W657250293 title "Étude numérique 0D-multiD pour l'analyse de perte de réfrigérant dans une enceinte de confinement d'un réacteur nucléaire" @default.
- W657250293 hasPublicationYear "2005" @default.
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