Scaling considerations about LWR core thermalhydraulics
Résumé
This work is a step in a long term effort to build and validate a more physically based 3D modelling of flows in a reactor core in both single-phase and two-phase situations. Light Water Reactor (LWR) core thermalhydraulics may be simulated in system codes and component codes by 3D numerical tools using the porous body approach with various possible space resolutions. In quasi-axial flow conditions, the radial transfers by cross-flows, by turbulent diffusion and/or by dispersion effects –including momentum, energy and void dispersion- may play a very important role in many situations of interest but are not sufficiently validated for macroscopic porous models. Turbulent diffusion and dispersion phenomena are associated to time and space filtering and their modelling should depend on the filter scale in the same way as turbulent viscosity in LES depends on the filter scale. First scaling considerations are presented which show that rather simple experiments without rod heating, without high pressure steam-water conditions, can bring valuable validation data on radial transfers using low pressure water, water with addition of a passive scalar, water mixed with some heavier component, and low pressure air-water. In particular nondimensional numbers are identified to simulate most important effects when crossflows exist in presence of density differences. A critical review of available data and models shows that available interfacial friction models are rather empirical and have a high uncertainty due to the absence of a “flow regime map” for twophase flow in a rod bundle. Non-dimensional numbers which should be respected in future experimental programs are discussed.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...