Abstract
At present, there are two possible approaches which are used in practice for the thermal-hydraulic analysis of the reactor core in simulations with relevant crossflow effects are : the representation of the core by a system of separated parallel flow subchannels with provision of a forced crossflow mixing by implementation of additional formulations and the porous body approach, where the core geometry is replaced by a structure of homogenized zones of porous media. If crossflow is comparable with flow along the bundles, the porous body approach is the only one suitable method to perform steady-state and transient flow calculations for safety analyses. The CFD - code CFX-4 offers the porous region model for the modeling of the core geometry as a homogenized medium. This model is characterized by a set of properties (volume porosity, resistance to flow and so on). The Core Crossflow Experimental Facility (CCEF) was built with the objective to obtain experimental data for the flow in a rod bundle under the conditions of forced crossflow with relatively low Reynolds numbers and variable flow angle. The test section of CCEF (a plexi-glass model) contains the test rod bundle. The test rod bundle is based on the geometry of a typical PWR with a pitch/diameter ratio of 1.33 and was scaled with a factor 1.5. The crossflow was induced by an asymmetrical outlet condition for the bundle. The test bundle consists of the 100 plexiglass rods, arranged in 4 rows. Additional internals, which are typical for a reactor core geometry, were not installed in the test section. The working fluid in the experiments was water. For the velocity measurements the one-component laser-Doppler anemometer (LDA) was used. Calculations for the comparison with experimental data were performed in two different approaches. The detailed geometry was created for the calculation of flow fields with κ-ε turbulence model and a relative simple geometry of the test section was built by means of the CFX-4 PreProcessing for the flow simulations in the porous region approach. The results of the experimental investigations on the CCEF and the comparison with the calculations, performed with CFX-4 Code in the geometry of the test section are presented in this paper.
