Direct contact condensation modeling in pressure suppression pool system

The pressure suppression pool of boiling water reactor as a safety system has vital importance from the nuclear reactor safety point of view and it is an interesting challenge for numerical simulations of flow with rapid phase change. This paper presents the recent analysis of computational fluid dynamics (CFD) simulations of chugging direct contact condensation (DCC) mode observed in the drywell-wetwell suppression pool (PPOOLEX) experiments of Lappeenranta University of Technology. A pattern recognition algorithm was employed to determine the bubble volume and the chugging frequency during the test. The numerical simulations were performed by using Eulerian-Eulerian two-fluid approach of the compressible flow NEPTUNE_CFD software and the OpenFOAM CFD code. The interfacial heat transfer between steam and water was modeled by using three DCC models. Flow turbulence was solved by employing two k-ε turbulence models. The significance of interfacial area modeling on the chugging DCC was tested by implementing Rayleigh-Taylor Interfacial area model. The performance of different DCC models, the effects of turbulence modeling and interfacial area modeling are presented. The sensitivity of chugging DCC to the initial conditions and to the modeled domain, and the effect of interfacial momentum transfer closure modeling on the chugging are briefly discussed. The choice of DCC model, accuracy of interfacial area modeling and the magnitude of liquid turbulence near the interface are all needed to replicate chugging in a drywell-wetwell suppression pool system. In coarse grid case, the DCC model of Coste 2004 with the Rayleigh-Taylor interface instability model of Pellegrini et al. (2015) provided best results.