D33.32.15 – CFD modelling of condensation in suppression pools; final report

Publication Details
Authors: Tanskanen Vesa, Hujala Elina, Puustinen Markku, Pyy Lauri, Telkkä Joonas
Publication year: 2016
Language: English
JUFO-Level of this publication: 0

In NURESAFE subtask 33.3, work was done to develop a more generally applicable and carefully validated condensation model for pressure suppression pool modelling by using CFD. The separated flow condensation models were used as a starting point as those produced previously promising results in direct steam blowdown into a water pool. These models were tested further by using the DCC-05-4 test results from the drywell-wetwell suppression pool facility PPOOLEX. Pattern recognition data was used as an indirect measurement of condensation rate in the chugging condensation mode.The simulations were done using the NEPUNE_CFD code. The 3D simulations of the system showed that chugging condensation mode cannot be initiated with the stratified flow condensation models tested. The drywell-wetwell system revealed stricter requirements for physical capabilities of condensation modelling. Although different interfacial drag models had significant effects on the results, the main reason for poor results was the interfacial area density modelling with the computational grid resolution used. Two optional ways to improve the DCC modelling in this case were proposed: 1) the usage of high resolution grids, and 2) a separate model for modelling the interfacial area increase under acceleration.The simulated sample with dense grid indicated clearly better chugging behavior than obtained with the coarser grids. As a drawback, such transient simulations were found numerically expensive even with the 2D model tested. To simulate chugging with coarser grids, a Rayleigh-Taylor Interfacial area model proposed by Pellegrini et al. (2015) was implemented to the NEPTUNE_CFD code and tested. With that model, chugging was reproduced in 2D simulations with some DCC heat transfer models. The chugging frequencies with these simulations were notably near the frequencies seen in the experiment. Further validation and development work is needed and it continues until and beyond the end of the NURESAFE project.

Last updated on 2017-22-03 at 13:23