CFD simulation and pattern recognition analysis of the chugging condensation regime

The chugging direct contact condensation mode in BWR suppression pools is challenging to be analysed either with experiments or numerical simulations. The POOLEX suppression pool test STB-28 of Lappeenranta University of Technology was simulated by using Eulerian-Eulerian 2D-axisymmetric approach of the compressible flow NEPTUNECFD software by applying the model of Hughes and Duffey (1991) for interfacial heat transfer between vapour and liquid. As the condensation rate could not be measured experimentally, a pattern recognition algorithm was employed in order to reveal information of the bubble size and the chugging frequency during the chugging condensation mode. With the help of that data it was possible to compare test and simulation results. The simulation results were promising; the bubble size and chugging frequency increased as the pool water heated up, and the results were in the correct range compared to the tests. Simulated chugging mimicked notably well the chugging observed in the tests. It would be possible to improve the accuracy of these results with modest efforts by employing multiple cameras in the tests and by conducting 3D simulations