Direct contact condensation modeling in pressure suppression pool system

Pattern recognition algorithm for analysis of chugging direct contact condensation

“…14. The velocity and acceleration values are crucial when choosing nodalization resolution and interfacial area density models for Eulerian two-fluid CFD simulations of chugging cases (Patel et al, 2017). The commonly used interfacial area density calculated from the gradient of the void fraction yields effectively the minimum surface area allowed by the nodalization density (Pellegrini et al, 2015).…”

“…Interfacial details smaller than the node size are filtered out if no additional sub-grid scale interfacial area density models are included. Interfacial area increase due to interfacial instabilities can reach almost arbitralily high values, but a preliminary maximum for node size can be assumed to be at least less than the critical wave length for the Rayleigh-Taylor instability (Patel et al, 2017). However, better results can be obtained by decreasing node size further.…”

“…In such a case, the condensation mass flow rate is high, and it is possible that the pressure decrease within the lighter phase causes interfacial accelerations higher than the acceleration of gravity. Interfacial accelerations of order of 100-1000 m s −2 magnitude have been observed in suppression pool cases (Patel et al, 2017). Such high accelerations invoke interfacial instabilities, i.e., Rayleigh-Taylor (Strutt, 1883;Taylor, 1950), Kelvin-Helmholz (Drazin, 2002) and Richtmyer-Meshkov (Richtmyer, 1960;Meshkov, 1969;Brouillette, 2002) instability, which cause roughening of the steam-water interface.…”

“…As DCC has a major role in nuclear power plant safety, test facilitiessmall (Aya et al, 1980;Aya and Kobayashi, 1983;Aya and Nariai, 1987;Simpson and Chan, 1982;Gregu et al, 2017) and large (Motoaki Utamura and Uozumi, 1984;Kukita et al, 1984Kukita et al, , 1987Pellegrini et al, 2016) -have been used to study condensation modes. The experimental results have been used for improvement and validation of different condensation models of computational fluid dynamic (CFD) codes (Patel et al, 2017;Mimouni et al, 2011). Validation of CFD models for two-phase flows often requires measurement techniques that are currently not feasible (Bestion, 2014).…”

Frequency analysis of chugging condensation in pressure suppression pool system with pattern recognition

“…Already, even in the old experiments, movie cameras were used for visual observation, but the observation results were hardly published. At first, the data analysis concentrated for pressure data analysis, but the arrival of the CFD made possible to model the physical behavior of the condensation more accurately than with simplified analytical models (Lahey and Moody, 1993;Lahey, 2005) Different condensation modes have been modeled by using CFD (Patel et al, 2017;Mimouni et al, 2011). As the modeling of two-phase flows using CFD has challenges (Bestion, 2014), a new measurement methods for CFD model validation purposes has been put into operation.…”