Frequency analysis of chugging condensation in pressure suppression pool system with pattern recognition
Hujala, Elina; Tanskanen, Vesa; Hyvärinen, Juhani (2018-12-01)
Post-print / Final draft
Nuclear Engineering and Design
School of Energy Systems
© 2018 Elsevier B.V.
In this work, the formation and collapse of the steam bubbles in chugging condensation mode are evaluated by using the pattern recognition algorithm. The pattern recognition algorithm is based on video material recorded during the direct contact condensation experiment DCC-05 of the PPOOLEX test facility. The formation speed, the shape and size of the steam bubbles and the acceleration of collapsing bubbles are estimated with the algorithm. Fast Fourier transform (FFT) is used for frequency analysis of the pattern recognized data. The frequencies found are compared to the frequency data of the pressure transducers collected during the experiment and to the previous results of the NEPTUNE_CFD simulations of the same experiment.
The frequency analysis shows that the chugging frequencies of the steam bubbles range from 1 to 3 Hz, as predicted. Also the natural frequencies of the bubbles are visible around 53 Hz. Another frequency spike was observed close to the 125 Hz. This frequency is close to the mechanical resonance frequencies of the suppression pool and the blowdown pipe. Because of neither the pressure suppression pool nor the blowdown pipe are visible to the pattern recognition, the spike of the higher frequencies is most likely from the interfacial area of the bubble which resonates with the suppression pool system, affecting rapid condensation at a certain point.
Hujala E., Tanskanen V., Hyvärinen J. (2018). Frequency analysis of chugging condensation in pressure suppression pool system with pattern recognition. Nuclear Engineering and Design, Vol. 339. Pp. 244-252. DOI: 10.1016/j.nucengdes.2018.09.018
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