Browsing by Author "Airaksinen, Robert"

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Harrastuksia tukevat robotit
(2016-04-23) Airaksinen, Robert
Insinööritieteiden korkeakoulu | Bachelor's thesis
Simulation of Marviken two-phase critical flow tests
(2021-06-14) Airaksinen, Robert
Insinööritieteiden korkeakoulu | Master's thesis
The aim of this thesis was to examine the recently updated critical flow calculation in the Apros program by comparing the predictions of different critical flow models to empirical data. A model of Marviken Critical Flow Test facility was created with the Apros program, and a total of 26 blowdown experiments were simulated. The tested nozzle geometries varied in diameter and length in range representative of the primary circuit of a typical water-cooled nuclear reactor. Moody and Henry-Fauske critical models with local average pressure and stagnation pressure were compared with experimental data. The Henry-Fauske model consistently predicted higher flow rates than the Moody model. Taking dynamic pressure into account also increased the estimated flow rates. Subcooled flow was more accurately predicted than saturated. The recommended values for grid density and time-step length were adequate and no significant increase in accuracy could be achieved by differing from them. Heat transfer between the fluids and the pressure vessel had no effect on the results. The results suggest Henry-Fauske model with stagnation pressure the recommendable option when underprediction must be strictly avoided. For best estimate calculation, the models of Henry-Fauske with static pressure and Moody with stagnation pressure seem more accurate.