Pressure oscillation due to vapor condensation in subcooled water at large vapor mass flux

Pressure oscillations due to vapor condensation in subcooled water were investigated experimentally focused on the large vapor mass flux above 400kg/m2s. First of all, condensation behavior at large mass flux was classified into three patterns according to subcooling of pool water, such as Regime I: Core condensation, Regime II: Condensation with bubble separation, and Regime III: Vapor penetration. The condensation behavior in Regime I is characterized by the unstable oscillation of bubble at the pipe exit, and the pressure oscillation frequency in closely related to the bubble oscillation frequency. The condensation behavior in Regime II is characterized by the separation of bubbles from the core bubble and the pressure transient is related to the collapse of the separated bubble. The very high pressure pulse was observed at the collapse of the separated bubble. (author)