Experimental investigation on steam contact condensation in emergency makeup tank

Highlights: • Experiment was conducted to obtain the steam direct contact condensation characteristics in makeup tank. • Three types of spargers were designed and their performance were evaluated. • The heat transfer coefficients were obtained and the effects of spargers were studied. • The steam flow rate and pressure oscillations were analyzed in the experiment. • The spargers could enhance the safety performance of passive safety system in accident scenarios. The emergency makeup tank (EMT) is an important component of passive residual heat removal system (PRS) in Hualong Pressurized Reactor (HPR1000). However, the steam direct contact condensation (DCC) occurred in the EMT brings pressure and injection flow oscillation in station blackout scenarios, affecting the safety injection performance of EMT. Experimental facility was constructed to obtain the steam DCC characteristics under various initial and boundary conditions. The experimental phenomenon was observed and test data were obtained and analyzed. Three types of spargers were designed and installed to alleviate the pressure and flow rate oscillation in EMT. The test results reveal that spargers can significantly reduce the DCC duration and promote the water thermal stratification in EMT. The heat transfer coefficient of steam condensation substantially decreases after the spargers are installed. The steam flow rate and pressure oscillates vigorously at the early stage of the sparger-free experimental condition, and the oscillations are greatly reduced after the spargers are installed. In EMT drain experiment, the maximum steam flow rate and minimum pressure are reached simultaneously when the steam supply rate is balanced with the steam condensation rate. The drain of water begins at the start of the experiment while the liquid level in the EMT is not reduced due to the water supplement via rapid steam condensation. The EMT evacuation duration is significantly reduced when the spargers are installed, which could enhance the safety performance of passive safety system in accidental scenarios.