Heat transfer assessment of the COSMEA facility cooling side

Reliable performance of passive safety systems – which function using natural physics laws such as density difference without external interventions during an accident- is an important issue with respect to nuclear power plant (NPP) safety. Investigation of thermal behavior and the operational stability of passive safety systems in Generation III and III+ nuclear reactors is the objective of the German project PANAS (PAssive Nachzerfallswärme-AbfuhrSysteme – Passive Residual Heat Removal System) funded by the German Federal Ministry of Education and Research (BMBF). In this context, experiments are being performed in the high-pressure COSMEA test facility at HZDR (Helmholtz Zentrum Dresden Rossendorf) to assess the emergency condenser (EC) based on the KERENA boiling water reactor. The objective of the presented work is to complement previous efforts related to the primary side heat transfer coefficient with the focus on heat transfer assessment of the secondary side. The assessment of state-of-the-art heat transfer models has been presented, and it shows that they often fail to predict the heat transfer behavior of the secondary side in COSMEA test facility. Therefore, because of the system’s sensitive heat transfer behavior due to different factors such as mass flow rate, it is important to have an accurate determination of heat transfer performance in the system. In this regard, a 3D CFD simulation of the COSMEA secondary side by ANSYS CFX has been proposed to show the flow pattern, temperature gradient and heat transfer performance of the system. The COSMEA experiments serve as validation basis for the CFD simulation.