Numerical Simulation and Analysis of Condensation-Induced Water Hammer in Heat Exchangers for Residual Heat Removal System in Nuclear Power Plant

Abstract Condensation-induced water hammer can occur due to the sudden condensation of steam in pipelines, resulting in pressure surges that can damage the system components. The aim of the study is to investigate the potential occurrence of water hammer phenomena during the condensation process, which can lead to significant damage to the heat exchanger and surrounding components. We employed FLUENT to simulate an abnormal transient in the heat exchangers for waste heat discharge system using a hybrid heat transfer model. The development of this model takes into consideration the constraints of the Lee model and the hybrid heat transfer coefficient (HTC) model. The simulation results show that when the cooling water and hot steam come into direct contact and condensation occurrs, the liquid level in the pipe rises rapidly, leading to an unstable gas-liquid interface. A liquid bridging structure is formed near the pipe wall, which may induce slug flow and lead to gas pocket collapse water hammer, causing significant pressure fluctuations and posing a safety hazard to the stable operation of the system. Key water hammer parameters are also monitored in this study, providing theoretical guidance for engineering design and accident prevention.