Effect of rolling motion and hole structure on flow and heat transfer characteristics of steam jet condensation through numerical simulation

In the pressure relief system of nuclear power plants, through multi-hole spargers, steam is blown off into subcooled water in the form of multi-hole steam jets. The flow pattern and heat transfer (HT) characteristics of multi-hole steam jets might differ greatly from single-hole steam jets, significantly affecting the system's performance. Thus, the transient flow pattern and HT characteristics of multi-hole steam jets were investigated, and how rolling motion affects the heat transfer characteristics was also investigated. Besides, forces acting on the steam volume were investigated for steam jets under different conditions, and the HT characteristics were explored from the perspective of force analysis. Compared with single-hole steam jets, the heat transfer coefficient (HTC) of multi-hole steam jets was significantly lowered, and the steam plume penetration length and phase interface area were much larger. Besides, the increase in hole number might advance the transition of the flow regime. Under rolling conditions, the HTC was larger but did not vary much with the rolling parameters. The dominant forces were different for different situations, and the weaker effect of rolling motion on steam jets in the condensation oscillation regime may result from smaller inertial force compared with steam jets in the chugging regime.