Numerical simulation of condensate-induced water hammer with dynamic valve control using an advanced phase change model

This paper centers on the intricate phenomenon of water hammer observed in steam pipelines during nuclear power plant diagnostics. Utilizing computational fluid dynamics (CFD), the paper simulates the transient response of condensate-induced water hammer (CIWH) behavior. A sophisticated phase transition model is applied with the goal of precisely delineating the phase change process and its subsequent impact on system dynamics. For purposes of investigating the influence of atmospheric vent valves on CIWH, the study introduces a resistance term in the simulation model to embody the dynamic valve control, thereby comprehensively examining its interplay with CIWH phenomena. The correspondence between simulation findings and actual steam pipeline operations is carefully compared for verification. Moreover, this paper explores the influence of key parameters on CIWH and evaluates the strength of CIWH by using Froude (Fr) and modified Jakob (Ja) numbers. Within a certain range, it is found that smaller Fr and Ja result in segmental plug flow in the tube and the strength of CIWH increases with increasing Fr and Ja. However, larger Fr and Ja cause the flow pattern in the tube to change and the intensity of CIWH also changes. We have analyzed in depth the effect of different thermodynamic parameters on the mass transfer rate during CIWH and made an assessment in conjunction with the dynamics of the valves. Ultimately, the numerical simulation method established in this paper effectively reproduces the process of complex water hammer and lays the foundation for subsequent model optimization and triggering mechanism studies.