Flow instability analysis of lead bismuth cooled helical coiled once-through steam generator

Flow instability of steam generator may lead to significant oscillations of flow rate and wall temperature, thereby affecting the safety and reliability of the system. In this work, flow instability of lead bismuth cooled helical coiled once-through steam generator (HCOTSG) is analyzed based on computational fluid dynamics (CFD) simulation, where the coupling heat transfer process on two sides of the HCOTSG is considered. The oscillation characteristics of parameters such as mass flow rate, heat flux and temperature in the lead bismuth cooled HCOTSG are evaluated. It is found that the divergent oscillation can cause the backflow of inlet mass flow rate. In the clear two-phase zone, there are obvious high-frequency oscillations. At the same time, the influence of tube side inlet temperature on flow stability is also investigated. The results reveal that the decrease of tube side inlet temperature can suppress the flow instability.