Based on the actual operating process of the steam generator in Daya Bay Nuclear Power Plant

a transient simulation of load down from 100% to 50% operating condition was carried out by utilizing the CFD technologies to reveal the dynamic variation rule of steam generator heat-transfer characteristics in the load down process.The simulation results show that fluid thermal parameters of the primary and secondary sides decrease over time in the load down process.With the decrease of heat transfer intensity

the perturbation impact of tube support plates(TSPs)on steam quality

fluid velocity

and surface heat transfer coefficient in the secondary side decrease gradually.Corresponding to the operating condition of 100%

70% and 50%

the fluid temperature of primary outlet is 297.2

295.6 and 294.8℃ and the steam quality at the outlet of secondary outlet is 24.5%

16.7% and 12.1%

respectively

which are in consistent with actual operating parameters of steam generator in Daya Bay Nuclear Power Plant.These results can provide theoretical support to the safe operation and optimization design of steam generator.