CFD investigating the impacts of changing operating conditions on the thermal-hydraulic characteristics in a steam generator

A three-dimensional computational fluid dynamics (CFD) boiling model is proposed in this paper to investigate the impacts of changing operating conditions on the thermal-hydraulic characteristics in the secondary side of steam generator (SG). This model encompasses the mass, momentum, energy equations, turbulent models, and property variation model for the two-phase mixture. The changes of SG operating conditions selected in current works mainly include the decrease of inlet temperature and the increase of inlet flowrate, respectively. Based on the simulation results, the local velocity, temperature, enthalpy, and void fraction distributions, etc in the SG secondary side can be reasonably captured. With these localized thermal-hydraulic distributions, the fluid energies across the SG tubes of U-bend region can be also obtained, which are strongly associated with the fluid-induced vibration (FIV) damage. Comparisons of these key parameters between different conditions can clearly demonstrate the impacts of changing SG operation conditions. Therefore, this CFD boiling model can provide the useful information for the plant staff to take the appropriate actions for the alleviation of SG tube degradation or elevation of the operating power.