Analysis of Flow Excursion Instabilities in Helically Coiled Tube Steam Generator of High Temperature Gas-Cooled Reactor

Flow excursion in helically coiled tube steam generator of high temperature gas-cooled reactor（SG） was analyzed by numerical simulation based on a one-dimensional model.Drift-flux model for the water/steam side and compressible flow model for helium side were used.Results of dynamical simulation show that flow excursion may occur under certain conditions,which results in remarkable differences of mass flow rate and temperature between the parallel tubes.The analysis of pressure-drop versus mass flow rate curve reveals that power input is the main parameter that affects the onset of flow excursion.With the increasing of power input,flow excursion occurs at larger range of mass flow rate.To increase the inlet resistance and sub-cool degree is helpful to avoid the onset of flow excursion.Stability maps were also presented.