Thermal-hydraulic Simulation Of Once-through Steam Generator

The Once-through steam generator (OTSG) is one of the most important unit of the nuclear power unit. Whether the OTSG can run safely and normally or not plays a significant role in the safety and economy of nuclear power equipment.The steady-state and dynamic thermal-hydraulic mathematical model for the OTSG are developed, the simulation code is programmed and compiled at the same time. The homogeneous model is employed in the modeling process; five regions along the heat transfer tube are divided according to the different heat transfer mechanism in different point, they are convective heat transfer to liquid region, subcooled boiling region, saturated nucleate boiling and convective heat transfer through liquid film region, liquid deficient region, convective heat transfer to vapor region. As to the numerical calculation method, the fully implicit method is adopted to solving the thermal-hydraulic equation. Meanwhile, in order to make the solving process has good stability, the under-relaxation process is adopted. There are two meshing methods introduced in the paper, i.e. uniform meshing and non-uniform meshing,which both can meet the computational accuracy well, while the latter reduce the computing time consumption. As to the transient model, the disturbance simulation as well as the start-up and shut-down procedure to the once-through steam generator are primary studied.The steady-state simulation and the disturbance simulation results tallies well with the results published in literature. The result of start-up and shut-down procedure conform to the theory of two-phase flow and boiling heat transfer through the quantity analysis.The simulation model developed in the paper has good portability, can be applicable to study the thermal-hydraulics of helical-coiled once-through steam generator in nuclear power plant.