DYNAMIC BEHAVIOR OF NATURAL-CIRCULATION STEAM-GENERATORS

The article includes methods for the numerical simulation of instationary operational conditions of natural-circulation steam generators. Mathematical models am presented for the description of the dynamic behaviour of the drum, or the distributor and the collector, respectively, and of the non-adiabatic pipe flow. The numerical handling of the pipe flow, leading to a system of partial differential equations, is carried out by the explicit ''up-wind '' method. The ordinary differential equations, describing the distributor and the drum, are discredited by an explicit differences methods. The result of the simulation of a warm start of a natural-circulation steam generator is discussed extensively.