Dynamic simulation of once-through steam generator with concentric annuli tube

Based on the conservation equations of mass, energy, and momentum, the mathematical model of once-through steam generator (OTSG) with concentric annuli tube is developed by moving boundary. The heat transfer section of OTSG is divided into three regions: subcooled, nucleate boiling and superheated regions. An effective heat transfer length concept is used in superheated region. The stable and dynamic simulation equations are solved by Gear method. The stable results are validated by experimental data and the transient results are validated through code to code comparison using RELAP5 code as the basis. The results show that the developed model and code are accurate, effective and can be used to simulate the steam generator dynamics in real time.

► Moving boundary model can effectively simulate OTSG transient characteristics.
► The concept of effective heat transfer length is introduced.
► The calculation speed of this code is fast enough for real time simulations.