Development of a model for thermal-hydraulic analysis of helically coiled tube once-through steam generator based on Modelica

Abstract

The Helically coiled tube Once-Through Steam Generator (H-OTSG) is a critical component for compact small reactors. The present study developed and verified a model in Modelica language and simulated steady-state and transient situations of the model. The Modelica model takes double-pipe heat exchanger as a prototype and adopts counter flow design. Different heat transfer correlations and pressure drop correlations for helically coiled tubes are reviewed and applied to the model. The model is verified by comparing the simulation results with the design parameters of the Marine Reactor X steam generator, and with the results performed by other dedicated programs. After verification, a 100 MW H-OTSG is proposed and steady-state conditions of the four main operating conditions, i.e. 100 MW, 75 MW, 50 MW, 25 MW, are simulated, and analyzed. Transient analysis is then performed in order to investigate the effects of different control strategies of the H-OTSG. The H-OTSG model developed with Modelica can be utilized for the safety analysis of small reactors in the future.