Simulation of Operation Characteristics of Helical Coiled Once-Through Steam Generator in Start-Up Stage

Helical coiled once-through steam generator (HOTSG) has advantages of compact structure and high heat transfer efficiency, which is widely used in the design of advanced small reactor. During the start-up stage, the water inside HOTSG would change from subcooling state to two-phase state, and further be heated to superheated state. Thus, the phase change process in start-up stage is easy to induce flow instability and lead to the helical tubes burning dry, even threaten the safe operation. Several start-up schemes was proposed in this study and analyzed with self-developed code WISTARIA. The variations of flow rate and pressure were analyzed, which were employed to evaluate the system stability. The results shows that by reasonably controlling the changes of key operating parameters, such as flow rate and pressure, it can quickly pass through the unstable two-phase region and reduce the fluctuation of flow rate, which provides guidance for the design and operation of HOTSG start-up stage.