Thermal-hydraulic characteristics of helical coiled once-through steam generators in inclining condition of ocean.

• A simulation code for the HCOTSG under appropriate inclination state is developed and verified; • The variation of the main parameters of the HCOTSG in IRIS reactor under different inclination state is investigated; • The influences of the input parameters perturbation on HCOTSG thermal–hydraulic Characteristics are analyzed; • The variations of thermal–hydraulic parameters under different input parameters perturbation in inclination state and vertical state are compared. This paper develops a one-dimensional thermal–hydraulic analysis program to simulate the main thermal–hydraulic parameter changes of helical coil once-through steam generator (HCOTSG) under inlet thermal–hydraulic parameters perturbation in inclining and vertical conditions. The inclining process is divided into the process of rotating from the vertical position to the inclining position and the stable inclining process. The rotating process is regarded as swaying motion. The swaying and inclining motions are achieved by modifying the momentum equation. What's more, the code was verified through experiments on two-phase heat transfer and friction pressure drop, as well as comparisons with the design parameters of the HCOTSG of the International Reactor Innovative and Secure (IRIS) reactor. The results of the simulation indicate that the direction of incline has an obvious impact on the safety of the HCOTSG, with inclination towards the y-axis having the greatest impact. In the stable inclining process, an increase in the angle of inclining results in a rise in primary-side outlet temperature and a reduction in heat transfer, while the secondary-side pressure drop increases. Furthermore, the HCOTSG underwent testing with eight types of transient perturbations, including four sudden perturbations and four linear perturbations. Results indicated that during sudden perturbations, apart from the secondary-side pressure drop, there were no substantial differences in simulated results between the inclined and vertical states at the same time during the transition process. However, during linear perturbations, due to the slow changes in parameters, the differences between the inclined and vertical states at the same time were more distinct. Regardless of the perturbation type, the inclined state led to a deterioration in the dynamic condition of the system compared to the vertical state. [ABSTRACT FROM AUTHOR]