Theoretical and experimental study on single-phase natural circulation under inclined conditions

The natural circulation reactor is widely used in marine environments where thermo-hydraulic performance is heavily affected by the heaving, pitching, and inclining of a ship. This paper theoretically and experimentally investigated steady-state single-phase natural circulation under inclined conditions. Results showed that energy transported by natural circulation was proportional to 1.5times the power of the temperature difference between the hot leg and the cold leg. Furthermore, a parameter, k, was presented that revealed the comprehensive influence of working fluid properties, resistance characteristics, gravity fields, and loop configurations. k was treated as the criterion for the circulation ability of a loop and it also acted as the basis for evaluating and optimizing different designs. Analysis under the guidance of k was confirmed by a series of experiments performed on a symmetrical two-circuit loop. Both theoretical and experimental results showed that the inclination restrained overall circulation due to the decrease in average altitude difference between the steam generators and the electric heater. The disparity in branch circulations increased with the increase in the inclined angle. A loop design consisting of a large altitude difference and a small width was preferable to confine the influence of inclination. However, if the loop width was too small, it caused a severe reduction in the circulation ability for large angle inclinations.