Dynamic Characterization of Supercritical Natural Circulation Loop under Periodic Excitation

Characterization of supercritical natural circulation loop under the influence of periodic power profile has not been explored in open literature, despite the promise of producing intriguing dynamics. Present study employs a one-dimensional numerical model to explore the transients on imposing a sinusoidal excitation on the heater power. The resultant dynamics are found to be strongly correlated with the heat transfer regime. The time period of excitation plays a more dominating role compared to the amplitude in deciding the characteristics. System attains dynamic steady-state and persists with a periodic profile at both low and high power levels. But introduction of natural frequency emanates into flow reversal at power levels within the transition regime. Chaotic oscillations can be identified for an intermediate band of imposed frequency, transforming to bidirectional pulsing at higher time periods. Frequency locking within the chaotic zone and frequency pushing for double-periodic nature is also identified, and the appearance of chaos is substantiated using the Poincaré map.