Computational investigation on dynamic response of supercritical natural circulation loop under rolling motion condition

Abstract

Abstract This study examines the performance of a supercritical natural circulation loop (sNCL) under rolling motion using a one-dimensional transient numerical model. Heating powers of 1000, 1250 and 1500 W are analyzed with rolling amplitudes of 5% and 15% relative to gravitational acceleration (g), and periods ranging from 4 s to 75 s. At 1000 W, the system maintains dynamic steady-state. However, at 1500 W, when the rolling frequency (0.196 Hz) matches the system’s natural frequency, large oscillations and flow reversal occur. Heater outlet temperatures fluctuate near the pseudocritical point (307.8 K), affecting buoyancy and friction forces. For the operating conditions investigated in the present study, the buoyancy parameter was observed to vary approximately between 2570 and 3100. A 4 s rolling period at 15% amplitude leads to flow reversal within 20 s, whereas longer periods (75 s) stabilize the loop. The findings highlight the importance of accounting for rolling-induced instabilities in marine sNCL applications, providing preliminary physical insights relevant to sNCL operation under dynamic gravity environments.