Experimental and numerical study on fluctuations and distributions of fluid temperature under rolling motion conditions

Highlights: •The waveform of the fluid temperature deviates from sine curve and is complex. •The outlet temperature fluctuation depends on the flow rate fluctuation. •The in-house code can simulate the temperature fluctuation correctly. •The temperature fluctuation amplitude in heated zone increases along flow direction. •The temperature distribution in heated zone is roughly linear if no reverse flow. -- Abstract: An experimental and numerical study is conducted on a narrow rectangular channel of a loop under natural circulation conditions with rolling motion to investigate temperature fluctuations and mechanisms that influence such fluctuations. Meanwhile, the temperature distribution along the channel under rolling motion conditions is predicted based on a self-developed code. The results show that the cycle-averaged liquid temperature at the outlet of the test section under rolling motion conditions is higher than that under vertical conditions. The waveform of fluctuations in fluid temperature is complex and deviates from the standard sine curve, which is the law of the rolling platform. In the single-phase natural circulation loop, temperature fluctuations at the outlet of the test section are spurred from flow rate fluctuations caused by rolling motion in a dominant manner. Instantaneous temperature fluctuations are successfully predicted from the self-developed code for the single-phase natural circulation loop of a heated narrow rectangular channel under rolling motion conditions. Under rolling motion and constant heat flux conditions, the amplitude of temperature fluctuations in the heated zone increases along the flow direction. Along the flow direction, phases of the temperature crest at different locations of the heated zone exhibit a lag effect. In the adiabatic section between the outlets of the heated zone and test section, the amplitude of temperature fluctuations decreases, and the waveform is smoothed along the flow direction. Moreover, the instantaneous temperature distribution in the heated zone is approximately linear along the flow direction when the flow rate remains positive during rolling motion.