Experimental study on flow and heat transfer of helically-coiled tube heat transfer components under ocean conditions

<bold>Background</bold>Under ocean conditions, additional force is introduced by the heaving, rolling or other complicated motions of nuclear power platform, which may generate additional flow while the fluid flows through heat exchange components. The nonlinear additional flow acts together with the flow of the working fluid itself, forming a more complex flow pattern that affects the flow and heat transfer characteristics of the heat exchange component.<bold>Purpose</bold>This study aims to investigate the flow and single-phase heat transfer characteristics of helical tube under ocean conditions.<bold>Methods</bold>Natural circulation experimental loop of flow and heat transfer characteristics in helical tube component was designed and built. An experiment on flow and heat transfer characteristics in helical tube under typical ocean conditions was conducted. Ocean conditions were simulated by a six-degree of freedom motion platformwith swing condition amplitude in the range of 5°~15° and period range of 6~14 s. During the experiment, the natural circulation process was established prior to the launch of motion platform, thereafter data was collected under steady sinusoidal motion conditions.<bold>Results</bold>Experimental results show that under rolling conditions, the natural circulation flow rate of the circuit and the pressure drop of the test section both fluctuates sinusoidally with motion conditions, and the fluctuation amplitude increases with the increase of swing angle and the decrease of period. Due to the different speed of pressure and response of flow rate, there is a certain phase difference between the flow rate and pressure drop fluctuations in the circuit. Under the experimental conditions, the phase difference between the flow rate and pressure drop is constant despite the rolling angle and period of motion. The turbulence of system parameters becomes weaker with the increase of motion amplitude and decrease of period. The friction pressure drop of the helical tube was modified based on the motion additional pressure drop data, and the friction resistance coefficient of the helical tube under rolling conditions slightly increased compared to static conditions. Wall temperature of helical tube and bulk temperature both fluctuates sinusoidally with rolling and pitching motions. The change in heat transfer characteristics of helical tube mainly depends on the change in inlet temperature of test section.<bold>Conclusions</bold>Results of this study demonstrate that the flow resistance coefficient of test section under ocean motions is slightly higher than that under static condition. The heat transfer coefficient under motion conditions is weaker than that under static condition, and there is a certain extreme value of wall temperature and bulk temperature during the transition process from static condition to steady motion.