Experimental study on natural circulation flow fluctuation characteristics in tube bundle channels under marine conditions

Abstract

Natural circulation steam generators are of most importance for floating nuclear power plants and nuclear propulsion systems. Marine U-tube steam generators have the characteristics of natural circulation with free liquid surface, and lateral non-uniform heating, coupled with ocean motion, making the flow behavior extremely complex. Therefore, the paper built an experimental platform for natural circulation flow in tube bundle channels with the ability of non-uniform heating under marine conditions, conducting a series of experiments to study the effects of inclination, rolling motion, non-uniform heating, and the above-coupled action on flow fluctuation behavior of natural circulation. The experimental results indicate that rolling motion can cause periodic fluctuations in the natural circulation flow rate, but there are two peaks of the flow rate during one rolling period, which is caused by the periodic aggregation and discharge of bubbles. The increase in heat flux can increase the number of bubbles, making them more susceptible to rolling motion, and it can also increase the steam flow rate, resulting in a more stable flow. The fluctuation of the flow rate increases with the increase of rolling amplitude and frequency, and it is more sensitive to variations in rolling amplitude. The introduction of non-uniform heating results in a significant difference in the two peaks of flow rate during one rolling cycle, thereby exacerbating the degree of flow fluctuations under rolling motion.