Transient flow dynamics behaviors during quick shut-off of ball valves in liquid hydrogen pipelines and storage systems

The cryogenic nature of liquid hydrogen can lead to brittleness in materials, posing a significant risk of severe safety incidents due to liquid shock. In this study, the compressibility of liquid hydrogen and the rapid closing of the valve are described by user defined function (UDF) using Fluent software, and the reliability of the calculation simulation is verified based on the water hammer experiment and theoretical model. The results show that the rapid closure of a valve causes liquid hydrogen to generate a significant pressure change, leading to a swift drop of flow velocity in the liquid hydrogen pipeline. The pressure fluctuation amplitude near the valve is greater than the pressure fluctuation amplitude away from the valve, and the pattern for velocity is reversed. For valve closing time of tvalve is 0.84, 1.68, and 3.36 times of Tp, the maximum transient flow pressure in the pipe is 60.96 kPa, 48.49 kPa, and 39.06 kPa, respectively. The transient flow pressure is 2.4, 1.9, and 1.5 times for the inlet pressure at valve closing times of 0.01, 0.02, and 0.04 s, suggesting that the quicker the valve closes, the higher the maximum transient pressure in tubes. Furthermore, a new pressure fluctuation coefficient is introduced to describe the transient flow characteristics of the liquid hydrogen in the pipelines. The valve closing time is halved, and the pressure fluctuation coefficient doubles. The research results are expected to provide a technical basis for liquid hydrogen pipelines' design and vibration reduction.