60m3卧式液氮贮罐预冷过程试验

为进一步了解大型卧罐预冷过程，搭建了60 m3卧式液氮贮罐预冷试验台，对小流量下贮罐预冷过程的降温和罐体应变特性开展了研究。结果表明：预冷过程罐内气体温度首先整体迅速降低，然后缓慢下降，且呈现分层现象；预冷初期液氮在罐底难以积累；靠近底部的罐壁降温过程分为三个阶段，首先与低温氮气进行自然对流传热，温度缓慢下降，液位增长到相应高度后与液氮进行沸腾换热从而温度迅速下降，最后稳定在液氮温度；对于最终液位以上的罐壁，一直维持着平稳的降温速率；贮罐轴向应变全为负值，随着预冷过程进行轴向应变随之增大，与液氮接触的局部罐壁轴向应变会迅速增加。该项试验的成功进行有力地补充了国内大型卧罐预冷试验数据的空白，为低温贮罐可靠性及寿命预测等相关研究提供数据支撑。

Experimental on chilldown performance of 60 m3 horizontal storage tank with liquid nitrogen

In order to further understand the pre-cooling process of large horizontal storage tanks, an experimental setup was built to investigate the chilldown performance of 60 m3 horizontal storage tank with liquid nitrogen. Accordingly, the cooling and strain features during the chilldown process were studied. The results showed that the vapor temperature experienced overall sharp reduction and subsequent slow reduction. Moreover, thermal stratification occurred in the tank. In the preliminary stage, liquid nitrogen accumulated rarely in the bottom tank. The precooling process of the bottom tank wall could be classified into three stages, namely the mild decline of wall temperature by the cryogenic nitrogen vapor, sharp drop of wall temperature by the boiling heat transfer with liquid nitrogen when the liquid accumulated in the bottom, and the final unchanged temperature with the finish of chilldown. Meanwhile, the upper tank wall kept the mild precooling rate. Besides, the axial strain of tank wall increased with the ongoing pre-cooling. Moreover, a rapid increase of axial strain occurred at the wall in contact with liquid nitrogen. The success of this experiment strongly supplemented the blank of precooling data of large horizontal storage tanks in China and provided data support for related researches such as reliability and life prediction of cryogenic tanks.