低温液体BOG再液化系统压力及蒸发率试验研究

Experimental study on pressure and evaporation rate of cryogenic liquid boil-off gas re-liquefaction system

为研究低温液体吸热产生蒸发气(Boil-Off Gas,BOG)的动态过程,寻求合理调控低温液体压力和温度的方法,搭建了一套低温液体BOG再液化试验系统。以液氮为工质对120L高真空变密度多层绝热储罐进行了压力、温度及蒸发率测试试验,分析了以上参数与时间的变化规律,计算了储罐静态蒸发率与漏热量。结果表明:储罐压力随时间增加而逐渐上升,在480min之前压力上升速率较快,为10.9Pa/s,之后上升速率逐渐减小。从液相到气相的温度依次升高,液相内部的温度相差较小,约为1.2℃;随时间的增加,液相和气液分界面的温度逐渐升高,气相的温度逐渐降低,480min后达到相对稳定的状态。初始充装率为0.7时,自然蒸发的BOG流量随时间增加逐渐减小;经计算,储罐静态蒸发率为2.04%/d,漏热量为4.1W。试验结果为后续开展低温液体BOG再液化研究提供了相关依据。

In order to study the dynamic process of Boil-Off Gas(BOG） produced by decalescence of cryogenic liquid,and find the method of reasonably controlling pressure and temperature,a set of cryogenic liquid BOG re-liquefaction test system was established. Experiments on pressure,temperature and evaporation rate of a 120 L tank with the high vacuum variable density multilayer insulation(VD-MLI） were conducted with liquid nitrogen as working medium. Besides,the static evaporation rate and heat leak-rate of the tank were calculated. The following findings were obtained based on the experiments.（1）The tank pressure gradually increases with the storage time,and the rising rate is about 10. 9 Pa/s before 480 minutes,then gradually decreases..（2）The temperature increases from the liquid phase to the gas phase,the temperature inside the liquid phase difference is small,about 1. 2℃. The temperature of the liquid phase and the gas-liquid interface increases with the storage time,the temperature of the gas phase declines gradually,and reaches a relatively stable state after 480 minutes.（3）When the initial filling rate of the tank is 0. 7,the average flow rate declines with storage time. The static evaporation rate is 2. 04%/d and heat leak-rate is 4.1 W. The results provide a theoretical support for the subsequent research of cryogenic liquid BOG re-liquefaction.