氦冷却法制备氮浆中液滴凝固过程的模拟与分析

Numerical analysis on droplets solidification in slush nitrogen preparation by method of helium cooling

采用氦冷却法制备氮浆的工艺所制氮浆颗粒尺寸均匀,制备过程中杜瓦内可维持正压,从而防止周围空气的漏入。通过对氦冷却法制备氮浆过程中液滴凝固时固氮颗粒的形成过程进行分析,建立起相应的物理模型以及微分方程,并对微分方程进行数值求解。着重考察了液滴的凝固过程,并对液滴群完全凝固时的氦气温度、压力、流速以及扩散腔长度进行了研究,进而探讨了采用该方法制备氮浆时氦气工作参数、喷管尺寸以及扩散腔长度等的选择问题。

Slush nitrogen produced by helium cooling method can have the particles with more uniform size. During the production process, the pressure in vessel can be maintained higher than the atmospheric pressure so as to prevent the air intruding to the vessel. Upon analyzing the process of droplet solidification during the slush nitrogen produced by helium cooling method, a physical model and the corresponding dif- ferential equations have been established. From these equations, the process of droplets solidification and the conditions of helium temperature, pressure and flow rate and length of diffusion cavity for producing completely solidified droplets are investigated and analyzed. The selection principle for the operating condi- tions of helium, the size of nozzle, and the length of diffusion cavity were then discussed.