Abstract:

Based on the flash evaporation theory of a liquid droplet under low pressure, a visual vacuum flash evaporation device was designed for experiment of a suspension droplet. The experiment was performed to investigate the depressurized flash evaporation characteristics of ethanol solution droplets with the mass fraction of 0, 5%, 10% and 20%, and record the nucleation crystallization process. The liquid droplet went through five morphological changes, respectively:liquid evaporation process, evaporation with bubble growth process, steady evaporation ice process, ice formation with bubble growth process and external ice and internal bubbles escape eventually burst under depressurization. The research showed that the higher the ethanol solution concentration was, the lower the droplets freezing point and the longer the droplet freezing time were. Moreover, it was also found that the ethanol solution in some concentration could increase the pressure of flash chamber when the droplets crystallized and reduced the vacuum requirements of the system.

Key words: solution, evaporation, crystallization, concentration, vacuum degree

摘要：

基于液滴低压闪蒸理论，设计了一套悬垂液滴的真空闪蒸可视化实验装置，研究了质量分数为0、5%、10%、20%的乙醇溶液液滴的降压闪蒸特性，记录了液滴的成核结晶过程。液滴在降压条件下会经历液态蒸发、伴随气泡生长的蒸发、稳态蒸发结冰、伴随气泡生长的结冰、外部结冰内部气泡逸出最终爆裂5种形态。研究表明乙醇溶液的浓度越高，液滴的凝固点越低，液滴结晶所需时间越长；同时还发现一定浓度的乙醇溶液可以提高液滴结晶时的闪蒸室压力，降低了对系统真空度的要求。

关键词: 溶液, 蒸发, 结晶, 浓度, 真空度