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.