盐水溶液液滴真空闪蒸特性实验研究

Experimental Study on Flash Evaporation Characteristics of Saline Droplet in Vacuum

针对盐水(Na Cl)溶液液滴真空环境下的闪蒸过程进行实验研究,获得了不同浓度下盐水液滴的形态及温度变化特征。结果表明:由于盐水液滴浓度和真空压力的影响,其真空闪蒸过程较纯水液滴更为复杂;盐水液滴在真空环境中会经历五种典型形态:稳态蒸发,气泡生长-蒸发,稳态蒸发-凝固,气泡生长-凝固,析盐。当盐水浓度达到共晶浓度22.4%时,会发生析盐现象;盐水浓度较低(<5%)时,会发生凝固现象。盐水液滴析盐过程较凝固过程持续时间长,且会持续放出热量,将液滴加热至较高温度。多次实验对比发现,最终环境压力较低(pa<1000 Pa)且液滴初始温度较高时,析盐过程明显且迅速。

Flash evaporation of saline（ aqueous NaCl solution） droplet in vacuum was experimentally studied with the lab-built test platform. The influence of the pressure,NaCl concentration and initial temperature on the flash-evaporation behavior and phase transition of the droplets was investigated. The results show that the pressure,NaCl-concentration and initial temperature of saline droplet all had a major impact. To be specific,depending on the NaCl-concentration and pressure,the vacuum flash evaporation of saline-droplet,much more complicated than that of water-droplet,displayed five distinctive phenomena,including the steady water-evaporation,bubble growth-evaporation,steady evaporation-solidification; bubble growth-solidification and salt precipitation. At the eutectic concentration（ 22. 4%）,NaCl precipitation occurred,lasting longer than solidification and continuously releasing some heat; whereas at the brine concentration（〈 5%）,droplet solidification happened. Salt can be much more rapidly extracted from saline droplets at a higher initial temperature and a lower pressure（ 〈1000 Pa）.