盐水溶液液滴真空闪蒸特性实验研究

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 (p_a<1000 Pa) 且液滴初始温度较高时, 析盐过程明显且迅速。

Experimental Study on Flash Evaporation Characteristics of Saline Droplet in Vacuum

Flash evaporation of saline (aqueous Na Cl solution) droplet in vacuum was experimentally studied with the lab-built test platform.The influence of the pressure, Na Cl concentration and initial temperature on the flash-evaporation behavior and phase transition of the droplets was investigated.The results show that the pressure, Na Cl-concentration and initial temperature of saline droplet all had a major impact.To be specific, depending on the Na Cl-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%), Na Cl 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).