Abstract: The study on evaporation processes of brine solution at reducing pressure mainly concentrates on falling film evaporation in the sea-water desalination and flat surface evaporation in industrial processes.In this study, the phase change of droplets was investigated.Various factors influencing the temperature of multicomponent droplet were examined experimentally, with brine solutions of 15% and 6% as working medium, initial environmental pressure of 94.5—97 kPa and final pressure of 50—3000 Pa, initial droplet temperature of 7—30℃, and initial diameter of 1—3 mm.The experimental data show that with the change of central temperature of salt water droplets at reducing pressure, the process can be divided to that with salting and without salting.As the water evaporates, reaching droplet density of 22.4% and temperatures low enough, the salt precipitated, otherwise the salting would not appear.At different concentrations, final pressures, initial temperatures and sizes, the relationship between the temperature change in the phase change of droplet and the environmental pressure was obtained.

Key words: depressurized evaporation, droplet, crystallization

摘要： 盐水溶液在降压环境下的蒸发过程的研究,主要集中在海水淡化领域的降膜蒸发过程应用方面和工业制盐方面的平坦表面的蒸发过程的研究。而本文主要集中研究各种实验因素对于液滴温度变化的影响。对于多组分液滴降压环境下相变过程的研究,实验采用浓度为15%和6%的盐水溶液作为一组比较工质,在初始环境压力为94.5～97 kPa,最终环境压力范围为50～3000 Pa,液滴的初始温度范围为7～30℃,初始直径范围为1～3 mm的条件下进行实验。通过实验数据分析可知:盐水液滴在降压蒸发过程中的中心温度变化有析盐和不析盐两种现象,随着水分不断地蒸发,当液滴浓度达到22.4%而且温度足够低时就会析出盐分,否则,不会出现析盐现象;同时分析不同浓度、不同最终环境压力、不同初始温度和不同初始直径对液滴相变过程和温度变化的影响,并且观察环境压力降低和液滴温度变化之间的关系。

关键词: 降压蒸发, 液滴, 盐析