摘要
利用真空闪蒸系统对乙酸液滴在真空环境下的过冷凝固过程进行了动态观测,建立了针对单个乙酸液滴在真空环境下过冷凝固过程的传热传质数学模型。模型考虑了液相和固相内的温度分布,引入过冷凝固的动力学条件以及表面升华的传质方程描述凝固界面与升华界面的运动。综合实验测量数据和模型计算结果,掌握了乙酸液滴在环境下过冷凝固过程中的温度变化,比较了乙酸液滴和纯水液滴过冷凝固过程中温度变化的特征,分析了环境压力对液滴温度变化的影响。结果显示:与纯水液滴相比,乙酸液滴具有更高的凝固平衡温度,在实验过程中更早开始凝固。由于乙酸凝固潜热较小,再辉阶段温度上升较为缓慢,凝固时间较短。环境压力越低,凝固过程中液滴过冷度越大,凝固速度越快,液滴最终温度越低。
The transfer of heat and mass in rapid solidification of subcooled acetic acid droplets in vacuum was empirically approximated,mathematically modeled,theoretically analyzed,numerically simulated and experimentally evaluated. The impact of the pressure and thermal properties of acetic acid on the temperature profile and the heat /mass transfer in the surface condensation and sublimation of the droplets was qualitatively investigated. The temperature of the droplets changed in a sequence of decrease→abrupt-increase→slow-decrease→fast-decrease→constant,showing the heat-absorption in the surface evaporation / sublimation and heat-release in the surface condensation,respectively. The calculated and measured results were in good agreement and the results show that the acetic acid droplet condensed easier than water because of its higher equilibrium condensation temperature,and it condensed in a shorter time due to its lower latent heat. We found that a lower pressure results in a faster surface condensation rate and a colder droplet.
出处
《真空科学与技术学报》
EI
CAS
CSCD
北大核心
2017年第2期119-124,共6页
Chinese Journal of Vacuum Science and Technology
基金
国家自然科学基金项目(51406055
51506053)
中央高校基本科研业务费专项资金资助项目(2014MS106
2014ZD34)
关键词
真空
乙酸
过冷凝固
传热传质
Vacuum
Acetic acid
Subcooled solidification
Heat and mass transfer
