快速降压下Tween20 液滴真空闪蒸特性

为探究闪蒸喷雾冷却的微观机理, 设计并搭建了液滴悬挂式真空闪蒸实验装置, 利用可视化窗口探究Tween20 液滴闪蒸过程中的闪蒸特性及气泡生长机理. 液滴在快速降压过程中形态会经历气泡成核、气泡生长、伴随气泡生长、爆裂这四个阶段的变化, 并反复循环这一过程直至液滴稳定蒸发. 对于液滴温度的变化, 闪蒸室的终态压力起到了决定性的作用, 并且其终态温度随压力的升高明显上升. 同时通过液滴闪蒸过程形态图分析发现, 液滴在剧烈爆炸阶段其温度也发生明显下降; 在稳定蒸发阶段, 其温度也将开始稳定不变. 因此可知液滴的剧烈爆炸会带走其自身的大量热量. 而 Tween20 浓度对液滴温度的影响微乎其微, 但其会使液滴内气泡的初始成核时间发生明显滞后, 并抑制液滴内的气泡发生破裂.

Flash Evaporation Characteristics of Tween20 Droplets during Quick Depressurization

In order to investigate the microscopic mechanism of flash spray cooling,a droplet-suspended vacuum flash evaporation experimental setup was designed and built to investigate the flash characteristics and bubble growth mechanism during the flash evaporation of Tween20 droplets using a visualization window.The droplet morphology undergoes four stages of rapid pressure drop,namely bubble nucleation,bubble growth,accompanying bubble growth and bursting,and the process is repeatedly cycled until the droplet evaporates stably.For droplet temperature changes,the final state pressure of the flash chamber plays a decisive role and its final state temperature rises significantly with increasing pressure.The morphological analysis of the droplet flashing process also shows that the temperature of the droplet drops significantly during the violent explosion phase;during the stable evaporation phase,the temperature will also start to stabilize.Therefore,it can be seen that the violent explosion of the droplet will take away a large amount of its own heat.The effect of Tween20 concentration on the temperature of the droplet is minimal,but it causes a significant lag in the initial nucleation time of the bubbles within the droplet and inhibits the rupture of the bubbles within the droplet.