乙醇水溶液单液滴碰撞热壁面的动态演化特性

乙醇添加剂能显著改变去离子水基液滴碰壁动态特性。本文设计并搭建了液滴碰壁动态演化及传热研究实验台，并就溶液表面张力、液滴韦伯数（We）、壁面温度等对液滴碰壁的特性影响进行了实验研究。结果表明乙醇添加剂能够有效增强液滴润湿特性，促进液滴的雾化和破碎现象，同时抑制液滴反弹能力。并且这一能力随着乙醇溶液浓度的增大而增强。润湿特性随着液滴We的增大呈现出先增强后发生反弹现象的趋势，乙醇添加剂能够有效地抑制这种反弹趋势，并使混合液滴继续发生铺展现象。壁面温度125℃时，当We由15增大到33时，水基液由铺展阶段过渡到反弹阶段，而添加乙醇使得液滴继续铺展，没有发生反弹现象。乙醇添加剂能够明显地提高液滴由铺展到反弹的临界转变温度（T_CHF），扩大液滴核态沸腾对应的温度区域，延迟液滴进入过渡沸腾阶段。

Dynamic evolution characteristics of an ethanol-water droplet on a heated surface

Ethanol additive can significantly change the dynamic impact characteristics of deionized water. An experimental system was established to study the dynamic evolution and heat transfer of an ethanol-water droplet impacting on a heated surface. The effects of solution surface tension, Weber number (We) and wall temperature etc. on the characteristics of droplet impinging on the wall were studied. The results showed that ethanol additive could effectively enhance the wettability of the liquid droplets, promote atomization and fragmentation, and inhibit the rebound ability. Meanwhile, this ability increased with the concentration of ethanl solution. With the increase of droplet Weber number, the wettability was strengthened first and then rebound. Ethanol additive could effectively inhibit the rebounding and make the mixture droplets spread continuously. At wall surface temperature of 125℃, the deionized water changed from spreading stage to rebounding when Weber number increased from 15 to 33. However, the introduced ethanol could make the mixture droplets spread continuously without rebounding. Ethanol additive could significantly increase the critical transition temperature (T_CHF) from spreading to rebound, expand the temperature region corresponding to the nucleate boiling, and delay the droplet to enter the transition boiling stage.