超疏水表面液滴蒸发内部流体流动与传热分析

摘要

基于椭球模型,模拟了超疏水表面上固着纯水液滴的蒸发过程,探究了蒸发过程中液滴外形、体积、接触角、表面温度和蒸发速率的变化,以及液滴内部温度和流线的分布情况.结果表明:液滴蒸发过程中,液滴顶部局部表面温度最大,接触线处最小,且随蒸发的进行表面温度逐渐减小.液滴体积演变行为区别于亲水表面,这表明基板特性影响了液滴蒸发机理.液滴蒸发初始时刻,全局蒸发速率最大,随蒸发的进行,全局蒸发速率逐渐减小.液滴表面温度分布不均匀使得液滴表面产生了张力梯度,张力梯度引起了液滴内部流体流动;近气液界面处流体由液滴顶部向下流动,液滴内部流体由下向上流动,形成了Marangoni流.流体流动伴随着热量的传递,导致接触线附近温度较低,液滴内部中心处温度较高.%The evaporation process of fixing purewater-droplet on superhydrophobic surface based on ellipsoidal cap geometry was simulated.The droplet shape,volume,contact angle,surface temperature,evaporation rate,the distribution of internal temperature and streamline were investigated.The results indicate that the local surface temperature is maximum at the drop's top and is minimum near the contact line,and decreases along the vaporwater interface in the process of droplet evaporation.The evolution of droplet volume is different from the droplets on the hydrophilic surface,indicating that the substrate characteristics influence the droplet evaporation mechanism.The global evaporation rate is maximum at the initial time of droplet evaporation and decreases with evaporating.The surface tension of the droplet is caused by the non-uniform temperature distribution on the droplet surface,which causes the fluid flow inside the droplet.The liquid near the vapor-water interface flows downward from the top of the droplet to the contact line,and the liquid at the inner of the drop flows upward.Marangoni motion occurs.The liquid is flowing with heat transfer,resulting in a lower temperature near the contact line and a higher temperature at the inner center of the droplet.