摘要
利用疏水/超疏水表面获得滴状冷凝进而提高冷凝器传热系数是目前冷凝器强化传热的重要方法。然而,由于冷凝形成的液滴呈黏性极强的Wenzel状态,在重力作用下很难脱落,使得冷凝传热性能尤其在低冷凝负荷时并不能得到显著提高。研究表明:对粗糙表面施加垂直振动,可观察到其表面上液滴浸润状态的转变。今利用聚二甲基硅氧烷(PDMS)为基底采用光刻技术制备了方柱状和方孔状粗糙表面,对振动作用下Wenzel状态液滴的浸润状态转变特性进行了对比研究。结果表明,在一定的频率和振幅下,微方柱状表面的Wenzel状态液滴可以发生向Cassie状态转变,而方孔状表面的液滴则依然保持Wenzel状态。分析认为,在振动作用下粗糙表面Wenzel液滴能否向Cassie状态转变和其表面微观几何结构密切相关,气液固界面三相接触线的连续性是影响液滴浸润状态转变的重要指标,结合表面物理化学和液滴动力学,建立了物理模型对该现象进行了分析。
Using hydrophobic or superhydrophobic surfaces for forming droplet condensation is an important approach to enhance heat transfer in condensers. However, the condensed droplets appearing on the rough surfaces are in Wenzel state. They can hardly be removed from the surfaces, which is detrimental to heat transfer, especially when the loading of a condenser is low. The transition between the Wenzel and Cassie wetting regimes has been previously observed for droplets on a superhydrophobic surface when the surface is vibrating vertically. In this work, the surfaces with square-post and square-pore were prepared respectively on the polydimethyl-siloxane （PDMS） substrate by using photolithography techniques. The wetting transition of the vibrated droplets on the surfaces was analyzed. The experimental results show that the Wenzel state droplets on the surface with square-post can change into Cassie state during vibration at certain frequencies. However, the Wenzel state droplets on the surface with square-pore can not change. The surface structure plays a very important role in the wetting transition of the vibrated droplets on the surface. The triple line is the key factor for the transition of wetting state of the droplets on the surface. Using physical chemistry theory of the surfaces on the surface, combining with the droplet dynamics, a model was proposed to explain the mechanism.
出处
《高校化学工程学报》
EI
CAS
CSCD
北大核心
2015年第1期58-63,共6页
Journal of Chemical Engineering of Chinese Universities
基金
国家自然科学基金(51176123)
上海市自然科学基金(11ZR1424800)
高等学校博士学科点专项科研基金资助课题(20103120120006)
关键词
粗糙表面
Wenzel状态
振动
浸润转变
rough surfaces
Wenzel state
vibration
transition of wetting status
作者简介
贾志海（1975-），男，河北唐山人，上海理工大学副教授，博士。通讯联系人：贾志海，E-mail：jzhihai@163．com
