热功转换实现冷态液滴驱动的实验研究  

Experimental investigation of droplet propulsion driven by thermal power conversion

作　　者：王超强 马骁婧 徐进良[1,2] WANG ChaoQiang;MA XiaoJing;XU JinLiang(Bejing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy,North China Electric Power University,Beijing 102206,China;Key Laboratory of Power Station Energy Transfer Conversion and System,Ministry of Education,North China Electric Power University,Beijing 102206,China)

机构地区：[1]华北电力大学低品位能源多相流与传热北京市重点实验室,北京102206 [2]华北电力大学电站能量传递转化与系统教育部重点实验室,北京102206

出　　处：《中国科学：技术科学》2024年第5期848-860,共13页Scientia Sinica(Technologica)

基　　金：国家自然科学基金(批准号:52206196);北京市自然科学基金(编号:3222045)资助项目。

摘　　要：液滴操控是微流控领域的关键技术.基于Leidenfrost效应驱动液滴实现热功转换的方式获得广泛关注,然而该方法基于高温环境,同时工质消耗较大,热功转换效率低.本文将部分沸腾传热面与超疏水表面相结合,利用冷态液滴和过热壁面之间部分沸腾产生的动力驱动液滴直线运动,实现低工质消耗与高热功转换效率.实验系统主要包含两个功能性表面:水平超疏水表面和竖直部分沸腾换热面,部分沸腾换热面布置在超疏水直通道的两侧.建立了随竖直换热面温度变化的液滴振荡运动分区图,在部分沸腾模式下,液滴撞击壁面实现热功转换并加速,同时液滴在两侧壁面之间振荡运动,其平均撞击频率达到8.3 Hz,平均运动速度达到156.2 mm/s.在原本平直的轨道上液滴出现了纵向振荡,其纵向偏移量的峰值随着液滴直径的减小表现出增加的趋势.该纵向运动由液滴发生接触沸腾产生的驱动力切向分量强化,在液滴重力作用下被抑制,二者的相对大小决定了液滴纵向振荡运动规律.本文提出了冷态液滴驱动新思路,有望在微流控等领域得到重要应用.Droplet manipulation plays an important role in the field of microfluidics.Droplet propulsion driven via the Leidenfrost effect has received widespread attention.However,this method requires ultrahigh temperatures,leading to the consumption of a large amount of the working medium and low thermal power conversion efficiency.In this study,the droplet was driven by the thrust force generated by explosive boiling between the cold droplet and superheated wall,which was achieved through the partial boiling of the heattransfer and superhydrophobic surfaces,to realize a low consumption of the working medium and high efficiency.The experimental system mainly consisted of two functional surfaces:A horizontal superhydrophobic surface and a vertical partial boiling heat-transfer surface.The partial boiling heat-transfer surface was arranged on both sides of the superhydrophobic straight channel.A regime map of the variation in the droplet oscillatory motion with the temperature of the vertical surface was established.In the partial boiling mode,the droplet was accelerated in one collision upon contact with the vertical surface.Moreover,the droplet oscillated between the two side surfaces,with an average impact frequency of 8.3 Hz,and the average motion speed reached 156.2 mm/s.The longitudinal motion of a droplet was observed on the straight orbit,and the peak values of its longitudinal offsets increased with decreasing droplet diameter.Gravity suppressed the droplet's longitudinal motion,while the tangential component of the thrust force promoted the droplet's longitudinal motion.The relative magnitude of the two forces determined the longitudinal oscillation dynamics of the droplet.Overall,this paper proposes a novel idea of cold droplet propulsion,which has application potential in the field of microfluidics.

关 键 词：液滴驱动 传热模式 液滴动力学 热功转换 

分 类 号：TB306[一般工业技术—材料科学与工程]