油面上相邻Leidenfrost液滴的相互作用及运动机制  

Interaction and motion of two neighboring Leidenfrost droplets on oil surface

作　　者：王浩[1] 徐进良[1,2] Wang Hao;Xu Jin-Liang(Beijing 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：《物理学报》2023年第5期226-237,共12页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:52130608,51821004)资助的课题。

摘　　要：热油面液滴蒸发是自然现象,已有研究侧重于单滴蒸发,对于热油面上多滴蒸发的认识较少.本文研究了热硅油面两个等直径FC-72液滴的Leidenfrost蒸发,油温为74.0—130.0℃,液滴初始直径为1.5 mm,采用红外热成像及高速摄影测量,发现热油面液滴蒸发存在非聚合、弹跳、分离3个阶段.本文理论分析了液滴在水平方向的受力,包括非均匀液滴温度产生的Marangoni力、重力水平分量、润滑推动力、黏性力.尺度分析表明Marangoni力和重力水平分量起关键作用,Marangoni力趋向于液滴分离,重力水平分量趋向于液滴聚合.在非聚合蒸发阶段,重力水平分量克服Marangoni力,但两液滴间存在气膜夹层,解释了两个液滴看似接触但不聚合的现象.随液滴尺寸减小,重力水平分量减小,不足以克服Marangoni力,这是导致蒸发后期两滴分离的主要原因.最后通过将模型得到的不同阶段间的转换时间同测量值进行对比,证实了上述解释.本文研究有助于理解复杂的Leidenfrost液滴动力学现象和机理.Evaporation of droplets on a hot oil surface is a natural phenomenon.However,most of existing studies focus on the evaporation of a single droplet,and the evaporation of multiple droplets is insufficiently understood.Here,we explore the Leidenfrost evaporation of two identical FC-72 droplets on the surface of a hot oil bath.The oil temperature ranges from 73.6 to 126.6 ℃,and the evaporation of droplets each with an initial diameter of 1.5 mm is recorded by an infrared thermographer and a high-speed camera.The shallow oil depth keeps the oil temperature uniform relatively in the slot compared with that in the deep liquid pool due to the larger ratio of the surface area for copper-oil contact to the slot volume.We find that the neighboring droplets evaporate in three stages:non-coalescing,bouncing,and separating.The radius of neighboring Leidenfrost droplets follows the power law R(t)~(1-t/τ)n,where τ is the characteristic droplet lifetime and n is an exponent factor.Moreover,the diffusion-mediated interaction between the neighboring droplets slows down the evaporation process compared with the action of isolated Leidenfrost droplet and leads to an asymmetric temperature field on the droplet surface,thereby breaking the balance of the forces acting on the droplets.A simple dual-droplet evaporation model is developed which considers four forces acting horizontally on the droplet,namely,the Marangoni force resulting from the non-uniform droplet temperature,the gravity component,the lubrication-propulsion force,and the viscous drag force.Scale analysis shows that the Marangoni force and gravity component dominate dual-droplet evaporation dynamics.In the non-coalescence stage,the gravity component induces the droplets to attract each other,while the vapor film trapped between droplets prevents them from directly contacting.When the droplets turn smaller,the gravity component is insufficient to overcome the Marangoni force.Hence,the droplets separate in the final evaporation stage.Finally,we conclude that the compet

关 键 词：Leidenfrost液滴 液滴动力学 蒸发 热量传递 

分 类 号：O552.6[理学—热学与物质分子运动论]