流激超疏水表面振动与凝结液滴运动耦合强化传热机理研究

Main power system (nuclear power, steam power) is the key part of warship and submarine. Vapor condensation is a necessary part during their working process, and super-hydrophobic surface is expected to achieve dropwise condensation which improves condensation heat transfer efficiency by an order of magnitude. The droplets produced on tube surface due to condensation cause flow distortion while inspiring tube vibration, and coupling happens between the vibration and condensation droplets. Solving this problem using traditional single method of micro or macro is difficult because of the multi-scale and strong nonlinear coupling of flow-induced vibration, buoyant effect, droplet internal circulation, phase-change heat transfer and droplet jumping under the effect of three-phase interface. A new multi-scale numerical method based on molecular dynamics and continuum mechanics will be developed in this project and verified by experimental study. Tube vibration and the dynamic behavior of droplets will be taken into account by a coupled method. Droplet dynamic characteristics and mechanisms of heat transfer enhancement on vibrating tube surface with super-hydrophobic properties are studied. The main contains of this research are followed: (1) Develop the multi-scale simulation approach for droplet motion with the effect of interfacial interaction; (2) Explore the movement of condensation droplets on super-hydrophobic surface and energy conversion and transmission mechanism; (3) Analysis of fluid flow and heat transfer model during dropwise condensation on vibrating tube surface; (4) Experimental study of dropwise condensation model on super-hydrophobic surface under vibration excitation.

核动力、蒸汽动力等主动力系统是舰艇的"心脏"。蒸汽凝结是其工作过程的必要环节，而超疏水表面有望实现珠状凝结，使效率提高一个量级。蒸汽流在管束表面凝结成液滴引起流场畸变，同时激励管束振动，管束振动与凝结液滴产生耦合效应。由于存在流激振动、浮升效应、液滴内部环流、相变传热、三相界面作用下液滴弹跳等多尺度、强非线性耦合作用。传统单一的微观或宏观方法在解决上述问题时存在巨大挑战。本项目拟结合分子动力学、连续介质力学方法，建立考虑管束振动与液滴动态行为耦合的多尺度数值模拟方法，并采用模型试验验证该方法。探索具有超疏水特性振动管束表面液滴动态行为与强化传热机理。主要研究内容：（1）建立考虑界面效应的液滴运动多尺度耦合模拟方法；（2）探索超疏水表面冷凝液滴运动规律以及液滴运动过程的能量转化和传递机制；（3）分析振动管束表面珠状凝结过程流动与传热模式；（4）振动激励下超疏水表面珠状凝结模型实验研究。

核动力、蒸汽动力等主动力系统是舰艇的“心脏”。蒸汽凝结是其工作过程的必要环节，而超疏水表面有望实现珠状凝结，使效率提高一个量级。蒸汽流在管束表面凝结成液滴引起流场畸变，同时激励管束振动，管束振动与凝结液滴产生耦合效应。由于存在流激振动、浮升效应、液滴内部环流、相变传热、三相界面作用下液滴弹跳等多尺度、强非线性耦合作用。传统单一的微观或宏观方法在解决上述问题时存在巨大挑战。本项目拟结合分子动力学、连续介质力学方法，建立考虑管束振动与液滴动态行为耦合的多尺度数值模拟方法，并采用模型试验验证该方法。本项目主要开展四项研究内容： 1、建立考虑界面效应的液滴运动多尺度耦合模拟方法； 2、 探索超疏水表面冷凝液滴运动规律以及液滴运动过程的能量转化和传递机制； 3、振动管束表面珠状凝结过程流动与传热模式分析； 4、振动激励下超疏水表面珠状凝结模型实验研究。提出了一套适用于蒸汽来流横略冷凝管束过程的汽液两相流动和凝结传热多尺度数值仿真方法，研究并探明流激管束振动、 超疏水效应和珠状凝结相互耦合作用下流动与强化传热模式；归纳总结出蒸汽物性参数和流动参数、 超疏水表面微纳米结构以及冷却管束结构参数和冷却液流动参数对流动和传热的影响规律。在项目组研究人员的共同努力下，完成了计划的研究内容，达到了预期的研究目标。