用于沸腾传热关键过程协同优化的仿生超浸润多尺度界面研究

Continuous and rapid renewal of phase-change bubbles is considered as a fundamental strategy to enhance boiling heat transfer efficiency, regarding the key processes of vapors’ nucleation, growth, and departure. Boiling enhancement based on micro-/nanoscale surfaces has attracted so much attention; however, the complexity of structures and chemical components limits the further discovery on its intrinsic scientific laws. Bio-inspired multi-scale super-wetting surfaces that always consider not only structures but also components bring a new insight to study the nucleation, growth, and departure of boiling phase-change vapors; so far, few works focus on the co-optimization of key processes during boiling heat transfer through manipulating multi-scale structures and tuning super-wettability. Herein, I propose to study on bio-inspired multi-scale super-wetting surfaces toward co-optimization of the key processes during boiling heat transfer. Laser direct-writing technology is applied to fabricate a series of multi-scale (micro-, submicro-, and nano-) structures onto various metal surfaces (stainless steel, aluminum, copper, etc.). Atomic layer deposition is used to provide different confined controls of chemical components. Micro-sized high-speed camera plays an important role for in situ monitoring the boiling bubbles’ motion on the heat transfer surfaces. By deep exploring the co-operative controlling laws of key processes during boiling heat transfer based on complex multi-scale structures as well as surfaces’ wetting features, final aim of this project is to develop a new high-efficient boiling-enhanced functional surfaces for responding to the urgent demands of our country's energy saving and emission reduction strategy.

促进相变气泡持续、快速更新是提高沸腾传热效率的主要手段，涉及沸腾蒸汽的成核、生长与脱离等关键过程。微/纳米多尺度界面强化沸腾备受关注，但结构和化学组成的复杂性制约了对其内在作用机制的探讨。仿生超浸润界面研究兼顾结构与组成的特点为考察沸腾相变蒸汽的成核、生长与脱离等行为提供了新思路，目前，通过多尺度结构的精密制备和超浸润性质的可控调节来协同优化沸腾传热关键过程鲜有报道。本项目拟开展用于沸腾传热关键过程协同优化的仿生超浸润多尺度界面研究，通过激光直写技术在不锈钢、铝、铜等金属表面刻蚀一系列具有微米、亚微米、纳米等特征的多尺度结构，采用原子层沉积方法限域调控其化学组成，依靠微区高速摄像实时监测气泡运动；深度解析复杂多尺度结构和界面超浸润性质对沸腾传热关键过程的协同调控规律，从而指导开发新型高效的强化沸腾功能界面，以服务国家节能减排战略的迫切需求。

实施表面工程强化沸腾传热长期以来备受研究者关注，但结构和化学组成的复杂性制约了对其微观作用机制的探讨，涉及相变气泡成核、生长与脱离等关键过程。为此，本项目利用纳秒脉冲激光加工技术在铜表面构筑了由微米凹槽-微米乳突-纳米褶皱组成的周期性阵列结构，并在氟化液（C6H5F9O）中获得了长效稳定的超亲液/超疏气性质，实现了液体动态超铺展（时间小于134.1ms）和超低液下气泡黏附力（1.3μN）。在上述体系发现了独特的“射流沸腾”现象——相变气泡以条带状束流高速喷射，能够极大程度限制气泡之间的并聚，这在以往二维平面强化沸腾研究中鲜有报道。进一步，通过原位红外、高速摄像和理论计算深入剖析了射流沸腾的微观形成机制以及相变气泡的成核、生长与脱离规律，阐明了超铺展液体持续重复浸润纳米褶皱形成动态气膜是促进界面液-气更新的关键。协同调控液体动态铺展和液下气泡脱离的动力学优化了射流沸腾结构参数，显著增强了沸腾传热性能，可将C6H5F9O临界热流密度（CHF）提升至42.6W/cm2，热传递系数（HTC）增加到72.9kW/(m2·℃)，较之平滑表面增幅分别为80%和608%；且起始过热温度更低，仅1.5℃，降幅达84%，能实现在低过热温差下的高效沸腾传热。该优选结构可直接拓展至浸没式相变冷却用强化沸腾散热板表面，在超级计算整机系统中进行了性能实测，与现有商用强化沸腾技术相比，射流沸腾强化CPU芯片在320W高功耗场景下工作温度降低2.7℃，波动范围由从±4.3℃缩窄至±1.0℃。由此形成了射流强化沸腾技术工艺包，完成了成果转化，相关液冷服务器已布局至国内多家超算数据中心，实现了国际领先的超低系统能源效率PUE<1.04。综上，本项目基于多尺度结构与界面浸润性调控液体动态铺展、液下气泡脱离等动力学行为，开发出高效射流沸腾功能界面，为沸腾传热关键过程协同优化提供了崭新思路、理论指导和实践支撑。