相变传热装置多尺度协同性及构造

In order to resolve the conflict that phase change heat transfer processes depend on a particulate scale, the concept of “separation in processes, synergy in scales” is proposed to avoid the multiple competitive processes occurring in the same scale. This work will start with building up models for phase change heat transfer and the criteria numbers among different scales, by virtue of bionic principles multi-scale structures will be constructed to enhance heat transfer significantly. The following studies will be carried out: Through low-cost nano- and micro-scale fabrication technology, multi-scale structures will be fabricated to investigate liquid droplet dynamics; Sintering of multi-scale structures will be explored by mixing nano-inorganic salt and metal powder, tree-type networks of micro-channels will be introduced, based on which multi-scale pool boiling and heat transfer in heat pipes will be investigated, then the mechanism and characteristics will be revealed on the effect of multi-scale structures on the maximum capillary pressure and critical heat flux; By mimicking the rebounding of liquid droplets due to conversion from surface energy to kinetic energy during coalescence of condensing liquid droplets on the surface of ballistospore, the nano- and micro-scale structures will be fabricated on the surface of coppers, the mechanism of heat transfer enhancement and friction reduction will be investigated. Nano-scale membranes will be fabricated within the metal framework to construct the condensing tubes to capture droplets, the mechanism of droplet capture driven by the gradient of surface energy will be revealed, as well as the mechanism and effect of liquid droplet capture on the thermal performance of condensing tubes. In this study, the bionic principles are adopted in phase change heat transfer and the relationship between micro-scales and macro-scales will be built up to provide the theoretical and technological support in improving the performance of devices for phase change heat transfer.

为解决相变传热过程依赖单一尺度造成的冲突，提出“过程分解，尺度协同”的学术思路，避免多个竞争性过程发生在同一尺度内。从建立相变传热过程与尺度关联准则数入手，借助仿生学原理，构造多尺度结构，大幅提升传热性能。拟研究：采用低成本微纳米制备方法制备多尺度结构，进行液滴动力学研究；探索纳米盐掺混金属粉末烧结多尺度结构，引入树形通道网络，研究多尺度结构池沸腾及热管传热，揭示多尺度结构对最大毛细压及临界热流密度的影响规律及机理；仿担子菌孢子表面冷凝液滴合并将表面能转化为动能，使液滴弹跳现象，制备紫铜管表面微纳米结构，研究冷凝传热强化及减阻机理；以金属丝网为骨架，制备纳米修饰丝网膜管，构造丝网膜捕液型冷凝管，揭示丝网膜管表面能梯度驱动的捕液机理，揭示捕液对冷凝管传热的影响规律及机理。本项目将仿生学原理引入到相变传热中，建立微观和宏观的联系，为提升相变传热装置性能提供理论和技术支撑。

单一尺度相变传热已建立起理论框架，指导了大量工程设计。多尺度相变传热具有广泛应用背景，也是国际学术前沿。然而如何构造多尺度结构成为难点和瓶颈。本项目以沸腾、冷凝及热管为研究对象，从理论、实验及机理验证三个层面开展了创新性研究，主要发现如下：针对对流沸腾系统，将加热面温度信号小波分解，证明了大幅度/长周期脉动为压力降脉动，发现通道尺寸小于流体毛细长度时，不稳定性加剧；提出孔隙尺度小于通道尺度1-2个量级的多孔壁微通道，通道间质量及动量交换是消除不稳定性核心机理。建立了液滴在表面上滑动及滚动的模式筛选准则，首次发现当接触角大于147°时，液滴只发生滚动，小于126°时，只发生滑动，126°-147°间可发生滑动，也可发生滚动；将该模式准则融合到滴状冷凝传热模型中，发现纳米结构表面产生正负效应，传热系数是正负效应的耦合结果，提出高长径比密集排列的纳米结构是强化滴状冷凝传热的思路。研究了亲疏水表面对流冷凝传热，发现其性能优于疏水表面冷凝传热，亲水点增强冷凝核化并降低接触热阻，疏水区域有利于液滴去除。鉴于热管存在不同过程依赖单一尺度产生冲突，还存在对流传热和核态传热的竞争，提出亲水蒸发器/疏水冷凝器热管，使蒸发器和冷凝器均按照核态机理运行，实现了传热系数随热负荷增大而增大的自适应传热。蒸发器采用了多尺度毛细芯，解决了气泡核化和蒸汽溢出依赖单一尺度的冲突。以上研究奠定了多尺度相变传热理论基础。 .项目共发表论文101篇(包括国际杂志SCI收录论文63篇，5篇代表作论文包含Advanced Materials期刊论文1篇（影响因子25.8），Nano Energy 2篇（影响因子15.5）)。申请专利17项（获授权14项，其中美国授权发明专利1项）。谢剑博士获“吴仲华”优秀研究生奖，硕士生郑雅文获国际会议论文奖等6项奖项。培养2名中青年业务骨干（1人为创新群体核心成员，1人获玛丽•居里学者称号），博士后出站3人，博士毕业8人，硕士毕业16人。冷却端扩展型一体化平板热管散热技术获技术转让并得到了应用。