超疏水微通道层流流动减阻与强化传热的协同机制研究

With continuous developing of micromachining technology, the level of specific surface area, heat transfer efficiency and compactness on microscale heat exchanger are being vastly improved, which also bring out that sharply increasing of flow resistance in microchannel. For building microchannel heat exchanger featured by both low flow resistance and high heat transfer efficiency, it is an effective way to put super hydrophobic surface as microchannel wall. Aiming at reducing flowing resistance, strengthening heat transfer and improving synergism of aforementioned both in super-hydrophobic type microchannel, this project will carry on researches from views of laminar flowing and heat transfer mechanisms, micro/nanoscale form and structure, microsize superposition effects and wettability of super-hydrophobic surface, explore the main dominant factor of flowing and heat transfer in super-hydrophobic type microchannel, and find an efficient way to improve the synergism of flowing drag reduction and heat transfer enhancement in super-hydrophobic type microchannel, employing the conjunct approaches of theoretical analysis, numerical simulation and experimental study. Then on the basis, the design of the super-hydrophobic type microchannel heat exchanger will be optimized. As a result, our study has important academic significance on disclosing the laminar flowing and heat transfer laws in microchannel with super-hydrophobic surfaces, the combined influence on flowing and heat transfer characteristics in super-hydrophobic type microchannel by micro/nanoscale form and structure, microsize superposition effects of super-hydrophobic surface, as well as the synergism of laminar flowing drag reduction and heat transfer enhancement by wettability. Further, it will also provide theoretical guidance for studying and developing super-hydrophobic type microchannel heat exchanger featured by both low flow resistance and high heat transfer efficiency.

随着微加工技术的不断发展，微尺度换热器件的比表面积、换热效率、紧凑性均大幅提高，这同时也导致了微通道内流动阻力激增。为了实现微通道换热器件的低流阻高效换热的效果，对微通道进行超疏水壁面处理是一种有效的方法。本项目旨在以流动减阻、强化传热及提高两者的协同性为目标，采用理论分析、数值模拟及实验研究相结合的方法，从超疏水表面层流流动传热机理、超疏水表面微纳结构、微尺度叠加效应以及壁面润湿性等方面展开研究，探寻影响超疏水微通道流动换热的主要因素，发现提高流动减阻与强化传热协同性的途径；并在此基础上对超疏水微通道换热器进行优化设计。本项目的研究对揭示超疏水表面层流流动与传热规律、表面微观形态结构与微尺度叠加效应对超疏水微通道的流动与传热特性的综合影响以及壁面润湿性对超疏水微通道层流流动减阻与强化换热协同性的影响具有重要的学术意义，可为开发低流阻高效换热的超疏水型微通道换热器提供理论指导。

微通道换热器是目前解决高集成度大功率芯片散热难题的理想选择。针对微通道换热器强化换热与流动减阻难以协同的瓶颈问题，本项目研究了微流道表面结构、粗糙度、超疏水表面微纳结构、壁面浸润性等对微通道换热器流动换热特性及协同性的影响规律。研究成果如下：针对表面微纳结构对微通道流动换热的影响规律，首先构建了新型随机高斯粗糙度模型，揭示了粗糙度自相关长度对流动换热特性的影响规律，将所构建的粗糙度模型应用于平直通道、波纹通道及钉泡通道中，探究了表面微纳结构对单相流动及传热规律的影响机制，证明了粗糙度能够提高微通道换热器的换热性能。构建了综合考虑气液界面粘性剪切和气液界面耦合传热的超疏水表面简化模型，并探究了不同超疏水结构和工况下的流动换热特性，揭示了表面微纳结构对两相流流动及传热规律的影响机制。在微尺度综合效应对超疏水微通道流动及传热的影响规律方面，揭示了壁面滑移长度和温度跳跃系数与壁面剪切应力间的关系，并利用此关系对超疏水模型进行改进。进而，基于改进的模型对超疏水平直通道和钉泡通道中的流动换热特性进行了数值分析，揭示了壁面浸润性对复杂微通道流动换热特性的影响规律，发现超疏水表面能够实现微通道换热器高效换热与流动减阻的良好协同。最终，对通道和钉泡几何结构参数进行了单因素及多因素分析，并采用遗传算法对钉泡微通道进行了多目标优化设计，获得了一系列换热器设计参数最优解集。以上成果可为开发低流阻高效换热微通道换热器和发展高效换热技术提供理论指导，具有一定的学术和工程意义。相关研究成果在流动传热领域顶级期刊发表SCI论文19篇，其中JCR一区11篇，高被引1篇。