微重力下柱状微结构表面流动沸腾换热及其强化机理研究

In order to solve the severe deterioration problem of heat transfer performance under microgravity due to the lack of buoyancy, flow patterns and heat transfer characteristics of flow boiling on smooth surface and self-developed micro-pin-finned surfaces will be experimentally investigated in microgravity by utilizing the drop tower facility in Beijing. Micro-pin-fins are fabricated on silicon surface via the dry etching technique. A thin film of indium tin oxide (ITO) is deposited on the back side of the Si substrate by physical vapor deposition, and is used as the heater. Copper electrodes are patterned on the ITO using chemical vapor deposition. Visual observation of flow patterns and their transitions of flow boiling in microgravity can be observed by using high speed CCD camera with high shock resistance. Through measuring and analyzing the heat transfer performance of micro-pin-finned surfaces which can be obtained through isolated industrial signal conditioning modules and differential input independent storage devices, we aim at revealing the mechanism of two-phase flow boiling heat transfer and its enhancement in thermal management of aerospace engineering. Besides, we will find the formation and transition boundary conditions of the special flow patterns and its influences on heat transfer of micro-pin-finned surfaces which may be different from smooth surface in microgravity. From the mechanisms of flow pattern transition, we build well-predicted flow patterns correlations and flow pattern maps over micro-pin-finned surfaces, which can be used to describe the flow patterns and heat transfer characteristics of enhanced flow boiling heat transfer in microgravity. Meanwhile, we will develop efficient surface microstructures for enhancing boiling heat transfer in microgravity. The study will improve and supplement the theories and technologies of enhanced boiling heat transfer.

为解决微重力下缺乏浮力导致的沸腾换热性能恶化的问题，以光滑表面和自主开发的微米级柱状微结构表面为研究对象，利用落塔对其在微重力下流动沸腾流型及强化换热特性进行实验研究，以半导体硅片作为加热面，采用干法腐蚀技术加工柱状微结构，利用物理气相沉积法和化学气相沉积法研发流动沸腾加热模块；通过抗冲击高速CCD对微重力下流动沸腾流型及其界面行为进行观察；采用隔离信号调理模块和差分输入独立存储设备对其换热特性及发展规律进行测量和分析；揭示柱状微结构在微重力下的流动强化沸腾换热机理和规律，找到柱状微结构表面在微重力下不同于光滑表面的流型特征，包括其形成及转变边界条件及对换热的影响规律；建立柱状微结构表面上流型预报关联式和流型图，从流型转变的机理出发，提出具有良好流型预测能力的关系式，用于描绘微重力下强化流动沸腾换热的流型变化规律及流动换热规律；开发新型强化表面结构，补充及完善强化沸腾换热理论和技术。

为解决微重力下缺乏浮力导致的沸腾换热性能恶化的问题，以光滑表面和自主开发的微米级柱状微结构表面为研究对象，利用落塔对其在微重力下流动沸腾流型及强化换热特性进行了实验研究，以半导体硅片作为加热面，采用干法腐蚀技术加工了柱状微结构，利用物理气相沉积法和化学气相沉积法研发了流动沸腾加热模块；通过抗冲击高速CCD对微重力下流动沸腾流型及其界面行为进行了观察；采用隔离信号调理模块和差分输入独立存储设备对其换热特性及发展规律进行了测量和分析。通过实验获得了微重力下流动沸腾换热性能及气泡动力学行为，发现了不同于常重力下的流型转变特征。提出了换热系数预测关联式，发现韦伯数、通道尺寸、强化换热面积是微重力下影响临界热流密度的关键参数，提出了微重力下临界热流密度预测关联式，可准确预测实验结果，为微重力下的流动沸腾换热调控提供了实验和理论依据。本项目获得的理论成果可有效指导微重力高效强化沸腾换热表面的研究，同时利用激光加工技术发展了新型微结构表面，未来有望应用于微重力高热流密度散热的场合。在人才培养方面，项目负责人张永海博士从讲师晋升为副教授，并入选“中国科协第四届青年人才托举工程”；已培养从事强化传热研究的硕士生1人，并转为在读博士生。经过三年的研究，共发表国际期刊SCI/EI 论文8篇，EI 论文1篇，国际会议论文13篇(邀请报告3篇，最佳会议论文1篇)，国内会议论文11篇(邀请报告1篇)。授权发明专利1项，申请发明专利3项。