承载散热一体化X芯多孔蜂窝内单相与两相对流传热机理及传热强化研究

For seawater-cooled jet blast deflectors (JBDs) currently used on the flight deck of aircraft carriers, failures induced by excessive corrosion, etc., are key issues. To mitigate such severe problems and to further improve the cooling performance of JBDs, this project proposes a closed-cycle active cooling scheme for JBDs. A new cellular material (i.e., the X-cored honeycomb) is taken as the multifunctional core of the cooling modules, which consists of the cheap but mechanically/thermally superior X-type metallic lattice and square honeycombs with straight or corrugated walls. By using a purposely designed experimental system for convective heat transfer and numerical simulation, overall heat transfer and pressure drop characteristics of single-phase forced convective flow and flow boiling of deionized water in the X-cored honeycomb will be investigated under different heat fluxes, coolant flow rates and pressures. Exploration of physical mechanisms underlying the complex single-phase primary/secondary flow and local heat transfer pattern induced by the complex material morphology will be conducted. Thermo-fluidic mechanisms of the two-phase flow pattern and their coupling with local heat transfer pattern will be clarified. Based on the thermo-physical insight, methods for synergetic control of the single/two-phase flow and local heat transfer will be explored; and correspondingly, heat transfer enhancement by modification of the material morphology, etc., will be carried out. This project will academically make a contribution to the understanding of complex convective heat transfer phenomena. In addition, the results obtained will become theoretical guidance for subsequent thermo-mechanical optimization of the X-cored honeycomb material and the development of the novel high-performance JBD.

为改善航空母舰燃气偏流板的散热性能、缓解现役海水冷却偏流板腐蚀严重等突出问题，本项目提出闭式循环冷却偏流板新思路；将成本低、力学和散热性能优越的X型点阵与平壁及波纹壁方孔蜂窝结合，形成新型X芯蜂窝多孔材料，拟将其作为偏流板的冷却芯体。以去离子水为工质，通过搭建对流传热实验系统并建立数值模型，系统研究不同热流密度、工质流量及压力下该新材料内单相对流与流动沸腾的总体传热和阻力特性；探究材料形貌所致复杂单相主流、二次流及材料表面局部传热的物理机制，探究复杂两相流型的流体动力学原理，探究两相流与材料表面沸腾传热的耦合机制；以机理分析为指导，探索单相及两相流动与局部传热的协同调控方法，继而通过改变材料形貌等方式，逐步改善材料的综合传热性能。本项目的研究可拓展对复杂对流传热现象的认识，具有重要的学术价值；研究成果将为该新材料的热学与力学联合优化奠定基础，为我国高性能燃气偏流板的研制提供理论指导。

为改善燃气偏流板的散热性能、缓解现役海水冷却偏流板腐蚀严重等突出问题，本项目提出了闭式循环冷却偏流板新思路，将新型X芯蜂窝作为冷却模块的芯体。采用实验与数值模拟相结合的方法，系统研究了该多孔材料的总体散热性能和对流传热机理；研究了主控形貌参数对材料内流动与传热的影响规律；基于球凸、球凹及扰流柱，开展了对流传热强化研究。首先，在多孔材料传热特性与机理方面：给定雷诺数，X芯波纹壁蜂窝的总体Nusselt数相较于X芯平壁蜂窝的优势达12%，X芯平壁蜂窝相对于方孔蜂窝及X型点阵的优势分别高达360%和55%；给定泵功，X芯波纹壁蜂窝的总体Nusselt数最高，X芯平壁蜂窝相对于X型点阵的优势高达42%；在原X芯三明治板中引入蜂窝壁致使通道四角处的分离涡增大且在翅片表面引起了新的分离涡，这致使切向流速减小，翅片施加的无滑移约束使主流湍动能显著降低且限制高湍动能向基板表面的对流和扩散输运，因而基板和点阵杆件表面的平均Nusselt数下降30%和9%；然而X芯所致复杂湍流场使蜂窝壁面的平均Nusselt数提高约2.3倍。其次，对该材料的调控研究表明：冲压位置对材料内的流动与传热具有非常显著的影响，随着相对冲压位置的逐渐增大，流动由平行流逐渐向大尺度螺旋流转变，相应二次流和流动混合逐渐增强，但存在最优冲压位置使材料的散热性能最优，此时其平均Nusselt数比标准X型点阵高约10%；此外，主流螺旋流和二次流越强，引入翅片对其湍动能输运的负面影响越强，对应材料总体散热性能改善的幅度越小。最后，基于球凸、球凹及扰流柱的传热强化研究表明：将强化元件放置于靠近基板流动的二次流影响区域时，二次流对强化元件的冲刷作用更明显，传热强化效果更好；且增设扰流柱的强化效果优于增设其他强化元件；湍流度越小，增设强化元件的效果越显著。本项目的机理揭示可丰富学术界对超轻多孔材料内复杂湍流流动与传热的认识，可启发新型材料拓扑的开发；所提出的新型多孔材料在承载散热一体化换热与热管理系统中具有较好的应用前景。

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