水射流冲击高温粗糙靶面的换热特性研究

Water jet impinging boiling heat transfer is a highly effective heat transfer technique. Numerous researches indicate that the water jet velocity, surface microstructure of target plate are the two of the most important factors which affect the effectiveness of water jet impinging heat transfer. Most of researchers focus on the heat transfer characters at stagnation point in the condition of water jet velocity lower than 7.0m/s. And only the roughness parameters are selected to describe the surface microstructure of target plate, which leads to some conflictive results. During the study of this project, fractal parameters are introduced to describe the surface microstructure of target plate. This project concentrates on the heat transfer characters caused by high velocity water jet (velocity in the region of 15.0m/s～70.0m/s) and rough surface of target plate. These researches try to clarify the relation between water jet impinging boiling heat transfer intensity and fractal parameters of rough surface of target plate. Compare the effectiveness of fractal parameters and roughness parameters in the describing of the boiling characters of target plate's surface. Reveal the space and time distribution of heat flux on surface of target plate, and especially explain the reason why the heat flux at stagnation point is relative lower than other points under the condition of high velocity water jet impinging. The research of this project will deepen the understanding of the characters of high velocity water jet impinging boiling heat transfer, and lay a foundation to improve the heat transfer intense of water jet impinging.

水射流冲击沸腾换热是一种高效传热技术。研究表明水射流速度、靶面微观形貌是影响水射流冲击沸腾换热强度的重要因素，多数研究主要关注于低速射流(<7.0m/s)在驻点区的换热特性，并且由于采用粗糙度参数表征靶面微观形貌，导致一些实验研究得出相互矛盾的结论。本项目采用分形参数表征靶面微观形貌，采用实验测试和导热反问题分析的方法，针对高速(15.0m/s～70.0m/s)水射流冲击高温粗糙靶面沸腾换热特性开展研究，阐明靶面微观形貌的分形参数、粗糙度参数对水射流冲击沸腾换热的影响规律，分析比较分形参数、粗糙度参数在靶面沸腾换热特性描述中的合理性。揭示在高速射流条件下，水射流冲击沸腾换热中靶面上热流密度的空间、时间分布规律，特别是揭示驻点处换热热流密度相对较低的原因。该项目的研究为进一步系统深入地认识高速水射流冲击高温粗糙靶面沸腾换热的特性，提高水射流冲击沸腾换热的强度奠定基础。

围绕水射流冲击高温靶体沸腾换热开展相关研究。基于小波分析获得靶体表面分形参数；开发二维瞬态导热反问题分析方法，考察了参数测量误差对导热反问题分析精度的影响，采用单相射流冲击换热实验，验证了该方法的精确性，在此基础上获得靶体表面局部沸腾换热特性；通过实验测试的方法，证明了表面温度波动与沸腾换热状态具有密切的关联，过渡态沸腾阶段温度波动幅度最大，膜态沸腾阶段温度波动幅度适中，核态沸腾阶段温度波动最小；开发了基于多松弛格子波尔兹曼方法的介观尺度模型，建立了开放式的软件平台，在验证了其准确性的基础上，用于粗糙表面微流动模拟、单相射流冲击模拟，并将该方法推广应用到多孔介质内的微流动和换热研究；通过实验测试，获得不同粗糙度靶体沸腾换热特性，证明了粗糙度参数在描述靶体微观形貌对沸腾换热的影响存在不足，而表面分形参数相对合理；在上述工作的基础上，针对水雾/气雾射流冲击高温靶体沸腾换热开展实验研究，获得了膜态沸腾、过渡态沸腾、核态沸腾换热热流密度的经验公式，揭示了换热热流密度与壁面过热度、韦伯数、水流量密度等参数之间的关系。. 后续研究中，拟定采用稳态实验的方法，继续考察表面粗糙度、水温、流量等参数对沸腾换热特性的影响规律，构建沸腾换热模型。相关实验平台已经搭建完毕。