周向非均匀热流下圆管内湍流大尺度拟序结构调控及其传热强化研究

Enhancing the convective heat transfer performance in a pipe is an effective solution to the local overheating and thermal stress problem caused by the circumferentially non-uniform heat flux on the pipe wall. The use of the existing techniques for turbulent convective heat transfer enhancement usually leads to much pumping power due to the lack of awareness of turbulent structures. This project proposes the study of heat transfer enhancement based on the local control of the large scale coherent structures in turbulent pipe flow under the circumferentially non-uniform heat flux condition. Large Eddy Simulations and PIV experiments are firstly used to evaluate the interaction between the transient velocity and temperature fields, aiming at revealing the mechanism of the large scale coherent structures on thermal transport, and figuring out the optimal mode of the large scale coherent structures for thermal transport. Then, flow control techniques are applied to control the optimal mode locally, and the relationship between the turbulent kinetic energy of the large scale coherent structures and convective heat transfer enhancement in the pipe is built. On this basis, optimization of the control of the turbulent kinetic energy of the large scale coherent structures is conducted for heat transfer enhancement at the same pumping power. Finally, the heat transfer enhancement performance by controlling the coherent structures locally is verified by experiments. This research project may provide useful guidelines for turbulent convective heat transfer enhancement in a pipe under the circumferentially non-uniform heat flux condition, which has significant academic value and wide application prospect.

强化管内对流传热性能是解决周向非均匀热流下流体输运管道局部过热和热应力问题的一种有效方法。现有管内湍流对流传热强化技术的应用过程由于缺乏对湍流结构的认识往往导致流动功耗显著增加。本项目针对圆管非均匀受热特性，提出基于圆管内湍流大尺度拟序结构局部调控的传热强化研究。拟先采用大涡模拟与PIV测试相结合的方法，研究周向非均匀热流下圆管内瞬时速度场与温度场之间相互影响规律，旨在揭示大尺度拟序结构对圆管内热量输运的作用机制，获取适合热量输运的大尺度拟序结构的最优模态；然后采用流动控制技术局部调控上述最优模态，建立大尺度拟序结构湍动能与对流传热强化关联，通过优化对大尺度拟序结构湍动能的调控，提高相同流动功耗下圆管内对流传热性能；最后通过实验对大尺度拟序结构局部调控下圆管内对流传热强化性能进行验证。本项目研究可为周向非均匀热流下圆管内湍流对流传热强化提供有效指导，具有重要的学术价值和广泛的应用前景。

对流传热广泛存在于能源、动力、交通、化工等领域。据统计工业过程能量传递75%以上依靠对流传热，因此，强化对流传热对于节能减排、提高能源利用效率具有重要意义。现有圆管内湍流对流传热强化技术的应用过程由于缺乏对湍流结构的认识往往导致流动功耗显著增加。本项目首先系统性总结了基于纵向旋流的圆管内单相对流传热强化理论与技术，讨论了现有研究中存在的不足与挑战，并为后续传热强化理论与技术研究提供了新思路；然后开展了均匀受热圆管内湍流结构调控及对流传热强化研究，揭示了矩形翼涡发生器传热强化机理，获得了矩形翼涡发生器最优参数组合；在此基础上，探究了矩形翼涡发生器排布形式对圆管内湍流结构的影响，建立了湍流结构与传热强化性能之间的内在关联，获得了适合于圆管内传热强化的湍流结构；最后，针对热槽式太阳集热管非均匀受热问题，设计了多种内置环状翼涡发生器，重点探究了全局流动控制与局部流动控制对热管内对流传热强化性能的影响，证实了局部流动控制相比全局流动控制在传热强化与降低功耗方面均具有明显优势。本项目已在国际SCI期刊上发表论文10篇，授权国家专利3项。相关研究成果可以为高效低阻传热元件或者换热设备的开发和工程应用提供理论和技术指导。