换热通道内纵向涡干涉机理研究

Longitudinal vortices can potentially enhance heat transfer with small pressure loss penalty and have been widely applied in the field of heat transfer enhancement of heat exchangers. Researchers have long remained at state of experimental observation and qualitative analysis due to the complexity of the vortices and the lack of quantitative description parameters. The intensive study of the heat transfer enhancement by longitudinal vortices is an active demand of recognizing and application of longitudinal vortices. For the tube bank fin heat transfer exchangers, there are many rows of tubes and can apply many rows of vortex generators. The longitudinal vortices generated by vortex generators will interact with the boundary layer, the horseshoe-like vortices and also the vortices generated upstream and downstream. The interaction of vortices is complex and depending on many parameters, such as the shape of vortex generator, the arrangement configuration (the attack angle, the stream wise and span wise distance of vortex generators) of vortex generator and so on. The current understanding and description of the vortex interaction can't be used to control the movement of vortices. However, some of interactions of vortices can enhance the intensity of vortices and heat transfer performance, but some of them decrease the intensity of the vortices and weak the heat transfer enhancement. In this project, we intend to investigate experimentally and numerically the interaction of vortices and to find contributions of the interaction to heat transfer enhancement in the fin-side channel of typical tube bank fin heat exchangers, in which either circle, flat or elliptical tube is used. The main studied aspects are: (1) Interaction between the longitudinal vortex and the horseshoe-like vortices generated by the tubes; interaction of longitudinal vortex with the boundary layer; interaction of vortices generated by common-flow-up or common-flow-down type vortex generator pairs; the interaction of vortices generated upstream and downstream. (2) The effect of the interaction on the heat transfer enhancement and the pressure loss penalty. (3) The rule can be used to design heat exchanger through arranging vortex generators. The main object are: insighting the mechanism of the interaction between vortices and their effect on heat transfer enhancement; generalizing the rule for arrangement of vortex generators to avoid harmful interaction of vortices which decreases the heat transfer enhancement. The research results of this project will reveal in-depth the phenomenon of longitudinal vortex interaction and guide the application of longitudinal vortex for heat transfer enhancement. Therefore, the outcoming of this project has not only academic significance, but also the sound background of engineering application.

纵向涡因能以较小的压力损失获得较大程度的传热强化而得到了广泛研究和应用。管翅式换热器沿主流方向有较多的管排，可以在肋片上布置多排涡产生器，这样就会出现上游产生的纵向涡与下游纵向涡、管子产生的马蹄形涡及边界层中涡的干涉现象。该现象非常复杂，但又决定着纵向涡的传热强化效果。在对上述涡干涉现象揭示不足的研究现状下，项目采用实验和数值分析方法，拟在圆管、扁管、椭圆管管翅式换热器肋侧通道内开展三方面研究：(1)纵向涡与马蹄形涡，纵向涡与边界层、纵向涡对之间干涉以及纵向涡与来流中纵向涡之间的干涉特性；(2)纵向涡干涉对强化换热性能和流动阻力的影响；(3)对纵向涡及其干涉有效控制的方法。目标是：揭示涡干涉本质及其对传热和阻力的影响机制；获得避免不利于强化传热涡干涉的涡产生器布置原则。项目结果可增进对纵向涡干涉现象的认识，还可对纵向涡在强化传热中的应用提供指导，具有较大的学术意义和较高的工程应用价值。

纵向涡是主流垂直截面上的流动，因其可以较大程度的强化传热而不引起较大的阻力损失，在工业上得到了广泛研究和应用。为了提高纵向涡的强度，通常在肋片上布置多排涡产生器，这样在流动通道内就存在多个涡产生器产生的纵向涡。纵向涡能向下游传递到较远的位置远远超过涡产生器间距，因此就会出现上游产生的纵向涡与下游纵向涡的干涉现象。项目采用数值分析方法研究了换热通道内两个相反旋转方向纵向涡之间的干涉、两个相同旋转方向纵向涡之间的干涉以及换热通道内多个纵向涡之间的干涉现象。通过项目的开展，对纵向涡间干涉现象有了新的认识。研究发现旋转方向相同的两个纵向涡在相互干涉时，两个纵向涡之间发生了融合现象，而旋转方向相反的两个纵向涡在相互干涉时未发生融合现象。相同、相反旋转方向纵向涡间具有不同的干涉特性。项目明晰了相同、相反旋转方向纵向涡间的不同干涉特性以及纵向涡干涉对流动结构、纵向涡强度、强化传热、流动阻力的影响；获得了提高换热性能的换热器翅片表面涡产生器布置合理方式；获得了纵向涡强度与换热强度间的对应关系，揭示了纵向涡强度对通道内换热强度的决定作用。项目结果可增进对纵向涡干涉现象的认识，还可对纵向涡在强化传热中的应用提供指导，具有较大的学术意义和较高的工程应用价值。项目部分研究成果已在国内外发表标注期刊论文和会议论文11篇，已被SCI收录5篇，EI收录2篇；授权发明专利9项；项目培养研究生4名。