纵向涡发生器在翅片管束中的位置优化

采用经过验证的层流模型,对带纵向涡发生器的单排翅片管束的流动换热进行建模分析,就距离圆心4种距离、5种角度的纵向涡发生器对翅片管束性能的影响机理展开分析,发现涡发生器对翅片管束的作用表现在翅片上弱换热区大小的改变和沿流动方向涡量强度的改变两个方面.涡发生器能够推迟圆柱绕流的分离点进而减小管后弱换热区,同时能够利用较大涡量的主涡使局部核心区的流体混合,提高流体的温度梯度.对比结果表明,在雷诺数范围为600～2 600,对单排圆管翅片管束而言,涡发生器相对翅片管束圆管中心为130°同时离圆心相对距离为1.36时效果最好,综合性能指标提高7%～30%;对于两排翅片圆管管束,顺排和叉排都在第二排涡发生器角度为120°时效果最好,综合性能指标提高分别可达15%和28%.

Location Optimization of Longitudinal Vortex Generators in Finned Tube Bundles

The flow and heat transfer characteristics of the single row finned tube bundle with longitudinal vortex generator are modeled using a validated laminar flow model. The cases of four different distance and five angles from the tube center are studied. It is found that the effect of vortex generator on the finned tube bundle is manifested in two aspects. One is the change of the size of the weak heat exchange zone behind tubes and the other is the change of vorticity intensity along the flow direction. Vortex generators can postpone the pipe flow separated point, mix the fluid of local and core areas, and increase the temperature gradient of the fluid. The results indicate that vortex generators have a good effect with an angle of 130 degrees and a distance ratio of 1.36 for single row finned tube in the Re range of 600 to 2 600, and the corresponding comprehensive performance increased by 7% to 30%. The application of the above optimization theory in 2 row find tube heat exchangers indicates that the comprehensive performance of both inclined and staggered tube arrangements reaches the largest when the second row vortex generator is placed about 120 degrees around the related tube center, improving by 15% and 28% respectively.