管束排列及管间距对换热器传热性能的影响

通过改变圆形翅片管换热器管束排列及管间距的传热性能实验，得到雷诺数(Re)、纵向管间距(S_l)及管束排列方式对圆形翅片管换热器传热性能的影响，再利用数值模拟方法分析这3个因素影响的原因。结果表明，圆形翅片管换热器的努赛尔数(Nu)及阻力系数(f)均随Re的增加而增加，且增加趋势逐渐下降。增大S_l可提高顺排圆形翅片管换热器的传热性能，但是提高幅度随S_l的增加而减小，在S_l为110 mm时换热效果最好；增大S_l反而会降低叉排圆形翅片管换热器的传热性能，其换热效果在S_l为66 mm时最好。相对于顺排方式，叉排圆形翅片管换热器的换热效果更好。速度场与温度场间的协同角度大小、回流区面积及尾流涡尺度大小与换热器传热性能的提高有关，可以从这3个方面进行分析，以寻找改善换热器结构的途径。

Effects of Tube Arrangements and Longitudinal Tube Spacing on Heat Transfer Performance of Heat Exchanger

Experiments were performed for turbulent heat transfer and fluid flow characteristics of annular finned tube heat exchanger to examine the effects of Reynolds number (Re), longitudinal tube spacing (S_l) and tube arrangements on the heat transfer performance. Then numerical simulations were performed to analyze the experimental results. The results showed that Nusselt number（Nu）and friction factor（f）increased with the increase of Re for both annular finned tube heat exchangers with inline or staggered arrangements, and the increasing trend decreased. For the annular finned tube heat exchanger with inline arrangement, the heat transfer performance became better with the increase of S_l and reached its best value when S_lwas 110 mm. However, the heat transfer performance became worse with the increase of S_l for the annular-finned tube heat exchanger with staggered arrangement and reached its best value when S_l was 66 mm. Compared with the annular-finned tube heat exchanger with inline arrangement, the heat transfer performance of the annular-finned tube heat exchanger with staggered array was better. It was found that the effects of the three factors on the heat transfer performance of the annular-finned tube banks could be well described by the field synergy principle, the area of recirculation region and the wake vortex scale, by analysis of which the way to improve the structure of heat exchanger could be found.