以水为介质，对垂直放置的急扩加速流缩放管(CD) 等间距内插旋流片的自然对流换热进行了实验研究和数值模拟，通过实验研究得到不同内插旋流片个数时自然对流换热系数的变化，并将实验值与光滑管的作比较，同时运用Fluent 模拟得到了管内的速度分布、温度分布、传热系数和热通量沿轴向的变化．结果表明，随着旋流片个数的增加，传热系数明显增大，但旋流片个数达到 7 后传热系数不再明显增大，且两种类型的旋流片均有同样效果．数值模拟还表明，插入的旋流片个数越多阻力越大，其中等间距内插 7 个旋流片的效果最优．文中还对缩放管与旋流片对自然对流的两区协同强化传热机理进行了初步分析，通过模拟得到强化传热的原因在于壁面切向速度的提高，同时还给出了截面平均切向速度沿轴向的变化规律．

The natural convection heat transfer of water in a vertical converging- diverging tube (CD) with regularly-spaced twisted tapes was experimentally investigated and numerically simulated,and the natural convection heat transfer coefficient varying with the twisted tape number was explored.Then,the results were compared with those of smooth tubes,and the distributions of velocity and temperature,as well as the variations of heat transfer coeffi-cient and heat flux with axial distance,were simulated with Fluent.It is found that the heat transfer coefficient re-markably increases with the number of twisted tapes and keeps unchanged when 7 twisted tapes are inserted,and that the heat transfer enhancement is independent of the type of twisted tapes.Simulated results indicate that the flow resistance increases with the number of twisted tapes and that the optimal number of regularly- spaced twisted tapes is 7.The authors also primarily analyze the mechanism of the natural convection heat transfer enhancement interrelated by the CD and the regularly- spaced twisted tapes,discuss the change of average tangential velocity with the axial distance and point out that the enhancement of heat transfer is due to the increase of tangential wall velocity.