三叶膨胀管管内传热与阻力特性研究

Research on heat transfer and flow resistance performance of trefoil expansion tube

通过搭建单管换热性能实验装置,对三叶膨胀管管内传热与阻力特性进行了测试。以实验测试结果为基础,对数值计算模型的可靠性进行了验证,采用FLUENT软件对不同规格参数的三叶膨胀管管内传热与阻力特性进行了数值研究。模拟计算结果表明,三叶膨胀管管内的强化传热机理主要是由于管内特殊的螺旋通道,使得流体呈现出三维纵向旋流的流动形态,管内产生了垂直于主流方向上的二次流,二次流主要分布在换热管的3个膨胀区,二次流的产生促进了流体间的径向混合,增强了对壁面换热边界层的扰动。在文中研究范围内,三叶膨胀管的传热性能和摩擦阻力随着扭距的减小而增大,随着内切圆直径的减小而增大,随着过渡圆弧直径的减小,先减小后增大。

An experimental apparatus was established to study the heat transfer and flow resistance characteristic of trefoil expansion tube. Based on the experimental results, the reliability of the computational model was verified, and the performance of trefoil tubes with different structure parameters was investigated by FLUENT software. The simulation results show due to the special spiral shape, the flow pattern is presented as three dimensional longitudinal helical flow. The secondary flow which is perpendicular to the main stream is formed in the tube, and it is mainly distributed in the three expansion areas. The generation of secondary flow promotes the fluid radical mixture, and increases the disturbance of boundary layer, thus enhances the heat transfer. The heat transfer and resistance factor increase with twisted pitch and inscribed circle diameter decreasing, reduce first and then increase with transitional arc diameter decreasing.