双扭旋叶片组合形式对管内湍流换热性能的影响

在圆管内一个截面上安装两个扭旋叶片的组合形式会产生多个纵向涡，纵向涡的形式与强弱受相邻两组叶片旋向和错位角的综合影响。为探究各种组合形式对湍流换热性能的影响，研究了6种不同组合形式某一截面上速度与温度梯度和压力梯度的协同程度，得出结论：错位角对Nu和压力降的影响明显大于叶片旋向的改变。在近壁区，增加错位角可以提高速度与温度梯度的协同程度，而且相邻两组叶片旋向相反形式优于旋向相同的形式；但旋向相同形式的速度与压力梯度的协同程度优于旋向相反形式，然而这种差距会随着错位角的增加而减小，当错位角为90°时，在y/R<0.75时协同程度非常接近。

Effect of combination method of double-twisted blades on turbulent convective heat transfer

Multiple longitudinal vortex was made in a tube by double-twist elements incorporated in a section. Longitudinal vortex form and strength were affected by two adjacent twist elements rotate direction and dislocation angle. The effect of dislocation angle on Nusselt number and pressure drop was more significant than on the elements rotate direction. To study the influence of different combinations of twisted element on turbulent heat exchange performance, the coordination between velocity, temperature gradient and pressure gradient were studied using six different combinations of twisted element in a section. The results show that in the near wall region, increasing dislocation angle can improve the coordination between velocity and temperature gradient and two adjacent twist elements in opposite rotate direction are better than that in the same each other. For the coordination between velocity and pressure gradient, two adjacent twist elements in the same rotate direction are superior to that in opposite each other, but the difference decreases with the increasing dislocation angle. When the dislocation angle is 90°, the difference is minimal in the range of y/R < 0.75.