同轴套管间涡旋流动及强化传热数值模拟

相对旋转两同轴套管间的涡旋流动,能够带来二次流强化传热传质作用,在航空、水处理、生态保护、生物工程和膜分离等领域都具有广泛的应用价值。本文使用Fluent软件,对同轴套管间涡旋流动及传热特性进行数值模拟,考察了内管转速、内外管壁面温差等操作参数变化对同轴套管间流体传热性能的影响,分析了涡旋流动与传热效率之间的关联关系。模拟结果表明:内管转速增加在流场中形成泰勒涡,涡流扰动增大了高温壁面与流体间的热流密度,增强了流体传热效率。增大内外管壁面温差,也可加强流体传热性能,但其强化作用不及内管转速的强化作用显著。受流场中泰勒涡影响,流体速度、温度及热流密度沿轴向的分布都呈正弦状周期性波动,在相邻两涡交界面处,流体传热性能最好,在涡中心处的传热性能最差。

Numerical simulation of vortex flow and heat transfer enhancement between coaxial casingpipes

The vortex flow which occurs in annulus between rotating inner cylinder and concentric fixed outer cylinder can enhance heat transfer and mass transfer performances of fluid, and has wide application value in engineering fields such as air, water treatment, ecological protection, biotechnology and membrane separation.The paper used fluent software to simulate the vortex flow in annulus between rotating inner cylinder and concentric fixed outer cylinder and feature of heat transfer, and investigated the effect of varying inner cylinder rotating velocities and temperature differences between the two cylinders on heat transfer performances, and analyzed the relation between flow characteristics and heat transfer efficiencies. Results show that Taylor vortices is formed in flow field with the increase of inner cylinder rotating velocity, intensive disturbance increases the density of heat transfer between high temperature face and fluid,and strengthens the efficiency of fluid heat transfer. The increase of temperature difference can also improve heat transfer efficiency of fluid, but the effect of its improvement is less obvious than that of inner cylinder rotating velocity. Due to the influence of Taylor vortices, the distribution of velocity field, temperature field and heat flux density presents a sinusoidal periodic fluctuation along axial direction.The heat transfer performance at the interface between two vicinity vortices is the best and that at the center of vortices is the worst.