同心圆柱体间旋转气隙内对流换热的数值模拟研究

摘要

In the present study, the convective heat transfer characteristic of air gap between rotating inner cylinder and concentric fixed outer cylinder has been simulated using commercial Computation Fluid Dynamic (CFD) software. Distributions of velocity field, temperature field and heat flux have been analyzed at different Taylor number. Comparing with the Nusselt number calculated by empirical formula, the average relative error of the averaged Nusselt number calculated by CFD simulation is at a reasonable scope, which validates the effectiveness of numerical simulation. Results show that, due to the existence of Taylor vortexes, distributions of velocity field, temperature field and heat flux fluctuate periodically along axial direction, and the frequency of the fluctuation correspond with the number of vortexes in the fluid field. Fluctuation of velocity and temperature has same change trend, while the trend of heat flux is opposite. Averaged Nusselt number enlarges with the increase of Taylor number, and the larger Nusselt number is, the better convective heat transfer performance is. Additionally, the convective heat transfer characteristic of air gap with slots has also been simulated, and reasons why Taylor-Couette Flow can enhance heat and mass transfer have been analyzed.%本文利用商用CFD软件对发电机气隙简化模型——同心旋转圆柱体间环形气隙内流体对流换热情况进行数值模拟，得到了不同泰勒数Ta下流场的速度分布、温度分布和热流密度分布。将模拟得出的平均努赛尔数Nu与经验公式的计算值进行了对比，误差在合理的范围之内，证明了数值模拟的有效性。计算结果表明，受流场中泰勒涡的影响，速度、温度、以及热流密度沿轴向的分布呈现周期性波动，波动频率与泰勒涡的数量相同，其中，速度与温度分布波动的变化趋势相同，热流密度波动的变化趋势与前两者相反；泰勒数Ta越大，流场的平均努赛尔数Nu越大，流场的对流换热性能越好。另外，本文还对带凹槽气隙模型进行了流动模拟，分析了泰勒-库特流能够强化传热传质的原因，为后续发电机环形气隙对流换热特性的模拟做准备。