浮升力对旋转U型通道流动与换热影响的数值研究

Numerical Investigation of Buoyancy Influence on Flow and Heat Transfer Characteristics in Rotating Square U-Duct

关键词:  浮升力  U型通道  旋转  数值研究

Key words:  Buoyancy  Square U-duct  Rotation  Numerical investigation

摘要:

为研究浮升力对高旋转数(0～2.013)U型通道流动与换热的影响，采用k-ω SST两方程模型对其展开数值研究。分别对相同旋转数，不同温比(0.12，0.17和0.22)和相同温比(0.22)，不同旋转数条件下的U型通道进行研究。结果表明:在径向外流直通道中，浮升力诱发通道前缘面发生流动分离，前缘面的换热能力随旋转数的增大先减小而后增大；在径向内流直通道中，受浮升力影响流体呈双峰流型。随旋转数增大，前后缘面间Nu/Nus的差别减小，当旋转数增大到1.0左右时，后缘面的Nu/Nus的值超越前缘面。在静止通道内，温比越小换热能力越强；旋转通道与之相反。计算结果验证了浮力数在评价壁面换热能力的变化时，综合考虑了旋转数和温比对壁面换热的影响。

Abstract:

To investigate buoyancy influence on flow and heat transfer characteristics of U-duct in high rotation number range from 0 to 2.013，k-ω SST two-equation turbulence model was adopted. The same rotation number，different temperature ratios (0.12，0.17 and 0.22) and the same temperature ratio(0.22)，different rotation numbers U-duct were studied. The results show that in radial outward passage buoyancy induces the flow seperation in the vicinity of leading surface. Heat transfer intensity of leading surface firstly increased and then decreased with the increasing of rotation numbers. In radial inward passage，due to buoyancy effect the velocity profile presents in double peaks pattern. With the increasing of rotation number，the Nu/Nus difference between leading surface and trailing surface is reduced. When the rotation number increases approximately to 1.0，the Nu/Nus value of trailing surface is beyond that of leading surface. In stationary U-duct，heat transfer is enhanced at lower temperature ratio，while it is just reversed in rotating U-duct. The calculation results prove that buoyancy number is appropriate to evaluate the combined effect of rotation number and temperature ratio on heat transfer.