小扭率扭曲椭圆管层流流动与传热的数值分析

采用数值计算的方法,研究分析了层流状态下扭曲椭圆管内的流动与换热情况.在保持其他参数不变的情况下,管内的Nu随着Re的增大而增大,随着扭率Tr的增大而减小,随着椭圆管几何参数b/a的增大而减小,而阻力系数f随着Re、扭率Tr以及椭圆管几何参数b/a的增大均减小.另外,从速度场和温度场耦合的情况来看,层流状态下的换热得以强化的原因在于扭曲椭圆管内流体发生旋转,产生了二次流,而与主流相比较小的二次流可大大强化传热,使得管内流体的换热得到强化.

The Numerical Analysis of Low Prandtl Number Laminar Flow and Heat Transfer in Oval Tubes with a Small Twisted Ratio

Laminar fluid flow and heat transfer in twisted oval tubes are simulated by numerical analysis method.Numerical results show that when other parameters remain constant,the Nusselt number increases with increasing Reynolds number,and decreases with the increasing ratio of short axis to long axis b/a and twisted parameter Tr;the friction factor decreases with increasing Reynolds number,Tr and b/a.Besides,considering the coupling between the velocity and temperature fields,the reason for heat transfer enhancement is that the fluid rotates in the twisted oval tube and a secondary flow is induced.Small amplitude of secondary flow compared with the amplitude of the main flow will enforce heat transfer enhancement greatly,then the fluid heat transfer in the twisted oval tube is enhanced.