渐扩渐缩波纹通道内脉动流的传热强化

采用曲线坐标系下压力与速度耦合的SIMPLER算法, 数值研究了周期性渐扩渐缩波纹通道内脉动流动与换热情况,流动Re数的范围为10～1000,Pr数为0.7.计算考察了不同Re数、脉动频率以及振幅对通道内强化传热和压力损失的影响.研究结果表明,稳态下Re数大于40以后,流动出现分离,Re数大于600以后,流动显得复杂和混乱;受入口脉动流的影响,通道内的旋涡发生周期性的脱落、增长和迁移,从而增强了流体之间的扰动和掺混,强化了传热;传热的强化效果随着流动Re数、脉动频率以及振幅的增大而增强;另外,流动阻力随着无量纲时间呈正弦规律变化,但与脉动频率无关.

Heat Transfer Enhancement inside Converging-Diverging Wavy Channel by Pulsating Flow

The fully developed convective heat transfer characteristics inside two-dimensional periodically converging-diverging wavy channel with pulsating flow due to imposed entry pulsating mass flow under constant wall temperature was investigated numerically. Based on SIMPLER algorithm in the curvilinear body-fitted coordinates, the calculations were performed for Pr = 0.7, Re= 10~1000 on non-orthogonal non-staggered grids which are generated by elliptic equation systems. Effects of Reynolds numbers, pulsating amplitude and frequency on heat transfer enhancement and flow friction were studied. The results show that, in the steady regime, flow separates after Re>40, and becomes unsteady and chaotic after Re >600. Heat transfer can be enhanced by fluid pulsating and mixing which is caused by the vortices sweeping, diminishing and growing up due to the pulsating flow. The intensity of heat transfer enhancement increases with the increase of Reynolds numbers, pulsating frequency and amplitude. On the other hand, the flow friction varies periodically and sinusoidally with the dimensionless time, while it is independent of the pulsating frequency.