Influence of Double-sided Rectangular-wing Tape Insert on Heat Transfer Enhancement in a Heat Exchanger Tube

The paper presents an experimental study of turbulent flow friction and heat transfer characteristics in a constant heat-fluxed circular tube fitted with double-sided rectangular-wing pairs in straight tapes. In the experiments, the winged tape was inserted into the test tube with a constant wing attack angle (?) of 45? in order to generate longitudinal vortex flows through the tube. The insertion of the winged tapes was performed with five ratios of wing-pitch to tube-diameter (PR=P/D=0.5, 1.0, 1.5, 2.0 and 2.5). The measurements were conducted for the airflow rate in turbulent regime, Reynolds number from 4200 to 25,000. The experimental results show that the Nusselt number increases with the rise in Reynolds number but decreases with the increment of wing-pitch ratio. The mean Nusselt number and friction factor are, respectively, up to 445% and 47.5 times over the smooth tube and the maximum thermal performance is 1.42. In addition, the winged tape with PR=0.5 provides the highest heat transfer and friction factor but the one with PR=1.0 yields the best thermal performance.本文针对加装带双侧矩形翼对的直扰流带的恒热流圆管，开展了其内湍流流动阻力与传热特性的实验研究。实验中，将带翼扰流带以45°的恒定翼攻角插入试验管内，以在管内生成纵向涡流。本次实验采用5种翼间距与管径之比（间距比PR=P/D分别为0.5、1.0、1.5、2.0及2.5）安装带翼扰流带。实验针对雷诺数区间为4200~25000的湍流工况下的气流开展了相关参数测量。实验结果表明，努塞尔数（Nusselt number）随雷诺数升高而增大，随翼间距比增大而减小。平均努塞尔数与摩擦阻力系数分别最高可达光滑管的445%与47.5倍，最大热性能系数为1.42。此外，PR=0.5的带翼扰流带可实现最高的传热性能与摩擦阻力系数，而PR=1.0的带翼扰流带则具备最优的热性能。