This paper addresses the experimental study of heat transfer enhancement of laminar flow in a tube fitted with Koflo Blade™ inline mixer as the swirl-flow generator and under constant surface heat flux. Experiments were carried out with air as heat transfer fluid and two different types of the mixer having blades crossing angles of 90° and 120° The flow swirling in the mixer is mainly due to the centrifugal force induced by the angle between the blades, which is responsible for heat transfer augmentation. The results show that the mixer with 90° blades supplies Nusselt numbers higher than the 120° mixer but, likewise, results in higher pressure drop. The rate of heat transfer in the tube equipped with inserts was augmented up to 78% and 47% for 90°-blades and 120°-blades mixers, respectively. The enhancement in heat transfer was correlated with the Graetz number that supports the experimental data for both mixers by a deviation within ±10%. Furthermore, the tube fitted with a 120°-blades mixer yields higher thermal performance with a maximum value of 1.77. As well, the 120°-blades mixer provides thermal performance factors up to 17% greater than that for 90°-blades mixer for the same pumping power, which implies that heat transfer effects significantly dominate pressure drop effects.

本文讨论了在装有 Koflo Blade™ 在线混合器作为涡流发生器并在恒定表面热通量下的管中层流增强传热的实验研究。使用空气作为传热流体和两种不同类型的叶片交叉角为 90° 和 120° 的混合器进行了实验。混合器中的流动涡流主要是由于叶片之间的角度引起的离心力，即负责传热增强。结果表明，具有 90° 叶片的混合器提供的 Nusselt 数高于 120° 混合器，但同样会导致更高的压降。对于 90° 叶片和 120° 叶片混合器，装有插件的管中的传热率分别增加了 78% 和 47%。传热的增强与支持两种混合器实验数据的 Graetz 数相关，偏差在 ±10% 以内。此外，配备 120° 叶片混合器的管子可产生更高的热性能，最大值为 1.77。同样，在相同的泵送功率下，120° 叶片混合器提供的热性能系数比 90° 叶片混合器高 17%，这意味着传热效应显着支配压降效应。