The results of experimental studies on heat transfer and pressure drop during forced convection of air and liquid ethylene glycol in pipes with inner fins are presented. Tubes with integrated fins were made by extrusion from an aluminum alloy; the fins were straight or twisted spirally along the tube and their tips almost reached the tube axis. Depending on the process parameters, the heat transfer coefficients of the finned tubes that were obtained with these liquids were higher by a factor of 3 to more than a factor of 8 compared to plain tubes. The pressure drop was correspondingly higher for finned than for smooth tubes. The improvement in heat transfer cannot be explained quantitatively simply by linear coupling with the enhancement in the surface area due to finning. In addition to this quantitative effect, there is also a qualitative effect that is caused by the shape of the fins. The real improvement in heat transfer appears to be determined by efficient secondary flows that form in the flow channels between adjacent fins and interact with the vortex core flow in the middle of the tube cross section.

中文翻译：

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带有内部扭曲鳍的水平管中的强制对流传热和压降

给出了在带有内部散热片的管道中空气和液体乙二醇强制对流过程中传热和压降的实验研究结果。带有集成散热片的管是由铝合金挤压制成的；鳍片沿管子呈笔直或螺旋形扭曲，其尖端几乎到达管子轴线。取决于工艺参数，与普通管相比，用这些液体获得的翅片管的传热系数要高3到8倍以上。翅片的压降比光滑管的压降高。传热的改善不能简单地通过线性耦合与由于翅片形成的表面积的增加而定量地解释。除了这种量化效应之外，翅片的形状也有定性作用。传热的真正改善似乎取决于有效的二次流，该二次流形成在相邻散热片之间的流道中，并在管横截面的中间与涡流芯流相互作用。