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首页> 外文期刊>International communications in heat and mass transfer >Thermal characteristics in a heat exchanger tube fitted with dual twisted tape elements in tandem
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Thermal characteristics in a heat exchanger tube fitted with dual twisted tape elements in tandem

机译：装有双扭带元件的换热器管中的热特性

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The paper presents a comparative investigation of enhanced heat transfer and pressure loss by insertion of single twisted tape, full-length dual and regularly-spaced dual twisted tapes as swirl generators, in a round tube under axially uniform wall heat flux (UHF) conditions. The investigation encompassed the Reynolds number based on the inlet tube diameter (D) ranging from 4000 to 19,000. The experiments are performed using single twisted tapes and full-length dual twisted tapes with three different twist ratios (y/w =3.0,4.0 and 5.0) and also regularly-spaced dual twisted tapes with three different space ratios (s/D = 0.75, 1.5 and 2.25). The effects of major parameters on heat transfer and friction factor are discussed and the results from both single and dual twisted tape inserts are compared with those from the plain tube. The result shows that the heat transfer of the tube with dual twisted tapes is higher than that of the plain tube with/without single twisted tape insert. For both single twisted tape and full-length dual twisted tapes, Nusselt number (Nu) and friction factor (f) tend to increase with decreasing twist ratio (y/w). The average Nusselt number and friction factor in the tube fitted with the full-length dual twisted tapes at y/w = 3.0, 4.0 and 5.0, are respectively 146%, 135% and 128%; and 2.56, 2.17 and 1.95 times of those in the plain tube. For the regularly-spaced dual twisted tapes, the heat transfer rate is decreased with increasing space ratio (s/D). The average Nusselt numbers in the tube fitted with the regularly-spaced dual twisted tapes (s/D) of 0.75, 1.5 and 2.25 are respectively, 140%, 137% and 133% of that in the plain tube. With the similar trend mentioned above, all dual twisted tapes with free spacing yield lower heat transfer enhancement in comparison with the full-length dual twisted tapes (s/D = 0.0).
机译：本文通过在轴向均匀壁热通量（UHF）条件下，在圆管中插入单股扭曲带，全长双股和规则间隔的双股扭曲带作为旋流发生器，来增强传热和压力损失的比较研究。研究包括基于入口管直径（D）的雷诺数，范围为4000至19,000。实验是使用具有三种不同扭曲比（y / w = 3.0、4.0和5.0）的单股扭曲带和全长双股扭曲带以及具有三种不同空间比例（s / D = 0.75）的规则间隔的双股扭曲带进行的。 ，1.5和2.25）。讨论了主要参数对传热和摩擦系数的影响，并将单扭和双扭带插入件的结果与普通管的结果进行了比较。结果表明，双扭带管的热传递比带/不带单扭带插入物的普通管的传热要高。对于单扭带和全长双扭带，努塞尔数（Nu）和摩擦系数（f）均会随着扭曲比（y / w）的降低而增加。装有全长双绞带的管子的y / w = 3.0、4.0和5.0时，其平均努塞尔数和摩擦系数分别为146％，135％和128％。分别是普通管的2.56倍，2.17倍和1.95倍。对于规则间隔的双绞带，传热率随着空间比率（s / D）的增加而降低。装有规则间隔双扭带（s / D）的管中的平均努塞尔数分别为0.75、1.5和2.25，分别为普通管的140％，137％和133％。在上述类似趋势下，与全长双绞线带（s / D = 0.0）相比，所有具有自由间距的双绞线带产生的传热增强都较低。

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