摘要
The influences of circular-ring turbulators （CRT） and twisted tape （TT） swirl generators on the heat transfer enhancement, pressure drop and thermal performance factor characteristics in a round tube are reported. The circular-ring turbulators were individually employed and together with the twisted tape swirl generators in the heated section of the tube. Three different pitch ratios （I/D = 1.0, 1.5, and 2.0） of the CRT and three different twist ratios （y/W= 3, 4, and 5） of the TT were introduced. The experiments were conducted using air as the working fluid under a uniform wall heat flux condition, for the Reynolds number between 6000 and 20000. The experimental results reveal that the heat transfer rate, friction factor and thermal performance factor of the combined CRT and qT are considerably higher than those of CRT alone. For the range examined, the Sncreases of mean Nusselt number, friction factor and thermal performance, in the tube equipped with combined devices, respectively, are 25.8%, 82.8% and 6.3% over those in the tube with the CRT alone. The highest thermal performance factor of 1.42 is found for the combined device consisting of the CRT with l/D = 1.0 and TT with y/W= 3. The correlations of the Nusselt number, friction factor and thermal performance factor of the tubes with combined devices are also developed in terms of Reynolds number, Prandtl number, twist ratio and pitch ratio.
circular-ring turbulators (CRT ) 和扭曲的磁带(TT ) 的影响打漩在一个圆试管的热转移改进，压力落下和热表演因素特征上的发电机被报导。circular-ring turbulators 个别地被采用并且和扭曲的磁带打漩在试管的激烈的节的发电机。三不同沥青比率(l/D = 1.0， 1.5，和 2.0 ) CRT 和三不同扭曲比率(y/W = 3， 4，和 5 ) TT 被介绍。实验在一个一致的墙热流动条件下面作为工作液体用空气被进行，为在 6000 和 20000 之间的雷纳兹数字。试验性的结果表明热转移率，磨擦因素和联合 CRT 和 TT 的热表演因素独自比 CRT 的那些更加高。为检验的范围，在与联合设备装备的试管，分别地，吝啬的 Nusselt 数字，磨擦因素和热性能的增加在在试管的那些上是 25.8% ， 82.8% 和 6.3% 与 CRT 独自一个。1.42 的最高热的表演因素被作出对有利的裁决与 l/D = 由 CRT 组成的联合设备 1.0 并且有 y/W = 的 TT 3。Nusselt 数字，磨擦因素和有联合设备的试管的热表演因素的关联也以雷纳兹数字， Prandtl 数字，扭曲比率和沥青比率被开发。
基金
Supported by the Thailand Research Fund (TRF)
