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Entrance Region Heat Transfer in a Channel With a Ribbed Wall

机译：肋壁通道内的入口区域传热

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Direct numerical simulation was performed for the heat transfer of airflow in the entrance region of a channel with repeated rib protrusions. The rib-pitch to rib-height ratio (Pi/H) was increased from 2.0 to 16.0 by four steps. The rib-height ratio (H/δ) was maintained constant at 0.20. The distribution of heat transfer coefficient numerically simulated agreed with the experiment by Kattchee and Mackewicz (1963, "Effects of Boundary Layer Turbulence Promoters on the Local Film Coefficients of ML-1 Fuel Elements," Nucl. Sci. Eng., 16, pp. 31-38). The enhancement parameter was used to evaluate the heat transfer performance by a ribbed channel. This parameter was defined as the ratio of the mean Nusselt number for the ribbed channel against the smooth channel consuming the same pumping power. The simulation result revealed that the enhancement parameter was maximized for Pi/H= 2 to 4 over the upstream ribs (x/δ<2) and was remained high for Pi/H= 4, 8, and 16 over the downstream ribs (x/δ>4). Therefore, the optimal rib pitch was smaller for the upstream ribs, and increased to the developed region. The mechanisms underlying this trend were discussed through observation of the streamlines, mean temperature, turbulence statistics, and instantaneous structures. The turbulence was increased over the ribbed wall for the cases of medium to wide rib pitch (Pi/H = 4, 8, and 16), whereas the turbulence increase appeared only over the upstream ribs (x/δ < 2) for the cases of narrow rib pitch (Pi/H = 2). The excellent performance of the wider rib pitch (Pi/H = 4, 8, and 16) at the downstream ribs (x/δ >2) was resulted from the turbulence increase activating the turbulent heat transport. Whereas, the superiority by the narrower rib pitch (Pi/H = 2, 4) comes from the turbulence activation, and the renewed thin boundary layer which continues due to the densely allocated ribs.
机译：对具有重复肋状突起的通道入口区域中气流的传热进行了直接数值模拟。肋距与肋高之比（Pi / H）通过四个步骤从2.0增加到16.0。肋骨高度比（H /δ）保持恒定在0.20。数值模拟的传热系数分布与Kattchee和Mackewicz（1963，“边界层湍流促进剂对ML-1燃料元件的局部膜系数的影响”）的实验一致，Nucl。Sci。Eng。，16，pp。 31-38）。增强参数用于评估带肋通道的传热性能。该参数定义为肋状通道的平均努塞尔数与消耗相同泵浦功率的平滑通道之比。仿真结果表明，在上游肋上，Pi / H = 2到4时，增强参数最大（x /δ<2），在下游肋上，Pi / H = 4、8和16时，增强参数保持较高。 /δ> 4）。因此，最佳的肋节距对于上游肋条来说较小，并且增加到展开区域。通过观察流线，平均温度，湍流统计数据和瞬时结构，讨论了这种趋势的潜在机理。对于中等至较宽的肋骨间距（Pi / H = 4、8和16），湍流在肋壁上增加，而对于肋骨，湍流仅在上游肋骨上出现（x /δ<2）肋间距变窄（Pi / H = 2）。下游肋（x /δ> 2）处较宽的肋节距（Pi / H = 4、8和16）的出色性能归因于湍流增加，从而激活了湍流热传递。而更窄的肋节距（Pi / H = 2、4）的优越性来自湍流的激活，并且由于肋条分布密集，新的薄边界层得以延续。

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  • 来源
    《Journal of Heat Transfer》 |2016年第12期|122001.1-122001.7|共7页
  • 作者

    Koji Matsubara; Hiroyuki Ohta; Takahiro Miura;

  • 作者单位

    Mechanical and Production Engineering,Niigata University,Ikarashi 2-Nocho 8050,Nishi-Ku, Niigata 950-2181, Japan;

    Hokuetsu Co., Ltd.,Shinjuku-Ku 160-0023, Tokyo;

    Tonets Corporation,Chuo-Ku 104-8324,Japan;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
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  • 正文语种 eng
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