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Comparative study of mass transfer distributions and oil-flow visualizations with image analysis on long and short 90° elbows
Experimental Thermal and Fluid Science ( IF 3.2 ) Pub Date : 2020-12-24 , DOI: 10.1016/j.expthermflusci.2020.110332
Nobuyuki Fujisawa , Tomohiro Takizawa , Takayuki Yamagata

To understand the mass transfer mechanism of 90° elbows, a comparative study of mass transfer measurements and oil-flow visualization with image analysis is carried out for long and short 90° elbows in the Reynolds numbers Re = 5 × 104 –2 × 105. The mass transfer distributions are evaluated by using the plaster-dissolution method, while the oil-flow fields are quantitatively visualized by oil-flow technique combined with cross-correlation image analysis, which allows observation of the oil-flow velocity magnitude and direction on the elbow walls. The mass transfer evaluations in the sub-critical Reynolds number indicate an increase in mass transfer distribution along the center wall of the long elbow and a further increase in the downstream of the short elbow. These are highly suppressed on the center wall as the Reynolds number increases, and the mass transfer distributions become almost independent of the elbow curvatures in the post-critical Reynolds number. These observations of mass transfer distributions are well correlated with the oil-flow visualizations with image analysis, which indicate formation of low oil-flow-velocity on the center wall of the long elbow, occurrence of flow separation and reverse flow downstream of short elbow at sub-critical Reynolds number. These features of oil-flow fields on the elbows are highly suppressed and becomes independent of the elbow curvature in the post-critical Reynolds number.



中文翻译:

90度长和短弯头的传质分布和油流可视化与图像分析的对比研究

为了了解90°弯头的传质机理,在雷诺数Re = 5×10 4 –2×10中对长和短的90°弯头进行了传质测量和油流可视化以及图像分析的对比研究。5。使用灰泥溶解法评估传质分布,同时通过油流技术结合互相关图像分析来定量显示油流场,从而可以观察油流速度大小和方向。肘壁。亚临界雷诺数下的传质评估表明,沿长弯头中心壁的传质分布增加,而短弯头下游的传质进一步增加。随着雷诺数的增加,它们在中心壁上受到高度抑制,传质分布几乎变得与后临界雷诺数中的弯头曲率无关。这些传质分布的观察结果与通过图像分析进行的油流可视化效果密切相关,这表明在长弯头的中心壁上形成了低的油流速度,在亚临界雷诺数下短弯头的下游出现了流分离和逆流。肘部上油流场的这些特征被高度抑制,并且变得与后临界雷诺数中的肘部曲率无关。

更新日期:2021-01-02
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