渦流產生器應用於熱交換之可視化研究

Flow Visualization of Wave-type Vortex Generators Having Inline and Staggered Fin-tube Arrangement

羅文明(Jerry Lo)

指導教授 ： 林育才

元智大學/工程學院/機械工程學系/碩士(2001年)

摘要

本文旨在探討渦流產生器應用於型鰭管式熱交換器之可視化研究。目的在瞭解渦流產生器對鰭片表面的影響，為了觀察鰭片表面流場變化，本實驗的測試模型採放大製作，分別以In-line和Staggered兩種管排排列方式進行實驗，共7個測試件。
實驗發現當Re=500時，染料撞擊管排時所產生的Horseshoe vortex，以平板型所觀察到的流場較弱，且在管排間有明顯的回流現象產生（re-circulation zone）。
Re=1500時，此時可清楚觀察到Horseshoe-vortex捲動頻率變快渦漩半徑變小，但是管壁間的回流區仍然存在可見。實驗中更發現具渦流產生器的鰭片，在管壁間行成縱向渦旋（longitudinal vortex），使得管壁後方回流現象消失，其中以交錯管排，弦翼角為60°高度3mm所產生的縱向渦漩較緊實、連續性較佳。
壓降部分，平行管排中以具渦流產生器-弦翼角60°者較大， 壓降平均增加約40﹪；交錯管排中以具渦流產生器-弦翼角60°/高度6mm的壓降較高，壓降平均比平板型高出約54﹪。

關鍵字

渦流產生器 ； 迴流區 ； 縱向渦流

並列摘要

This study presents visual observation of enlarged fin-and-tube heat exchangers with and without the presence of vortex generators. A total of seven samples of fin-and-tube heat exchangers having inline and staggered arrangements are examined, including two plain fin and five wave-type vortex generators.
For plain fin geometry at Re = 500, the horseshoe vortex generated by the tube row is not so pronounced, and a very large secondary flow circulation is seen between the first and second row. This flow re-circulation phenomenon is almost disappeared with the presence of proposed vortex generator. The presence of vortex generators significantly increases the vortrical motions of the horseshoe vortices hitting on the tubes. A much better mixing phenomenon is seen by introducing the vortex generators.
For sample with αVG= 60°and HVG= 3 mm of vortex generator, the longitudinal vortex motion is clearly seen between the first and second row. When the circulation phenomenon is disappeared, one can see the vortrical motions of the longitudinal vortex is so intensity and clear.
In the inline arrangement part, the frictional penalty of the proposed vortex generator (VG-5) is about 40% higher than that of the plain fin geometry. The staggered arrangement part, the frictional penalty of the proposed vortex generator (SV4) are about 54% higher than that of the plain fin geometry. The penalty of pressure drops of the proposed vortex generators relative to plain fin geometry is comparatively insensitive to change of Reynolds number.

並列關鍵字

Vortex Generator ； re-circulation zone ； Longitudinal Vortex

參考文獻

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