網格式鰭片之蒸發性能研究

A Study of Evaporation Performance on Mesh-covered Fins

黃浩林(Hao-Lin Huang)

指導教授 ： 簡良翰

國立臺北科技大學/機電學院/能源與冷凍空調工程系碩士班/碩士(2008年)

摘要

本研究主旨是探討以不同的網格數目纏繞於不同鰭片管上之池沸騰熱傳性能研究。本實驗工作流體為R134a，測試之飽和溫度為5℃、10℃與26.67℃；鰭片管之鰭片密度為42FPI、50FPI與60FPI，鰭片高為0.2mm與0.4mm；而纏繞網格目數分別有#80目紅銅、#80目黃銅、#100目黃銅，與#120目黃銅，其網格之孔隙寬範圍約0.139 ~ 0.268 mm。
實驗結果發現：鰭片管在纏繞 #80 ~ #100目的網格後，可使鰭片表面形成許多大小適當的氣孔，並且氣體較容易殘留於渠道內，而大幅度增加熱傳性能。當飽和溫度為5℃與10℃時，鰭片管纏繞 #100目黃銅網格之熱傳性能最佳；但飽和溫度為26.67℃時，以纏繞雙層 #80目紅銅最佳。所有測試管中以60FPI鰭片管、鰭片高0.4mm纏繞雙層 #80目紅銅網格最佳；相對於光滑管之熱傳性能，在飽和溫度為5℃、10℃與26.67℃時，其平均熱傳性能分別提升10.93、7.53與6.16倍。50FPI鰭片管之鰭片高由0.2mm增加為0.4mm時，其熱傳性能增加42%；鰭片密度由50FPI增加為60FPI並將鰭片寬(Wt) 從0.322mm縮小為0.212mm時，其熱傳性能增加59%。本實驗之成果可利用於空調主機之蒸發器上，以間接增加主機效率而提升空調主機性能。

關鍵字

氣泡 ； 沸騰 ； 網格 ； 鰭片 ； 測試管 ； 冷媒

並列摘要

This study investigates a new enhanced boiling surface, which is made by wrapping wire mesh on finned tubes. Pool boiling performance of the new enhanced tubes has been tested in Refrigerant-134a at 5, 10, 20, and 26.67oC saturation temperatures. Brass or copper mesh of 80, 100, or 120 meshes per inch was wrapped on finned tubes of 42, 50, or 60 FPI (fins per inch). The fin heights were either 0.2 mm or 0.4 mm. The test results show that the mesh covered fin tubes significantly enhanced the boiling performance by forming many pores of proper sizes on the surface and sustaining vapor in the tunnels formed by the mesh and fins. The enhanced surface formed by single layer of #100 (100 mesh per inch) brass mesh results in the best boiling performance at 5, and 10oC. However, the double layers of #80 copper mesh results in the best performance at 26.67oC. The best surface was made by wrapping two layers of # 80 copper mesh on the 0.4 mm fin height, 60 FPI tube. The boiling heat transfer coefficient of this surface is enhanced by 10.93 folds in average as compared with the smooth surface at 26.6oC saturation temperature. The enhancement ratio decreases as the saturation temperature decreases from 7.53 folds at 10oC to 6.16 folds at 5oC.

並列關鍵字

bubble ； boiling ； mesh ； fin ； tube ； refrigerant

參考文獻

[1] Chien, L. H., and Webb, R. L., 1998, “Parametric studies of nucleate pool boiling on structured surfaces, part I: Effect of tunnel dimensions,” Journal of Heat Transfer, Vol. 120, pp. 1042-1048.

[2] Chien, L. H., and Webb, R. L., 1998, “Parametric studies of nucleate pool boiling on structured surfaces, part II: Effect of pore diameter and pore pitch,” Journal of Heat Transfer, Vol. 120, pp. 1049-1054.

[3] Webb, R. L., 2004, “Odyssey of the Enhanced Boiling Surface,” J. of Heat Transfer, 126 (6): 1051-1059.

[4] Chien, L. H., and Webb, R. L., 1998, “A nucleate boiling model for structured enhanced surfaces,” International Journal of Heat and Mass Transfer, Vol. 41, No. 14, pp. 2183-2195.

[5] Das, A. K.,Das, P.K.,S.Bhattacharyya, and Saha, P., 2007, “Nucleate boiling heat transfer from a structured surface-Effect of liquid intake,” Int. Journal of Heat & Mass Transfer 50, pp. 1577-1591.