網格式鰭片管之R-134a冷媒沸騰性能研究

A Study of Boiling in R-134a on Mesh-Fin Tubes

簡良翰 ； 黃浩林 ； 吳忠駿

《冷凍空調與能源科技雜誌》 57期 (2009/06) Pp. 70-78

https://doi.org/10.7087/JEHVACE.200906.0070

摘要

本研究探討以各種的網格數目纏繞於鰭片管上之池沸騰熱傳性能。本實驗工作流體為R-134a，測試之飽和溫度為5℃、10℃與26.67℃；鰭片管之鰭片密度為42FPI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之鰭片管纏上雙層#80目紅銅網格的效果最佳；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。

關鍵字

核沸騰熱傳性能 ； 測試表面幾何形狀 ； 冰水機 ； 蒸發器

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 26.67℃ 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 one layer of #100 (100 mesh per inch) brass mesh results in the best boiling performance at 5, and 10℃. However, the surface formed by two layers of #80 copper mesh results in the best performance at 26.67℃. 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 26.6℃ saturation temperature. The enhancement ratio decreases from 7.53 folds at 10℃ to 6.16 folds at 5℃ as the saturation temperature decreases.

並列關鍵字

Nucleate boiling ； surface geometry ； chiller ； evaporator