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姓名 黃兆雄(Chao-hsiung Huang) 查詢紙本館藏 畢業系所 機械工程學系 論文名稱 低風速狀態下鰭片之熱傳性能增強研究 相關論文 檔案 [Endnote RIS 格式]
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摘要(中) 本研究之目的為探討在低風速下之熱邊界層變化，據以設計應用於該條件下之斷續型鰭片及百葉窗型鰭片。在固定鰭片節距為1.2 mm時，改變兩種葉片長度分別為0.7 mm和1 mm，於風速範圍0.5 m/s至2.5 m/s，且加熱量為30W的條件下，討論影響性能之主要參數，與鰭片內部的流動狀態。並與風扇結合，探討風扇選用對於熱傳增強鰭片之重要性。
由壓降實驗結果可知，在斷續型鰭片時，縮小葉片長度，因剪應力較大，會使壓降上升；而百葉窗型鰭片，縮小葉片長度，可使通道流動的阻力下降，進而降低壓降。而熱傳方面，在風速小於1m/s時，本研究的斷續型和百葉窗型鰭片，氣流皆已完全發展；而在風速大於1m/s時，相同型式的鰭片受葉片長度的影響極低。
此外，若壓降大的熱傳增強鰭片，與平板鰭片使用相同之風扇，流量會下降許多，而使鰭片熱傳性能下降。因此，需根據各鰭片的壓降，選擇匹配之風扇，方可發揮鰭片原有的性能。摘要(英) The purpose of research is to discuss how the thermal boundary layer changes its thickness in lower air velocity. With very low air velocity executed in the experiment, we have designed two types of fins, which are the louver fin and the offset strip fin to perform experiment with the following parameters.
Under the given air velocity at 0.5 m/s to 2.5 m/s and heat addition in 30 Watt, we fix the fin pitch in length of 1.2mm and vary two different louver length with two types of fins at 0.7 mm and 1 mm respectively to observe the main factor to affect the performance of our system. In addition, we also combine fan into our system so as to discuss if the selection of fans could better the heat transfer enhancement significantly.
From the result of pressure drops, the shear stress will become larger when reduced the louver length and the increase of the pressure drop in the offset strip fin. However, in the louver fin, the pressure drop is decreased with reducing the louver length. It is because the flow resistance also decreased with the louver length.
According to our experimental study, the flow structure of both the two types of fin in air velocity below 1 m/s have been fully developed. When the air velocity increase upper than 1 m/s, the changing of louver length have nothing to do with the performance.
If the same fan used in different type of fin , the volume flow rate will be different with the pressure drop. So we have to choose the fan that fitting the individual fin hoping the heat transfer performance is good as we designed.關鍵字(中) ★ 低風速
★ 熱傳增強
★ 百葉窗型鰭片
★ 斷續型鰭片關鍵字(英) ★ low air velocity
★ heat transfer enhancement
★ louver fin
★ offset strip fin論文目次 摘要 i
Abstract ii
表目錄 v
圖目錄 vi
符號說明 viii
第一章、前言 1
1.1 研究動機與背景 1
1.2 研究目的 2
第二章、文獻回顧 6
2.1 鰭片節距 6
2.2 鰭片角度 8
2.3 葉片長度 9
2.4 總結 11
第三章、實驗方法 17
3.1 散熱鰭片的設計 17
3.2 測試段製作 18
3.3 實驗系統 19
3.3.1 銅棒加熱系統 19
3.3.2 風洞測試系統 20
3.3.3 模擬加壓平台 20
3.4 實驗量測儀器與設備 20
3.4.1 溫度量測 21
3.4.2 差壓測量 21
3.4.3 流量測量 21
3.4.4風速量測 22
3.4.5 資料擷取系統 23
3.5 實驗步驟 23
3.6 數據換算 24
3.6.1 加熱瓦數 24
3.6.2 熱傳係數 24
3.6.3 Nu紐賽爾數 24
3.6.4 Colburn j factor 24
3.6.5 friction factor 25
3.6.6 無因次熱邊界層發展長度 25
3.6.7 平板局部摩擦係數 26
第四章、實驗結果與討論 42
4.1 各類型散熱鰭片之壓降特性 42
4.2 各類型散熱鰭片之熱傳性能 43
4.2.1 葉片長度對於熱傳性能的影響 43
4.2.2 雷諾數對於熱傳性能的影響 43
4.2.3 鰭片類型對於熱傳性能的影響 44
4.2.4 各類型散熱鰭片之流動情形 44
4.3 使用FG-1a評估方法比較各鰭片之性能 45
4.4 使用FN-2評估方法比較各鰭片之性能 45
4.5 固定風扇與不同鰭片之流動特性 45
4.6 固定風扇與不同鰭片之熱傳特性 46
第五章、結論 60
參考文獻 61
附錄、實驗誤差分析 64參考文獻 Achaichia, A., and Cowell, T. A., 1988, “Heat Transfer and Pressure Drop Characteristics of Flat Tube and Louvered Plate Fin Surfaces,” Experimental Thermal and Fluid Science, Vol. 1, pp. 147-157.
DeJong, N. C., and Jacobi, A. M., 2002, “Localized Flow and Heat Transfer Interactions in Louvered-Fin Arrays,” International Journal of Heat and Mass Transfer, Vol. 46, pp. 443-455.
Dong, J. Q., Chen, J. P., Chen, Z. J., Zhang, W. F., and Zhou, Y. M., 2006, “Heat Transfer and Pressure Drop Correlations for the Multi-Louvered Fin Compact Heat Exchangers,” Energy Conversion and Management, Vol. 48, pp. 1506-1515.
Dong, J. Q., Chen, J. P., Chen, Z. J., and Zhou, Y. M., 2007, “Air-Side Thermal Hydraulic Performance of Offset Strip Fin Aluminum Heat Exchangers,” Applied Thermal Engineering, Vol. 27, pp. 306–313.
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Yang, K. S., Chiang, C. M., Lin, Y. T., Chien, K. H., and Wang, C. C., 2007, “On the Heat Transfer Characteristics of Heat Sinks: Influence of Fin Spacing at Low Reynolds Number Region,” International Journal of Heat and Mass Transfer, Vol. 50, pp. 2667-2674.
王啟川，2007，熱交換設計，五南圖書股份有限公司，台灣。
吳信昌，2008，具渦流產生器之散熱鰭片實驗研究，國立中央大學機械工程研究所碩士論文，中壢。指導教授 楊建裕(Chien-Yuh Yang) 審核日期 2013-7-16 推文 plurk
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