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研究生:羅翊文
研究生(外文):Yi-Wen Lo
論文名稱:噴嘴幾何形狀與多孔材貼附層對平板衝擊熱傳之影響
論文名稱(外文):Effect of Nozzle Geometry and Attached Porous Layer on Jet Impingement Heat Transfer of a Flat Plate
指導教授:吳佩學
指導教授(外文):Pey-Shey Wu
學位類別:碩士
校院名稱:大葉大學
系所名稱:機械與自動化工程學系
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2010
畢業學年度:98
語文別:中文
論文頁數:61
中文關鍵詞:衝射多孔介質中心孔數值模擬中心孔深度雷諾數
外文關鍵詞:jet impingementporous mediumcenter holenumerical modelingcenter hole depthReynolds number
相關次數:
  • 被引用被引用:3
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衝射在工業界是一項很重要的熱傳技術,例如金屬與玻璃退火、雷射冷卻、氣渦輪葉片冷卻與微電子散熱等。衝射的熱傳增強技術,目前在學術界仍是被積極探討的問題。
本論文以數值模擬方式探討在衝擊目標平板上覆蓋一層有或無中心孔之多孔介質厚層對於衝射熱傳之增強效果。在模擬中,純流體區域選擇RNG 紊流模型,而多孔介質區域則採用Forchheimer延伸達西的模型。數值模擬結果以文獻可獲得的實驗數據做合理性驗證,對於現有模型在高雷諾數的缺失,本文也提出修改的建議。
計算結果顯示,貼附一層有足夠深度的中心孔多孔介質層可以有效提升熱傳效果,但若是附加一層沒有中心孔、或是有不夠深的中心孔多孔層則會不利於散熱。這些物理現象可經由模擬之流動觀察獲得良好的解釋。在固定孔系率與穿透性的條件下,本文探討的熱傳問題中具有影響力的參數包括:衝射雷諾數、噴嘴幾何(含噴嘴長度以及噴嘴與中心孔的直徑比)、噴嘴至平板距離以及中心孔深度。適當的中心孔幾何可引導冷空氣進入多孔區並與沿著加熱平板進行熱傳;噴嘴與中心孔直徑相同時得到的熱傳效果最佳;對於噴嘴長度的選用,在低雷諾數時噴嘴越短使流體越趨近均勻流的熱傳效果越好;高雷諾數時,噴嘴長度應可使流體達到完全發展流所得到的熱傳效果較好。最後,本文對於此探討的問題提出紐賽數與雷諾數之關係式,期能供設計者對於平板貼附有中心孔多孔介質層之衝擊冷卻設計之用。
Jet impingement is an important heat transfer technique in industries, such as metal and glass annealing, laser cooling, gas turbine blade cooling, and cooling of microelectronics. Nowadays, enhancement techniques for jet impingement heat transfer are still under intensive investigation by academic researchers.
In this study, the enhancement of impingement heat transfer on a flat plate covered with a thick layer of porous medium with or without a center hole was numerically investigated. The renormalization group (RNG) turbulence model is selected for the fluid region while Forchheimer extended Darcy’s model is used for porous region. The numerical modeling was justified by comparisons with available experimental data. A modification to the existing model which shows drawbacks for high Reynolds number applications is also suggested in this study.
Computational results show that an attached porous medium having a sufficiently deep center hole can effectively enhance jet impingement heat transfer while an attached thick porous layer without a center hole, or having a center hole with insufficient depth, has detrimental effect. The physics of these results are supported and well explained by the detailed flow patterns. Under the condition of fixed porosity and permeability, the influential parameters for the investigated heat transfer problem include the jet Reynolds number, nozzle geometry (including nozzle length and jet-to-hole diameter ratio), jet-to-plate distance, and the center hole depth. A good hole geometry should well trap the jet and direct the coolant along the heated plate. The heat transfer performance is the best when the jet-to-hole diameter ratio equals one. To give better heat transfer performance, the nozzle should be shorter, resulting in more uniform flow at the exit, at low Reynolds numbers, and it should be long enough at high Reynolds numbers so that the exit flow is fully developed. Finally, corre3lations of Nusselt number versus Reynolds number are proposed for the investigated problem. It is hoped that the correlations are helpful to the designers who will use an attached porous layer in an impingement cooling design.
封面內頁
簽名頁
博碩士論文暨電子檔案上網授權書.....iii
中文摘要.........................iv
ABSTRACT ........................vi
誌謝.............................viii
圖目錄...........................xi
表目錄...........................xiii
符號說明.........................xiv

第一章 緒論......................1
1.1 研究背景...................1
1.2 研究目的...................2
第二章 文獻回顧......................5
第三章 問題描述與數值模型...........12
3.1 各模擬幾何形狀與網格.........12
3.2 基本假設....................12
3.3 統御方程式..................13
3.4 離散方法....................20
3.5 數值計算.....................21
3.5.1. 收斂條件...............21
3.5.2. 鬆弛因子...............22
第四章 平板加入多孔材之模擬與討論.....26
4.1 完全發展流與均勻流的差異.......26
4.2 中心孔深度的影響..............26
4.3 雷諾數的影響..................27
4.4 噴嘴幾何的影響................28
4.4.1 噴嘴直徑的影響............28
4.4.2 噴嘴長短的影響............29
4.5 噴嘴與平板間距離的影響..........30
4.6 雷諾數與紐賽數之關係............31
4.7 總結..........................32
第五章 結論..........................54
參考文獻...............................56
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[36] FLUENT 6 User’s Guide Volume 1-4,Tutorial Guide Volume 1-2使用手冊
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