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研究生:鄒珀全
研究生(外文):Po-Chuan Zou
論文名稱:結合強制脈衝流動與多孔熱沉用於電子元件之散熱增強分析
論文名稱(外文):Augmentation of Electronic Cooling by Flow Pulsating and Porous Insert
指導教授:黃博全黃博全引用關係
指導教授(外文):Po-Chuan Huang
口試委員:黃仁智傅武雄
口試日期:2011-07-26
學位類別:碩士
校院名稱:國立臺北科技大學
系所名稱:能源與冷凍空調工程系碩士班
學門:工程學門
學類:其他工程學類
論文種類:學術論文
論文出版年:2011
畢業學年度:99
語文別:中文
論文頁數:99
中文關鍵詞:脈衝流多孔質熱沉熱傳增強
外文關鍵詞:Pulsating flowPorous heat sinkHeat transfer enhancement
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近代電子產品面臨微小化後散熱不易的嚴重問題,導致需要尋求一種更快速有效的散熱技術。本文目的嘗試結合多孔質熱沉與脈衝流兩種熱傳增強方法同時施加於發熱之矩形電子元件之對流熱傳中,探討其散熱增強之效益。
研究方法為以數值模擬分析於強迫脈衝流下,兩平行管道內之三矩形發熱元件間插入多孔材料的熱流場分佈及其熱傳特性。文中純流體區內遵守unsteady Navier-Stoke方程式,多孔材質區內則因考慮多孔質微結構造成之邊界不滑移與慣性效應,故採用transient Forchheimer-Brinkman-Darcy模式模擬多孔質熱沉內部流動狀態。導入流線函數-渦度公式,將無因次化複合層熱流場系統方程式轉成為電腦可解的差分方程式。對於介面不連續處之物性則以調和平均公式處理,以確保參數之連續性。藉由變化各項參數,包括達西數Da、頻率參數St、振幅參數A、雷諾數Re、熱源間隔 以及多孔材料之 與 值,用以探討熱流場變化及其對熱傳增強效益。經數值模擬結果顯示,由脈衝流場與多孔質所引發位於兩熱源體間與下游之循環渦流的週期性結構變化,對第二塊以下之熱源體之對流散熱有增強的效益,且此散熱增強的效益會隨著達西數 、脈衝頻率 、脈衝振幅 、雷諾數 及熱傳導率 等增加而增加,但隨多孔質高度的增加而減少。


Modern microelectronics thermal management is facing considerable challenges in the wake of miniaturizing of components leading to higher demands on net heat flux dissipation. The main motivation of this study is to explore the effects of both the heat transfer enhancement factors by flow pulsation and porous-cover heat sink on the convective cooling of electronic device.
The present work presents a numerical study of heat transfer enhancement by forced pulsating convection at the vertical walls of heat generating blocks evenly mounted on the lower plate of a channel through the insertion of porous materials between the blocks. The flow over the fluid region is governed by the unsteady Navier-Stokes equation, and the flow through the porous medium is governed by the transient Darcy-Brinkman-Forchheimer equation that account for the effects of the impermeable boundary and inertia. Through the use of a stream function-vorticity transformation, solution of the coupled governing equations for the porous/fluid composite system is obtained using the control-volume method. The harmonic mean formulation was used to handle the discontinuous thermophysical properties across the interface. In addition, the dependence of streamline, isotherm, and enhanced heat transfer rate on the governing parameters defining the problem is examined in detail.
The results show that the periodic alteration in the structure of recirculation flows inside the inter-block region and the downstream block, caused by both porous block and flow pulsating, significantly enhances the heat transfer rate on the second and subsequent heat blocks. This cooling enhancement increases with the Darcy number Da, Reynolds number Re, pulsation amplitude A and frequent St, and conductivity ratio , but decreases with the thickness of porous insert Hp*.


目錄

摘要 i
Abstract ii
致謝 iv
目錄 v
表目錄 vii
圖目錄 viii
第一章 緒論 1
1.1 前言 1
1.2 文獻回顧 2
1.2.1 多孔材質熱傳研究 2
1.2.2 脈衝流與多孔材質的應用 4
1.3 研究目的 5
第二章 基礎理論 6
2.1 系統描述 6
2.2 基本假設 7
2.3 系統方程式 7
2.3.1 純流體區 7
2.3.2 多孔材質區 8
2.3.3 熱源體區 9
2.3.4 解析區域之起始條件 9
2.3.5 解析區域之邊界條件 9
2.4 無因次化分析 11
2.4.1 無因次化純流體區 11
2.4.2 無因次化多孔材質區 12
2.4.3 熱源體區 12
2.4.4 無因次化邊界條件 13
2.4.5 紐賽數及壓力的計算 14
第三章 數值分析 16
3.1 差分方程(流體區) 17
3.2 差分方程(多孔材質區) 21
3.3 差分方程式(熱源體區) 25
3.4 流體與多孔材質介面 26
3.5 低鬆弛係數(Relaxation factor) 28
3.6 求解步驟 29
第四章 結果與討論 31
4.1 網格獨立與時間獨立 31
4.2 數值評估 33
4.3 數值驗證 35
4.4 穩定流場下多孔材質所引起之熱流場變化 39
4.5 脈衝流下多孔材質所引起之熱流場變化 44
4.5.1 達西數Da之影響 49
4.5.2 雷諾數Re之影響 55
4.5.3 脈衝流振幅A之影響 61
4.5.4 脈衝流頻率參數St的影響 66
4.5.5 熱源間隔Ss*之影響 72
4.5.6 多孔介質高度Hp*之影響 77
4.5.7 多孔介質與流體熱傳導比Rk 之影響 83
4.6 參數變化對流場壓力降的影響 88
第五章 結論 91
參考文獻 93
符號彙整 96



參考文獻

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