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研究生： 李明哲
Lee, Min-Jer
論文名稱： 電液動熱增強技術應用於鰭管式熱交換器之 性質研究
Heat Transfer and Fluid Flow Analysis in a Finned-Tube Heat Exchanger with Electrohydrodynamic Enhancement
指導教授： 張錦裕
Jang, Jiin-Yuh
學位類別： 碩士
Master
系所名稱： 工學院 - 機械工程學系
Department of Mechanical Engineering
論文出版年： 2004
畢業學年度： 92
語文別： 中文
論文頁數： 75
中文關鍵詞： 板鰭管式熱交換器 、電液動力學 、橢圓管
外文關鍵詞： oval finned-tube heat exchanger, Electrohydrodynamics (EHD), 3-D, numerical simulation
相關次數： 點閱：106  下載：3 
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    • 　　本文利用電液動( EHD，Electrohydrodynamic )理論探討一外加電場對板鰭管式熱交換器的熱液動性能特性的影響。文中針對四種不同的管排列(對齊、交錯)和電極排列(正方、對角), 以三維數值模擬相關的電場、速度場、壓力場以及溫度場，並且描述在不同的供給電壓( VE = 0 ~ 16KV )和雷諾數( Re = 100~1000 )時壓降及熱傳特性的變化。數值結果顯示外加電場的供給電壓增大時，科本因子(Colburn factor j )和摩擦因子(friction factor f )都會增加，但是當流場雷諾數增加時，熱傳增強的效果j/j0及壓損的增加f/f0會隨雷諾數的增加而減少，其中j0和f0為不施加電場下的Colburn factor和Fanning friction factor。由模擬結果得知在低雷諾數及高供給電壓時能夠產生最大的EHD熱傳增強效果。另外，交錯形( staggered )管排列方式、正方形( square )電極排列為探討的四種排列中具有最佳的熱傳增強效果。例如當供給電壓VE=16kV時，圓管的j/j0 = 2.18，f/f0 = 2.28，橢圓管(長短軸比2.5)的j/j0 = 2.43，f/f0 = 1.58，另外當供給電壓VE=16kV，交錯形( staggered )管排列方式、正方形( square )電極排列當中橢圓管的面積縮減能夠到達69﹪。總體來說在不同的供給電壓下橢圓管的面積縮減率約為圓管的1.6~3.3倍，此乃因橢圓管具流線形狀，若放置方向平行於流場則其壓損相對於圓管較小，因此EHD技術應用在橢圓管的效果比圓管佳。

    　　The paper discusses the electrohydrodynamic (EHD) enhancement through 3-D laminar fluid flow and heat transfer over plate oval-finned heat exchangers. The effects of different tube pitch arrangements (in-lined and staggered) and electrode arrangements (square and diagonal) with different applied voltage (VE = 0KV to 16KV) are numerically investigated in detail for the Reynolds number (based on the fin spacing and frontal velocity) ranging from 100 to 1000. It is found that the EHD enhancement is more effective for lower Reynolds number and higher applied voltage. The case of square wire electrode arrangement gives the best heat transfer augmentation. This study identifies a maximum improvement of 243% in the average Nusselt number and a reduction in fin area of 69% as compared that without EHD enhancement. The results are also compared with the corresponding circular tube having the same perimeter. It is shown that EHD is more pronounced in elliptic tube.

    摘要...................................................I 英文摘要..............................................II 致謝.................................................III 目錄..................................................IV 表目錄................................................VI 圖目錄...............................................VII 符號說明...............................................X 第一章 序論............................................1 1.1 前言...............................................1 1.2 電液動力學(EHD)之簡介..............................2 1.3 文獻回顧...........................................3 1.4 研究目的...........................................9 第二章 理論分析.......................................15 2.1 物理模型..........................................15 2.2 基本假設..........................................16 2.3 統御方程式........................................16 2.4 邊界條件..........................................20 2.5 熱傳係數、紐賽數、科本因子及阻力係數之計算........21 2.6 熱交換器之性能評價方法(PEC).......................23 第三章 數值方法.......................................30 3.1 數值模型..........................................30 3.2 數值方法..........................................30 3.3 解題流程..........................................36 3.4 格點測試..........................................37 第四章 結果與討論.....................................42 第五章 結論...........................................70 參考文獻..............................................71

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