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系統識別號 U0026-1906201710421400
論文名稱(中文) 電液動增強技術應用於水蒸發之質傳及最佳化分析
論文名稱(英文) Mass Transfer and Optimal Analysis of Electrohydrodynamic Enhancement of Water Evaporation
校院名稱 成功大學
系所名稱(中) 機械工程學系
系所名稱(英) Department of Mechanical Engineering
學年度 105
學期 2
出版年 106
研究生(中文) 吳懿軒
研究生(英文) Yi-Hsuan Wu
學號 N16044145
學位類別 碩士
語文別 中文
論文頁數 120頁
口試委員 口試委員-林建南
口試委員-呂金生
口試委員-陳寒濤
指導教授-張錦裕
中文關鍵字 電液動  水蒸發率  最佳化分析 
英文關鍵字 optimization  EHD  evaporation 
學科別分類
中文摘要 本文利用數值模擬及實驗方法研究電液動(Electro-hydrodynamic)技術對食品或物品表面水分蒸發速率的影響。在理論及數值部份,以三維紊流流場探討線狀(wire)電極及針狀(needle)電極在不同供電電壓、電極間距、電極高度下,電液動效應對一強制對流通道流場濕水面的水蒸發率及薛吾爾德數(Sh)的影響。實驗方面,建立一套風洞系統,用以量測電流值並調整電荷密度分布,使得電液動效應更加接近真實情況,並進一步量測水蒸發率與數值結果做比對。本文包括 (1) 首先建立電腦數值模擬分析之物理模型,包括紊流流場、非均勻電場以及水蒸氣濃度場。 (2) 開發一套副程式(subroutine)可求解風洞系統內之電壓V與電荷密度 之分布並進一步取出電流值,以便將來與計算流體力學(CFD)軟體相互結合。 (3) 再配合商業計算流體力學軟體CFD-ACE+,以數值方法探討不同電場參數(供電電壓、電極間距、電極高度)對質傳效率的影響,並計算薛吾爾德數(Sh)。 (4) 最後,結合實驗與模擬之結果並利用最佳化方法-簡易共軛梯度法(SCGM),以單位功率之下電液動質傳增益作為其目標函數,搜尋最佳的電極間距、電極高度值。
由數值模擬及實驗結果顯示,隨著供電電壓的增加,薛吾爾德數增加。質傳增益會隨著電極間距的增加而增加,隨著電極高度的增加而降低。但是若考慮單位功率消耗的質傳增益,不同電壓下皆有一個最佳的間距、高度值,且最佳間距、高度值均會隨著電壓的增加而變大。最後,數值模擬與實驗結果得到一致性的趨勢,最大誤差約19%。
英文摘要 Numerical and experimental analyses have been carried out to study the electrohydrodynamic (EHD) effect on the evaporating rate of a channel forced convection flow. Three-dimensional steady turbulent flow equations combined with Maxwell equations were solved in two different kind of electrode shape : wire and needle. Parametric evaluation including the applied voltage, electrode location was executed in details. The results show the EHD effect on the evaporating rate is increased with increase of voltage and electrode pitch (SL) and decrease of electrode height (H) and inlet velocity. Furthermore, the optimization of the wire electrode height (H) and longitudinal pitch (SL) was investigated numerically along with a simplified conjugate-gradient method (SCGM). The mass transfer gain per power consumption is the objective function to be maximized. A search for the optimum electrode height (H) and electrode pitch (SL), ranging from 15 mm < H < 27 mm and 40 mm < SL < 100 mm, respectively, was performed for specific applied voltage V (V0=13~17 kV). The results show that the mass transfer gain enhance 316.7% to 179.7% per Watt power consumption combined with the optimal design of (H, SL) at V0=13 to 17 kV. Furthermore, comparing the mass transfer gain per power consumption of wire and needle electrode. The result show the wire electrode is better when the electrode height is low and the applied voltage is small. On the contrary, the needle electrode is better. Finally, the comparisons of numerical results and experimental data get a satisfactory consistency within a discrepancy of 5% to 19%.
論文目次 中文摘要 I
致謝 XXII
目錄 XXIII
表目錄 XXVI
圖目錄 XXVIII
符號說明 XXXIV
第一章 緒論 1
1.1 前言 1
1.2 文獻回顧 2
1.3 研究動機與目的 6
第二章 理論分析 7
2.1 物理模型與基本假設 7
2.2 統御方程式 8
2.2.1 Maxwell電場統御方程式: 8
2.2.2 流場統御方程式: 9
2.2.3 雙方程式模式: 10
2.3 質傳遞係數及薛吾爾德數Sh之計算 12
2.4 單位功率下之質傳增益效率 12
2.5 邊界條件 13
2.5.1 流場邊界條件: 13
2.5.2 電場邊界條件: 14
2.5.3 濃度場邊界條件: 15
第三章 最佳化理論及數值方法 20
3.1 最佳化理論 20
3.1.1 共軛梯度法 20
3.1.2 簡易共軛梯度法 21
3.1.3 最佳化執行流程 22
3.1.4 目標函數的定義 23
3.2 數值方法 24
3.2.1 通用守恆方程式(Generic Conservation Equation) 24
3.2.2 有限容積法(Finite volume method) 25
3.2.3 SIMPLEC 演算法 28
3.2.4 電場統御方程式之離散 30
3.2.5 邊界條件之離散 31
3.3 網格測試 32
3.4 電荷密度計算方法 33
3.5 解題流程 34
3.6 收斂條件 34
第四章 實驗設備與方法 45
4.1 測試本體 45
4.2 實驗設備 46
4.3 實驗規劃 47
4.4 操作程序 47
4.5 實驗結果 48
第五章 結果與討論 58
5.1 線狀電極 58
5.1.1 實驗與模擬比對 58
5.1.2 電荷密度分布 59
5.1.3 電液動效應對流場造成的影響 59
5.1.4 電極間距的影響 60
5.1.5 電極高度的影響 62
5.1.6 最佳化分析 63
5.1.7 不同入口速度之比較 64
5.2 針狀電極 65
5.2.1 實驗與模擬比對 65
5.2.2 電荷密度分布 65
5.2.3 電液動效應對流場造成的影響 66
5.2.4 電極間距的影響 66
5.2.5 電極高度的影響 67
5.3 線狀電極與針狀電極之比較 68
第六章 結論 114
參考文獻 116

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