臺灣博碩士論文加值系統

　　本文是針對前半段具加熱區的微渠道之三維流場與共軛熱傳作詳細的數值研究。文中在微渠道之流體區域應用有限體積法(finite-volume method)來解三維穩態、紊流及熱傳方程式，配合有限差分法及冪次法則來離散成差分方程式。在固體區域內，則解熱傳導方程式。對於紊流的結構則是以 紊流模式配合牆函數來描述，並以SIMPLE運算法則求解壓力-速度結合的問題。至於網格設計，則採用正交非均勻的交錯式網格設計。

　　本文研究的參數為雷諾數(Re=1500、2000、2500、3000)，熱通量(q"=34.6W/cm2、100W/cm2、200W/cm2、300W/cm2)，加熱段長度固定為1cm，工作流體為水。數值模擬結果顯示，微渠道中速度發展為完全發展流區大約在沿著流動方向X=6mm處。在微渠道中溫度分佈會受到後方無加熱區之固體影響，造成溫度下降，因而存在最大溫度分佈之截面。由於熱邊界層的發展，紐塞數的變化在入口附近最大，而熱阻在進口處有最小值，沿著流動方向增加，直到經過溫度分佈最大截面處後開始下降。數值模擬結果預測了熱阻最大值與加熱區邊緣之熱阻值下降的位置。文中之三維模型提供對於這種合併熱對流與熱傳導效應之複雜渠道中熱流場的基礎了解。

　The detailed numerical study is carried out to investigate three-dimensional fluid flow and heat transfer in microchannels with a half heated section. The three-dimensional, steady, turbulent and heat transfer equation are discretized by finite-volume method based on a finite-difference method with power-law scheme. In the solid section, heat conduction equation is solved. The well-known turbulence model and its associate wall function are used to describe the turbulent structure. In addition, the SIMPLE algorithm is adopted to solve the pressure-velocity coupling. An orthogonal non-uniform staggered gird are used for the establishment of mesh grids.

　The parameters studied include Reynolds number (Re=1500, 2000, 2500, 3000), constant heat flux (q"=34.6W/cm2, 100W/cm2, 200W/cm2, 300W/cm2), constant length of heated section =1cm, and using water as the working fluid. The numerical simulation indicated that velocity profile becomes completely development regime at X=6mm along the microchannel. The temperature distribution will be affected by the solid at rear side where has no heating section. Then it leads to temperature dropped and hence the largest temperature distribution cross-sections exists. The variation of Nusselt number is large near the entrance because of the development of the thermal boundary layer. Thermal resistance has the minimum value at the entrance while it increases along the flowing direction of the fluid in the channel. The thermal resistance keeps increasing until it reaches the section with maximum temperature distribution, and then it starts to decrease after passing through the maximum temperature distribution section. The numerical results predicted the location of the maximum thermal resistance and the drop in the thermal resistance towards the trailing edge of the heater. The three-dimensional model provides a fundamental insight into the complex heat flow pattern established in the channel due to combined convection-conduction effect.

中文摘要...............................................................I
英文摘要.............................................................III
誌謝...................................................................V
目錄..................................................................VI
表目錄............................................................... IX
圖目錄.................................................................X
符號說明.............................................................XIV
第一章 緒論...........................................................1
1-1 研究動機及背景..........................................1
1-2 文獻回顧......................................................2
1-3 本文探討之主題及方法.................................5
第二章 理論分析.............................................8
2-1 空間流場解析.............................................8
2-2 紊流模式...................................................12
2-3 邊界條件...................................................20
2-4 局部紐賽數(Nusselt number)和熱阻(Thermal resistance)
計算.........................................................24
第三章 數值方法............................................27
3-1 概述.........................................................27
3-2 格點位置的配置............................................28
3-3 之差分方程式...............................................30

3-4 u、v、w動量方程式之差分方程式...............................36
3-4-1 壓力修正方程式............................................37
3-5收斂標準......................................................39
3-6 差分方程式解法.......................................41
3-6-1數值程序............................................42
3-6-2電腦計算時間............................................43
第四章 結果討論............................................45
4-1 計算空間與網格獨立測試....................................46
4-2 流場特性分析............................................47
4-2-1 速度分佈............................................48
4-2-2 紊流動能分佈............................................49
4-3 溫度場與熱傳分析............................................49
4-3-1溫度分佈............................................50
4-3-2局部紐賽數 ...........................................51

4-3-3熱阻(R....................................................52
第五章 結論與建議............................................77
5-1 結論.......................................................77
5-2 未來研究方向之建議.......................................79
參考文獻.......................................................80

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