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論文名稱(外文):Laminar Convective Heat Transfer Performance of Alumina-Water Nanofluid Flow in a Circular Tube:Effects of Inlet Temperature and Temperature-Dependent Properties
指導教授(外文):Ching-Jeng Ho
外文關鍵詞:NanofluidVariable propertyLaminar forced convection
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本文採用數值模擬與實驗並行方式,在數值模擬部分藉由改變進口溫度、流量和加熱功率且固定加熱段長度lh+/(di+Pef,0)=0.1所定義的無因次進口溫度參數範圍in=1.04~16.51並針對其對流場、熱傳遞及熵生成量的影響進行研究,結果顯示當in=1.04時,在考慮可變物性與固定物性下結果的比值,壓降與熵生成量有最小值;對流熱傳係數有最大值。實驗上針對氧化鋁奈米流體進行粒徑、黏度和熱傳導係數上的確認,所測得在水中懸浮粒徑為109.6 nm,並將其應用在等熱通量加熱水平圓管內的層流強制對流熱傳實驗;所用的圓管分為兩種:外徑分別為4 mm與6.3 mm,內徑分別為3.4 mm與6 mm,無因次管壁厚度tw=0.17和0.05,實驗相關條件參數:氧化鋁-水奈米流體濃度為ω_np^ =2~10 wt.%;進口溫度Tin = 25℃和50℃;Ref,0 =186~2095;外管壁等效熱通量q_(eff,o)^'=1066~7362 W/m2,實驗結果在進口溫度為50℃時,氧化鋁-水奈米流體與水的平均對流熱傳效益比值最大達1.18。本文研究中,局部壁溫與局部對流熱傳係數在數值模擬與實驗比對大致相符。

關鍵字: 奈米流體、可變物性、層流強制對流

In the present study, the laminar forced convection heat transfer characteristics of a horizontal tube partially heated with constant heat flux have been investigated experimentally and numerically. In numerical simulation, dimensionless inlet temperature parameter, θ_in^ , defined by inlet temperature, flow rate and heating power and dimensionless heating length lh+/(di+Pef,0) was fixed to 0.1, ranges from 1.04 to 16.51.
Under the consideration of the ratio of variable thermal physical property and constant thermal physical property, convection heat transfer coefficient and minimum value in the pressure drop and entropy generation. In thermal physical properties verification, Al2O3-water nanofluid was conducted for particle size test, about 109.6 nm in suspension fluid, viscosity and thermal conductivity. On the other hand, experiments have been performed using two copper tube of inner and outer radii, one is 3.4 mm and 4 mm, the other is 6 mm and 6.3 mm, for the relevant parameters in the following ranges: the mass fraction of nanoparticles, np = 2 ~ 10 wt.%; the Reynolds number, Ref,0 = 186 ~ 2095; the inlet temperature, Tin = 25℃ and 50℃, and the imposed heat flux, qo = 1069 ~ 7362W/m2 . The laminar cooling effectiveness of the nanofluid flow can be enhanced up to 1.18 at inlet temperature 50℃. The experimental results clearly exhibit a good agreement with the corresponding numerical simulations.

Key words: nanofluid, variable property, laminar forced convection.

第一章 緒論 1
1-1 前言 1
1-2 文獻回顧 1
1-3 研究動機與目的 5
1-4 論文架構 5
第二章 物理/數學模型與數值模擬方法 11
2-1 物理模型 11
2-2 數學模式 12
2-2-1 統御方程式 12
2-2-2 邊界條件 15
2-2-3 無因次統御方程式及邊界條件 16
2-2-4 流體熱物理性質 20
2-3 數值方法 34
2-4解題流程 35
2-5格點測試 38
2-6 熱傳相關參數定義 40
2-7 管內對流熱傳所致熵生成量計算 43
第三章 實驗方法與數據處理 44
3-1 實驗設備 44
3-1-1 實驗迴路 44
3-1-2 實驗流程 45
3-2 奈米流體的製備和熱物性質量測 46
3-2-1 奈米流體製備方法 46
3-2-2 奈米流體相關熱物性質測定 47
3-3 數據處理 51
3-4 實驗不準度分析 56
第四章 結果與討論 65
4-1 數值模擬結果 65
4-1-1流體進口溫度對熱傳遞之影響 66
4-1-2 隨溫度變化熱物性質對熱傳遞的影響 68
4-1-3 流體進口溫度伴隨熵產生率之影響 70
4-1-4 隨溫度變化熱物性質對熱傳遞伴隨熵產生率影響 70
4-2 實驗結果 71
4-2-1 平均對流熱傳係數 71
4-2-2 平均紐賽數與數值模擬關係式的比較 72
4-3 實驗與數值模擬的比較 73
4-3-1 溫度分布 73
4-3-2 局部對流熱傳係數的比較 74
第五章 結論 121
5-1 結論 121
5-2 未來研究建議 122
參考文獻 123

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