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研究生:張丞硯
研究生(外文):Cheng-Yan Chang
論文名稱:一個渦捲式熱交換器之熱傳增強
論文名稱(外文):Heat Transfer Enhancement of a Spiral Heat Exchanger
指導教授:沈君洋
口試委員:陳石法盧昭暉
口試日期:2016-07-29
學位類別:碩士
校院名稱:國立中興大學
系所名稱:機械工程學系所
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2016
畢業學年度:104
語文別:中文
論文頁數:100
中文關鍵詞:渦捲式熱交換器摩擦因子紐塞數增強指數紐塞數
外文關鍵詞:spiral heat exchangerDancy friction factorNu enhancement indexNusselt number
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本研究以實驗方法來探討一個渦捲式熱交換器在具有流體擾動棒時對熱傳增強之影響。實驗之熱交換器是由同一中心點出發之四條阿基米德渦捲線分別構成兩個相鄰不等距之流道,其中較寬之冷流體(空氣)流道之間距為10 mm,另一較窄之熱流體(水)流道之間距為1 mm。本實驗採用之擾動棒為 之牙條,共計七根,分別垂直固定於空氣管道內不同位置處,以擾動空氣之流動。研究中空氣流道之管壁考慮為等溫,熱交換器最外一圈假設為絕熱。在不同空氣體積流率(0.214、0.446、0.716、0.89、1.055、1.385 m3/min)下,分別針對有或無流體擾動棒之情況,以量測管道中各位置點之壓力降與溫度,同時計算摩擦因子及紐塞數,並獲得其與雷諾數間之相關性公式。量測結果顯示,在雷諾數介於4000至24000之範圍內整個熱交換器(包含入口區域與渦捲管道)之Nu增強指數(r1)在1.380至1.503之間,而渦捲管道之r1值則在1.541至1.796之間,此顯示流體擾動棒確實能有效地提升渦捲式熱交換器之熱傳性能。整個熱交換器之Nu增強與摩耗增加之比值(r2)在0.357至0.400之間,而渦捲管道之r2值則在0.164至0.230之間,由於流體擾動棒之直徑較大,流道截面積被擋住大半,故造成渦捲管道之r2值較小。

The heat transfer enhancement due to flow disturbance rods in a spiral heat exchanger constructed by four Archimedes’ spirals originated from the same center is experimentally investigated. The four spirals form two channels. The widen one with spacing of 10 mm is the cold fluid channel (air), while the narrower one with spacing of 1 mm is the hot fluid channel (water). Isothermal wall condition is assumed and the outer most surface of the heat exchanger is considered to be insulated. Seven threaded rods ( ) are vertically installed at different locations in the air channel. At various air volumetric flow rates ( 0.214、0.446、0.716、0.89、1.055、1.385 m3/min ) and with/without the flow disturbance rods, the air-side fluid friction factors (f) and average Nusselt numbers (Nu) for the heat exchanger (including inlet and spiral channel) and the spiral channel alone are measured, respectively. Using the data, a set of correlation equations are established. The result shows that, for 4000 ≤ Re ≤ 24000, the Nu enhancement index (r1) for the heat exchanger is in the range of 1.38 to 1.503 ; for the spiral channel, it is in the ranger of 1.541 to 1.796. This verifies that the flow disturbance rods are quite effective to enhance the heat transfer in the heat exchanger. The mechanical energy consumption indexes (r2) for the heat exchanger and the spiral channel are in the range of 0.357 to 0.4 and 0.164 to 0.23, respectively. In the spiral channel, 60% of the cross-sectional area is blocked by the flow disturbance rods. This causes the r2 values to be small.

摘 要 i
Abstract ii
目 錄 iii
表目錄 vi
圖目錄 viii
符號說明 x
第一章 緒論 1
1.1 前言 1
1.2 文獻回顧 3
1.3 研究目的 10
第二章 渦捲式熱交換器之熱傳面積之計算 11
2.1 直角坐標下一條曲線之長度之計算 11
2.2 極坐標下一條曲線之長度之計算 12
2.3 在極座標下之阿基米德渦捲線之長度 13
2.3.1 管壁內表面之長度 (虛線) 14
2.3.2 相位差角度 與 之決定 19
2.3.3 管壁外表面之長度(實線) 22
2.4 渦捲式熱交換器之熱傳面積之計算方法 24
2.4.1 各管壁熱傳面積之計算 25
2.4.2 熱交換器之熱傳面積 26
第三章 系統操作與實驗設備之介紹 27
3.1 系統運轉之介紹 27
3.1.1 壓降實驗系統之介紹 27
3.1.2 熱傳實驗系統之介紹 28
3.2 實驗設備之介紹 29
第四章 熱傳與流力特性之實驗量測結果 33
4.1 流力與摩擦特性之相關性 33
4.1.1 壓力降與體積流率之關係 33
4.1.2 達西摩擦因子(f)與雷諾數(Re)之計算 34
4.2 熱傳實驗中溫度量測之結果 36
4.2.1 流道內空氣之溫度分佈 36
4.3 熱對流係數與平均紐塞數 37
4.3.1 不具流體擾動棒時之熱對流係數與平均紐塞數 37
4.4 摩擦因子與平均紐塞數之相關性公式 40
4.4.1 摩擦因子之相關性公式 40
4.4.2 平均紐塞數之相關性公式 41
4.5 r1與r2值之比較 42
4.6 實驗結果與文獻資料之比較 44
4.6.1 渦捲管道之Nu與f實驗值與文獻資料之比較 44
4.6.2 渦捲流與平行流之比較 45
第五章 不準確度分析 46
5.1 達西摩擦因子之不準確度分析 46
5.2 平均紐塞數之不準確度分析 47
第六章 結論 50
6.1 結論 50
6.2 未來展望及建議 52
參考文獻 53


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