臺灣博碩士論文加值系統

由於彎管內的流場具有次流場的特性，且因邊界層的發展被週期性變曲率彎管反方向的管壁曲率所打斷，產生邊界層即使在完全發展流下依然較薄的現象，所以熱傳效率較相同長度和管徑之直管為佳，也因此彎管得以應用在於熱交換器、化學反應器和太陽能集熱器等設備上，但諸多關於彎管的文獻中，大多以數值摸擬彎管流的速度場和熱傳現象，或討論螺旋彎管和波狀渠道流，而週期性變曲率彎管流則較少被提及。
本文研究之目的就在於以實驗方法求證週期性變曲率彎管所產生之熱傳增強與壓降增加的現象，以實驗證實數值模擬的結果，並進一步對各種不同振幅(a)與週期參數(k)之週期性變曲率彎管，與直管做比較。其中針對影響彎管形狀的a，k參數及流場型態之Re數和Pr數進行比較，以提供應用之參考。

The curvature of a pipe can induce a secondary flow for the flow in the pipe. The effect of the secondary flow enhances the heat transfer rate significantly. Therefore, curved pipe is widely applied in heat transfer devices . However, in the literature, most of studies for the curved pipe flow is dealing with coroidal flow with constant curvature. There are few articles dealing with varying curvature curved pipe flow despite the fact that non-uniform curved pipes have as much practical use as coroidal. The solar collector with periodical s-shaped pipe is a practical example for varying curvature curved pipe flow and heat transfer. In this article, experiments were conducted in a double-pipe heat exchanger with water as the working medium. The heat transfer coefficients were obtained using the Wilson plot method. The effect of the Dean, Prandtl, Reynolds number and curvature ratio on the flow resistance , average heat transfer rate and friction factor are presented.

目 錄
摘要................................................ Ⅰ
英文摘要............................................ Ⅱ
目錄................................................ Ⅲ
圖表目錄.............................................. Ⅴ
符號說明............................................Ⅷ
第一章 緒論........................................ 1
1-1 研究背景動機及文獻回........................... 1
1-2 研究目地....................................... 2
第二章 數據分析之理論基礎.......................... 4
2-1 基本理論....................................... 4
2-1.1 熱傳係數................................ 6
2-2 熱傳性能與壓力降的定義及運算 .................. 10
2-2.1 熱傳係數比................................... 10
2-2.2 管內摩擦係數.................................. 11
2-2.3 摩擦比....................................... 12
2-2.4 幫浦動力..................................... 12
第三章 實驗設備及方法.............................. 14
3-1 實驗系統....................................... 14
3-1.1 測試段...................................14
3-1.2 熱水迴路.................................15
3-1.3 冷水迴路.................................15
3-2 量測儀器與實驗設備.............................15
3-3 實驗系統:第二部分..............................17
3-4 實驗條件.......................................18
3-5 實驗步驟....................................... 18
3-5.1 第一部分.................................18
3-5.2 第二部分.................................19
第四章 實驗結果....................................24
4-1 k參數的影響....................................24
4-2 a參數的影響....................................24
4-3 測試管的壓力降................................. 25
4-4 摩擦係......................................... 26
4-5 幫浦動力的比較.................................26
4-6 Pr數的影響.....................................26
4-7 曲率比的影響...................................27
4-8 狄恩數(De)的影響...............................27
4-9 無因次參數分析................................. 27
4-9.1 熱傳係數.................................28
4-9.2 摩擦係數.................................29
第五章 結論與建議..................................31
5-1 結論...........................................31
5-1.1 紊流範圍.................................31
5-1.2 層流範圍和過渡區.........................31
5-2 建議...........................................33
參考文獻............................................ 65
附錄A...............................................67
附錄B...............................................70

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