臺灣博碩士論文加值系統

本研究以暫態液晶實驗法量測中間分隔具多個不同角度穿孔之180度直角轉彎通道其外側壁與底壁之細部熱傳係數，實驗流體為空氣，通道截面為方形，等距安排多個穿孔於中間分隔上，則冷流可經由穿孔提早進入第二通道來調節熱傳，變動參數包括(1)雷諾數(Re=2468~12340)、(2)穿孔孔徑與通道水力直徑之比值(d/Dh=0、1/4與2/4)、(3)穿孔角度(=0、+45與45)、(4)穿孔孔數(n=1、2與3)、與(5)中間分隔擺置的角度(=80、85與90) 。實驗結果指出氣流流動慣性與衝擊冷卻影響導致在轉彎區與第二通道時外側壁熱傳較底壁為佳，所有測試構型中，無穿孔構型具有最佳之整體熱傳能力，而穿孔構型中，(d/Dh=1/4、q=45°與n=1)之整體熱傳能力最接近無穿孔構型，在d/Dh=2/4時，紐塞數( )沿流向之分布強烈受穿孔角度()的影響，其中=+45度時產生最大的旁通氣流量，可增強第二通道下游的散熱能力，且第二通道的Nu分布變成沿流向漸增，完全不同於其他構型，證明中間分隔具穿孔的構型確實能調節180度轉彎通道的熱傳部位；另外，中間分隔擺置角度為=80之構型，其通道具有非均勻截面，在第一與第二通道上游因通道截面較小，通過之氣流速度較大，使該區段原本就較佳的熱傳獲得進一步的增益，若將中間分隔擺置為負的角度，應可有效平均化通道內部熱傳的分配，這是未來研究的方向。

This work performed detailed measurements of heat transfer coefficients in the 180-deg turned channel by using the transient liquid crystal method. The fluid was air and the cross section of the channel was square. The divider of the 180-deg turned channel had several perforations with equal interval, then the fluid in the first duct can early flow into the second duct through the perforations, adjusting the heat transfer. Variable parameters were the Reynolds number (Re=2468-12340), the ratio of the perforation’s diameter to the channel’s hydraulic diameter (d/Dh=0, 1/4 and 2/4), the angle of perforation (=0, +45 and 45), the numbers of perforations (n=1, 2 and 3), and the arranged angle of the divider (=80, 85 and 90). The results indicated that, at the turned and second duct regions, the effects of fluid flow inertia and the impinging cooling induced better heat transfer on the outer side surface than the bottom one. Among all the test configurations, the non-perforation configuration had the best heat transfer capacity. The total heat transfer performance of the perforation mode with (d/Dh=1/4, q=45° and n=1) was most near that of the non-perforation one. Besides, the distribution of the Nusselt number (Nu) was strongly influenced by the angle of perforation () as d/Dh=2/4. Different from others configurations, the mode of (d/Dh=2/4 and =+45) grew the Nu along the streamwise direction in the second duct due to the biggest amount of bypass fluid, greatly improved the heat transfer at the downstream of the second duct. It demonstrates that the perforations of the divider did can adjust the spatial heat transfer of the 180-deg turned channel. Furthermore, for the mode of =80, the cross section of the channel is not uniform. It resulted in higher heat transfer enhancement at the upstream regions of the first and second ducts due to the bigger velocity than the mean value. If the arranged angle of the divider is changed to be negative, it should effectively smooth the spatial heat transfer distribution in the channel. This issue will be studied in the future.

中文摘要 Ⅰ
英文摘要 Ⅱ
誌謝 Ⅲ
目錄 Ⅳ
表目錄 VI
圖目錄 Ⅶ
符號說明 XⅢ
第一章 緒論 1
1-1 研究背景與動機 1
1-2 文獻回顧 2
1-2-1暫態液晶實驗法文獻 2
1-2-2 180度轉彎平滑壁流道 4
1-2-3 180度轉彎壁面加肋流道 4
1-2-4 其它特別設計之180度轉彎流道 6
1-3 研究目標 8
第二章 實驗方法 11
2-1暫態液晶實驗法理論 11
2-2 實驗設備 13
2-2-1氣源供應系統 13
2-2-2空氣加熱系統 14
2-2-3實驗測試段 14
2-2-4數據資料擷取系統 15
2-2-5影像分析系統 15
2-3液晶與影像校正 16
2-4 實驗步驟 18
2-5 實驗參數之不確定性分析 20
第三章 中間分隔具穿孔構型之熱傳特徵－穿孔孔數、孔徑、角度對熱傳之影響 37
3-1 通道底壁與側壁之細部熱傳係數分布特性 37
3-2 局部紐塞數沿主流道之分布特性 42
3-3 整體熱傳增益 47
第四章 通道具非均勻截面構型之熱傳特徵－中間分隔擺置角度對熱傳之影響 100
4-1 通道底壁與側壁之細部熱傳係數分布特性 100
4-2 局部紐塞數沿主流道之分布特性 102
4-3 整體熱傳增益 104
第五章 結論與未來展望 114
5-1結論 114
5-2未來展望 116
參考文獻 118
附錄A 實驗工作流體(空氣)性質參數表 124
附錄B 實驗設備 125
附錄C 影像擷取卡規格表 129
附錄D Pansonic WV-CP480規格表 130

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