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研究生:李國光
研究生(外文):Lee, Kuo-Kuang
論文名稱:波浪型旁通流室對紊流場流經具單排加熱凸塊之三維矩形流道熱傳增益之研究
論文名稱(外文):Heat Transfer Enhancement for Turbulent Flow over a Row of Heated Blocks in a 3D Rectangular Channel with Wavy Bypass Flow Chamber
指導教授:鄭仁杰鄭仁杰引用關係
指導教授(外文):Jen-Chieh Cheng
學位類別:碩士
校院名稱:國立虎尾科技大學
系所名稱:航空與電子科技研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2009
畢業學年度:97
語文別:中文
論文頁數:87
中文關鍵詞:三維紊流矩形流道波浪斜板旁通流加熱凸塊熱傳增進
外文關鍵詞:3-D turbulent rectangular channelWavy plateBypass flowArray of heated blocksHeat transfer enhancement
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工程系統中對流體流經加熱凸塊的熱對流應用甚廣,例如電子元件散熱、熱交換器及太陽能集熱器等。當流道中按裝有多個加熱凸塊時,位於下游的加熱凸塊熱傳效果甚差,而加熱凸塊之間的迴流也會影響熱傳性能,這些可能導致系統產生高溫熱點甚至超過容許工作溫度。
本文所探討的物理系統為一具有波浪型底板的三維紊流矩形流道,在矩形流道底板上按裝單排加熱凸塊,當流體進入矩形流道時,流體分隔為主流及旁通流兩部份,主流直接流向下游,旁通流則由旁通流室下方斜板槽孔流出以加強位於後側加熱凸塊之熱對流特性。透過旁通流與主流的交互作用來控制及平衡各加熱凸塊之熱對流特性,並經由波浪型底板來增加主流的動態性,改善整體加熱凸塊的熱傳效果。本文以數值方法進行模擬二維及三維之層流及紊流場的模擬,探討旁通流室之相關參數(旁通比、波浪底板設計、槽孔位置與開闔配置模式)對於單排加熱凸塊系統流體流動結構、溫度分佈與熱傳遞特性的影響。
計算分析結果顯示,當Pr =0.7、k = 0.0263、L = Hb = Wb =0.2、Da = 0.6、Ih = 0.7、Lbp = 4.8、Hd = 0.4的情況下,分別改變旁通比0.2 ≦BP≦0.6、旁通流室進口寬度0.8≦Wbp≦1、槽孔大小0.05≦Lh≦0.2、波浪底板波長Da≦WAl≦2Da、波浪底板波高0.06≦WAh≦0.1以及多種槽孔開闔模式等參數,在二維流場時,Re=500、Gr/Re^2=2的層流問題分析中,加熱凸塊的平均紐賽爾數最高可提升124%,熱點溫度最多可降低36.8%。在Re = 10^4、Gr/Re^2 = 0.05的紊流問題分析中,加熱凸塊的平均紐塞爾數最高可提升93%,熱點溫度最多可降低51.1%。在三維問題的探討中,當Re = 500、 Gr/Re^2 = 4的層流分析時,加熱凸塊的平均紐塞爾數最高可提升166%,熱點溫度最多可降低36.8%。在Re = 10^4、 Gr/Re^2 = 0.05的紊流情況下,加熱凸塊的平均紐塞爾數最高可提升98%,熱點溫度最多可降低55.9%。
本文藉由數值方法針對流道系統中按裝旁通流室的設計進行嚴謹探討,並建立系統各項參數與流體參數及熱對流效應的相關性,對旁通流在具單排加熱凸塊之三維流道熱流特性的影響提出工程上的關切點(Concern Point),提供作為散熱系統設計的參考。
Convective heat transfer from heated blocks to fluid stream is widely encountered in engineering applications, such as electronic equipment cooling, heat exchanger, solar engineering applications, etc. For the system of multiple heated blocks mounted on a channel, the heat transfer performance of the downstream heated blocks is poor, especially on the rear surface of the blocks due to the existence of circulations. This results in hot spots which may exceed the tolerant temperature in the system.
The physical system to be considered is a 3-D rectangular channel. The bottom plate of rectangular channel is mounted with a row of heated blocks, and a wavy bypass flow chamber mounted on the upper plate. The flow enters the channel and divides into main streams and bypass streams. The main stream flows onto the heated blocks directly. The bypass stream flow out through the holes on the bottom plate of the bypass flow chamber to enhance the heat transfer performances. Using the interactions of main flow and bypass flow, as well as the flow mixing caused by the wavy bottom plate of bypass chamber, to control and balance the heat convection characteristics of the overall heated blocks are investigated. This study performs the laminar and turbulent numerical simulations for 2-D and 3-D flow system. Efforts are devoted to investigate the influences of the arrangement of the wavy type bypass flow chamber on the flow structures, temperature distributions and the heat transfer characteristics of this system.
The results of the cases with and without the bypass chamber under parameters of Pr = 0.7, k = 0.0263, Lb = Hb = Wb =0.2, Da = 0.6, Lbp = 4.8, Hd = 0.4, 0.2≦BP≦0.6, 0.8≦Wbp≦1, 0.05≦Lh≦0.2, Da≦WAl≦2 Da, 0.06≦WAh≦0.1 and open-modes of holes, are shown as follow. For the 2-D laminar flow with Re=500, Gr/Re^2=2, the maximum enhancement of the overall average Nusselt number is about 124% for the heated blocks, and the maximum reduction in the hot spot temperature is about 36.8 %. For the 2-D turbulent flow with Re = 10^4, Gr/Re^2=0.05, the maximum enhancement of the average Nusselt number is about 93%, and the maximum reduction in the hot spot temperature is about 51.1 %. For the 3-D laminar flow with Re = 500, Gr/Re^2 = 4, the maximum enhancement of the average Nusselt number is about 166%, and the maximum reduction in the hot spot temperature is about 36.8 %. For the 3-D turbulent flow with Re = 10^4, Gr/Re^2 = 0.05, the maximum enhancement of the average Nusselt number is about 98%, and the maximum reduction in the hot spot temperature is about 55.9%.
The convective characteristics and heat transfer enhancement for turbulent flow over a row of heated blocks in a 3-D rectangular channel with wavy bypass flow chamber have been studied. The relations of parameters of this system and effects of flow and heat transfer are investigated and can provide useful information for practical design and operation.
中文摘要………………………………………………………i
英文摘要………………………………………………………iii
誌謝……………………………………………………………v
目錄……………………………………………………………vi
圖目錄…………………………………………………………viii
表目錄…………………………………………………………xii
符號說明………………………………………………………xv
第一章 前言…………………………………………………1
1.1 研究動機…………………………………………………1
1.2 研究目的…………………………………………………1
1.3 參考文獻…………………………………………………2
第二章 分析……………………………………………………6
2.1 物理模式…………………………………………………6
2.2 統御方程式………………………………………………6
2.3 邊界條件…………………………………………………7
第三章 數值方法與驗證………………………………………9
3.1 簡述………………………………………………………9
3.2 網格系統…………………………………………………9
3.3 程式測試與驗證…………………………………………10
3.3.1 二維流道計算區域測試………………………………10
3.3.2 二維層流網格密度測試………………………………10
3.3.3 三維流道計算區域測試………………………………10
3.3.4 二維層流程式驗證……………………………………11
3.3.5 三維程式驗證…………………………………………11
4.1二維流道中具旁通流室問題探討……………………………12
4.1.1旁通流室旁通比的影響…………………………………13
4.1.2旁通流室底板槽孔大小的影響…………………………15
4.1.3旁通流室槽孔開闔配置的影響…………………………16
4.1.4旁通流室波浪底板波長的影響…………………………17
4.1.5波浪底板波高的影響……………………………………18
4.1.6旁通流室位置的影響……………………………………19
4.2 三維流道中具旁通流室問題探討…………………………20
4.2.1旁通流室寬度的影響……………………………………22
4.2.2旁通流室旁通比的影響…………………………………23
4.2.3旁通流室槽孔大小的影響………………………………24
4.2.4旁通流室中槽孔開闔配置的影響………………………25
4.2.5旁通流室波浪底板波長的影響…………………………26
4.2.6波浪底板波高的影響……………………………………27
4.2.7層流測試壓力降討論……………………………………29
第五章 紊流流場之結果與討論…………………………………30
5-1統御方程式…………………………………………………30
5-2數值方法之驗證……………………………………………32
5.2.1 二維網格密度測試……………………………………32
5.2.2 二維程式驗證…………………………………………32
5.3二維紊流場問題探討………………………………………33
5.4三維紊流場問題探討………………………………………35
第六章 結論………………………………………………………37
未來工作與展望…………………………………………………38
參考文獻…………………………………………………………79
Extend Abstract…………………………………………………82
作者自述…………………………………………………………81
參考文獻
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