針狀鰭片陣列與水平板在自然對流下之散熱效能研究

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研究生：	沈季儒 Shen, Chi-Ju
論文名稱：	針狀鰭片陣列與水平板在自然對流下之散熱效能研究 Natural Convection for Pin-Fin Arrays and Horizontal Flat Plate
指導教授：	王訓忠 Wong, Shwin-Chung
口試委員:
學位類別：	碩士 Master
系所名稱：	工學院 - 動力機械工程學系 Department of Power Mechanical Engineering
論文出版年：	2007
畢業學年度：	95
語文別：	中文
論文頁數：	121
中文關鍵詞：	針狀鰭片陣列、水平板、自然對流
外文關鍵詞：	Pin-fin arrays, Horizontal flat plate, Natural cnvection
相關次數：	點閱：2 下載：0
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本研究以數值模擬軟體Fluent探討不同截面形狀與幾何配置的針狀鳍片陣列在自然對流下的散熱效能。首先針對底板垂直擺設的針狀鰭片陣列探討針狀鳍片的形狀、直徑與針狀鳍片陣列的間距、遮蔽層與針狀鳍片頂距離、排列方式、及擺放角度等幾何配置參數對散熱效能的影響。研究發現在自然對流下，流阻與散熱面積是影響效能的兩項最大因素，如過度增加散熱面積而使流阻增加反而造成有效散熱面積的縮減，因此必須視驅動力大小等條件在兩者之間取得平衡。具有較大表面積而較少流阻的鰭片形狀具較佳散熱效能，而不同的排列方式與擺設角度則隨Ra值與空隙度的不同而有不同的最佳應用範圍，鳍片直徑與間距等造成流阻與散熱面積消長的因素則有隨著不同的Ra值而有不同的最佳值。在與針狀鰭片頂適當距離處增加遮蔽層可減低流體黏滯效應並增加流入冷空氣，使散熱效能提升。
而在底板水平擺置的情況下，本文則首先探討水平平板在層流流場下的流場特性與散熱效能，並加入紊流效應觀察在較高的Ra值下，微小的紊流效應對於整體散熱效能的影響。本研究發現在氣流交會撞擊處紊流動能有增加的現象，且其散熱效能與前人之實驗結果具相同趨勢，足可反應一般認為層流區域的流場其實早已發生紊流之可能。而在底板水平擺設的針狀鳍片陣列散熱效能之探討上，本文則針對針狀鰭片的直徑、間距、位置等因素對散熱效能的影響進行探討。結果發現在水平擺設的情況氣流受熱後產生浮力而減少繼續通過較內側針狀鳍片的驅動力，因此與垂直擺設的狀況相比，流阻的影響就更為重要。

目　錄
摘要    ii
誌 謝    iii
表目錄    vii
圖目錄    viii
符號表    xi
第一章 序論    1
1    前言    1
2    文獻回顧    2
2.1幾何配置    3
2.2 幾何截面形狀    10
3    研究目的    17
第二章 理論基礎與模型建立    25
1 物理模型    25
2 數學模型    26
2.1 The Boussinesq Model    27
2.2 無因次化參數表示    27
2.3 統御方程式    28
2.4 邊界條件    29
2.4.1 垂直及具小傾斜角度擺置的模型    29
2.4.2水平擺置的模型    30
2.5 初始條件    31
3 數值方法    32
3.1 速度與壓力求解方案    32
3.1.1 SIMPLE演算法    33
3.1.2 SIMPLE 與 SIMPLEC    34
3.2 其餘離散化計算方案    35
3.4 相關參數    36
第三章 數值模擬方法    42
1 網格建立    42
2 格點測試    42
2.1垂直及具傾斜角度擺置的模型格點測試    42
2.2水平擺置的模型格點測試    45
2.2.1水平擺置的加熱平板計算模型格點測試    45
2.2.2 水平擺置的針狀鰭片陣列計算模型格點測試    47
3 模擬參數    48
3.1 通用參數    48
3.2 變因參數    49
3.2.1底板垂直擺放之針狀鰭片陣列    49
3.2.2底板水平擺放之針狀鰭片陣列    50
1遮蔽層與針狀鰭片頂距離影響之探討    57
2 針狀鰭片間距之影響    59
3 相同鰭片體積下效能之比較    62
4 針狀鰭片形狀之影響    63
5 排列方式之影響    64
6 底板傾斜之影響    66
7 渦漩流逸存在與否之判別    68
8 小結    68
第五章 水平擺設的加熱平板與針狀鳍片陣列之散熱效能    89
1 水平加熱平板之散熱效能    89
1.1 水平加熱平板之流場    89
1.2 水平加熱板之散熱效能探討    90
1.3 紊流對散熱效能的影響    91
2水平擺設針狀鰭片陣列之散熱效能    91
2.1水平擺設之針狀鳍片陣列的流場特性    91
2.2水平擺設之針狀鳍片陣列的散熱效能    93
2.2.1相同鰭片長度下改變幾何配置對效能的影響    93
2.2.2鰭片長度對散熱效能的影響    95
2.3 小結    96
第六章 結論與未來方向    113
1 結論    113
1.1底板垂直擺設之針狀鳍片陣列散熱效能    113
1.2水平加熱平板之散熱效能與流場特性    114
1.3底板水平擺設之針狀鳍片陣列散熱效能    115
2 未來方向    116

                                

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