臺灣博碩士論文加值系統

由於電腦中央處理器在高速運算時會產生大量熱量，為避免熱量累積使得溫度過高損壞中央處理器，在CPU上通常會加裝一散熱片，並以風扇強制空氣對流而增加其熱傳。其中散熱片之設計在整體散熱效果上更是有極大的影響。
在本文中，我們探討散熱片斜率對單片及多片散熱片之熱傳效果的影響。在單片散熱片的數值模擬中，我們發現在散熱片總表面積不變的前提下，當散熱片斜率為負時(即在主要對流方向上散熱片高度遞減)，其最高溫度隨著斜率改變並無顯著的變化；但在斜率為正時，斜率的增加將導致最高溫度的昇高。而在多片散熱片的數值結果中我們則發現，當散熱片斜率較大時，流場中最大溫度會隨著散熱片斜率的絕對值(與正負無關)增加而降低。在文中我們除了以簡化之理論計算來解釋上述數值模擬結果外，也提出了一套可有效增進散熱片熱傳效果之造型設計方向。

The central processing unit (CPU) of a typical personal computer produces a large amount of heat when it operates at a high frequency. In order to keep the CPU at a suitable temperature, so that it would function properly, a plate-fin heat sink typically is installed on top of the CPU. In addition, a cooling fan is used to direct the heat generated by the CPU out of the fin surface through forced convection. Clearly, fin geometry is one of the most important factors in the design of CPU cooling systems.
In this thesis, with the aid of the commercial software FloWorks®, we discuss the influence of fin geometry on the overall heat transfer rates of heat sinks, which may consist of one or a plural of plate fins. Results of our simulations for single-fin heat sinks indicate that, when the total fin surface area is kept constant, and the fin has a negative slope (meaning that the height of the fin decreases in the flow direction), the temperature in the flow field is not significantly affected by the fin slope. However, when the fin slope is positive, the maximum temperature of the heat sink increases with increasing fin slope. In order to explain the results of numerical simulations, simple approximate theories are also presented in this thesis.
Meanwhile, for multiple-fin heat sinks, when the fin slope is sufficiently large, results of numerical simulations indicate that the maximum temperature of the heat sink would decrease with the absolute value of the fin slope. On the basis of this observation, a simple fin geometry design, which greatly enhances the heat transfer effects of heat sinks, is also proposed in this thesis.

摘要.......................................................i
英文摘要..................................................ii
誌謝.....................................................iii
目錄......................................................iv
表目錄...................................................vii
圖目錄..................................................viii
第一章 緒論...............................................1
1.1 研究動機............................................1
1.2 文獻回顧............................................3
1.3 研究目的............................................6
1.4 本文架構..............................................6
第二章 幾何模型與分析軟體架構.............................8
2.1 幾何模型............................................8
2.2 FloWorks之理論架構簡介.............................11
2.3 邊界條件與流體性質.................................15
第三章 FloWorks的操作與設定..............................18
3.1 模擬工作(project)的設定............................19
3.2 自訂介質之熱流性質設定.............................27
3.3 邊界條件、熱源與固體零件材質的設定.................30
3.3.1 邊界條件的設定......................................30
3.3.2 熱源的設定..........................................34
3.3.3 固體零件材質的設定..................................35
第四章 模擬結果與討論....................................37
4.1 Ledezma與Bejan的實驗及數值數據.......................37
4.2 單片散熱片的數值模擬結果與簡化理論模型...............40
4.2.1 模擬結果............................................40
4.2.2等熱通量理論.........................................42
4.2.3等溫理論.............................................43
4.3 多片散熱片模型的數值模擬結果.......................47
4.4 兩段式散熱片的熱傳效果.............................57
第五章 結論與展望........................................61
5.1 結論...............................................61
5.2 展望...............................................63
參考文獻..................................................64
表目錄
表2.1 Reynolds 數及其相對應的 ...........................16
表2.2 FloWorks 的參數設定表..............................17
表4.1 不同Reynolds數下的理論無因次最高溫度參數 ...........45
圖目錄
圖2.1 散熱片模型及其參數設定..............................9
圖2.2 模擬風洞的長形管道.................................15
圖3.1 模擬流程圖.........................................18
圖4.1 Ledezma與Bejan[1]在實驗中的熱偶佈置圖..............38
圖4.2 具有不同斜率參數散熱片上的溫度分佈圖(Re=7200)......38
圖4.3 在不同Re數下散熱片最大溫度與斜率參數b之關係........38
圖4.4 在三種Re數下單片散熱片上最大溫度與斜率參數b之關係..41
圖4.6 在Re=3750時的數值結果和理論無因次溫度參數的比較....45
圖4.7 在Re=6000時的數值結果和理論無因次溫度參數的比較....46
圖4.8 在Re=7200時的數值結果和理論無因次溫度參數的比較....46
圖4.9 在Re=7200時散熱片斜率參數 的溫度分佈...............47
圖4.10 在Re=7200時散熱片斜率參數 的溫度分佈...............48
圖4.11 在Re=7200時散熱片斜率參數 的溫度分佈...............48
圖4.12 在不同Re數時散熱片上最高溫度與斜率參數b之關係......49
圖4.13 在Re=3750時的各斜率參數下的溫度分佈................50
圖4.14 在Re=3750時的各斜率參數下的速度分佈................51
圖4.15 在Re=6000時的各斜率參數下的溫度分佈................52
圖4.16 在Re=7200時的各斜率參數下的速度分佈................53
圖4.17 在Re=7200時的各斜率參數下的溫度分佈................54
圖4.18 在Re=7200時各斜率參數下的速度分佈..................55
圖4.19 路徑對散熱片所造成的降溫效果.......................56
圖4.20 兩段式的散熱片模型.................................57
圖4.21 在Re數為3750時散熱片斜率參數 的溫度分佈............58
圖4.22 在Re數為6000時散熱片斜率參數 的溫度分佈............59
圖4.23 在Re數為7200時散熱片斜率參數 的溫度分佈............59
圖4.24 在不同Re數時散熱片上最高溫度與斜率參數b之關係圖....60

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