臺灣博碩士論文加值系統

由於電腦微處理器的運作時脈提高，晶體消耗功率大增，使得晶體溫度上升，而晶體必須在一定的溫度下才能正常運作且保有較長之壽命，散熱鰭片與風扇的組合是現在桌上型電腦中央處理器散熱的主流。本文將以鰭片陣列的鰭片外形及尺寸變化對散熱效果進行數值模擬探討，希望能找出分析散熱鰭片之規範並預測其效果，進而改進鰭片陣列之設計與使用。
本文以套裝軟體ANSYS為數值模擬工具，探討鰭片陣列在不同的幾何形狀、鰭片外形對熱傳量的影響。探討的主題為:1.鰭片厚度對熱傳之影響。2.改變熱對流係數及熱傳導係數對鰭片之熱傳量影響。3. 鰭片陣列中鰭片厚度與鰭片間距之關係。4.鰭片外形對整體鰭片陣列之影響。5.實例研究，以達找尋最少用料之鰭片陣列設計。
鰭片在設計上可朝增加鰭片厚度及形狀來著手，鰭片陣列存在最佳鰭片厚度與鰭片間隔之比值設計而達最高之熱效率，並可藉由不同的鰭片外形設計來減少其長度及用料或增加熱傳效果。但增加厚度需考慮鰭片效率之變化，當鰭片效率高於八成時，其熱傳量增加趨緩，此時增加厚度對鰭片陣列尺寸縮減之設計並無太大幫助。
在本研究中得知，現今用鋁合金製造之鰭片熱沉應還有改善之空間。使用高熱導係數材料所製成之鰭片陣列可具備較高之熱傳量，但對鰭片陣列之尺寸改善並無太大之影響。
現今鰭片設計上最大挑戰之一為熱對流係數之估算，相信在未來電腦計算速度的繼續提升後，能有效的計算熱流場資訊並按此求得較準確之熱對流係數，突破此一環節，俾能更精準的掌控鰭片陣列之設計。

The heat and temperature generated inside a high performance CPU have been increased dramatically in recent years due to the demands in CPU speed. A combination of fin array and motor fan is the most common engineering practice in CPU’s heat dissipation for current desk top and lap top PC computers. It is the objective of this thesis to study the effects of fins configurations and dimensions to its heat transfer rate. The analysis and models developed in the thesis can be applied to the thermal design and analysis of the fin arrays used in the CPU of desk top computers .
The well known commercial code “ANSYS” is used in the simulations of the fin array thermal models. The objective of this study is to minimize its fin sizes and weights so that a more compact fin array design can be achieved. The investigations are divided into five parts as following : 1. Fin thickness effect 2. Convection coefficient effects 3. Fin array spacing effect and its relation with thickness 4. Fin shape effect 5. A practical case study.
It is found that both the thickness and spacing have strong effects in fin array overall efficiency. A ratio of 1.5 to 1.6 between base thickness and spacing is the “golden ratio” for 3 different fin shapes studied. The base thickness can be increased to obtain higher fin efficiency and more compact size fin array if the original overall efficiency is below 0.8.
The thickness, spacing and fin shape effects stated above are irrelevant to the fin materials used (aluminum or copper alloy). However, the material with higher conductivity such as copper alloy can increase total heat transfer rate.
The estimation of convection heat transfer coefficient, which is one of the most critical values in the design of fin array, is studied. Further detail flow analysis in the vicinity of the fin array can help in more precise design analysis of the fin arrays used in the cooling of high performance CPU.

中文摘要…………………………………………………………..Ⅰ
英文摘要…………………………………………………………..Ⅲ
目錄………………………………………………………………..V
符號說明…………………………………………………………..ⅥI
第一章 緒論……………………………………………………..1
1-1前言…………………………………………………1
1-2研究動機…………………………………………....2
1-3文獻回顧…………………………………………....3
第二章 研究方法與步驟………………………………………..8
2-1有限元素法簡介……………………………………8
2-2 ANSYS CODE 簡介與基本架構………………….9
2-3統御方程式之推導…………………………………10
2-4物理模型設定………………………………………13
第三章 結果與比較討論………………………………………..16
3-1估算熱對流係數……………………………………16
3-2一維散熱鰭片熱傳分析與驗證 …………………..18
3-3鰭片陣列之熱傳效率與熱傳量分析與驗證………21
3-4鰭片外形影響之分析比較…………………………24
3-5實例研究─最佳化鰭片陣列設計…………………25
第四章 結論與未來展望………………………………………..46
4-1結論…………………………………………………46
4-2未來展望……………………………………………47
參考文獻………………………………………………………..…49
附圖………………………………………………………………..52
附表………………………………………………………………..68
附錄………………………………………………………………..70

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