多孔散熱鰭片熱傳性能之研究

A Study of Heat Transfer for Porous Heat Sink Characterized by Straight Circular Tubes

李爵辰(Jay-Chen Lee)

指導教授 ： 蔡瑞益

中原大學/工學院/機械工程研究所/碩士(2005年)

https://doi.org/10.6840/cycu200500514

摘要

中文摘要
筆記型電腦的快速發展，所產生的高溫廢熱的問題也越來越多，如何在小且薄的有限體積下，找出有效排除廢熱的方式，一直是研究的方向。並在高功率化及微小化研發中，帶動了以往傳統散熱鰭片的改良，舊有的流體衝擊鰭片模式，可能無法有效採用。為了有效節省研究成本及花費時間，運用計算流體力學工具的模擬分析能力日益重要。
本研究主要探討多孔性散熱鰭片，在冷卻流體通過孔隙的情況下，以達到對鰭片降溫的效果。除了採用兩種不同的冷卻流體來比較之外，流體雷諾數的變更、孔隙度的改變也是本文研究的方向。本文研究之鰭片模型為長60㎜、寬2.4㎜、高12㎜的多孔性散熱鰭片，鰭片上壁面為加熱面，並給予一固定瓦數100瓦特，除此之外其他壁面皆假設絕緣；流體流經的孔隙壁面設為光滑無摩擦，孔隙直徑為1.5㎜。並針對改變孔隙直徑的大小，來改變散熱鰭片整體的孔隙度。計算過程採用CFDRC計算流體力學套裝軟體，計算結果包括溫度分布情形，流體狀態為層流模式。
本文經模擬分析後我們得出，冷卻流體以採用水的效果為佳，並在孔隙直徑1.4與1.5㎜的大小下，採用雷諾數500時，對於加熱壁面均溫及下壁均溫的降溫效果最為顯著。反觀採用空氣當作冷卻流體，在雷諾數的增加下並沒有對鰭片整體的降溫效果有明顯的變化。

關鍵字

多孔性 ； 散熱鰭片

並列摘要

ABSTRACT
Since the rapid development of notebook computers, there are more and more problems related to high temperature. To find out an efficient method to eliminate heat in a small and limited space is always a direction to research. Also, the research of high performance and miniaturization drives the improvement of traditional heat sink. The old method of using jet to cool may not be applied efficiently. For saving the research cost and time, it is more and more important to use the analysis simulation ability of CFD calculation tool.
The main purpose of this study is to research a porous heat sink and the working fluid flows through straight circular ducts to decrease the temperature of heat sink. Besides, we use two kinds of working fluids; we also discuss the Reynolds number and porosity of heat sink in this paper. The porous heat sink is 60 mm long, 2.4 mm wide and 12 mm high. Constant power of 100-Watt imposed at upper sidewall of the heat sink. Besides, the other walls are adiabatic. The diameter of each duct is 1.5 mm and the wall surface of duct is smooth. We also change diameter of duct to change porosity of heat sink. The CFDRC software package is used for required calculation in temperature field. The flow fields consider only laminar flow.
From this study we can find that the working fluid water is better than air to decrease the temperature of heat sink. For diameter 1.4 mm and 1.5 mm, the best cooling efficiency occurs on the mean temperature of upper wall and lower wall at Reynolds number 500. On the other hand, if we adopt air as the working fluid, the porous heat sink doesn’t have effective ability for cooling when Reynolds number increases.

並列關鍵字

porous heat sink

參考文獻

1.D.B. Tuckerman, R.F.W. Pease, High-performance heat sinking for VLSI, IEEE Electron Device Lett. 2（1981）126-129.

3.X. Yin, H.H. Bau, Uniform channel micro heat exchangers, J. Electron. Packag. 119（1997）89-94.

4.T.M. Kuzay, Cryogenic cooling of X-ray crystals using a porous matrix, Rev. Sci. Instrum 63（1992）468-472.

5.M.L. Hunt, C.L. Tien, Effects of thermal dispersion on forced convection in fibrous media, Int. J. Heat Mass Transfer 31（1988）301-309.

6.F.C. Chou, W.Y. Lien, S.H. Lin, Analysis and experiment of non-Darcian convection in horizontal square packed sphere channels-I. Forced convection, Int. J. Heat Mass Transfer 35（1992）195-205.