雙層毛細結構於迴路式熱管之性能提升

Loop Heat Pipe Performance Enhancement With Bilayer Wick Structure

陳政宏(Zheng-Hong Chen)

指導教授 ： 陳瑤明

國立臺灣大學/工學院/機械工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.00451

摘要

迴路式熱管為一種具相變化的被動熱傳裝置，相較於傳統熱管，其優點有：遠距熱傳輸、低熱阻與高熱傳量等優勢。有鑑於電子產品走向輕薄短小與高發熱密度的趨勢下，迴路式熱管往小型化的發展，伴隨著散熱面積減小而產生高熱通量的散熱需求。因此，本研究旨在克服迴路式熱管典型的單孔徑毛細結構蒸發器於高熱通量時，熱傳性能急速衰退之問題。
本研究利用二次燒結來製作雙層毛細結構，安置於蒸發器受熱面之外部主毛細結構(primary wick)來排除蒸氣，而於吸收液體面之內部次毛細結構(secondary wick)則負責吸收液態工質補充至蒸發器核心，造成毛細結構之內外部為液氣分離流動，能降低蒸氣對流熱洩漏到補償室。由於文獻上對於毛細結構厚度參數於迴路式熱管之熱傳性能影響的相關報導仍屬缺乏，因此本研究針對結構厚度參數作探討。
研究結果顯示，在固定主毛細結構1.75mm之下，隨著次毛細結構厚度在0.75~1.5mm之增加範圍內，蒸發器壁面溫度有顯著的降低。當厚度從1.5mm增加到2.25mm時，有出現反趨勢，熱傳性能變差，這顯示雙層毛細結構具有一最佳厚度。而在本研究之厚度範圍內最佳的次毛細結構厚度為1.5mm。
此外，在熱沉溫度設定10℃與蒸發器壁面溫度不超過100℃之情況下，單孔徑毛細結構之最大熱傳量為600W，系統總熱阻為0.15℃/W；雙層毛細結構之最大熱傳量為1000W，系統總熱阻低於0.09℃/W。相較於單孔徑毛細結構除有熱傳量提高400W以上且於系統總熱阻方面上約有70%的降低。

關鍵字

迴路式熱管 ； 雙層毛細結構 ； 熱洩漏 ； 高熱通量

並列摘要

Loop heat pipe (LHP) is a passive two phase heat transfer device, which have ability to transport long-distance, low thermal resistance, and high heat transfer capacity advantages as compared with traditional heat pipe. In recent years, the high heat flux thermal solution requirement follows the electronic device become more powerful and smaller size.LHP developed smaller evaporator size. Therefore, the purpose of this article is to overcome the LHP heat transfer performance decrease sharply when using mono-porous wick in evaporator.
In this study, nickel powder were used to produce bi-layer wick structure by sintered twice. The primary wick is arranged for vapor escape and the secondary wick is for the purpose of managing the fluid flow between the compensation chamber and evaporator. The configuration of wick’s place is in order to separate the vapor and liquid flow that could reduce the heat leakage from evaporator to compensation chamber. According to the present research, it is lake of parametric studies on wick thickness in loop heat pipe. So that, the aim of this study is to understand the thickness effect and find the optimized case.
Experiment result show that the evaporator temperature had significant decrease at the situation of primary wick thickness 1.75mm and the secondary wick thickness increase from 0.75mm to 1.5mm.But when the secondary wick thickness increase from 1.5mm to 2.25mm, there is a sharp decrease in heat transfer performance. So as the result show that there exist an appropriate thickness which have the best heat transfer performance. And in this study, the best secondary wick thickness is 1.5mm.
On the other hand, when the sink temperature set at 10℃and the evaporator temperature not to exceed 100℃, the mono-porous wick have the maximum heat load 600W and total thermal resistance is 0.15℃/W; Bilayer wick structure have the maximum heat load up to 1000W and total thermal resistance is below 0.09℃/W. The bilayer wick structure not only increases at least 400W heat load but also decreases the total thermal resistance about 70%.

並列關鍵字

Loop heat pipe ； bilayer wick ； heat leakage ； high heat flux

參考文獻

[1] Rosenfeld, J. H. and North, M. T.,“Porous Media Heat Exchangers for Cooling of High-power Optical Components,” Optical Engineering, Vo1.34, No.2, pp.335-341, 1995.

[3] Z. Q. Chen, P. Cheng and T. S. Zhao, “An experimental study of two phase flow and boiling heat transfer in bi-dispersed porous channels,”International Communications in Heat and Mass Transfer, Volume 27, Issue 3, Pages 293-302, 2000.

[5] M. A. Hanlon and H. B. Ma, “Evaporation Heat Transfer in Sintered Porous Media,”Journal of Heat Transfer, Volume 125, Issue 4, 2003.

[6] Maydanik, Yu. F., “Loop Heat Pipes,” Applied Thermal Engineering, Vol. 25, No. 5–6, pp. 635–657, 2005.

[7] T. Semenic and I. Catton, “Boiling and Capillary Limit Enhancement of a Heat Pipe Wick Using Biporous Capillary Structure,”Annals of the Assembly for International Heat Transfer Conference 13, pp.RPT-18, 2006.