複合式迴路式熱管應用於高效能筆電散熱之研究

The Study on the Application of Hybrid Loop Heat Pipe System in High Performance Notebook

陳彥君(Yan-Chun 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(2017年)

https://doi.org/10.6342/NTU201701290

摘要

近年來由於半導體製程的進步，電子設備朝向高密度與高性能的目標邁進，在晶片尺寸不斷微小化的同時，單位面積內所包含的電晶體數卻持續增加，也致使單位面積的發熱量一再創新高。散熱問題一直是筆記型電腦的技術瓶頸與挑戰，其關係到筆記型電腦的整體穩定度與效能評比。目前筆記型電腦散熱方式常見的有風扇、熱管與散熱片等，但伴隨著晶片製成的進步持續進化，單位面積的發熱量逐漸升高，在未來必使傳統的散熱方法不敷使用，故發展新的散熱方式有其必要性。
因此本研究欲開發製造適用於高效能筆記型電腦散熱之複合式迴路式熱管系統。本研究先針對傳統迴路式熱管發展具液體溝槽之毛細結構的製程技術，以降低流動阻力及增加吸收工作流體表面積，藉以改善平板迴路式熱管熱傳性能，此後在傳統的迴路式熱管中增添微型液體泵與液體儲存槽，用少量的動力換取倍數成長的熱傳性能，使其除了毛細結構本身的毛細力外尚有微型液體泵來提供整體系統循環所需的壓降，儲存槽則能保有充分的工作流體，並藉由液體泵將工作流體源源不絕輸往毛細結構進行相變化，避免毛細結構乾涸。另外本研究更進一步探討不同流量效應下對複合式迴路式熱管性能的影響，進而開發出適用於高效能筆記型電腦之散熱模組。
實驗結果顯示，具液體溝槽之毛細結構迴路式熱管在鐵氟龍毛細結構並搭配丙酮為工質的配置下，最大熱傳量可達到225W(熱通量為33.3 W/cm2)，最低總熱阻為0.63℃/W，較傳統迴路式熱管性能提升約50%。而複合式迴路式熱管在將其蒸發器壁面控制溫度在100℃，最大熱傳量可達到400W (熱通量為59.2 W/cm2)，最低總熱阻為0.22℃/W，較傳統迴路式熱管性能提升約700%，進一步探討流量效應之影響發現在有限程度的增加流量可提升最大熱傳量並降低熱阻，但過大的流量，熱傳性能提升效果並不顯著，此時反而會浪費幫浦的電功率。實驗結果發現在液體泵流量為100ml/min時，最大熱傳量可達到400W，總熱阻最低為0.22℃/W。
總結本研究之成果，複合式迴路式熱管系統以少量動能的輸入，即可有效提升傳統迴路式熱管之熱傳性能，對於未來高效能筆電等高功率產業的散熱而言，複合式迴路式熱管系統有極大的發展潛力。

關鍵字

複合式迴路式熱管 ； 鐵氟龍 ； 丙酮 ； 液體泵 ； 高效能筆電

並列摘要

In recent years, due to the progress of semiconductor manufacturing process, electronic equipment goes toward high-density and high-performance goals. While the wafer size is minimizing, the unit area that contains the number of transistors is continuously increased, and the heat released per unit area reached a new high. The problem of heat dissipation has always been a technical bottleneck and challenge for notebooks, which relates to the overall stability and performance of notebooks. At present, the cooling methods of notebook computer are fans, heat pipes and fins, but with the progress made by the wafer continued to evolve, the heat released per unit area will gradually increase in the future, it will make the traditional cooling method not enough to use. The development of new cooling methods has its necessity.
Therefore, this study aims to develop a Hybrid Loop Heat Pipe system for high-performance notebook computer cooling. At first, this study develop a technology in wick structure with liquid grooves for the traditional Loop Heat Pipe to reduce the flow resistance and increase the absorption of working fluid surface area, in order to improve the Flat Plate Loop Heat Pipe heat transfer performance, then add the micro-fluid pump and reservoir in traditional Loop Heat Pipe, it uses small amount of power in exchange for exponential growth in the heat transfer performance, in addition to capillary force provided by wick structure itself, there are micro-liquid pump to overcome pressure drop of the overall system cycle, The reservoir is able to keep sufficient working fluid to the wick structure in order not to make it dry out, In addition, this study further explores the effect of different flow rate on the performance of the Hybrid Loop Heat Pipe, and then develops a heat dissipation module suitable for high performance notebook computers.
The experimental results show that the maximum heat transfer of wick structure with liquid grooves can reach 225W (heat flux is 33.3 W/cm2) in the Teflon wick structure with acetone as working fluid, the thermal resistance is 0.63℃/W, increased by about 50% than the traditional Loop Heat Pipe. The maximum heat transfer of Hybrid Loop Heat Pipe system can reach 400W (heat flux is 59.2 W/cm2), and the total thermal resistance is 0.22℃/W, which the temperature is controlled at 100℃ .The performance of Hybrid Loop Heat Pipe is improved by about 700% than traditional Loop Heat Pipe. It is found that the increase of the flow rate can increase the maximum heat transfer and reduce the thermal resistance, but the heat transfer performance improvement is not significant at excessive flow rate, at this time, it will waste the pumping power. The results show that the maximum heat transfer can reach 400W and the total thermal resistance is 0.22℃/W when the flow rate of liquid pump is 100ml / min.
Based on the results of this study, with a small amount of kinetic energy input, the Hybrid Heat Pipe system can effectively enhance the heat transfer performance of traditional Loop Heat Pipe system, for the future high-performance notebook and other high-power industry, the Hybrid Loop Heat Pipe system has great potential for development.

並列關鍵字

Hybrid Loop Heat Pipe ； Polytetrafluoroethylene(PTFE) ； Acetone ； Liquid Pump ； High Performance Notebook

參考文獻

[4] Gernert, Nelson J., Gregg J. Baldassarre, and Joseph M. Gottschlich. Fine pore loop heat pipe wick structure development. No. 961319. SAE Technical Paper, 1996.

[6] Maydanik, Y. F, ” Loop heat pipes” Applied Thermal Engineering, Vol.25, 635-657, 2005.

[7] Launay.S, Vallée.M, "State-of-the-art experimental studies on loop heat pipes." Frontiers in Heat Pipes (FHP) , 2011.

[8] Siedel.B, Sartre.V, Lefèvre.F. "Literature review: Steady-state modelling of loop heat pipes." Applied Thermal Engineering ,Vol.75, 709-723, 2015.

[10] Maidanik, Y.F., Vershinin.S.V, Chernysheva.M.A, Development and tests of miniature loop heat pipe with a flat evaporator. No. 2000-01-2491. SAE Technical Paper, 2000.