複合式迴路式熱管應用於資料中心之散熱

The Application of Hybrid Loop Heat Pipe System in Data Center Cooling

李典儒(Tien-Ju Lee)

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(2016年)

https://doi.org/10.6342/NTU201601395

摘要

現今熱門的雲端產業，人們藉由網際網路不斷使這些資料中心的伺服端產生更大的運算量，進而衍生出更多運算廢熱。目前大多數資料中心所採用的冷卻方式主要以空調氣冷的方式來降溫(如 Google、Apple & Facebook )且需選擇濱臨河海的地區利用天然的水資源協助冷卻。不過，氣冷的散熱方式轉換效率不彰且也需要使用相當耗能的空調系統或冰水主機，因此發展新的散熱方式有其必要性。
故本研究欲開發製造複合式迴路式熱管系統，在傳統迴路式熱管系統中增添液體泵與儲存槽，使其除了毛細結構本身的毛細力外尚有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。本研究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。
實驗結果顯示，複合式迴路式熱管以鎳作為毛細結構，並搭配水為工質的配置下最大熱傳量可達1500W，熱阻值從0.226℃/W 降至0.0788℃/W；而搭配丙酮為工質的配置下，最大熱傳量可達900W，熱阻值從0.35℃/W 降至0.091℃/W。
另外，在相同的配置條件下並控制溫度在100℃±1℃，進一步探討流量效應對性能的效應，結果顯示：流量為0.9L/min 時，有著最大熱傳量600W 和最低熱阻0.09℃/W。最終以複合式迴路式熱管系統展示資料中心之散熱，極限熱負載為700W；操作溫度110℃；最低熱阻0.078℃/W，在100℃的限制下也有著500W的優異性能。
總結本研究之成果，複合式迴路式熱管系統以不到 50W 的液體泵電能功
率，即可有效提升傳統迴路式熱管之熱傳性能與增加熱傳距離，也能抵抗重力對於整體性能的影響。對於未來雲端資料中心等高功率產業的冷卻而言，複合式迴路式熱管系統有極大的潛力。

關鍵字

複合式迴路式熱管 ； 資料中心 ； 液體泵

並列摘要

People nowadays use the Internet to make data centers leading to more and more waste heat in a cloud industry. Currently, the majority of cooling methods in data centers is air conditioning cooling (such as Google, Apple & Facebook), requiring to be located near
the river or ocean to assist cooling. However, the efficiency of air-cooling is not sufficient enough due to the requirements of energy-consuming air conditioning systems or chillers.
The cooling element can be roughly distinguished into two types: passive cooling element and active cooling element. Traditional Loop Heat Pipe system is a passive element, using phase-change effect to transfer heat without adding external power source when operating, while Hybrid Loop Heat Pipe system is an active cooling advice, designed to add the pump. These system uses a small amount of electrical power in exchange for exponential growth of heat transfer performance.
From 2004, the US military cooperated with energy organizations to provide concepts of the combination of capillary force and liquid pump in two-phase circuits. In 2009, the same team discussed the influence of liquid pumps in loop heat pipes. In 2015, the professor Eduard Or considered with developing new cooling method, used in data centers in order to save energy.
As a result, this study develops and manufactures Hybrid Loop Heat Pipe system by adding water pump and storage tank into a conventional loop type heat pipe system. Not only the capillary force but also pumping force provides the overall pressure drop of the system. The reservoir is able to keep sufficient working fluid to the wick structure from making it dry out. Therefore, further investigation of the effect of flowrate in Hybrid Loop Heat Pipe system is needed.
Experimental results show that Hybrid Loop Heat Pipe system used Nickle as wick structure and water as working fluid, resulting in the maximum heat transfer capacity up to 1500W, 275%, better than traditional loop heat pipe, the thermal resistance from 0.226 ℃ / W down to 0.0788℃ / W; while using Nickle as wick structure and acetone as working fluid has the maximum heat transfer capacity up to 900W, 500% , better than traditional loop heat pipe, the thermal resistance from 0.35℃ / W down to 0.091℃ /W. In addition, this study used the same condition and controlled the temperature at 100℃ ± 1 ℃ to explore the effect of flowrate on performances. The results show that it is the flowrate of 0.9L / min which has the maximum heat transfer capacity of 600W and the lowest thermal resistance of 0.09 ℃ / W. Finally, this study used Hybrid Loop Heat Pipe system to demonstrate the cooling of the data center, showing the results that the extreme heat load is of 700W; operating temperature of 110 ℃; the lowest thermal resistance of 0.078 ℃ / W. Furthermore, It also has excellent performance of 500W within the limits of 100 ℃.
In summary, this study can effectively enhance the heat-transfer performance of traditional loop heat pipe and significantly reduce the thermal resistance by pumping
energy less than 50W. Hybrid Loop Heat Pipe system has extreme potential for high power density industrial such as cloud data centers.

並列關鍵字

Hybrid Loop Heat Pipe ； Data Center ； Liquid Pump

參考文獻

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