結合水冷與蒸汽壓縮冷卻之創新混合系統應用於高功率密度電子散熱之研究

A novel hybrid system in combination of water cooling and vapor compression systems for high-power density electronic cooling

鄭龍嶽(Lung-Yue Jeng)

指導教授 ： 卓清松

國立臺北科技大學/機電學院/機電科技研究所/博士(2011年)

摘要

因應電子產品高功率與高密度配置，研究發展新型複合式多流道散熱器應用於電子散熱，藉由其高移熱能力與均溫特性提高電子產品之可靠度。本論文內容包含四個研究主題，其分別為液體循環式電子晶片冷卻系統之研究、蒸氣壓縮循環式電子晶片冷卻系統之研究、碳氫冷媒應用於蒸氣壓縮循環式電子晶片冷卻系統之研究與複合式電子晶片冷卻系統之研發。
文中第一部份藉由理論分析與實驗研究的方式來決定奈米流體的最佳配置進行散熱實驗研究。研究結果顯示添加0.05wt.%甲聚醣分散劑於1.0wt.%之Al2O3奈米流體中，在流速、液溫及加熱瓦數分別為2.0 L/mim、40 ℃、150 W下，其總熱傳導係數可增進17.4%。
文中第二部份首先找出最適合本系統的R-134a冷媒充填量，並進行系統測試與調校，最後再進行穩態與動態的散熱實驗。研究結果顯示本系統R-134a冷媒最佳填充量為150g。在考量不結露的情況之下，蒸發溫度為23 ℃時，可對CPU熱源有最佳的散熱性能。在動態實驗中，多流道蒸發器的出入口端之溫度顯示冷媒脫離了兩相區，且冷媒流量的增加使得吸氣管的過熱度降低，皆有助於系統的散熱性能。
文中第三部份探討將原本R-134a冷媒之VCRS電子晶片冷卻系統置換成異丁烷/丙烷（50:50, by mass）的碳氫冷媒的可行性評估。研究結果顯示在不變更VCRS電子晶片冷卻系統原設計下進行冷媒更換，其最佳冷媒充填量的範圍在46.6%(70g)∼57%(85.5g)。當HC碳氫冷媒充填量為R-134a的53.3%時，CPU表面溫度與蒸發器底板溫度均略高於R-134a系統，其COP增加約16%。
文中第四部份整合單相液體冷卻的散熱器與兩相流沸騰變化蒸氣壓縮循環系統的蒸發器形成複合式電子晶片冷卻系統。實驗參數分別採用論文中第二、四部份所得之奈米流體與碳氫冷媒的最佳參數。研究結果顯示複合式電子晶片冷卻系統最佳的冷卻能力約在330 W，此時CPU表面溫度及複合式系統之耗功分別為56 ℃與29.6 W。此系統最大的冷卻能力約在500 W左右，熱阻分佈在0.03∼0.05 ℃/W。本複合式電子晶片冷卻系統能有效超越現有的電子冷卻系統的性能，具有極佳的散熱能力。

關鍵字

奈米流體 ； 總熱傳係數 ； 電子晶片冷卻 ； 液體冷卻 ； 蒸氣壓縮循環 ； 碳氫冷媒 ； 複合式多流道散熱器

並列摘要

To meet the high power and high-density allocation of electronic products, a new hybrid multi-channel heat sink was developed for applications with electronic heat sinks. The reliability of electronic products can be increased through the use of high efficiency heat removal and establishing a uniform temperature. The four sections of this paper are: 1. Liquid cooling system for electronic chip, 2. Vapor compression refrigeration systems for electronic chip, 3. Performance assessment of an R-134a VCRS for electronic cooling device retrofitted with the hydrocarbon mixtures, and 4. Hybrid cooling system for electronic chips.
The first section determines optimal experimental parameters of nanofluids using theoretical analysis and experimental research with heat dissipation experimentation. The results have shown that adding chitosan dispersants at 0.05 wt.% in Al2O3/water nanofluid at 1.0wt.% can enhance the overall heat transfer coefficient by 17.4% when the flow rate, liquid temperature, and heating power are 2.0 L/mim, 40℃ and 150 W, respectively.
The second section indicates the most suitable charged mass of R-134a refrigerant for this system can be found through conduct system testing and tuning. Finally, heat dissipation experiments using steady-state and dynamic will to be conducted. The results have shown that the optimal charged mass of R-134a refrigerant for the system is 150 g. The CPU heat source will have the best performance through heat dissipation when the evaporation temperature was 23 ℃ under without condensation. In the dynamic-state experiment, the refrigerant was detached from the two-phase zone and can be seen in the temperature of inlet and out let of the multi-channel evaporator. The superheat decreased in the suction when the refrigerant flow increased, as both contributed to system performance with heat dissipation.
The third section, this paper explored the feasibility of replacement of R-134a refrigerant in VCRS electronic chip cooling systems with hydrocarbon refrigerant combined with isobutene/ propane (50:50, by mass). The results have shown that without changing any components in the original VCRS for cooling electronic chips, the margin of optimal changed mass was 46.6 (70g)∼57 (85.5g) %. When HC refrigerant was charged with 53.3 % of the charged mass of R-134a, the CPU surface temperature and evaporator bottom temperatures were slightly higher than the R-134a systems and the COP increase of about 16 %.
The fourth section integrated a single-phase liquid-cooling heat sink and an evaporator with two-phase flow boiling change by vapor compression cycle system into a hybrid cooling system for electronic chips. The coolant and refrigerant in these two systems were the optimal parameter of nanofluid and hydrocarbon refrigerant, as in the second and third sections of this paper. The results have shown that the best cooling capacity of hybrid cooling system for electronic chips was about 330W, and the surface temperature of the CPU and total system power consumption was 56 ℃ and 29.6 W, respectively. The maximum cooling capacity of this system was around 500 W, and the thermal resistance distribution was 0.03∼0.05℃/W. The hybrid cooling system for electronic chips can go beyond existing electronic cooling system performance, with excellent heat dissipation, as well.

並列關鍵字

Nanofluid ； overall heat transfer coefficient ； cooling for electronic chip ； liquid cooling ； vapor compression refrigeration systems ； hydrocarbon refrigerant ； hybrid multi-channel heat sink

參考文獻

References of Chapter 1

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