肋結構用於鰭片與雙吹管內流的電子冷卻裝置 之熱傳與流體特性研究

Heat Transfer and Fluid Flows in Finned and Ribbed Channels with Cooling Applications to Electronic Chipsets

江貴鳳(Kuei-Feng Chiang)

指導教授 ： 陳炳煇

共同指導教授 ： 張始偉

國立臺灣大學/工學院/機械工程學研究所/博士(2008年)

https://doi.org/10.6342/NTU.2008.10438

摘要

本論文實驗探討 Rib 結構在fan-fin channel和twin blows channel的熱傳表現，同時應用商業軟體 Star CD 分析twin blows channel的流場現象。

Fan-fin管內流的研究目的是為了增益現有PC散熱器的熱對流係數，PC heatsink 一般為上方進風兩側出風，表面Fin片平滑。論文的第一部份研究在這些平滑的fin表面上增加45°Rib的熱傳增益效果與aspect ration (L/B)的最佳化關係。

Notebook PC或是通訊熱交換機都是單進單出的管內流，可是空間尚可放入兩個blower作為進風源，目前市場上的產品都是只有一個進風源。本論文的第二部份探討將兩個進風口 Twin blows channel的進風風量比例對整體散熱效應的影響，並使用商業軟體 Star CD 分析twin blows channel的流場對熱場的影響。

關鍵字

電子冷卻 ； 熱傳散熱 ； 肋, 管內流 ； 散熱器

並列摘要

Heat transfer and fluid flow in the finned and rib-roughened channels for electronic cooling device are investigated through experimental and numerical study. Two passive heat transfer augmentation techniques are proposed to improve PC cooler and telecom air heat exchanger. Fan-fin channel roughened by 450 staggered ribs could enhance heat transfer coefficient comparing with conventional heatsink of PC industry. As well, twin flows in rib-roughened channel were proposed to enhance effectiveness and cooling capacity of air heat exchanger of telecom. The thermal physics and heat transfer correlation of above thermal mechanism are discussed. In what follows, the summaries from these two parts of experimental investigations were described.

l Fan-fin channel roughened by 450 staggered ribs

The detailed heat transfer measurements of rectangular channel roughened by 450 full staggered ribs in both internal walls were performed using the infrared radiometer. The channel was three sides opened and bottom sealed. The present flow path simulated an enhanced coolant channel of the fin-type heat sinks for cooling of electronic chipsets such as CPU. The hydraulic diameter of three test experimental channels was 14.8 mm with different length-to-gap (L/B) ratios of 21.33, 17.11 and 13.56. The influences of L/B ratio on the local and spatially-averaged heat transfers over the rib-roughened surface at Reynolds numbers (Re) of 500, 1000, 2000, 3000 and 3300 were examined. Heat transfer results illustrated the combination effects of side-profile leakage-flow and the rib-induced flow, which were L/B ratio dependent. Heat transfer enhancement over the rib-roughened surface is consistently increasing as Reynolds number increasing and L/B ratio decreasing.

l 450 Rib-roughened test channel with twin blows

This series of experiment study performs the detailed heat transfer measurements over a skewed-rib roughened surface in a rectangular narrow channel with two equal-area flow entrances located on two adjacent edges of a channel-corner. The twin flow inlet was considered from the aspects of one big louder fan flow supplement replaced by two lower noise small fans. This flow configuration also allows for increasing the coolant-flow fed into the narrow channel without increasing the height of assembly in order to enhance the capacity of cooling duty for electronic chipsets. Four test scenarios, namely the single-blow from the side or upper entrance and the twin-blow with the coolant mass flow ratio of 1:1 or 2:1 between the side and upper blows are performed at Reynolds number of 500, 1000, 2000, 3000, 4000, 5000 and 6000 by conducting experimental tests; meanwhile, numerical studies were only performed for these four entrance conditions at Reynolds numbers of 4000. A commercial CFD software package, Star CD, was chosen as the numerical analysis tool to predict the velocity, turbulent kinetic energy distributions and heat transfer performances using RSM turbulence model. A selection of full-field heat transfer distributions over the rib-roughened surface illustrates that flow entry condition and Reynolds number affect the local and spatially averaged heat transfers. At fixed total coolant supplement, the twin-blow with coolant mass flow ratio of 2:1 between side and upper blows elevates the spatially averaged heat transfers to the levels of 150–180% of the single-blow references. A regression-type analysis is subsequently performed to develop correlation of spatially-averaged Nusselt numbers over rib-roughened surface to Reynolds number four test scenarios. For both single side and upper entry conditions, the predictions by RSM model show the good qualitative and quantitative agreements with the experimental heat transfer results. But the deviation of the RSM results for both twin blow conditions of Res=Reu and Res=2Reu are 31% and –34%

並列關鍵字

Electronic Cooling ； Heat Transfer ； Skewed Rib-roughened Fin-flow ； Twin-blow Ribbed Narrow Channel ； Star CD

參考文獻

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