标题: 改善毛细泵吸回系统在电子冷却上之实验研究
Experimental Study of an Improved Capillary Pumped Looped System for Electronics Cooling
作者: 洪义祥
Yi- Hsiang Hung
林清发
Tsing-Fa Lin
机械工程学系
关键字: 电子冷却;electronics cooling
公开日期: 2005
摘要: 本论文主要是改善毛细泵回路系统在电子冷却上之实验研究,使用一沟槽外形的铜块放置在蒸发器内部,其截面积尺寸为 ,并且此沟槽是由5个平行的矩形的通道构成用以提供蒸发器内的蒸气流往蒸气线,其每一个通道的尺寸为长 和宽为 、高为 ,并且在沟槽的上方和一多孔性材质紧密接触,其尺寸为 且平均孔隙平径为 。冷凝器是由水冷式的双套管来达到冷却的目地。另外,选用直径为 光滑的铁氟龙管来当作蒸气线和液态线并且选用去离子水来当作实验的工作流体,而在改善CPL系统的部份,我们将利用纯棉的薄纱布去覆盖在沟槽通道的侧面和底面,用以增加蒸发器的蒸发面积。实验的目的探讨在不同输入功率、冷凝器的冷却温度、工作流体的填充量、蒸发器和冷凝器之间的高度差及覆盖在沟槽表面的纱布对热传性能的影响。在实验参数的范围上,加热功率从5到260 W、冷却温度从20到40度、流体填充量从50 到75% 及蒸发器和冷凝器的高度差从0到10公分,此实验的操作中止是以蒸发器的平均温度到达80度为限。
由实验结果可以发现工作流体的填充量会影响到整个系统的热传能力,且在最高的散热功率以及最低的热阻值会发生在一最佳的充填量,而系统的热传能力仅稍微被冷却水温度所影响,并且蒸发器的操作温度会随着冷却水温度增加而提高。接着,当提高蒸发器和冷凝器的相对高度有助于改善CPL的热传能力。对于覆盖一纯棉的纱布在沟槽的侧面和底面并且在可靠条件下也可以大大地改善热传的能力,但是在其它的条件下则影响不显着。
最后,将提供有覆盖纱布和没覆盖纱布之下的最大的散热功率和最小的热阻值的经验公式以供设计CPL冷却的设计者参考,而所有的实验结果在本篇的论文中最高的散热能力约为255W。
An experiment is carried out in the present study to investigate an improved design of a CPL (Capillary Pumped Loop) system for electronic cooling. The evaporator of the CPL system is modeled by a grooved square copper plate of size glued onto another heated rectangular copper plate of the same size. The grooved copper plate contains five parallel rectangular open channels for the vapor generated in the evaporator to flow into a vapor transport line. Each channel is characterized by 30 mm in length, 2.4 mm in width, and 3 mm in height. A porous wick made from open-cell blowing foam of polyvinyl alcohol with a mean pore radius of 21μm and having a size of is placed on the grooved copper plate. The condenser is made of a double-pipe heat exchanger with liquid water flowing in the outer pipe. Besides, smooth teflon tubes of inside diameter 4.5 mm are chosen for the vapor and liquid transport lines. The deionized water is selected as the working fluid. Moreover, a thin cotton gauze layer of 150μm in thickness is covered on the side and bottom walls of the grooved channels to provide more surface area for liquid vaporization. Tests are conducted for the liquid inventory varied from 50% to 75%, cooling water temperature in the condenser from 20℃ to 40℃, condenser-evaporator relative height from 0 to 10 cm. The test is terminated when the mean evaporator temperature exceeds 80℃. In the study how the liquid inventory, cooling water temperature in the condenser, relative height between the condenser and evaporator, and cotton gauze layer covering affect the CPL performance is investigated in detail.
The experimental results show that the liquid inventory significantly affects the heat transfer performance of the system. An optimal liquid inventory exists at which the maximum power input to the evaporator is the highest and the minimum thermal resistance of the CPL is the lowest. The CPL heat transfer capability is only slightly affected by the cooling water temperature in the condenser. But the evaporator temperature is noticeably higher for a higher cooling water temperature in the condenser. An increase in the relative height between the condenser and evaporator results in a significant improvement in the CPL performance. Besides, for a larger relative condenser-evaporator height the influences of the liquid inventory on the performance of the CPL are milder. Covering a thin cotton gauze layer on the side and bottom surfaces of the grooved channels can substantially improve the heat transfer performance of the CPL system under certain conditions. For other conditions the improvement is comparatively smaller.
Finally, empirical correlations for the Qe,max and Rth,min are proposed for the CPL with and without cotton gauze covering for thermal design of CPU cooling. For all cases tested in the present CPL system the highest Qe,max is 255W.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT009314540
http://hdl.handle.net/11536/78514
显示于类别:Thesis


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