平板热管用于散热冷却强化传热试验研究

发布时间：2018-05-11 09:23

本文选题：平板热管 + 泡沫金属　；参考：《江苏科技大学》2016年硕士论文

【摘要】：本文在本课题组前期工作的基础上,对平板热管的结构进行改进,为了提高热管的冷却效果,使用了一体化的翅片管作为平板热管的冷凝端,选择质量浓度为0.5%的氧化铝纳米流体作为传热工质,选用泡沫铜作为吸液芯,搭建试验台架并设计试验方案对系列平板式热管进行传热特性试验,研究了不同制备方法泡沫铜吸液芯和孔隙率、连通孔、充液率、纳米流体基液、热源分布、倾角和冷却方式对平板热管的传热性能影响,并与本课题组前期平板热管的传热性能进行了对比。在前期平板热管的基础上研究了纳米颗粒沉积对平板热管传热性能的影响。本文试验结果如下:1)泡沫铜吸液芯孔隙率对纳米流体平板热管传热性能有明显的影响。其对平板热管传热性能因泡沫铜吸液芯制备方法引起的孔隙微观结构特点和表面特征而差异较大。试验范围Qg,电化学法泡沫铜吸液芯平板热管传热性能随孔隙率提高而降低,而粉末复合法泡沫铜吸液芯平板热管的传热性能随孔隙率提高而升高。与电化学法制得的泡沫铜吸液芯相比,粉末复合法制得的泡沫铜吸液芯具有更高的毛细抽吸力,粗糙度更大,理论上作为热管吸液芯具有更好的传热性能。但是过大的表面粗糙度产生过密的气泡反而会发生阻塞效应,表现为电化学沉积法制得泡沫铜吸液芯热管具有更好的传热性能。2)平板热管的连通孔不但能改善热管蒸发端的均温性,而且能减小热管热阻,提高热管的传热性能。3)在相同的条件下,本文的平板热管与本课题组前期的平板热管相比,最大传输功率提高了15%以上,具有更小的传热热阻。4)充液率过低或过高都会降低平板热管的传热性能,与42%和62%充液率相比,本文的最佳充液率为50%。5)与乙醇基和丙酮基纳米流体相比,水由于具有更高的汽化潜热和和更大的表面张力,水基纳米流体泡沫铜平板热管具有更小的换热热阻。6)相较于部分中间和部分侧面,在全部中间的加热方式下平板热管具有更小的传热热阻。在部分中间和部分侧面的负荷分布下,热源位置的改变只会改变热管蒸发端壁温最高点的位置,对热管的整体传热性能没有太大的影响。7)试验结果表明,随着热管轴向倾角的增加,热管的传热性能降低。在小角度范围内,热管热阻增加比较缓慢,当角度增加到一定程度时,传热性能迅速恶化,热阻急剧升高。8)在相同的条件下,冷却风速的增加能在一定程度上提高热管的传热性能。随着风速的增加,热管热阻降低,当风速增加到一定程度,热管热阻变化很小。9)经过一段时间放置的平板热管由于纳米颗粒的沉积不但使得热管的均温性变差,而且会降低热管的传热特性,随着加热功率的升高,一部分纳米颗粒悬浮起来,而使得这种减弱变得缓和。
[Abstract]:Based on the previous work of our group, the structure of flat heat pipe is improved. In order to improve the cooling effect of heat pipe, the integrated finned tube is used as the condensing end of flat heat pipe. The aluminum oxide nano-fluid with 0.5% mass concentration was selected as the heat transfer medium, and the foam copper was used as the liquid absorbing core. The test bench was built and the test scheme was designed to test the heat transfer characteristics of a series of flat heat pipes. The effects of different preparation methods on the heat transfer performance of flat plate heat pipe were studied, such as absorption core and porosity of copper foam, connected pores, liquid filling rate, nano-fluid based solution, heat source distribution, dip angle and cooling method. The heat transfer performance of flat heat pipe was compared with that of our group. The effect of nano-particle deposition on the heat transfer performance of flat heat pipe was studied on the basis of the previous flat heat pipe. The results are as follows: (1) the porosity of copper foam absorbent core has a significant effect on the heat transfer performance of nanofluid flat heat pipe. The heat transfer performance of flat heat pipe varies greatly due to the pore microstructure and surface characteristics caused by the preparation method of copper foam absorbent core. In the range of Qg, the heat transfer performance of copper foam absorbent flat heat pipe decreases with the increase of porosity, while the heat transfer performance of powder composite copper absorbent flat heat pipe increases with the increase of porosity. Compared with the copper foam absorbent core prepared by electrochemical method, the foam copper absorbent core prepared by powder composite method has higher capillary suction force and greater roughness, so it has better heat transfer performance as a heat pipe absorbent core in theory. But if the surface roughness is too big, too many bubbles will be blocked. The results show that the heat pipe with copper foam absorbent core obtained by electrochemical deposition method has better heat transfer performance. 2) the connected holes of the flat heat pipe can not only improve the uniformity of temperature at the evaporating end of the heat pipe, but also reduce the thermal resistance of the heat pipe. Under the same conditions, the maximum transmission power of the flat heat pipe in this paper is increased by more than 15% compared with the previous flat heat pipe of our group. The heat transfer performance of flat heat pipe is reduced when the liquid filling rate is too low or too high with smaller heat transfer resistance. Compared with 42% and 62% liquid filling rate, the optimum liquid filling rate in this paper is 50. 5) compared with ethanol-based and acetone based nano-fluids. Due to higher latent heat of vaporization and greater surface tension, water nanofluid foam copper flat heat pipe has a smaller heat transfer resistance. In all the intermediate heating modes, the flat heat pipe has a smaller heat transfer resistance. Under the load distribution of part middle and part side, the change of heat source position will only change the position of the highest point of wall temperature at the evaporative end of heat pipe, and have no great influence on the heat transfer performance of heat pipe. With the increase of the axial inclination of heat pipe, the heat transfer performance of heat pipe decreases. In a small angle range, the heat pipe thermal resistance increases slowly. When the angle increases to a certain extent, the heat transfer performance rapidly deteriorates, and the thermal resistance increases sharply. 8) under the same conditions, The increase of cooling wind speed can improve the heat transfer performance of heat pipe to some extent. With the increase of wind speed, the heat pipe thermal resistance decreases. When the wind speed increases to a certain extent, the heat pipe thermal resistance change is very small. Moreover, the heat transfer characteristics of the heat pipe will be reduced. With the increase of heating power, a part of the nanoparticles are suspended, which makes the weakening become more moderate.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK172.4

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