氧化石墨烯纳米流体热物性能及在热管中应用的研究

发布时间：2018-05-09 09:12

本文选题：氧化石墨烯 + 纳米流体　；参考：《济南大学》2017年硕士论文

【摘要】：“纳米流体”是指以传统传热工质作为基液,向其中加入纳米尺寸的添加物形成的一种多相体系,纳米添加物的性质对纳米流体性能至关重要。氧化石墨烯是种性能优异的独特二维材料,导热性良好且亲水性能极佳,是纳米流体的理想添加物。作为具有高效传热效能的新型传热介质,纳米流体在传热领域得以广泛应用。热管则是传热领域内一种常用的传热元件,因而将纳米流体应用于热管对于改善热管传热效能、进一步提高传热效率有重要意义。本论文将研究氧化石墨烯纳米流体的热物性能及在热管中的应用。首先制备出氧化石墨烯,其次将其分散在基液中形成氧化石墨烯纳米流体。实验研究了氧化石墨烯纳米流体的热物性能参数,初步探讨影响氧化石墨烯纳米流体热物性能的因素,进一步就其工作机理从理论上进行了简要分析。此外,还将实验制备的氧化石墨烯纳米流体填充于热管探究其对热管传热能力的影响。该研究不仅可以丰富氧化石墨烯纳米流体的热物性能数据,为氧化石墨烯纳米流体在传热领域内的应用奠定基础,还可以对纳米流体热管的设计开发及优化起到积极的推动作用。论文主要研究内容如下:(1)氧化石墨烯纳米流体的制备。首先采用Hummers法制备了氧化石墨,利用超声剥离的手段得到氧化石墨烯,通过调节剥离时间得到了三种片层尺寸(5μm、10μm、20μm)的氧化石墨烯。其次将不同片层尺寸的氧化石墨烯分别分散在基液水和乙二醇中制得质量分数分别为0.05%、0.1%、0.15%、0.2%、0.25%的氧化石墨烯纳米流体,无需添加任何表面活性剂。吸光度测量结果表明所制备的氧化石墨烯纳米流体具有良好的悬浮稳定性。(2)氧化石墨烯纳米流体热物性能研究。采用KD2-Pro导热系数仪、Brookfield粘度计、JK99B全自动界面张力仪等仪器研究了氧化石墨烯纳米流体在不同条件下的热物性能,包括导热性能、粘度特性、表面张力、接触角等参数。结果发现:在基液中加入氧化石墨烯后,基液的导热性能提高、粘度增加,表面张力和接触角则有所降低。此外实验还发现液体温度、纳米流体的质量分数以及氧化石墨烯片层尺寸对纳米流体的热物性能均有不同程度的影响。温度升高,氧化石墨烯纳米流体的导热性能提高,粘度和表面张力降低;质量分数增加,氧化石墨烯纳米流体的导热性能、粘度、表面张力均增大;片层尺寸减小会引起氧化石墨烯纳米流体的导热性和表面张力降低,粘度则增大。实验还将测得的氧化石墨烯纳米流体的导热系数值和粘度值与理论模型计算结果对比。(3)氧化石墨烯纳米流体热管性能研究。自行组装了氧化石墨烯纳米流体热管性能测试装置,探究了氧化石墨烯纳米流体对热管传热性能的影响,主要考察了热管的启动过程、壁面温度分布以及热管的热阻、传热系数、有效导热系数等。结果表明:氧化石墨烯纳米流体热管的传热性能显著高于以基液为工质的热管,表现为氧化石墨烯纳米流体热管的热阻比基液热管最多降低了50%、有效导热系数最大是基液热管的2.59倍。集总参数模型理论计算结果还表明:可以通过集总参数法预测氧化石墨烯纳米流体热管的启动过程。最后实验还发现氧化石墨烯纳米流体增强热管传热性能的原因主要与吸液芯表面的氧化石墨烯涂覆层有关。
[Abstract]:"Nanofluids" refers to a multiphase system formed by using traditional heat transfer fluids as base fluids and adding nano sized additives to them. The properties of nanoscale additives are crucial to the performance of nanofluids. Graphene oxide is a unique two-dimensional material with excellent performance, good thermal conductivity and excellent hydrophilic properties. It is the ideal of nanofluids. As a new type of heat transfer medium with efficient heat transfer efficiency, nanofluids are widely used in the field of heat transfer. Heat pipes are a common heat transfer element in the field of heat transfer. Therefore, the application of nanofluids to heat pipes is of great significance to improve heat transfer efficiency of heat pipes and to further improve heat transfer efficiency. This paper will study oxidation in this paper. The thermal properties of graphene Nanofluids and their applications in heat pipes. First, the graphene oxide was prepared, and then it was dispersed in the base liquid to form a graphene oxide nanofluid. The thermal properties of the graphite oxide nanofluids were investigated and the factors affecting the properties of the graphite oxide nanofluids were preliminarily discussed. In addition, the effect of the prepared graphene oxide nanofluid in the heat pipe on the heat transfer capacity of the heat pipe is also investigated. The study not only enriches the thermal property data of the graphite oxide nanofluids, but also lays the foundation for the application of the graphite oxide nanofluid in the field of heat transfer. It can also play an active role in the design, development and optimization of nanofluid heat pipes. The main contents of this paper are as follows: (1) the preparation of graphene oxide nanofluids. First, graphite oxide was prepared by Hummers method, and graphene oxide was obtained by ultrasonic stripping. Three kinds of lamellae were obtained by adjusting the stripping time. Graphene oxide of size (5 mu m, 10 mu m, 20 mu m). Secondly, the graphite oxide nanofluids of 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, respectively, were dispersed in the base liquid water and ethylene glycol, respectively, with different lamellar size of graphene oxide, respectively, without any surface active agent. The absorbance measurement results showed the prepared graphite oxide. Nanofluids have good suspension stability. (2) study on the properties of graphene oxide nanofluids. The thermal properties of graphene oxide nanofluids under different conditions, including thermal conductivity, viscosity properties and surface tension, were studied by using KD2-Pro thermal conductivity meter, Brookfield viscometer, and JK99B fully automatic interfacial tension meter. The results show that the thermal conductivity of the base liquid is improved, the viscosity increases, and the surface tension and contact angle decrease after the addition of graphene oxide in the base solution. In addition, the liquid temperature, the mass fraction of Nanofluids and the size of the graphene oxide layer have different degrees of influence on the thermal properties of the nanofluids. The thermal conductivity of the graphene oxide nanofluid increased, the viscosity and surface tension decreased, the mass fraction increased, the thermal conductivity, viscosity and surface tension of the graphene oxide nanofluids increased. The decrease of the lamellar size would cause the decrease of the thermal conductivity and surface tension of the graphene oxide Nanofluids and the increase of the viscosity. The experiment also increased. The thermal conductivity and viscosity values of the measured graphene oxide nanofluids were compared with the theoretical model results. (3) the properties of the graphite oxide nanofluid heat pipe. The performance test device of the graphite oxide nanofluid heat pipe was self-assembled, and the effect of the graphite oxide nanofluid on the heat transfer performance of the heat pipe was investigated. The starting process of the heat pipe, the distribution of the wall temperature, the thermal resistance of the heat pipe, the heat transfer coefficient, the effective thermal conductivity and so on. The results show that the heat transfer performance of the graphite oxide nanofluid heat pipe is significantly higher than the heat pipe with the base liquid as the working medium, which shows that the thermal resistance of the graphite oxide nanofluid heat pipe has been reduced by 50% and the heat conduction is effective. The maximum coefficient is 2.59 times that of the base liquid heat pipe. The theoretical calculation results of the lumped parameter model also show that the starting process of the graphite oxide nanofluid heat pipe can be predicted by the lumped parameter method. Finally, it is found that the reason of the heat transfer performance of the graphite oxide nanofluid enhanced heat pipe is mainly with the coating layer of the graphite oxide coating on the surface of the liquid sucking core. Of

【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11;TB383.1

【参考文献】