丙二醇基石墨烯纳米流体的制备与热性能研究

发布时间：2018-05-04 18:34

  本文选题：石墨烯 + 氧化石墨烯　； 参考：《西南石油大学》2017年硕士论文

【摘要】：目前,强化传热手段的创新,主要集中在新型换热器的开发,提高换热效率,降低能量损失,减小设备体积。虽然换热设备不断完善,但是由于以水、醇、油为代表的传统纯液体换热工质导热系数低,换热体系仍很难达到高负荷有效换热的要求。因此,研究者们开始尝试从换热工质着手,研究纳米流体的换热性能,希望攻克强化传热领域的这一技术瓶颈。其中,石墨烯具有超高的导热系数,丙二醇作为一种无臭无毒且生物可降解性的绿色换热介质,逐步替代乙二醇。因此,本文从高效性和环保性出发,制备了一种高效绿色的分散体系1,2-PG/RGO纳米流体,并分析研究了其热性能。本文具体研究内容总结如下:(1)在强酸性条件下,以石墨为原料,以高锰酸钾作为氧化剂,合成氧化石墨烯GO,在无水乙醇中,以水合肼为还原剂,合成石墨烯RGO;采用两步法,以1,2-丙二醇为基液,制备1,2-PG/RGO纳米流体和1,2-PG/GO纳米流体。然后,使用拉曼光谱、X射线衍射、扫描电子显微镜、透射电子显微镜对样品进行表征;最后,采用静置沉降实验、Zeta电位实验、分散稳定性分析仪研究纳米分散体系的分散稳定性,实验结果表明1,2-PG/RGO体系的分散稳定性优于1,2-PG/GO体系。(2)采用KD2-Pro热特性分析仪,测定1,2-PG/RGO纳米流体导热系数,实验结果表明随着RGO微粒体积浓度的升高,1,2-PG/RGO体系的导热系数不断增大。温度升高,低体积浓度下,体系导热系数减小,较高体积浓度下,体系导热系数增大。在40℃温度条件下,1.0%体积分数的1,2-PG/RGO体系导热系数值可达0.276 W/(m·K),比基液1,2-PG提高了 28.37%。(3)采用紫外-可见光分光光度计和MATLAB分别测定与计算了 1,2-PG/RGO纳米流体的吸光度、透射率、消光系数以及太阳能吸收分数,结果表明1,2-PG/RGO体系展现出全波段吸收特性,体积分数越大,光吸收性能越好。对于体积份额为0.02%的1,2-PG/RGO纳米流体,入射光光程为0.34cm时,可达到90%的太阳能吸收分数。(4)测定了不同条件下1,2-PG/RGO纳米流体的粘度,分析实验数据可知,随着体积浓度的升高,体系粘度值降低。剪切速率较小时,1,2-PG/RGO体系表现出剪切稀释特性,剪切速率较高时,表现出牛顿流体的特性。(5)通过Fluent软件,仿真模拟1,2-PG/RGO纳米流体在自然对流状态下的热量传递过程,发现RGO纳米微粒的添加在一定程度上改善基液的自然对流换热。基于以上研究,1,2-PG/RGO纳米流体可以考虑作为设备换热体系或者太阳能集热系统的工作介质。
[Abstract]:At present, the innovation of heat transfer enhancement mainly focuses on the development of new heat exchanger, improving heat transfer efficiency, reducing energy loss and reducing equipment volume. Although the heat transfer equipment has been improved continuously, it is difficult for the heat transfer system to meet the requirement of high load and effective heat transfer due to the low thermal conductivity of the traditional pure liquid heat transfer medium represented by water, alcohol and oil. Therefore, the researchers began to try to study the heat transfer performance of nanofluids from the perspective of heat transfer fluids, hoping to overcome this technical bottleneck in the field of enhanced heat transfer. Among them, graphene has a high thermal conductivity, propylene glycol as a odorless and biodegradable green heat transfer medium, step by step to replace ethylene glycol. Therefore, based on the high efficiency and environmental protection, a kind of high efficient green dispersion system (1hpPG- RGO) was prepared, and its thermal properties were studied. The specific research contents of this paper are summarized as follows: under strong acid conditions, graphene oxide (GOO) was synthesized by using graphite as raw material and potassium permanganate as oxidant. In anhydrous ethanol, hydrazine hydrate was used as reductant to synthesize graphene RGO.Two-step method was used. In this paper, 1 ~ (2) -PGR _ (R) nano-fluid and 1 ~ (2) -PGR _ (-go) nano-fluid were prepared by using 1 ~ (2) -propanediol as the base solution. Then, the samples were characterized by Raman spectrum X-ray diffraction, scanning electron microscope and transmission electron microscope. The dispersion stability of nanometer dispersion system was studied by dispersion stability analyzer. The experimental results showed that the dispersion stability of 1o 2-PGR / RGO system was better than that of 1H 2-PGR / RGO system. (2) the thermal conductivity of 1nc-PGR / RGO nano-fluid was measured by KD2-Pro thermal analysis instrument. The experimental results show that the thermal conductivity of the system increases with the increase of the volume concentration of RGO particles. With the increase of temperature, the thermal conductivity of the system decreases at low volume concentration, and increases at higher volume concentration. At the temperature of 40 鈩，

本文编号：1844137