不同形貌二氧化钛纳米流体的制备及其热物性能研究

发布时间：2018-05-26 00:04

本文选题：二氧化钛纳米流体 + 制备　；参考：《济南大学》2017年硕士论文

【摘要】：纳米流体是一种含有纳米级尺寸固体颗粒的悬浮液,是一种新型的高效传热介质。与传统的传热介质相比,其具有很高的导热性能,应用于换热设备里可以提高设备传热效率,满足换热系统高负荷的要求。作为目前国内外传热领域的研究热点之一,纳米流体的研究开发将会给热工工程领域带来新的发展,将丰富强化传热内容,不仅在理论上将具有较高的学术价值,对实际工程应用亦有很重要的指导作用,同时对于我国实现节能减排、促进保护环境具有更重要意义。本文以不同形貌二氧化钛纳米流体为研究对象,研究了纳米流体的制备过程,分析了不同形貌纳米流体的导热性能、粘度和润湿性等热物性能,主要研究工作如下:1、利用水热法,成功制备出棒状(金红石相,200nm,?30nm)、菱形(锐钛矿,105nm×15nm)和片状(锐钛矿,110nm×12nm)三种形貌质量分数为0.05wt.%~0.4wt.%的二氧化钛纳米流体,掌握了其制备工艺过程,并探究反应物浓度、反应时间和反应温度对棒状二氧化钛纳米颗粒形貌与晶型的影响,发现低浓度、长时间和高温度的反应条件有利于棒状颗粒的长大和晶体晶化程度的提高。2、对三种形貌二氧化钛纳米流体的导热系数进行实验研究,分析了温度、质量分数、颗粒形貌和晶型对二氧化钛纳米流体导热系数的影响,并进一步将实验值与经验模型计算值进行对比。研究发现,纳米流体导热系数随着温度升高和质量分数的增大而增大,与基液相比,导热系数最大增大49.10%,锐钛矿相二氧化钛纳米流体导热系数比金红石相纳米流体导热系数大3.28%~4.47%,片状纳米流体导热系数比菱形纳米流体导热系数大2.39%。同时,实验结果可以与Sharma模型计算值相吻合,误差范围为2.15%~5.13%,表明可以用Sharma模型预测纳米流体的导热系数。3、对三种形貌二氧化钛纳米流体的粘度进行系统研究,探究了温度、质量分数、颗粒形貌和晶型对纳米流体粘度的影响,并进一步将实验值与经验模型计算值进行对比。结果表明,纳米流体的粘度随着质量分数的增大而增大,随着温度的升高而降低,与基液相比,粘度最大增大19.73%,锐钛矿相二氧化钛纳米流体粘度比金红石相纳米流体粘度大2.5%,片状纳米流体粘度比菱形纳米流体粘度稍大。Bobbo模型可以准确计算质量分数较高的纳米流体的粘度值,其最小误差仅为0.19%。4、对三种形貌二氧化钛纳米流体的润湿性进行研究,并探究温度、质量分数、颗粒形貌和晶型对纳米流体润湿性的影响。结果表明:(1)纳米流体表面张力随着温度升高和质量分数的增大而减小,与基液相比,表面张力最大降低16.95%,锐钛矿相二氧化钛纳米流体表面张力比金红石相纳米流体表面张力大0.125~0.917mN/m;(2)与表面张力性质相似,纳米流体接触角随着温度升高和质量分数的增大而减小,与基液相比,接触角降低了21.98%~25%,锐钛矿相二氧化钛纳米流体接触角比金红石相纳米流体接触角大0.5°;形貌对二氧化钛纳米流体的润湿性无明显影响规律。
[Abstract]:Nanofluid is a kind of suspension liquid containing nanometer size solid particles. It is a new type of high efficient heat transfer medium. Compared with the traditional heat transfer medium, it has high thermal conductivity. It can improve the heat transfer efficiency of the equipment and meet the requirement of high negative charge in heat exchange system. One of the hot spots, the research and development of nanofluids will bring new development to the field of thermal engineering, and will enrich the content of heat transfer. It will not only have higher academic value in theory, but also have a very important guiding role in practical engineering application. It is of great significance to realize the reduction of energy saving and the protection of the environment in China. The preparation process of nanofluids with different morphologies was studied. The thermal properties, viscosity and wettability of different morphology nanofluids were analyzed. 1, 1, the rod like (Jin Hongshi phase, 30nm), rhombus (anatase, 105nm x 15nm) were successfully prepared by hydrothermal method. Three kinds of titanium dioxide nanofluids with the mass fraction of 0.05wt.%~0.4wt.% (anatase, 110Nm x 12NM) were prepared and the effects of the reaction time and temperature on the morphology and crystal shape of the TiO2 nanoparticles were investigated, and the reaction conditions of low concentration, long time and high temperature were found. The thermal conductivity of three kinds of titanium dioxide nanofluids was investigated by.2. The influence of temperature, mass fraction, particle morphology and crystal shape on the thermal conductivity of titanium dioxide nanofluids was investigated. The experimental values were compared with those of empirical models. It is found that the thermal conductivity of nanofluids increases with the increase of temperature and mass fraction, and the thermal conductivity of the anatase titanium dioxide nanofluids is larger than that of the rutile nanofluids, and the thermal conductivity of the anatase titanium dioxide nanofluids is 3.28%~4.47%, and the thermal conductivity of the flake nanofluids is 2 higher than that of the rhombus nanofluids. .39%. also coincides with the calculated values of the Sharma model, and the error range is 2.15%~5.13%. It shows that the thermal conductivity of nanofluids can be predicted by Sharma model, and the viscosity of three kinds of nanofluids is systematically studied. The temperature, mass fraction, particle morphology and crystalline form of nanofluid viscosity are investigated. The results show that the viscosity of the nanofluids increases with the mass fraction, and decreases with the increase of the temperature. The viscosity increases by 19.73% compared with the base solution, and the viscosity of anatase titanium dioxide nanofluids is 2.5% more than that of rutile nanofluids. The viscosity of nanofluids with a larger viscosity than the rhombus nanofluids can be accurately calculated by the.Bobbo model. The minimum error is only 0.19%.4. The wettability of three kinds of nanofluids is studied and the wettability of the nanofluids is investigated by the temperature, mass fraction, particle morphology and crystal type. The results show that: (1) the surface tension of nanofluids decreases with the increase of temperature and mass fraction, the maximum surface tension decreases by 16.95% compared with the base solution, and the surface tension of anatase titanium dioxide nanofluids is 0.125~ 0.917mN/m larger than that of rutile nanofluids; (2) the surface tension is similar to that of the nanofluids. The contact angle decreases with the increase of temperature and mass fraction. Compared with the base solution, the contact angle decreases by 21.98%~25%. The contact angle of anatase titanium dioxide nanofluids is 0.5 degrees larger than that of rutile nanofluids, and the morphology has no obvious influence on the wettability of titanium dioxide nanofluids.
【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】：TQ134.11;TB383.1

【参考文献】