论文总字数：24704字

摘 要

本文主要通过不同固体表面的黏附和结垢现象以及纳米流体的吸光度比变化，研究静态和动态纳米流体的对比。在动态纳米流体中还加入了分散剂、局部超声振荡、局部鼓泡作用等条件进行了前后对比。本文各部分主要工作及结论如下：

（1）研究了静态与动态情况下纳米流体结构特性，发现纳米流体静态明显比动态纳米流体的情况下更容易结垢，并且静态状态和动态状况下表现固体表面的结垢速度更快，从吸光度的变化与静置与动态的固体表面结垢相反，吸光度大，整体结垢少。

（2）研究了纳米流体结垢特性的影响因素，得到以下主要结论：

①纳米流体加入分散剂后，纳米流体的动态稳定性明显好于静置状态下的纳米流体的稳定性，与未加分散剂相比较，不同固体表面的结垢都减少了。所以如果在实际应用中，加入分散剂后，可以改善纳米流体的结垢性。

②超声可以在短时间内稳定地分散颗粒的大小，但当超声作用停止时，纳米流体与超声前的沉降速度相同，说明超声对于分散机制并没有实质性的改变，但可以利用周期性的超声作用使纳米流体的吸光度在一个较小范围内波动。

③鼓泡实质上是利用气泡将纳米流体再次搅拌，可以明显改变纳米流体的稳定性，其充分混合后的上下层浓度差异不大，固体表面的结垢也明显减少，同时从吸光度的角度比较，鼓泡前后纳米流体的稳定性明显上升，所以如果说在实际应用中，可以给纳米流体局部鼓泡，可以降低纳米流体在固体表面的结垢。

（3）对纳米流体的黏附特性进行了研究，发现石墨烯和碳纳米管对铁丝有选择黏附性，而且，在铁表面形成很多结垢，但是在其他表面几乎没有。在蒸馏水冲洗后，那些纳米颗粒表现为絮状物，分散在液体中，但是并没有再次形成纳米流体，而是浑浊的悬浊液。

（4）对不同固体表面对纳米流体的结构特性进行了研究，重点研究了铜片和不锈钢，可以判断出，在碳纳米管流体和石墨烯纳米流体上，铜片的结垢都比不锈钢更加均匀，不易在表面发生纳米颗粒的团聚。在二氧化钛纳米流体中，两者的结垢差不多。

关键词：纳米流体；黏附；结垢；稳定性；动态特性

Abstract

This article focuses on the comparison of static and dynamic nanofluids through the adhesion and scaling of different solid surfaces and the absorbance ratio changes of nanofluids. The dynamic nanofluids were also added with dispersants, local ultrasonic oscillations, local bubbling and other conditions before and after comparison. The main work and conclusions of each part of this paper are as follows:

(1) The structure characteristics of nanofluids under static and dynamic conditions are studied. It is found that nanofluids are significantly more static than those of dynamic nanofluids, and that the static state and dynamic conditions exhibit faster fouling on solid surfaces. The change of absorbance is opposite to static and dynamic solid surface fouling, with high absorbance and less overall scale.

(2) The influencing factors of nanofluid fouling characteristics were studied and the following main conclusions were obtained:

①After the nanofluids were added with dispersants, the dynamic stability of the nanofluids was significantly better than that of the nanofluids under static conditions. Compared with the non-dispersed agents, the fouling of different solid surfaces was reduced. Therefore, if the dispersant is added in practical applications, the fouling of the nanofluid can be improved.

②Ultrasound can stably disperse the size of particles in a short time, but when the ultrasonic action stops, the settling velocity of the nanofluid before the ultrasound is the same, indicating that ultrasound has no substantial change in the dispersion mechanism, but can use periodic ultrasound. The effect makes the absorbance of the nanofluid fluctuate within a small range.

③Bubbling is essentially the use of bubbles to stir the nanofluids again, which can significantly change the stability of the nanofluids. The well-mixed upper and lower layers have little difference in the concentration, and the fouling on the solid surface is also significantly reduced. At the same time, the comparison from the absorbance point of view The stability of the nanofluid before and after bubbling has risen significantly, so if it is said in practical applications, nanofluids can be bubbling locally, which can reduce the fouling of nanofluids on solid surfaces.

(3) The adhesion properties of nanofluids were studied. Graphene and carbon nanotubes were found to have selective adhesion to iron wire. Moreover, many scales formed on the surface of iron, but few on other surfaces. After rinsing with distilled water, those nanoparticles appeared as flocs, dispersed in the liquid, but did not form nanofluids again, but rather turbid suspensions.

(4) The structural characteristics of nanofluids on different solid surfaces have been studied. Copper sheets and stainless steels have been studied emphatically. It can be judged that the scales of copper sheets are more than stainless steel on carbon nanotube fluids and graphene nanofluids. Evenly, it is not easy to agglomerate nanoparticles on the surface. In titanium dioxide nanofluids, the fouling of the two is similar.

Key words: Nanofluids, Adhesion,Fouling,Stability,Dynamic characteristics

目录

摘要 I

Abstract II

第一章 绪论 1

1.1 研究背景 1

1.2 国内外研究现状 1

1.2.1 制备 1

1.2.2 稳定性 2

1.2.3 黏附和结垢 2

1.2.4 纳米流体的相变特性 3

1.2.5 能源应用 3

1.3 课题的研究方向 3

第二章 纳米流体动态与静态时在固体表面的黏附与结垢特性对比 5

2.1 实验目的与内容 5

2.2 实验系统 5

2.2.1 静态纳米流体实验运行装置 6

2.2.2 动态纳米流体实验运行装置 6

2.2.3 实验仪器的介绍 8

2.3 实验步骤 9

2.3.1 静态纳米流体黏附和结垢特性的实验步骤 9

2.3.2 动态纳米流体黏附和结垢特性的实验步骤 10

2.4 本章小结 11

第三章 实验结果分析 12

3.1 静态与动态纳米流体 12

3.1.1 固体表面结垢 12

3.1.2 固体表面黏附 13

3.2 分散剂对动态纳米流体中固体表面吸附和结垢特性的影响 15

3.3 超声对动态纳米流体中固体表面吸附和结垢特性的影响 16

3.4 鼓泡对动态纳米流体中固体表面吸附和结垢特性的影响 19

3.5 不同固体表面在纳米流体中的结垢 20

3.6 本章小结 22

第四章 纳米流体种类对固体表面黏附与结垢特性 24

4.1 二氧化钛 24

4.2 碳纳米管 24

4.3 石墨烯 27

4.4 本章小结 28

第五章 总结 29

5.1 研究总结 29

5.2 研究展望 29

致谢 30

参考文献 31

绪论

研究背景

随着科学的发展，我们提倡节约，提高能源的利用效率，而纳米流体是一种高效的换热材料，作为一种新型的材料，得到了国内外学者的广泛关注。起初是Choi^[1]提出纳米流体的基本概念。同时，纳米技术的不断提高推动纳米流体成为研究热点，特别是在新型材料和导热传热方面，纳米流体的导热性能和能源应用领域都在不断发展和开拓。其中研究最为广泛的是传热方面，尤其是纳米流体的导热性能的探索。

如今的制冷与空调技术设备都采用的是烃类化合物作为制冷剂，加速了温室效应和臭氧层的空洞，亟待人们的解决和保护。而在烃类化合物制冷剂的取代过程中，低导热系数的换热工质也是不可取的，虽然我们国家是能源大国，一次能源较为丰富，但是人口众多，能源危机感是始终存在的。

剩余内容已隐藏，请支付后下载全文，论文总字数：24704字