离子液体基纳米流体传递性质的研究

发布时间：2018-04-13 20:07

本文选题：纳米流体 + 导热系数　；参考：《大连理工大学》2015年硕士论文

【摘要】：吸收式热泵是一种重要的节能装置,它能有效的回收工厂废热和低温余热,大大地提高了能源利用率。然而,传统的循环工质对"H2O-LiBr"和"NH3-H2O"都存在严重缺陷,阻碍了吸收式热泵的推广及应用。近年来,国内外大量的研究表明,离子液体由于其具有高热稳定性,低蒸气压和液程宽等优点,具有作为热泵新吸收剂的潜能。对离子液体目前的研究进行分析发现,鲜少有关于离子液体二元溶液的传递性质的研究。而对于吸收式热泵工质对而言,传递性质至关重要。本文考虑到有机溶剂的导热系数偏低,提出以[EMIM][DEP]及其水溶液作为基液,以多壁碳纳米管(MWCNTs)作为分散粒子,得到的纳米流体作为吸收式热泵的工质对,并考察了以[EMIM][DEP]为基液的纳米流体INF和[EMIM][DEP]水溶液为基液的纳米流体SNF的导热系数、密度、粘度等性质。实验室合成了离子液体[EMIM][DEP],采用氢核磁共振波谱仪对其结构进行表征,用卡尔·费歇尔法分析离子液体中的水含量：对购买的MWCNTs进行酸化处理后,用透射电镜和红外吸收光谱对其进行表征,然后采用两步法制备纳米流体。采用西安夏溪导热系数仪测量了体系[EMIM] [DEP](1)+H2O(2)在298.15 K-353.15K的导热系数。随之测量了纳米流体INF和SNF在298.15K-353.15K的有效导热系数和298.15 K-323.15 K的密度和粘度。实验结果显示,与其基液相比INF和SNF导热系数有不同程度的增大,增大幅度在1.3%-9.7%之间；密度和粘度与基液相比也均有不同程度的增大,常温下,碳纳米管质量分数为1.0%时,与其基液相比密度增大在1%左右,INF的粘度是水的350倍,是SNF 2-4倍。INF和SNF的粘度随温度的升高迅速降低,高温时近似等于基液的粘度值,因此碳纳米管的添加不会阻碍吸收器中工质对的正常降膜流动。采用文献中的模型分别对导热系数,粘度和密度进行关联,通过拟合确定模型参数数值,计算值与实验值吻合的很好。采用GAUSSIAN 09软件中密度泛函理论确定了离子液体最优化结构,用Green-Kubo关系式计算了[EMIM][DEP]在不同温度下的导热系数和[EMIM] [DEP]+S WCNT体系的导热系数,模拟值与实验值比较吻合,表明所用的力场及方法可以用来推测纳米流体的有效导热系数。本文的研究,为吸收式热泵的实验及应用提供了重要的基础数据,为预测基液为[EMIM][DEP]的纳米流体体系导热系数提供了可靠的力场。
[Abstract]:Absorption heat pump is an important energy saving device. It can effectively recover waste heat and low temperature heat, and greatly improve energy efficiency.However, both "H2O-LiBr" and "NH3-H2O" have serious defects in traditional circulating fluids, which hinder the popularization and application of absorption heat pump.In recent years, a large number of studies at home and abroad show that ionic liquids have the potential as new absorbent for heat pump because of their advantages of high thermal stability, low vapor pressure and wide liquid path.It is found that few studies on the transport properties of ionic liquids in binary solutions have been carried out.For absorption heat pump, the transfer property is very important.In this paper, considering the low thermal conductivity of organic solvents, it is proposed that [EMIM] [DEP] and its aqueous solution are used as base solution and multiwalled carbon nanotubes (MWCNTs) as dispersed particles, and the resulting nanofluids are used as working pairs of absorbing heat pumps.The thermal conductivity, density and viscosity of nano-fluid SNF based on [EMIM] [DEP] and [EMIM] [DEP] aqueous solution were investigated.The ionic liquid [EMIM] [DEP] was synthesized in the laboratory, and its structure was characterized by hydrogen nuclear magnetic resonance spectrometer. The water content in ionic liquid was analyzed by Karl Fischer method. After acidizing the purchased MWCNTs,It was characterized by transmission electron microscope (TEM) and infrared absorption spectroscopy (IR), and then prepared by two step method.The thermal conductivity of [EMIM] [DEP] 1] H _ 2O _ 2] at 298.15 K ~ 353.15 K was measured by Xi'an Xiaxi thermal conductivity meter.The effective thermal conductivity of INF and SNF in 298.15K-353.15K and the density and viscosity of 298.15 K-323.15 K were measured.The experimental results show that the thermal conductivity of INF and SNF increases in varying degrees, ranging from 1.3% to 9.7%, and the density and viscosity also increase in varying degrees compared with the base solution. At room temperature, when the mass fraction of carbon nanotubes is 1.0?Compared with the base solution, the viscosity of water, SNF 2-4 times and SNF decreases rapidly when the density increases at 1% or so, and is approximately equal to the viscosity value of the base solution at high temperature.Therefore, the addition of carbon nanotubes does not hinder the normal falling film flow of the working pairs in the absorber.The model is used to correlate the thermal conductivity, viscosity and density, and the model parameters are determined by fitting. The calculated values are in good agreement with the experimental values.The optimal structure of ionic liquids is determined by using density functional theory of GAUSSIAN 09 software. The thermal conductivity of [EMIM] [DEP] at different temperatures and the thermal conductivity of [EMIM] [DEP] S WCNT system at different temperatures are calculated by Green-Kubo relation. The simulated results are in good agreement with the experimental values.It is shown that the force field and the method used can be used to predict the effective thermal conductivity of nanofluids.The research in this paper provides important basic data for the experiment and application of absorption heat pump, and provides a reliable force field for predicting the thermal conductivity of [EMIM] [DEP] nanoscale fluid system.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ021.4

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