本文選題：納米流體 + 導(dǎo)熱系數(shù)�。� 參考：《大連理工大學(xué)》2015年碩士論文

【摘要】：吸收式熱泵是一種重要的節(jié)能裝置,它能有效的回收工廠廢熱和低溫余熱,大大地提高了能源利用率。然而,傳統(tǒng)的循環(huán)工質(zhì)對(duì)"H2O-LiBr"和"NH3-H2O"都存在嚴(yán)重缺陷,阻礙了吸收式熱泵的推廣及應(yīng)用。近年來,國內(nèi)外大量的研究表明,離子液體由于其具有高熱穩(wěn)定性,低蒸氣壓和液程寬等優(yōu)點(diǎn),具有作為熱泵新吸收劑的潛能。對(duì)離子液體目前的研究進(jìn)行分析發(fā)現(xiàn),鮮少有關(guān)于離子液體二元溶液的傳遞性質(zhì)的研究。而對(duì)于吸收式熱泵工質(zhì)對(duì)而言,傳遞性質(zhì)至關(guān)重要。本文考慮到有機(jī)溶劑的導(dǎo)熱系數(shù)偏低,提出以[EMIM][DEP]及其水溶液作為基液,以多壁碳納米管(MWCNTs)作為分散粒子,得到的納米流體作為吸收式熱泵的工質(zhì)對(duì),并考察了以[EMIM][DEP]為基液的納米流體INF和[EMIM][DEP]水溶液為基液的納米流體SNF的導(dǎo)熱系數(shù)、密度、粘度等性質(zhì)。實(shí)驗(yàn)室合成了離子液體[EMIM][DEP],采用氫核磁共振波譜儀對(duì)其結(jié)構(gòu)進(jìn)行表征,用卡爾·費(fèi)歇爾法分析離子液體中的水含量：對(duì)購買的MWCNTs進(jìn)行酸化處理后,用透射電鏡和紅外吸收光譜對(duì)其進(jìn)行表征,然后采用兩步法制備納米流體。采用西安夏溪導(dǎo)熱系數(shù)儀測(cè)量了體系[EMIM] [DEP](1)+H2O(2)在298.15 K-353.15K的導(dǎo)熱系數(shù)。隨之測(cè)量了納米流體INF和SNF在298.15K-353.15K的有效導(dǎo)熱系數(shù)和298.15 K-323.15 K的密度和粘度。實(shí)驗(yàn)結(jié)果顯示,與其基液相比INF和SNF導(dǎo)熱系數(shù)有不同程度的增大,增大幅度在1.3%-9.7%之間；密度和粘度與基液相比也均有不同程度的增大,常溫下,碳納米管質(zhì)量分?jǐn)?shù)為1.0%時(shí),與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的粘度隨溫度的升高迅速降低,高溫時(shí)近似等于基液的粘度值,因此碳納米管的添加不會(huì)阻礙吸收器中工質(zhì)對(duì)的正常降膜流動(dòng)。采用文獻(xiàn)中的模型分別對(duì)導(dǎo)熱系數(shù),粘度和密度進(jìn)行關(guān)聯(lián),通過擬合確定模型參數(shù)數(shù)值,計(jì)算值與實(shí)驗(yàn)值吻合的很好。采用GAUSSIAN 09軟件中密度泛函理論確定了離子液體最優(yōu)化結(jié)構(gòu),用Green-Kubo關(guān)系式計(jì)算了[EMIM][DEP]在不同溫度下的導(dǎo)熱系數(shù)和[EMIM] [DEP]+S WCNT體系的導(dǎo)熱系數(shù),模擬值與實(shí)驗(yàn)值比較吻合,表明所用的力場(chǎng)及方法可以用來推測(cè)納米流體的有效導(dǎo)熱系數(shù)。本文的研究,為吸收式熱泵的實(shí)驗(yàn)及應(yīng)用提供了重要的基礎(chǔ)數(shù)據(jù),為預(yù)測(cè)基液為[EMIM][DEP]的納米流體體系導(dǎo)熱系數(shù)提供了可靠的力場(chǎng)。
[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.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ021.4

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相關(guān)期刊論文 前2條

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本文編號(hào)：1746006