【摘要】：在液體中添加納米級(jí)的金屬或金屬氧化物粒子制備成納米流體,具有優(yōu)異的熱傳輸性能以及良好的光譜吸收性能,將其用作直接吸收式太陽(yáng)能集熱器的集熱工質(zhì),可有效提高光熱利用效率。本文以不同形貌Ag-EG納米流體為研究對(duì)象,研究了納米流體的合成方法,分析了其導(dǎo)熱性能、粘度、潤(rùn)濕性能以及光熱特性等物理性能,主要研究?jī)?nèi)容如下:1.采用多元醇法成功制備了立方狀以及不同粒徑的線狀A(yù)g-EG納米流體;采用晶種法制備了銀納米棒,通過(guò)超聲振動(dòng)將其分散到EG中,制備出棒狀A(yù)g-EG納米流體。并通過(guò)XRD、SEM以及TEM等分析測(cè)試技術(shù)對(duì)三種形貌的Ag-EG納米流體進(jìn)行了表征。2.采用KD2 Pro導(dǎo)熱系數(shù)儀測(cè)量了Ag-EG納米流體的導(dǎo)熱系數(shù),并分析了溫度、質(zhì)量分?jǐn)?shù)、顆粒粒徑及形貌對(duì)其導(dǎo)熱系數(shù)的影響。結(jié)果表明,隨著溫度升高,Ag-EG納米流體的導(dǎo)熱系數(shù)增大,當(dāng)溫度從25℃升高到65℃時(shí),導(dǎo)熱系數(shù)最大增大率為48.60%;隨著質(zhì)量分?jǐn)?shù)增大,導(dǎo)熱系數(shù)增大,其中立方狀A(yù)g-EG納米流體增大率可達(dá)57.99%;同樣,粒徑和形貌也是影響導(dǎo)熱系數(shù)的兩個(gè)因素,立方狀A(yù)g-EG納米流體的導(dǎo)熱系數(shù)最大,其次為棒狀、線狀A(yù)g-EG納米流體;通過(guò)對(duì)不同粒徑的線狀A(yù)g-EG納米流體的導(dǎo)熱系數(shù)進(jìn)行分析,發(fā)現(xiàn)粒徑越小,導(dǎo)熱系數(shù)越大。最后,本文將實(shí)驗(yàn)值與理論模型模型的計(jì)算值進(jìn)行比較,發(fā)現(xiàn)實(shí)驗(yàn)值與H-C模型計(jì)算出的理論值基本吻合,誤差最小為0.18%。3.采用DV2T粘度計(jì)對(duì)Ag-EG納米流體的粘度進(jìn)行了測(cè)試,并研究了溫度、質(zhì)量分?jǐn)?shù)、銀納米顆粒的粒徑以及形貌對(duì)其粘度的影響。實(shí)驗(yàn)結(jié)果表明,隨著溫度的升高,Ag-EG納米流體的粘度減小,當(dāng)溫度從25℃升高到65℃時(shí),粘度減小率均在50%以上;銀納米顆粒質(zhì)量分?jǐn)?shù)增大,粘度增大;通過(guò)對(duì)不同粒徑線狀納米流體的粘度進(jìn)行對(duì)比分析發(fā)現(xiàn),隨著粒徑的減小,納米流體的粘度增大;立方狀A(yù)g-EG納米流體的粘度要小于棒狀以及線狀A(yù)g-EG納米流體。在65℃條件下,質(zhì)量分?jǐn)?shù)為0.020wt.%時(shí),立方狀A(yù)g-EG納米流體的粘度為6.83mPa·s,相對(duì)于基液EG增大了9.80%�；诖�,本文將實(shí)驗(yàn)值與理論模型模型的計(jì)算值進(jìn)行比較,發(fā)現(xiàn)實(shí)驗(yàn)值與Godson模型計(jì)算出的理論值最為接近。4.對(duì)Ag-EG納米流體的潤(rùn)濕性進(jìn)行了測(cè)試,通過(guò)表面張力和接觸角兩個(gè)方面進(jìn)行研究,分析了溫度、質(zhì)量分?jǐn)?shù)、顆粒粒徑以及形貌對(duì)Ag-EG納米流體表面張力和接觸角的影響,結(jié)果發(fā)現(xiàn),Ag-EG納米流體的表面張力和接觸角均小于基液EG,納米流體的潤(rùn)濕性均優(yōu)于基液EG。其中,立方狀A(yù)g-EG納米流體的表面張力和接觸角均為最小,質(zhì)量分?jǐn)?shù)為0.020wt.%時(shí),立方狀A(yù)g-EG納米流體的表面張力在65℃的條件下為45.042mN/m,25℃時(shí)接觸角為27.5°。5.采用UV-5500紫外可見分光光度計(jì)測(cè)試Ag-EG納米流體的透射率,并自行組裝悶曬集熱裝置研究Ag-EG納米流體的悶曬溫度隨環(huán)境溫度的變化情況,分析納米流體質(zhì)量分?jǐn)?shù)、納米顆粒粒徑和形貌對(duì)其光譜吸收性能和光熱轉(zhuǎn)換性能的影響。實(shí)驗(yàn)結(jié)果表明,納米流體的光熱轉(zhuǎn)換特性優(yōu)于EG,且當(dāng)質(zhì)量分?jǐn)?shù)從0.005wt.%增大到0.015wt.%時(shí),納米流體的最高平衡溫度和溫升速率均增大,但是當(dāng)質(zhì)量分?jǐn)?shù)繼續(xù)增加到0.020wt.%時(shí)光熱轉(zhuǎn)換特性反而下降。其中,立方狀納米流體的光熱特性最好,與基液EG的最大溫差為12℃,最高平衡溫度相對(duì)于基液EG提高了26.64%。
[Abstract]:The nano-fluid is prepared by adding nano-scale metal or metal oxide particles in a liquid, has excellent heat transfer performance and good spectral absorption performance, and can be used as a heat-collecting working medium of a direct absorption type solar heat collector, and the photo-thermal utilization efficiency can be effectively improved. In this paper, the synthesis of nano-fluid is studied by using Ag-EG nano-fluid with different morphology. The physical properties such as thermal conductivity, viscosity, wettability and photothermal properties of the nano-fluid are analyzed. The main contents of this study are as follows:1. The linear Ag-EG nano-fluid with cubic and different particle size was successfully prepared by using the polyol method, and the silver nanorod was prepared by the seed crystal method. The rod-shaped Ag-EG nano-fluid was prepared by dispersing it into EG by means of ultrasonic vibration. The Ag-EG nano-fluid was characterized by XRD, SEM and TEM. The thermal conductivity of Ag-EG nano-fluid was measured by the KD2 Pro thermal conductivity meter, and the influence of temperature, mass fraction, particle size and morphology on the thermal conductivity was also analyzed. The results show that, with the increase of the temperature, the thermal conductivity of the Ag-EG nano-fluid is increased, and when the temperature is raised from 25 鈩，

本文編號(hào)：2487945