本文選題：石墨烯 + 納米流體��； 參考：《華北水利水電大學(xué)》2017年碩士論文

【摘要】：納米流體作為一種新型高效的傳熱工質(zhì),在太陽能發(fā)電、工業(yè)余熱回收、相變材料、氫內(nèi)燃機(jī)散熱等領(lǐng)域具有廣泛的應(yīng)用前景。本文對(duì)石墨烯納米流體的制備、穩(wěn)定性、導(dǎo)熱性能、黏度、傳熱特性進(jìn)行了實(shí)驗(yàn)研究,并對(duì)實(shí)驗(yàn)所得的結(jié)論進(jìn)行了初步分析,為納米流體的理論研究和實(shí)際應(yīng)用提供依據(jù)。選用“兩步法”制備了石墨烯納米流體。靜置沉降實(shí)驗(yàn)證明實(shí)驗(yàn)室制備的石墨烯納米流體具有良好的穩(wěn)定性;通過不同基液石墨烯納米流體沉降情況的對(duì)比發(fā)現(xiàn),基液黏度越大,配置的納米流體穩(wěn)定性越好。采用基于瞬態(tài)熱探針法的液體導(dǎo)熱系數(shù)測試儀測量了石墨烯納米流體的導(dǎo)熱系數(shù),并將實(shí)驗(yàn)值與納米流體導(dǎo)熱系數(shù)模型計(jì)算值進(jìn)行比較。結(jié)果表明,石墨烯納米粒子的添加強(qiáng)化了基液的導(dǎo)熱性能;納米粒子的質(zhì)量份額、基液的性質(zhì)、流體溫度都是影響納米流體導(dǎo)熱系數(shù)的重要因素。依據(jù)實(shí)驗(yàn)結(jié)論從納米顆粒的布朗運(yùn)動(dòng)與微對(duì)流、溶液屬性等方面對(duì)納米流體導(dǎo)熱性能的強(qiáng)化機(jī)理進(jìn)行了初步分析。采用烏式黏度計(jì)對(duì)水基石墨烯納米流體的黏度進(jìn)行了測量,并將實(shí)驗(yàn)值與納米流體黏度模型計(jì)算值進(jìn)行比較。結(jié)果表明,納米粒子的添加增大了基液的黏度;納米粒子的質(zhì)量份額、粒子形狀、粒子尺寸以及流體溫度都是影響納米流體黏度的因素,其中流體溫度為主要影響因素。設(shè)計(jì)并搭建了管內(nèi)流動(dòng)與換熱實(shí)驗(yàn)系統(tǒng),測試了水基石墨烯納米流體在Re=8000-12000范圍內(nèi)的對(duì)流換熱性能。結(jié)果發(fā)現(xiàn),納米粒子的添加強(qiáng)化了基液的對(duì)流換熱性能,且納米流體對(duì)流換熱性能的增幅大于導(dǎo)熱性能的增幅;壁面熱流率、粒子的濃度、湍流強(qiáng)度都是影響納米流體強(qiáng)化對(duì)流換熱性能的因素。納米顆粒對(duì)圓管內(nèi)壁的修飾改性有利于能量的傳輸。基于流動(dòng)與換熱實(shí)驗(yàn)系統(tǒng),采用ANSYS Workbench對(duì)水基石墨烯納米流體管內(nèi)流動(dòng)與換熱進(jìn)行數(shù)值模擬。將實(shí)驗(yàn)結(jié)果與模擬結(jié)果對(duì)比可得,石墨烯納米流體內(nèi)粒子的無規(guī)則布朗運(yùn)動(dòng)是強(qiáng)化納米流體的傳熱性能的重要因素。從模擬結(jié)果中的溫度場、速度場以及壓力場對(duì)納米流體管內(nèi)流動(dòng)與傳熱的規(guī)律進(jìn)行了分析。
[Abstract]:As a new and efficient heat transfer medium, nano-fluid has a wide application prospect in the fields of solar power generation, industrial waste heat recovery, phase change material, heat dissipation of hydrogen combustion engine and so on. In this paper, the preparation, stability, thermal conductivity, viscosity and heat transfer characteristics of graphene nanofluids are studied experimentally, and the experimental results are analyzed preliminarily, which provides a basis for the theoretical research and practical application of nano-fluids. Graphene nanofluids were prepared by two-step method. The static settling experiment proved that the graphene nanofluids prepared in the laboratory had good stability, and the higher the viscosity of the base solution, the better the stability of the nano-fluids. The thermal conductivity of graphene nanofluids was measured by a liquid thermal conductivity tester based on transient thermal probe method, and the experimental values were compared with those calculated by the thermal conductivity model of nano-fluids. The results show that the addition of graphene nanoparticles enhances the thermal conductivity of the base solution, and the mass fraction of the nanoparticles, the properties of the base solution and the temperature of the fluid are the important factors affecting the thermal conductivity of the nano-fluids. Based on the experimental results, the strengthening mechanism of thermal conductivity of nanoscale fluids was preliminarily analyzed from the aspects of Brownian motion and micro-convection of nanoparticles and solution properties. The viscosity of water-based graphene nanofluids was measured by using a black viscometer, and the experimental values were compared with those calculated by the nano-fluid viscosity model. The results show that the viscosity of the base solution is increased with the addition of nanoparticles, and the mass fraction, particle shape, particle size and fluid temperature are the main factors affecting the viscosity of the nano-fluid, among which the temperature of the fluid is the main factor. An experimental system of flow and heat transfer in a tube is designed and built. The convection heat transfer properties of water-based graphene nanofluids in Re=8000-12000 range are tested. The results show that the convection heat transfer performance of the base solution is enhanced by the addition of nanoparticles, and the increase of convection heat transfer performance of nano-fluid is greater than that of thermal conductivity, the wall heat flux, particle concentration, The turbulence intensity is the factor that affects the convection heat transfer performance of nano-fluid. The modification of the inner wall of the tube by nanoparticles is beneficial to the energy transfer. Based on the experimental system of flow and heat transfer, ANSYS Workbench was used to simulate the flow and heat transfer in water based graphene nanofluid tube. By comparing the experimental results with the simulation results, it is found that the irregular Brownian motion of particles in graphene nanofluids is an important factor in enhancing the heat transfer performance of nano-fluids. From the temperature field, velocity field and pressure field in the simulation results, the flow and heat transfer in nanofluid tubes are analyzed.
【學(xué)位授予單位】：華北水利水電大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB383.1;TQ127.11

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