为了探究影响纳米流体稳定性和导热系数的因素，采用一步法和两步法分别制备了SiO2-EG/DW(50∶〖KG-2mm〗50)纳米流体和SiO2-EG纳米流体，探讨团聚体等效直径对纳米流体稳定性的影响。基于瞬态热线法的原理，测量一步法纳米流体的导热系数，分析温度和纳米颗粒质量分数对其导热系数的影响。结果表明：相比一步法制备的纳米流体，两步法纳米流体内团聚体的沉降速度增加了103倍，团聚体等效直径对纳米流体稳定性具有关键性的影响。纳米流体导热系数与温度和纳米颗粒质量分数呈线性正相关，纳米流体质量分数为15%时，80 ℃的样品导热系数相比40 ℃时提高了5.2%；60 ℃时，质量分数6%的纳米流体导热系数相比基液提高了6.4%;质量分数增加到15%时，导热系数相比基液提高了15.8%。

In order to explore the factors that affect the stability and thermal conductivity of nanofluids,SiO2EG/DW(50∶〖KG-2mm〗50) nanofluids and SiO2EG nanofluids were prepared by onestep and twostep method respectively.On this basis,the influence of aggregate size on the stability of nanofluids was discussed.Based on the principle of the transient hot wire method,the thermal conductivity coefficient of the onestep nanofluids was measured,and the effects of temperature and nanoparticle mass fraction on its thermal conductivity coefficient were studied.The results show that compared with the nanofluids prepared by the onestep method,the sedimentation speed of the aggregates in the twostep nanofluids is increased by 103 times,and the equivalent diameter of the aggregate has critical influence on the stability of the nanofluids.The thermal conductivity coefficient of nanofluids is linearly positively correlated with temperature and nanoparticle mass fraction.When the mass fraction of nanofluid is 15%,the thermal conductivity coefficient of the sample at 80 ℃ is increased by 5.2% compared with that at 40 ℃. At 60 ℃,the thermal conductivity coefficient of the nanofluids with a mass fraction of 6% is increased by 6.4% compared with the base fluid. When the mass fraction is increased to 15%,the thermal conductivity coefficient is increased by 15.8% compared with the base fluid.

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