纳米流体稳定性和粘度的影响因素分析

Analysis of Factors Influencing Stability and Viscosity of Nanofluids

采用“两步法”制备质量分数为0.5wt%~4.0wt%的Cu-乙二醇纳米流体,研究超声时间、浓度和温度对纳米流体稳定性及粘度的影响。研究结果表明,温度为20℃时,分析经过超声15~75min处理的Cu-乙二醇纳米流体(4.0wt%)粘度发现,超声45min时其粘度最大;分析超声45和60min的纳米流体透射电镜(TEM)图像发现,超声45min时其稳定性更优;在乙二醇溶液里添加Cu纳米颗粒会影响流体的粘度,且粘度随粒子质量分数增大而增大,流体稳定性随质量分数增大而减小;Cu-乙二醇纳米流体的粘度随温度的升高而变小。通过分析实验数据,在修正已有的粘度模型基础上,拟合纳米流体粘度与粒子浓度、温度的关系,提出了新的粘度计算公式。根据固溶体的形成机理和能量最低原理对以上现象进行了理论解释。

A two step method was used to prepare Cu-ethylene glycol(EG)nanofluids with mass fraction of 0.5wt%-4.0wt%.Effects of ultrasonic time,concentration and temperature on the stability and viscosity of nanofluids were investigated.Results show that the viscosity of Cu-EG nanofluids increases to the maximum at the ultrasonic time of 45min for mass fraction of 4.0wt%and temperature of 20℃.Compared with transmission electron microscope(TEM)images with 45min and 60min,the stability of Cu-EG nanofluids with 45min is better than that with 60min.Moreover,addition of Cu nanoparticles will affect the viscosity obviously.The viscosity increases with the increase in mass fraction and the decrease in temperature,respectively.Furthermore,the stability decreases with the increase in mass fraction.A new correlation of viscosity based on concentration and temperature was presented.And the above phenomena were presented based on the formation mechanism of solid solution and the lowest energy principle.