Amini Faezeh, Miry Seyed Ziaedin, Karimi Amir, Ashjaee Mehdi
Department of Mechanical Engineering, University of Tehran, Tehran 11155-4563, Iran.
J Nanosci Nanotechnol. 2019 Jun 1;19(6):3398-3407. doi: 10.1166/jnn.2019.16127.
In this study, the thermal conductivity and viscosity of SiO₂/multiwalled carbon nanotube (MWCNTs) hybrid nanofluids are investigated. The volume fraction of the nanofluids varied in the range of 0.5% to 2%, while the SiO₂ to MWCNTs volume proportion is either 95-5 or 90-10. The nanofluids are synthesized using a wet chemical method and a two-step technique is used to disperse nanoparticles in glycerol (base fluid). The thermal conductivities and viscosities of the nanofluids are measured using a modified transient hot-wire method and falling ball viscometer, respectively. The colloidal stability of the dispersion was investigated visually. Effective application of an ultrasonic disruptor and a suitable surfactant (gum arabic) enhance the dispersion behavior. When the effects of temperature and volume fraction on the thermal conductivity and viscosity of SiO₂/multiwalled carbon nanotube (MWCNTs) hybrid nanofluids are studied, the results showed that the thermal conductivity of nanofluids increased with an increase in the volume fraction and temperature. Further, their viscosities increased with an increase in the volume fraction but decreased when the temperature increased. The thermal conductivity and viscosity of the hybrid nanofluids increased by 16.7% and 105.4%, respectively, at a volume fraction of 2% and volume proportion of 90-10. The experimental results are compared with those predicted by classical theoretical models. Two correlations for thermal conductivity and viscosity of hybrid nanofluids are proposed on the basis of the experimental results.
在本研究中，对二氧化硅/多壁碳纳米管（MWCNTs）混合纳米流体的热导率和粘度进行了研究。纳米流体的体积分数在0.5%至2%的范围内变化，而二氧化硅与多壁碳纳米管的体积比为95 - 5或90 - 10。采用湿化学方法合成纳米流体，并使用两步技术将纳米颗粒分散在甘油（基础流体）中。分别使用改进的瞬态热线法和落球粘度计测量纳米流体的热导率和粘度。通过肉眼观察研究了分散体的胶体稳定性。有效应用超声破碎器和合适的表面活性剂（阿拉伯树胶）可增强分散行为。当研究温度和体积分数对二氧化硅/多壁碳纳米管（MWCNTs）混合纳米流体的热导率和粘度的影响时，结果表明纳米流体的热导率随体积分数和温度的升高而增加。此外，它们的粘度随体积分数的增加而增加，但随温度升高而降低。在体积分数为2%且体积比为90 - 10时，混合纳米流体的热导率和粘度分别增加了16.7%和105.4%。将实验结果与经典理论模型预测的结果进行了比较。基于实验结果提出了混合纳米流体热导率和粘度的两个关联式。
