Rheological behaviour of nanofluids

By Haisheng Chen, Yulong Ding, Chunqing Tan. 2007

577 citations recorded by the source corpus.

This work aims at a more fundamental understanding of the rheological behaviour of nanofluids and the interpretation of the discrepancy in the recent literature. Both experiments and theoretical analyses are carried out with the experimental work on ethylene glycol (EG)-based nanofluids containing 0.5–8.0 wt% spherical TiO2 nanoparticles at 20–60 °C and the theoretical analyses on the high shear viscosity, shear thinning behaviour and temperature dependence. The experimental results show that the EG-based nanofluids are Newtonian under the conditions of this work with the shear viscosity as a strong function of temperature and particle concentration. The relative viscosity of the nanofluids is, however, independent of temperature. The theoretical analyses show that the high shear viscosity of nanofluids can be predicted by the Krieger–Dougherty equation if the effective nanoparticle concentration is used. For spherical nanoparticles, an aggregate size of approximately 3 times the primary nanoparticle size gives the best prediction of experimental data of both this work and those from the literature. The shear thinning behaviour of nanofluids depends on the effective particle concentration, the range of shear rate and viscosity of the base liquid. Such non-Newtonian behaviour can be characterized by a characteristic shear rate, which decreases with increasing volume fraction, increasing base liquid viscosity, or increasing aggregate size. These findings explain the reported controversy of the rheological behaviour of nanofluids in the literature. At temperatures not very far from the ambient temperature, the relative high shear viscosity is independent of temperature due to negligible Brownian diffusion in comparison to convection in high shear flows, in agreement with the experimental results. However, the characteristic shear rate can have strong temperature dependence, thus affecting the shear thinning behaviour. The theoretical analyses also lead to a classification of nanofluids into dilute, semi-dilute, semi-concentrated and concentrated nanofluids depending on particle concentration and particle structuring.

Subfields: Biomedical Engineering, Computational Mechanics, Fluid Flow and Transfer Processes

View Paper: https://www.semanticscholar.org/paper/ed47ad4c84145ca47e59ef74b4be65c52c08a0a6

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In Biomedical Engineering

In Computational Mechanics

In Fluid Flow and Transfer Processes

Citations in the corpus

Thermal conductivity and viscosity of Al2O3 nanofluid based on car engine coolant (2010, background): “However, in comparison with the thermal conductivity of nanofluids, only a very few studies have so far been carried out on their rheological properties [17–23].”
Experimental investigations of the viscosity of nanofluids at low temperatures (2012, background): “[14] reported the rheological behavior of TiO2/Ethylene Glycol nanofluids.”
Temperature induced changes in ZnO–water nanofluid: Zeta potential, size distribution and viscosity profiles (2012, background): “[26] had reported temperature independency of relative viscosity of nanofluids.”
Rheological behaviour of ethylene glycol-titanate nanotube nanofluids (2009, methodology): “Such behaviour is different from the observed Newtonian behaviour of EG-TiO2 nanofluids containing spherical nanoparticles over similar shear rate range ( Chen et al. 2007b ) where the base liquid, EG, is the same as that used in the current wok.”
A comprehensive review of thermo-physical properties and convective heat transfer to nanofluids (2015, background): “Classifying nanofluids as non-Newtonian fluids is an intensely debated subject within the academic field [236,237,241].”