ISSN Online: 2377-424X
ISBN Print: 978-1-56700-421-2
International Heat Transfer Conference 15
Combined Influence of Size and Sonication on Constant Shear Viscosity of MgO-Ethylene Glycol Nanofluids
Resumo
Nanofluids prepared from the combination of MgO and Ethylene glycol have been shown to have high
thermal conductivity, higher than those from Al2O3, but almost no attention has been given to this nanofluid
with regard to its rheological behavior. In order to understand the suitability of this fluid in equipment and
devices such as heat exchangers, micro-channels, heat pipes etc., its viscosity needs to be investigated.
Therefore, this paper presents the result of experiments on three different sizes (20, 40 and 100 nm) of MgO
nanofluids sonicated for 30 min and 60 min respectively. The experiments were carried out for volume
fraction in the Einstein concentration regime (up to 2% volume fraction of MgO). From the present
experimental data, MgO-Ethylene glycol nanofluids respond exponentially to change in temperature as the
temperature was increased from 20 – 70 °C. Likewise increase in volume fraction shows a corresponding
increase in the viscosity, however, the 20 nm MgO nanoparticle shows higher viscosity in ethylene glycol
nanofluids compared to other sizes investigated. The TEM imagery suggests that 40 nm and 100 nm MgO
nanoparticles are averagely 86 and 110 nm respectively. This informed the close proximity of the results of
the nanofluids samples formulated from these two sizes. The relative viscosity was compared with some
existing classical and empirical models, especially for those developed for the volume fraction regime
investigated in this paper. Lastly, it was found than excess sonication energy leads to breakage of 100 nm
particles leading to a slight increase in the relative viscosity.