Investigation on stability and viscosity of SiO₂-CH₃OH (methanol) nanofluids

This work studied the stability and viscosity of methanol based nanofluids with SiO₂ nanoparticles at various volume concentrations and temperatures in order to investigate the enhancement in heat transfer. SiO₂ nanoparticles of 5~15 nm sizes were suspended into methanol base fluid at five different concentrations which were 0.005, 0.01, 0.05, 0.10 and 0.15 vol%. The nanofluid preparation was completed through sonication using an ultrasonic homogenizer. The viscosity of the prepared nanofluids was measured by LVDV III ultra-programmable viscometer at five different temperatures (5, 10, 15, 20 and 25 °C). The measurement deviations were about 3.96% and 2.4% for pure methanol and water, respectively. The results of zeta potential and UV-Vis spectrometer showed that SiO₂-methanol nanofluids were stable. It was found that shear stress and viscosity increased with volume concentration and shear rate and decreased in terms of temperature. These results showed that SiO₂-methanol nanofluids appeared as a non-Newtonian fluid. The maximum viscosity increment was 13.5% at 0.15 vol% base fluid and temperature of 25°C. Therefore, this study revealed that viscosity enhancement depends on both volume concentration and temperature.