Rheological behavior of dilute graphene-water nanofluids using various surfactants: An experimental evaluation

This study aims to experimentally investigate the effects of temperature and nanoparticle concentration on dynamic viscosity, which is one of the most significant thermophysical properties. Diluted water -based graphene nanoplatelets (GNP) nanofluids are prepared using a two-step approach, with concentra-tions ranging from 0.00005 to 0.001 vol.%. Surfactants such as Gum Arabic (GA) and Sodium dodecyl sul-fate (SDS) are dispersed in the nanofluid medium at 1:1 weight ratios with respect to GNP. The suspensions are rheologically characterized from 20 degrees C to 50 degrees C using a rotational rheometer at shear rates ranging from 10 to 100 (s-1). The rheological behavior of GNP nanofluids is examined to ultimately develop a regression model for viscosity, that considers the effects of nanoparticle concentration and temperature for different surfactant type. Results indicate that GNP-GA and GNP-SDS nanofluids at 0.001 vol.% retained their stability over a time frame of 21 days. An increase in viscosity with the increase in nanoparticle concentration and a decrease in viscosity with the rise in temperature is reported. GNP -GA nanofluid at 0.001 vol.% concentration depicts the highest viscosity value. The rheological analysis demonstrates a Newtonian flow behavior for GNP nanofluids throughout the studied shear rate range, except for GNP-SDS nanofluids that exhibit shear thinning behavior at highest nanoparticle loading, and GNP-GA nanofluids that exhibit shear thickening behavior at the lowest nanoparticle loading. The proposed regression model has high prediction accuracy (R2 > 99%) for GNP nanofluids with different surfactants. The outcomes of this work are anticipated to aid several industrial and engineering applica-tions like heat exchangers, refrigeration systems, cryogenic systems, air-conditioning units, power plants and solar panels. (c) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

This study experimentally investigates the effects of temperature and nanoparticle concentration on dynamic viscosity. Diluted water-based graphene nanoplatelets (GNP) nanofluids are prepared with concentrations ranging from 0.00005 to 0.001 vol.%. Surfactants such as Gum Arabic (GA) and Sodium dodecyl sulfate (SDS) are dispersed in the nanofluid medium. The study finds that viscosity increases with nanoparticle concentration and decreases with temperature, and a regression model with high prediction accuracy is developed.