Scientists have collaborated on a new paper in the Journal of Molecular Liquids on the influence of graphene nanoparticles on oil viscosity.
Study: The Mechanism of Oil Viscosity Reduction with the Addition of Graphene Nanoparticles. Image Credit: Forance/Shutterstock.com
Nanofluids are colloidal fluids that contain varying sizes of dispersed nanoparticles. They were first produced in the early 1990s by Masuda et al. Interest in these multiphase fluids has persisted, with several researchers studying them and their properties. Relatively easy to synthesize, they have flexible and beneficial optical, mechanical, electrical, and thermal characteristics.
At present, nanofluids have been widely applied in several branches of scientific research and technology. Graphene nanofluids have shown promising potential over metal oxide and metal-based nanofluids due to their properties such as high electrical and thermal conductivity.
Promising research has demonstrated their use in areas such as enhanced oil recovery, which makes graphene nanofluids attractive for the petrochemical industry. Indeed, research has already shown great advances in this area.
Oil viscosity is a key factor that determines the efficiency of oil recovery and other processes within the petrochemical industry. Oil is a non-Newtonian fluid, its viscosity influenced by shear deformation rates. Increased hydro-resistance occurs as a consequence of the structured states occurring within the oil. This can reduce oil recovery.
Graphene nanoparticles within graphene nanoparticles can penetrate oil when they interact with hydrocarbons. Identifying how nanoparticles influence oil viscosity is a key area of research. Understanding these interactions will help to solve problems with oil recovery and associated processes.
Fluid viscosity is directly determined by transport processes within the fluid. The influence mechanisms of nanofluids are associated with nanoparticle/carrier fluid molecule interactions.
In recent years, there has been a growing body of research on nanofluids. Several new physical properties of fluids caused by the introduction of graphene nanoparticles have been reported in the current literature. Some studies have indicated increased viscosity with the introduction of metal oxide nanofluids, whereas conversely, research has demonstrated reduced viscosity caused by the introduction of graphene nanoparticles.
There is, however, a contradictory nature to this observed property, as this behavior is in contradiction with established nanofluid viscosity theories. This behavior can be explained by a combination of nanoparticle structuring and percolation effects. However, direct observation of this nanoparticle structuring has not been so far reported.
The authors have designed an experimental setup to directly observe nanoparticle structuring in moving liquids. Based on the results of their study, the authors have proposed that their paper resolves the observed contradiction in graphene nanoparticle influence on the fluid viscosity of oil. Thirty-nine studies in the current literature have been reviewed by the authors.
Study Findings and Conclusions
Several important findings have been demonstrated in the paper that help to elucidate the influence of graphene nanoparticles on oil viscosity.
At low concentrations, the dynamic viscosity coefficient decreases in oil-based graphene nanofluids. Viscosity reduction mechanisms are associated with self-assembled micro fluctuations during nanofluid movement in the carrier fluid flow. This behavior only occurs in fluids.
In alcoholic and aqueous graphene nanoparticle solutions, this behavior was not observed. Current rheological studies confirm this. The authors have concluded that spherical nanoparticles create flow inhomogeneities, which makes this phenomenon impossible.
The authors have stated, however, that nanoparticle concentrations in base fluids can be increased. This can be achieved without a sacrifice in viscosity increases, which could improve the efficiency of nanofluid use in the energy and oil industries. This will need further study of graphene particle self-assembly in carrier fluids.
Other observations have been made by the authors. Firstly, the viscosity of oil-based graphene nanofluids can be reduced using increased nanoparticle concentrations. The maximum viscosity decrease was observed in the study at a temperature of 50 oC. At increased nanoparticle concentrations, there is a change in viscosity mechanisms. Viscosity correlates with a quadratic law which agrees with the current understanding of nanofluid rheology.
Most importantly, the authors have observed that reduced graphene nanofluid viscosity is only possible in oil-based nanofluids and planar graphene nanofluids. It is not possible to use aqueous or alcohol-based carrier fluids.
The paper has provided key findings on the influence of nanofluids containing graphene nanoparticles on oil viscosity, shining a light on the mechanisms within graphene nanofluids. It has helped to answer vital questions on how these nanofluids behave that will help to improve oil recovery processes in the petrochemical industry.
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Pakharukov, Y et al. (2022) The Mechanism of Oil Viscosity Reduction with the Addition of Graphene Nanoparticles Journal of Molecular Liquids 119551 [online, pre-proof] sciencedirect.com. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0167732222010893?via%3Dihub
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