Graphene-based nanofluids: A comprehensive review about rheological behavior and dynamic viscosity

Abstract

Graphene derivatives are promising nanomaterials for producing nanofluids due to their excellent intrinsic characteristics. Among thermophysical profile, and in addition to thermal properties, relevant property to evaluate the potential of graphene-based nanofluids as efficient and reliable heat transfer fluids is viscosity, and rheological behavior in a wider sense. Therefore, the aim of this review paper is to give a comprehensive overview of the current knowledge and results about the rheological properties of graphene-based nanofluids. After a brief description of the most common methods used for fabricating or extracting graphene derivatives, the main steps of graphenebased nanofluids preparation are introduced. Then, literature results on Newtonian/non-Newtonian behavior as well as variations in apparent dynamic viscosity of suspensions containing graphene derivatives are reviewed, analyzing the effects of shear rate, concentration, base fluids and temperature. Such an analysis is performed distinguishing the different types of graphene derivatives, namely graphene oxide, reduced graphene oxide, pristine graphene, graphene quantum dots, functionalized and doped graphene. Also, the impact of base fluid, temperature, concentration and surfactant on viscosity enhancement of graphene-based nanofluids is graphically and newly presented and discussed. In addition, the current models for viscosity prediction or correlation of those nanofluids are detailed. Finally, challenges and future works are summarized.

Experimental Study of Thermal Properties and Dynamic Viscosity of Graphene Oxide/Oil Nano-Lubricant

“…The most critical oil applications for engines include lubricating at both high and low temperature, reducing wear across multiple moving parts, cooling of moving parts, and so on. Therefore, the viscosity and thermal conductivity of the oil are critical properties that must be considered because viscosity directly impacts both pumping power and pressure drop; in addition, higher thermal conductivity means more excellent and better heat transfer performance [3][4][5]. Furthermore, the performance of the oil at temperatures close to zero and high temperatures is essential.…”

Viscosity and Rheological Properties of Graphene Nanopowders Nanofluids

“…While the most cited carbon-based nanomaterials for nanofluids applications are carbon nanotubes [26][27][28][29][30][31], recently other structures (such as graphene nanoplatelets (GNPs) and reduced graphene oxide (RGO)) have become more widespread [32]. Several researchers have studied the rheological properties of different graphene based nanofluids [9,[32][33][34][35][36]. Monireh et al [35] examined the impact of several parameters on the rheological properties of glycerol and multilayer graphene nanofluids.…”

A critical review on thermal conductivity enhancement of graphene-based nanofluids

“…This is the reason why using low GE concentration is crucial. Furthermore, apart from TC enhancement, viscosity and more generally rheological behavior of nanofluids (not studied here) is another important parameter to study for the designed GNFs [41]. The used GE amount is an important parameter to consider for evaluating the nanofluid TC performance.…”

“…The non-covalent approach consists in adding surfactants that adsorbs onto the GE's external surface [37] forming a coating layer known to be responsible for limiting heat transfer within the GE nanofluid [38,39]. In both chemical approaches, significant TC enhancements mainly require high GE concentration which is prejudicial for developing low energy consumption systems due to the consequently increase in nanofluid viscosity [40][41][42]. More generally, because of the relatively high production cost of NPs, and GE is not an exception [43], the GE amount has to be minimized within nanofluids.…”