Experimental investigation of the rheological behavior and viscosity of decorated multi-walled carbon nanotubes with TiO2 nanoparticles/water nanofluids

Abstract

The effects of temperature and concentration on the flow behavior and viscosity of nanofluids containing TiO 2 nanoparticles, pristine MWCNTs, oxidized MWCNTs and decorated MWCNTs with TiO 2 nanoparticles are experimentally investigated. The results of rheological characteristics of nanofluids revealed that nanofluid of TiO 2 nanoparticle and MWCNT-TiO 2 exhibits shear thickening or dilatant behavior. In contrast, nanofluids containing pristine and oxidized MWCNTs depict the shear thinning or pseudoplastic behavior. Also results demonstrated that the rheological characteristics of nanofluids are functions of temperature and concentration, whereas the viscosity of all prepared nanofluids decreases with increasing the temperature and decreasing the concentration. In addition, the results show that the oxidation of MWCNTs in nitric acid leads to the reduction in viscosity. The rheological behavior of decorated MWCNTs illustrates that viscosity decreases by increasing the attached TiO 2 nanoparticles. TEM results show that TiO 2 nanoparticles successfully attached to the outer surface of oxidized MWCNTs.

Effect of various surfactants on stability and thermophysical properties of nanofluids

“…It was observed that nanofluids exhibited both non-Newtonian and Newtonian behavior. The viscosity of a Newtonian fluid depends on the shear rate, whereas the non-Newtonian fluid shows a completely different rheological behavior [11,13,17].…”

“…In addition, the viscosity of a nanofluid shows significant influence on the heat transfer enhancement, and many researchers focused their interests in the nanofluid viscosity, and they found that the viscosity of the nanofluid was affected by the nanoparticle size, volume fraction, shear rate, temperature, and aggregate size. Abbasi et al [11] investigated rheological behaviors of various nanofluids. They found that high portion of multi-walled carbon nanotubes (MWCNTs) resulted in high viscosity of the MWCNT-TiO 2 nanofluid.…”

Numerical investigation for rotating flow of MHD hybrid nanofluid with thermal radiation over a stretching sheet

“…Due to the numerous heat transmission properties, this class of fluids is excessively used in industrial and engineering applications such as cooling of electronic equipment, cooling process in HVAC systems, refrigeration processes, food industry, solar collectors and micro channel heat sink etc. 2 – 5 . Solar collectors are the devices that convert the solar energy into heat energy in eco-friendly and convenient way.…”

Effects of ultrasonication time on stability, dynamic viscosity, and pumping power management of MWCNT-water nanofluid: an experimental study

“…There are many debates on the rheological properties of the nanoflu- www.nature.com/scientificreports/ ids containing carbon nanotubes (CNTs). While some researchers reported that CNT-based nanofluids show non-Newtonian behavior 46 , there are other researchers who observed that the CNT-based nanofluid with the solid concentrations less than 0.5 vol% show Newtonian behavior [47][48][49] , and increasing the solid concentration leads to changing the rheological behavior from Newtonian to non-Newtonian 50 . Thus, in the present study, the rheological properties of the studied nanofluid have been investigated over a different range of shear rates (100-800 1/s), temperatures, and solid concentration to realize that whether the studied nanofluid is a Newtonian or a non-Newtonian fluid.…”