Comparative characteristics of viscosity and rheology of nanofluids with multi-walled and single-walled carbon nanotubes

The purpose of this paper is to study the viscosity and rheology of nanofluids with single-walled (SWCNT) and multi-walled (MWCNT) carbon nanotubes, and compare the obtained data. In total, a series of different nanofluids have been studied. The same base fluids were used in all experiments; the range of weight concentrations of carbon nanotubes (CNTs) and surfactants (if used) was also the same. In total, about two dozen of different nanofluids have been studied. The weight concentrations of CNTs ranged from 0.05 to 1 %. It is shown that with the same weight concentration of CNTs, nanofluids with SWCNTs have a significantly higher viscosity than nanofluids with MWCNTs. In most cases, the studied nanofluids were pseudo- or viscoplastic, although all the base fluids were Newtonian. Correlations describing the rheology of all studied nanofluids are given. It is shown that the viscosity of the nanofluids increases with a decrease in the average hydrodynamic size of nanotubes. The microrheology of these nanofluids has been studied and the dependence of their elastic modulus on the concentration of CNTs has been determined.