Transport Properties of Nanosystems: Viscosity of Nanofluids Confined in Slit Nanopores

A fundamental nonequilibrium statistical mechanical approach due to Pozhar and Gubbins (PG) is used to study the Poiseuille flow and momentum transport in 20 model nanofluids confined in slit pores several molecular diameters in width. A simplified version of a general expression for the PG theoretical viscosity is applied to calculate the localized viscosity of the nanofluids in terms of the equilibrium structure factors (density and correlation functions) of nanosystems. These structure factors are calculated by means of the equilibrium molecular dynamics simulations. The localized theoretical viscosity so obtained is used further to calculate the theoretical pore-average viscosity of the nanosystems, and the latter is successfully compared with that extracted from nonequilibrium molecular dynamics simulation data. A simple correlation between the pore-average velocity, viscosity, nanofluid density, and the pore width for nanosystems of moderate density has been developed and recommended for applications in engineering.