Renewable Energy, Vol.145, 2435-2444, 2020
Preparation and enhanced thermal conductivity of molten salt nanofluids with nearly unaltered viscosity
In this work, a series of solar salt nano-fluids with 2.5 wt%, 3.5 wt%, 4.5 wt%, 5.0 wt% and 10.0 wt% MgO nanoparticles (similar to 60 nm, 18 W/m.K-) have been prepared and their thermal properties over 220 degrees C have been studied. The viscosity (eta), density (rho), specific heat capacity (c(p)) and thermal diffusivity (alpha) of the nano-fluids have been measured by rotary viscometer, Archimedean technique, differential scanning calorimeter (DSC) and laser flash analysis (LFA) respectively. The thermal conductivity (lambda) is determined by rho, c(p) and alpha. The results show that the viscosity and density of nano-fluids are about 5.1 cp similar to 2.4 cp and 1.96 g/cm(3)similar to 1.83 g/cm(3) at 240 degrees C-380 degrees C which is close to that of solar salt fluid. The average c(p) of the fluids with nano-MgO from zero to 5.0 wt% is 1.442-1.613 J/(g.K), and the l of fluids is 0.37-0.60 W/(m.K) at 375 degrees C. The enhancement of cp and l of nano-fluids reaches 11.9% and 62.1%, which increases the Nusselt number with improved heat transfer performance. It is suggested that the nano-fluid with 5.0 wt% MgO in solar salt is a promising fluid for application of heat transfer and thermal storage in a CSP system. (C) 2019 Published by Elsevier Ltd.