Rheological Characteristics of Molten Salt Seeded with Al2O3 Nanopowder and Graphene for Concentrated Solar Power

Abstract

HITEC salt (NaNO2-NaO3-KNO3) and solar salt (NaO3-KNO3) are typical molten salts used in concentrated solar power. Adding nanoparticles is an effective method to improve the thermo-physical properties of pure salt. It is indispensable to experimentally study the rheological behaviours of salt seeded with nanoparticles, which can increase the specific heat capacity of pure salt. In this work, the viscosities of HITEC salt were measured with different shear rates in the temperature range of 200 °C to 450 °C firstly, while those of solar salt were measured in the temperature range of 250 °C to 500 °C. The experimental data showed reasonable agreement with the literature correlations, which verify the Newtonian behaviours of pure salts. The evolutions of the viscosities of nanocomposites in the same temperature range were measured and analysed, where the nanocomposites were synthesized with 1 wt.% or 2 wt.% Al2O3 nanopowder and graphene, respectively. Results showed that the addition of Al2O3 nanopowder had relatively little effect on viscosity, and the variations were about −35.4%~8.1% for the HITEC salt nanocomposites and −9.2%~68.1% for the solar salt nanocomposites. While graphene would apparently increase the viscosities of HITEC salt and solar salt, HITEC salt with the addition of graphene showed slight non-Newtonian fluid behaviour.

A Comprehensive Physical Profile for Aqueous Dispersions of Carbon Derivatives as Solar Working Fluids

“…Remarkable efforts have been made to understand which nanofluid could better fit the requirements of the desired application [6,10,12,[14][15][16][17][18][19][20][21][22][23]. Concerning DASC systems, it is a hard task to find a nanofluid that provides suitable chemical, thermophysical, fluid-dynamics and optical properties at the same time, as it must work both as a heat carrier and as a light absorber.…”

“…However, some types of nanoparticles have become promising, such as the family of carbon-based nanostructures. Graphite [10,14], single and multi-walled nanotubes [12,[15][16][17][18], nanohorns [6,19,20], and graphene [21][22][23], were widely considered for solar energy applications. Carbon-based nanoadditives reach higher thermal conductivity enhancements at lower concentrations than other families of nanoparticles (metals, metal oxides).…”

High performance cooling of a HVDC converter using a fatty acid ester‐based phase change dispersion in a heat sink with double‐layer oblique‐crossed ribs

“…The influences of shear rate and temperature on PCM and emulsifier viscosities are illustrated in Figure A. At a shear rate lower than ~25 seconds −1 , an irregular fluctuation of the viscosity occurs mainly due to low torque resolution . An increase in the shear rate to ~25 seconds −1 leads to the viscosity of almost constant for a given temperature, exhibiting the Newtonian behaviour.…”

Molten Salt/Metal Foam/Graphene Nanoparticle Phase Change Composites for Thermal Energy Storage

“…where KB is Boltzmann constant, dnp is nanoparticle size, which is 350 nm in the present study [34].…”