Nano-colloidal suspensions of nanomaterials in a fluid, nanofluids, are appealing because of their interesting properties related to heat transfer processes. Whilst nanomaterials based on transition metal chalcogenides (TMCs) have been widely studied in catalysis, sensing, and energy storage applications, there are few studies of nanofluids based on TMCs for heat transfer applications. In this study, the preparation and analysis of nanofluids based on 2D-WS 2 in a typical heat transfer fluid (HTF) used in concentrating solar power (CSP) plants is reported. Nanofluids prepared using an exfoliation process exhibited well-defined nanosheets and were highly stable. The nanofluids were characterized in terms of properties related to their application in CSP. The presence of WS 2 nanosheets did not modify significantly the surface tension, the viscosity, or the isobaric specific heat, but the thermal conductivity was improved by up to 30%. The U r factor, which characterizes the thermal efficiency of the fluid in the solar collector, shows an enhancement of up to 22% in the nanofluid, demonstrating great promise for CSP applications. The Reynolds number and friction factor of the fluid were not significantly modified by the addition of the nanomaterial to the HTF, which is also positive for practical applications in CSP plants. Ab initio molecular dynamics simulations of the nanoparticle/fluid interface showed an irreversible dissociative adsorption of diphenyl oxide molecules on the WS 2 edge, with very low kinetic barrier. The resulting 'decoration' of the WS 2 edge dramatically affects the nature of the interface interactions and is therefore expected to affect significantly the rheological and transport properties of the nanofluids.
Nanofluids are colloidal
systems based on the suspension of nanoparticles
in a fluid. Their thermal properties mean that they are promising
heat transfer fluids with possible applications in different fields,
concentrating solar energy being one of particular interest. Thus,
this study presents the preparation of nanofluids based on WSe2 nanoparticles suspended in the eutectic mixture of biphenyl
and diphenyl oxide, which is a heat transfer fluid widely used in
concentrating solar power plants. To this end, solvothermal synthesis
was used to prepare WSe2 nanosheets, which were characterized
by means of scanning transmission electron microscopy, X-ray diffraction,
X-ray photoelectron spectroscopy, and Raman spectroscopy. The physical
and chemical stability of the nanofluids was analyzed, observing that
they became more stable when Triton X-100 was used as the surfactant.
The presence of WSe2 nanosheets did not result in a significant
increase in density or viscosity, but, by contrast, improvements were
obtained in their isobaric specific heat and thermal conductivity,
up to 4.7 and 64%, respectively. Spectral optical properties were
investigated as well, showing a significant effect of the WSe2 nanosheet addition to the extinction coefficient of the base
fluid in the wavelength range of the solar spectrum, promising for
direct absorption solar collectors. Finally, the efficiency of the
nanofluids was analyzed in a solar collector considering the U
r parameter, obtaining a remarkable increase
in the efficiency of up to 34% with respect to the pure heat transfer
fluid. This proves the possibility to obtain a sustainable production
of energy from the sun using these WSe2-based nanofluids.
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