CuO-containing oil-based nanofluids for concentrating solar power: An experimental and computational integrated insight

The thermal properties of the heat transfer fluid (HTF) used in concentrated solar power (CSP) technology are still considered one of the main limitations to the expansion of this energy source as a solid alternative to fossils fuels. The addition of nanoparticles has been shown to have a positive contribution in this sense. In this study, CuO nanoparticles were dispersed into the typical HTF used in CSP plants, their stability assured by using a surfactant which reduces the tension at the solid-liquid interlace. Three nanofluids were prepared using different sonication energy values in the dispersion process. All of them were characterised for stability and thermal properties over two months. The one prepared with the lowest energy value was the most stable and exhibited an improvement in the heat transfer coefficient of about 10%, also showing improvements in isobaric specific heat and thermal conductivity. In addition, a theoretical approach was applied to the system to provide more information about the heat transfer mechanisms, presented as one of the main challenges in this regard. Molecular dynamics simulations were performed under the same conditions as the experimental scenario, and once the model was validated it was used for a more in-depth molecular level understanding. The enhanced thermal conductivity was analysed by means of the heat flux autocorrelation function, which showed a larger phonon mean free path for the nanofluid system. Radial distribution functions showed the formation of a semi-rigid layer that could explain the increase in isobaric specific heat. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study focused on utilizing CuO nanoparticles to improve the thermal properties of heat transfer fluids in CSP plants. Nanofluids prepared with lower sonication energy values demonstrated the highest stability, a 10% increase in heat transfer coefficient, and improvements in isobaric specific heat and thermal conductivity. Molecular dynamics simulations were used to analyze the enhanced thermal conductivity and the formation of a semi-rigid layer which could explain the increase in isobaric specific heat.