Investigation of enhanced thermal properties in NiO-based nanofluids for concentrating solar power applications: A molecular dynamics and experimental analysis

• Published in: Applied energy Vol. 211; pp. 677 - 688
• Main Authors: Aguilar, Teresa, Navas, Javier, Sánchez-Coronilla, Antonio, Martín, Elisa I., Gallardo, Juan Jesús, Martínez-Merino, Paloma, Gómez-Villarejo, Roberto, Piñero, José Carlos, Alcántara, Rodrigo, Fernández-Lorenzo, Concha
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2018
• Subjects: Concentrating solar power; Molecular dynamics; Nanofluid; Solar energy; Thermal properties; Thermal properties; Molecular dynamics; Concentrating solar power; Nanofluid; Solar energy
• ISSN: 0306-2619; 1872-9118
• DOI: 10.1016/j.apenergy.2017.11.069

[Display omitted] •NiO-based nanofluid improves the heat transfer process in Concentrating Solar Power.•The thermal conductivity was improved up to 96%.•The heat transfer coefficient was improved by 50%.•The surfactant plays an important role in the properties of the nanofluid system.•The arrangement of the base fluid around the nanoparticles is revealed from MD results. Nanofluids could be a promising alternative to the typical heat transfer fluids (HTF) used in concentrating solar power. This study analyses nanofluids based on a typical HTF for concentrating solar power (CSP) applications and NiO nanoparticles. The optimum nanoparticle concentration was determined by analysing the stability of the nanofluids. Some of their properties, such as density, viscosity, isobaric specific heat and thermal conductivity, were characterized to evaluate their performance. Their thermal conductivity increased by up to 96% and the heat transfer coefficient by 50%. Molecular dynamics calculations were performed to explain from a molecular perspective how the presence of equal proportions of two surfactants, benzalkonium chloride (BAC) and 1-Octadecanethiol (ODT), enhanced the thermal properties of the NiO nanofluid. The isobaric specific heat and thermal conductivity values followed the same experimental tendency. The analysis of the radial distribution functions (RDFs) and spatial distribution functions (SDFs) revealed an inner layer of base fluid and surfactant molecules around the NiO cell. This first layer contained BAC molecules at all the temperatures, while ODT was only incorporated at higher temperatures. The exchange of surfactant and base fluid molecules around the NiO as the temperature increases may play an important role in the enhancement of the thermal properties.