Experimental Characterization and Theoretical Modelling of Ag and Au-Nanofluids: A Comparative Study of Their Thermal Properties

This article reports the preparation and characterization of nanofluids based on the heat transfer fluid (HTF) commonly used in concentrating solar power (CSP) plants. Nanofluids were prepared with commercial Ag nanoparticles and synthesized Au nanoparticles which were dispersed into a base fluid composed by a eutectic mixture of two stable compounds: diphenyl oxide and biphenyl. Both sets of nanofluids were characterized attending to its physical and chemical stability and the possible improvement on thermal properties respect to base fluid. Moreover, a theoretical analysis was achieved by Molecular Dynamics simulations to obtain a greater knowledge about this kind of systems through the study of the different interactions between the metal and the molecules of the base fluid. The results showed that the incorporation of Ag nanoparticles into a base fluid improves significantly thermal properties such as isobaric specific heat and thermal conductivity, giving an enhancement of its heat transfer coefficient. Theoretical analysis revealed that the arrangement of molecules of base fluid around the Ag nanoparticle favors the improvement of thermal properties. On his part, addition of Au nanoparticles into the base fluid did not produce any increment of thermal properties with regard to base fluid, and the theoretical analysis showed a minor participation of diphenyl oxide molecules in a first layer of Au nanoparticle.