Corrosion, rheology, and thermal ageing behaviour of the eutectic salt-based graphene hybrid nanofluid for high-temperature TES applications

Abstract

The eutectic salt-based nanofluids have recently been explored as a Thermal Energy Storage (TES) material for high-temperature applications due to their improved thermal properties. However, the investigation of such fluids in corrosion, rheology, and thermal ageing is minimal. This study focused on the effect of newly developed hybrid nanofluids based on GO/TiO2 nanoparticles and the eutectic salt mixture on thermophysical properties for high-temperature applications. The results showed that the SS316 immersed in hybrid nanofluid formed a protective layer to prevent corrosion compared to the eutectic salt mixture after 7 days. The surface morphologies and cross-sections were studied using SEM (Scanning Electron Microscope) and EDX (Energy-dispersive X-ray spectroscopy). The addition of hybrid nanoparticles into the eutectic salt mixture exhibits minimal effect on the viscosity that varies about −0.51–11.05% from 250–400 °C range at a shear rate of 250/s. Moreover, the rheological study displayed a strong correlation (R2 of 0.99) with the experimental data. Comparative studies showed that the viscosity values of both eutectic salt mixture and hybrid nanofluid showed good agreement with the literature. Finally, the thermal ageing behaviour of eutectic salt mixture and hybrid nanofluids was investigated for 15 days, and the samples were collected on the 1st, 7th, and 15th day. The average specific heat capacity of hybrid nanofluids and eutectic salt was reduced by 8.76% and 28.94%, respectively, after 15 days, indicating poor thermal stability of eutectic salt compare to hybrid nanofluids.