Functionalized graphene nanoplatelet-nanofluids for solar thermal collectors

This work reports on the characterization of new heat transfer fluids consisting in dispersions of functionalized graphene nanoplatelets (fGnP) in Havoline XLC Premixed 50/50 base fluid. Optical, stability and rheological properties have been considered, with the aim to assess the nano-suspension potential for volumetric direct solar absorbers. Nanoparticle addition leads to a considerably higher sunlight absorption with respect to the pure base fluid even at the investigated extremely low concentrations (0.005% and 0.05% wt). Rheology tests show a Newtonian behaviour in the shear rate range between 10 and 1000 s−1. Viscosity and thermal conductivities do not significantly increase with respect to the pure base fluid, showing that these new fluids will not require additional pumping powers to flow.