Lecture
WEB Surface modified graphene nanoplatelets in nanofluids for heat transfer applications
Wednesday (23.09.2020) 15:15 - 15:30 Z: Special Symposia I Part of:Increased demand for energy supply from sustainable energy sources such as concentrated solar power, has emerged as a key technology. The unique thermal conductivity of graphene makes it one of the most promising materials for next-generation heat transfer applications. The incorporation of graphene and graphene-like nanomaterials into conventional heat transfer fluids has been shown to significantly improve their thermal transport properties. Due to their cost-efficient carbon-based starting material, its high surface area and sheet-like structure, graphene nanoplatelets (GNPs) are suitable for colloidal thermal conductive fluids demonstrating enhanced heat transfer efficiencies.
Starting from low-dimensional hydrophobic graphene nanoplatelets, surface functionalization by acid treatments was performed to synthesize highly stable, exfoliated, surfactant-free, and highly concentrated (4 wt.%) graphene nanofluids maintaining high thermal conductivity. Investigations by SEM, XPS, XRD, Raman and FT-IR spectroscopy revealed a significant influence of shape, reaction period, acid volume and temperature on the resulting thermal conductivity values of the nanofluids relative to the carrier fluid. Thermal conductivities up to 0.586 W/m*K (base fluid: 0.391 W/m*K) in a dormant system were measured and the overall efficiency of these nanofluids, in combination with a low viscosity of 6.39 cP, could be increased to 77 % in comparison to the base fluid. The combination of both low viscosity and high thermal conductivity, even after 14h in a standing system, demonstrates the extraordinary properties of surface-functionalized graphene nanoplatelets prepared in this work in comparison to other nanofluidic systems.
