Investigation on stability and properties of water-based gold nanofluids

Nanofluids are potential alternative thermal vectors obtained by dispersing, into a common fluid, solid nanoparticles, which promise to significantly improve the base fluid thermal properties. In this paper, an investigation to evaluate stability and transport properties of water based nanofluids containing gold (Au) nanoparticles is proposed. Nanofluids were prepared with a one-step method by an eco-friendly route, which exploits the sodium citrate both as reducing and as chelating agent. Dynamic Light Scattering (DLS) technique was used to measure the diameter of nanoparticles in suspension. Thermal conductivity and dynamic viscosity data for nanofluids at a mass concentration of 0.02%, 0.05% and 0.1% were measured in the temperature range between 10°C and 70°C, at atmospheric pressure. In order to evaluate nanofluids potentiality to improve heat transfer efficiency with respect to the base fluid, the convective heat transfer coefficient was experimentally measured in a dedicated experimental set-up. A constant heat flux was supplied to the fluid and turbulent flow regime was investigated at various flow rates considering inlet fluid temperature around ambient temperature. Experimental thermal conductivity and dynamic viscosity data were used to calculate Reynolds and Nusselt numbers and nanofluid thermal coefficients were compared with pure water ones.