Experimental study on the thermal conductivity and viscosity of ethylene glycol-based nanofluid containing diamond‑silver hybrid material

Abstract

The development of carbon nanocomposites composed of nanodiamond nanostructures and metal nanoparticles has attracted much interest because of their large potential for technological applications such as nanofluids. In this experimental study, a new synthesis method was adapted for the addition of silver on the surface of functionalized nanodiamond nanoparticles (Di–Ag) in order to prepare hybrid nanofluids. The surface characterization of hybrid nanoparticles was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transforms infrared spectroscopy (FT-IR). The stability of the synthetized nanofluids was evaluated using UV–vis spectroscopy and visual detection of sedimentation. The thermo-physical properties (thermal conductivity, dynamic viscosity and density) of the prepared nanofluids were also investigated. The thermal conductivity of the hybrid nanofluid was measured using a thermal analyser based on the hot bridge methodology, and the measurements were performed at a temperature range of 10 to 60 °C and at a solid volume fraction range of 0 to 0.1% of nanodiamond. The results were compared with some well-known models for relative thermal conductivity, viscosity and density. The prepared nanofluids presented better thermal conductivity in comparison with the base-fluid, and the increase in thermal conductivity occurred as a function of the volumetric concentration of hybrid nanoparticles and of the temperature. The maximum increment obtained for thermal conductivity was from 6.92% to 0.1 vol%. For the viscosity, the maximum increment obtained was from 21.21% to 0.1 vol% at 10 °C. Therefore, the results indicate that the properties of these nanofluids are desirable and that they can be used as alternative fluids in heat transfer processes.