A comprehensive analysis of the thermo-physical behavior of a novel hybrid nanofluid for energy applications

Abstract

This study examines the synthesis, characterization, and thermo-physical properties of hybrid nanofluids containing silver nanoparticles (Ag NPs) and iron-based core–shell nanoparticles (Fe@C), dispersed in both water and a water-ethylene glycol (W + EG) mixture. The hybrid nanofluids were stabilized using carboxymethyl cellulose sodium salt (CMCNa) and prepared at three different weight concentrations: 0.5 %, 0.75 %, and 1 %. The study systematically analyzed several thermo-physical properties, including thermal conductivity, viscosity, density, thermal diffusivity, and thermal effusivity, over a temperature range from 20 °C to 50 °C. The findings indicated that the Ag + Fe@C/water nanofluid exhibited a more significant improvement in thermal conductivity, achieving a maximum enhancement of 9.0 % at the highest concentration. Additionally, the dynamic viscosity of the nanofluids decreased with increasing temperature but increased with higher nanoparticle concentration. Ag + Fe@C/water showed a more considerable decrease in viscosity as temperature rose, with an average relative deviation of 13.58 %, while Ag + Fe@C/W-EG demonstrated a smaller decrease in viscosity (4.16 %), suggesting a more stable fluid behavior at elevated temperatures. Moreover, both density and thermal diffusivity exhibited positive correlations with nanoparticle concentration. Specifically, the Ag + Fe@C/W-EG nanofluid exhibited a higher density increase (ranging from 1.15 % to 1.53 %) compared to Ag + Fe@C/water (ranging from 0.30 % to 0.90 %). For thermal diffusivity at 323 K, Ag + Fe@C/water showed an increase ranging from 17.40 % to 33.40 % depending on concentration, while the Ag + Fe@C/W-EG nanofluid demonstrated even higher thermal diffusivity, ranging from 19.4 % to 33.78 %. Finally, the current results were compared with data available in the literature.