Investigating heat transfer properties of copper nanofluid in ethylene glycol synthesized through single and two-step routes

Abstract Thermal efficiency improvement in conventional cooling fluids like water and ethylene glycol (EG) is a fundamental requirement in various industrial applications. Copper-EG nanofluid can be considered for this purpose; thus synthesized through single-step and two-step procedures using chemical reduction method in this study. Thermal properties of copper-EG nanofluid were investigated in both cases. Pure nano-copper was synthesized without inert environment using sodium hypophosphite as the reducing agent and Polyvinylpyrrolidone (PVP) and glycerol as capping agents resulting in 25 and 34.5 nm average size nanoparticles, respectively. A simple and low-cost synthesis route for pure and stable nano-copper in glycerol was provided that seems promising for large scale production. Heat transfer coefficient (HTC) calculations were performed at 68, 94.8 and 125.5 Reynolds numbers and 0.01, 0.03 and 0.05 wt% in a designed heat exchanger setup. The highest HTC enhancement of the two-step nanofluid occurs at 0.03 wt%. HTC of the one-step nanofluid is significantly increased compared with the base-fluid and increasing the nanofluid concentration leads to higher HTC values. The highest HTC enhancement was 73.34% at Re = 68 for the 0.05 wt% nanofluid.