Stable colloidal copper nanoparticles for a nanofluid: Production and application

•A layer of PVP is coated onto copper nanoparticles to minimize their agglomeration.•Stable colloidal copper nanoparticles were prepared and used to prepared a nanofluid.•Convective heat transfer properties of a colloidal copper nanofluid were studied.•The heat transfer coefficient increases with concentration of colloidal copper nanoparticles.•Enhancement in the heat transfer coefficient was observed at different Reynolds numbers. The present study deals with the synthesis of water based stable colloidal nanoparticles and the study of their heat transfer characteristics. Heat transfer analysis at different loading (0–1.1wt%) of copper nanoparticles in water was carried out at fixed Reynolds number. Enhancement in the heat transfer coefficient was also studied at different Reynolds numbers by keeping the wt% of copper nanoparticles in the range of 0.7–1.1wt%. The heat transfer analysis of the copper nanofluid was carried out in a copper tube at constant heat flux. Established correlations were used for the determination of thermal properties in the laminar flow regime. The results showed that the heat transfer coefficient increases with an increase in the concentration of colloidal copper nanoparticles and Reynolds number. For a 1.1wt% copper nanofluid, a 34% increase in the heat transfer coefficient was observed as compared to the base fluid (pure water).