Colloidal Fe₃O₄ nanoparticles-based oil blend ferro-nanofluid for heat transfer application

The thermal conductivity enhancement of oil blend-based ferro-nanofluids for heat transfer application is rarely reported. Herein, highly stable ferro-nanofluids were prepared by dispersing oleic acid coated Fe₃O₄ NPs into the blend of sunflower oil and mineral oil at varying volume ratios. The maximum thermal conductivity enhancement of ~ 91% was obtained for M10 (base fluid) oil blend-based ferro-nanofluid at 0.6 vol% of Fe₃O₄ NPs as compared to the pure mineral oil. The dispersed NPs into the oil blend-based ferro-nanofluid executed Brownian motion which led to the collisions between the NPs as well as with the molecules of the oil blend. The formation of a chain like network by small-sized NPs effectively led to a larger volume fraction of NPs, which caused the enhancement of the thermal conductivity of oil blend-based ferro-nanofluids. Moreover, a nano-adsorption layer of oil blend was formed on the surfaces of NPs, which served as a bridge for the heat exchange between NPs and oil blend. The experimental results were validated against a similar pre-existing thermal conductivity enhancement model. Hence, this study provides a more efficient method to prepare oil-based ferro-nanofluids with a tunable thermal conductivity for heat transfer applications. Graphic abstract: [Figure not available: see fulltext.].