Improving the heat transfer efficiency of synthetic oil with silica nanoparticles

► Stable suspensions of SiO2/Therminol 66 are formulated with cationic surfactant. ► The viscosity and thermal conductivity depend on the agglomerate sizes. ► Agglomerate sizes are controlled by surfactant-to-nanoparticle ratio and temperature. ► Nanofluid shows enhanced heat transfer at all temperatures in a laminar flow. ► In a turbulent flow nanofluid beneficial only at elevated temperatures.