Effect of Mechanical Technique on the Stability and Thermal Conductivity of MgO/Commercial Coolant-Based Nanofluid

Abstract

In recent years, nanofluid coolants enhanced with nanoparticles have attracted significant attention as promising alternatives because of their superior thermal properties. Magnesium oxide (MgO) nanoparticles, known for their high thermal conductivity, chemical stability, and environmental safety, offer a promising material for developing advanced automotive cooling fluids. This study investigates the influence of mechanical dispersion methods on the stability, thermal conductivity, and viscosity of MgO nanoparticles dispersed in a commercial automotive coolant. Nanofluids were prepared using a two-step method with variations in homogenization and sonication durations, and with or without polyvinylpyrrolidone (PVP) as a surfactant. Stability was assessed through visual observation, while thermal and rheological properties were analyzed across different temperatures and shear rates. The results show that PVP significantly improves nanoparticle suspension by delaying agglomeration and sedimentation. CNP-1 (with PVP and 60 min of sonication) exhibited the highest thermal conductivity at 60 °C (0.3157 W/mK), while maintaining moderate viscosity with shear-thinning behavior. CN-1, lacking PVP, showed poor dispersion and higher viscosity. CNP-4 demonstrated unusually high thermal conductivity at 40 °C, but instability at 60 °C, highlighting the delicate balance between dispersion and performance. Overall, the findings reveal that both surfactant usage and sonication duration are critical for enhancing the performance and long-term stability of MgO-based nanofluids for automotive cooling applications.