A study on the thermo-physical properties of EG/water-based nanofluids containing low and high concentrations of MgO nanoparticles

Nanofluids have gained significant attention for their enhanced thermophysical properties, making them suitable for high-performance cooling applications. This study investigates the thermal conductivity and stability of ethylene glycol (EG)/water-based nanofluids containing magnesium oxide (MgO) nanoparticles at low (0.02, 0.04, and 0.06 wt.%) and high (0.2, 0.4, and 0.6 wt.%) concentrations. MgO nanoparticles were synthesized via the sol-gel method and characterized using XRD, FTIR, SEM, and EDS analysis. Nanofluids were prepared using a two-step method with polyvinylpyrrolidone (PVP) as a stabilizing surfactant. UV–vis spectroscopy and visual observation were used to assess the colloidal stability over a 30-day period, while thermal conductivity and viscosity were measured at varying temperatures (25 °C, 40 °C, and 60 °C). The results demonstrate that thermal conductivity increased with both nanoparticle concentration and temperature, with a maximum enhancement of 40.51% observed at 0.6 wt.% and 60 °C. However, stability declined at higher concentrations, with notable sedimentation at and beyond 0.4 wt.%. The 0.2 wt.% sample exhibited the best balance between thermal enhancement and long-term stability. These findings suggest that MgO-EG/water nanofluids in the range of 0.2–0.4 wt.% offer optimal performance for thermal applications such as automotive coolants and photovoltaic thermal systems.