Abstract:
Nanofluids are effective heat transfer fluids, exhibiting enhanced heat transfer than conventional fluids such as deionized water (DIW) and ethylene glycol (EG). In this study, nanofluids with a volume concentration of 0.06% were prepared by dispersing silicon nitride (Si3N4) nanoparticles in DIW, EG, and different ratios (60:40 and 40:60) of DIW-EG using a two-step method. The phase and structural analysis of the nanoparticles were conducted using X-ray diffraction and scanning electron microscopy. The stability of the prepared nanofluids was investigated using visual sedimentation, zeta potential, and UV-VIS spectroscopy measurements. Thermo-physical properties such as thermal conductivity and viscosity of Si3N4/DIW, Si3N4/EG, Si3N4/DIW-EG (60:40), and Si3N4/DIW-EG (40:60) were evaluated across a temperature range from 30°C to
80°C. The results showed that Si3N4/DIW exhibited high stability as compared to Si3N4/DIW-EG (60:40), followed by Si3N4/EG and Si3N4/DIW-EG (40:60) nanofluids. The maximum thermal conductivity enhancements of 14% and 9.4% were observed for Si3N4/DIW and Si3N4/DIW-EG (40:60) nanofluids, respectively. The rheological properties of Si3N4 nanofluids exhibited Newtonian behavior in DIW, EG, and the (60:40 and 40:60) DIW-EG mixtures, with and without surfactant, as indicated by a linear relationship between shear stress and shear rate. However,
adding OLAM to the Si3N4/EG nanofluid changed its flow behavior from Newtonian to dilatant. At a constant volume fraction, the viscosity of the nanofluid decreased with increasing temperature, with the most significant reduction in viscosity relative to the base fluid observed at 80°C. The visual sedimentation, zeta potential, and UV-VIS spectroscopy, results indicated that Si3N4/DIW/OLAM nanofluid remained stable up to 5 months. Overall, the results suggest that Si3N4/DIW/OLAM is the most suitable nanofluid for enhancing heat transfer and energy efficiency in industrial applications.
