Condition Assessment of Aged Ester-Based Nanofluid Through Physicochemical and Spectroscopic Measurement

Vegetable oils (VOs) are based on natural ester oil that is considered as an alternative to mineral oil for transformer applications. The dispersion of nanofillers into the VO is expected to improve the physicochemical and electrical performances. Surface-modified insulating nanoparticle is dispersed into the VO to prepare the VO-based nanofluid (NF). An open-beaker oxidative aging study is carried out at 115 °C for VO and NF at three distinct aging durations such as 100, 300, and 500 h. Alterations in the molecular level of aged VO and NF are studied through the various spectroscopic and physicochemical analyses such as nuclear magnetic resonance, Fourier transform infrared, UV-vis absorbance, fluorescence, color, acid number, interfacial tension, and flash point. The fluorescence-based analysis is carried out for VO and NF at fresh and aged condition to monitor the comparative aging degradation. Oxidative aging of VO and NF results in the formation of flammable and harmful gases, which are analyzed using dissolved gas analysis technique. A comparative analysis of the electrical properties such as ac breakdown voltage, dielectric constant, and dielectric dissipation factor for fresh and aged sample of VO and NF is studied.