Performance analysis of vegetable oil-based nanofluids used in transformers

Abstract

Nanofluids (NFs) are an emerging technology in the field of dielectrics. These oils are used in transformers and other power apparatus for the purpose of insulation and cooling. The vegetable oil (VO) proposed in this study is the Pongamia pinnata oil (PPO), commonly known as karanji oil. The molecular structure of PPO is changed by the transesterification process and converted to Pongamia oil methyl ester (POME) as the crude oil is not suitable for direct use because of its high viscosity, high pour point, and acid number. For preparing the NF, 0.01 wt.% of exfoliated hexagonal boron nitride (Eh-BN) is dispersed in mineral oil (MO) and POME to prepare MO-based NF (MO-NF) and POME-based NF (POME-NF), respectively. This study explores the various thermophysical and electrical properties of four types of oils – MO, MO-NF, POME, and POME-NF. Thermophysical properties such as thermal conductivity, interfacial tension, flash point, and pour point, and electrical properties such as dielectric constant, dielectric dissipation factor, and dielectric strength are measured and a comparative analysis is carried out among all the four types of oils. The charging dynamics study has also been investigated to understand the phenomenon underlying the enhanced breakdown voltages of VO-based NFs.