Dielectric and Thermal Performance of Natural Ester Oil Based Nanofluid with Magnesium Oxide Nanoparticles

Abstract

Nowadays, nanoparticles are used in insulating oils to enhance their dielectric and thermal properties significantly. On the other hand, natural ester oil is considered one of the most environmentally friendly types of insulating oil. In this study, magnesium oxide nanoparticles with their excellent physical and thermal properties, are used to prepare natural ester oil-based nanofluids. Their electrical performance is investigated by subjecting samples of different nanoparticles concentration to lightning impulse voltage (1.2/50 µs) by following the step-up method. For the generation of the pulses, a one-stage impulse voltage generator was used, while measurements from 20 pulses per voltage level were applied to a needle-to-plane gap so as to estimate the relevant breakdown probabilities. Furthermore, relative permittivity and electrical conductivity are measured for a range of frequencies (0.1 Hz - IMHz) and a range of temperatures (30 °C – 90 °C) by means of broadband dielectric spectroscopy. The thermal properties are studied based on thermal diffusivity measurements by LFA (Laser Flash analysis) for different concentration values and a wide range of temperatures (30 °C – 90 °C). Results reveal the improved performance regarding the dielectric and thermal properties for the prepared natural ester oil-based nanofluids. A 15.15 % improvement in lightning impulse breakdown voltage, more specifically of the U50% voltage, is observed. Additionally, results show a 12.63 % improvement for thermal diffusivity.