Thermo-physical properties of naphthenic-palm oil methyl ester (POME) blended transformer oil

This study aims to investigate the thermal conductivity, viscosity and thermal degradation of naphthenic-based mineral oil, palm oil methyl ester (POME) and its blend. Mineral oil and POME were mixed at various mass ratios (70:30, 80:20 and 90:10) via homogenisation for 10 min at 25,000 RPM. The thermo-physical properties of oil studied were thermal conductivity, viscosity, density, flash point and thermal degradation. Results indicated enhancement in thermal conductivity with an increase in temperature. The highest enhancement (0.185 W mK⁻¹) was observed for the 70:30 blend ratio at 80 °C. The viscosity decreased as temperature increased, whereby POME resulted in lower values (2.3 mPa.s) than mineral oil (4.3 mPa.s) at 80 °C. Density also showed a decreasing trend with temperature with no significant difference between POME and mineral oil. However, POME (175.5 °C) resulted in a higher flash point compared to mineral oil (146.5 °C), resulting in the enhanced flashpoint of blend oils. Blend oil with a 70:30 ratio resulted in the highest thermal degradation of 274.56 °C in the air environment. Oxidation induction time (OIT) decreased with temperature from 160–180 °C where mineral oil resulted in higher induction time than POME. The results proved improvement in properties of mineral oil blend with POME, which can enhance the system performance and faster heat dissipation.