Influence of ZnO nanoparticles on thermophysical and tribological properties of polyolester oil

Abstract

An experimental assessment of thermo-physical, tribological, and eco-friendly properties of polyolester (POE) oil with zinc oxide (ZnO) nanoparticles for use as nanolubricant in refrigeration compressor. The ZnO nanolubricants were added in the mass fractions in the range from 0.1% to 0.5%, at the temperatures of 0 °C, 20 °C, 30 °C, 40 °C, and 60 °C. The thermophysical properties include thermal conductivity, kinematic viscosity, flash point, fire point, pour point, and cloud point with respect to various proportions. The morphology and size of ZnO nanoparticles are studied using the scanning electron microscope test. The tests findings suggest that ZnO nanoparticles greatly improved the friction characteristics of pure POE oil. The addition of the concentration decreases the pour point by 13.6%; at the same time, the flashpoint is improved by 3.5% when the POE oil is blended with ZnO. Zinc oxide nanoparticles could improve the refrigerants' performance by extending life and avoiding friction problems. The optimum ZnO content of nanolubricants is, therefore, 0.3% for the POE/ZnO nanoparticles addition. The COF values are reduced by 6.95% at the optimum concentration over that with POE oil. The nanoparticles' addition up to 0.3% results in less wear as they provide a defensive film between the surfaces during their motion. The mass loss value increased due to the aggregation of ZnO nanoparticles. The higher thermal conductivity is obtained for the 0.3% volume fraction of nanoparticles, and other 0.1% and 0.5% volume fractions lesser.