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Effect of Boundary Layer Modification and Enhanced Thermal Characteristics on Tribological Performance of Alumina Nanofluids Dispersed in Lubricant Oil
Cooling performance and energy conservation are important requirements in modern industries and machines. However, low thermal conductivity is the main limitation in developing energy-efficient heat-transfer fluids for cooling purposes. In this study, nanolubricants with alumina nanoparticles dispersed in a base oil for rotary machines were investigated for improved thermal and tribological performances. Initially, to improve the dispersibility of the nanoparticles in the base oil, the nanoparticles were surface functionalized via a (3-aminopropyl)triethoxysilane (APTES) coating, and the corresponding material and thermophysical properties were analyzed. Subsequently, the reliability of the nanolubricant for long-term operation was investigated by applying it to a small platform and performing a rolling contact fatigue (RCF) test that simulates the actual operating environment. The results show that the thermal conductivity improved with an increase in the particle concentration by up to 5.78% at 2 vol.% particle fraction as compared to that of the conventional lubricant (base oil). Furthermore, an RCF test of the nanolubricant performed in a real environment showed that the roller bearing life improved by approximately 3.23 times, owing to a ~ 5.88% reduction in lubricant temperature, modified frictional characteristics from polishing, and nanofin effects of the nanoparticles.