Thermal and rheological characteristics of refrigerant compressor oil with alumina nanoparticles—An experimental investigation

Abstract

An experimental investigation has been carried out to study the thermal and rheological characteristics of polyalkylene glycol (PAG) oil suspended with Al2O3 nanoparticles. The volume fraction is varied from 0.07 to 0.6% and temperature from 20 °C to 90 °C. The nanolubricant exhibits higher thermal conductivity and viscosity compared to the pure PAG oil. Conversely, both these properties decrease with increase in temperature. The highest thermal conductivity ratio is 1.48 at 0.6% concentration and temperature 20 °C. The maximum viscosity ratio is 18.42 at 0.6% concentration and shear rate 3.75/s. The Ostwald–DeWaele rheological model is fitted to predict the behaviour of nanolubricant with respect to temperature and shear rate. Interestingly, the pure lubricant, which is a Newtonian fluid, is transformed into non-Newtonian fluid with the addition of nanoparticles. PAG oil up to 0.4 vol% alumina can be considered as an energy efficient alternative for refrigerant compressor oils.