▎ 摘　　要

The addition of nanoparticles is a state-of-the-art method to enhance the thermophysical, heat transfer, and tribological characteristics of cooling and lubricating fluids. In the present study, a novel nanolubricant (graphene + polyalkylene glycol (PAG)) is prepared, experimental investigations are performed to evaluate the thermal, rheological, and tribological characteristics of the nanolubricant, and finally, the nanolubricant is applied in a vapour compression refrigeration system (VCRS) pose as an energy-efficient alternative lubricant in refrigeration systems. Furthermore, regression correlations are developed to predict the thermal conductivity and viscosity of the nanolubricant. The results show that the addition of graphene nano-platelets to the oil has the potential to improve the thermophysical properties and friction reduction and anti-wear characteristics. Moreover, the energy consumption in the hermetic reciprocating compressor is diminished by 5.7%, the heat transfer rate in the evaporator is increased by 5.5%, and eventually, the coefficient of performance (COP) of the system upsurges by 12.26%, when graphene nanolubricant is used within the system. The studies show that the application of graphene in PAG oil is an excellent option to improve energy efficiency and the COP of refrigeration systems.