Aplicação de nanopartículas de grafeno como aditivo de lubrificante POE em um sistema de refrigeração

Abstract

This study investigates the application of graphene-based nanolubricants in refrigeration systems, aiming to assess their primary effects on system performance. To achieve this, a dedicated experimental refrigeration bench was developed, specifically designed to minimize external interferences by incorporating advanced techniques and components to mitigate such influences. Key features include the use of plate heat exchangers for both evaporators and condensers, the integration of a secondary thermal load control system, thermal insulation, temperature sensors, and an automated control system. The experimental analysis focused on critical performance parameters, including cooling capacity, compressor power consumption, coefficient of performance (COP), discharge temperature, compressor shell surface temperature, and oil sump (crankcase) temperature. Graphene nanolubricants were tested at mass concentrations of 0.005%, 0.01%, 0.05%, and 0.1%, using R290 refrigerant under varying operating conditions: evaporation temperatures from -10 °C to 5 °C, condensation temperatures from 30 °C to 50 °C, and a fixed superheat of 10 K. In addition, the thermophysical properties of the graphene nanolubricants, such as density, viscosity, and thermal conductivity, were characterized through laboratory testing. The results show that, under certain conditions, the use of nanolubricants led to increases in cooling capacity and coefficient of performance, as well as reductions in power consumption. In some situations, increases in compressor discharge and surface temperatures, as well as reductions in crankcase temperature, were also observed.