Numerical and thermo-energy analysis of cycling in automotive air-conditioning operating with hybrid nanolubricants and R1234yf

Abstract

Studies on automotive air-conditioning (AAC) systems involving compressor on-off cycling are still limited. This study focuses on improving the cycling of the AAC system using hybrid nanolubricants and hydrofluoroolefin-1234yf refrigerant. A dynamic model for an AAC system with a thermostatic switch that controls the on-off compressor was developed. The model was built in MATLAB Simulink and based on the state-space model using the fundamental conservation principles at the condenser, evaporator, and expansion valve. The experimental data were used to calculate the AAC system pressure, compressor, heat transfer coefficient of the condenser-evaporator, and expansion valve setting. The validation of the experimental data and the predicted data by the simulation suggested that the dynamic model could predict the AAC system’s performance within ±5% deviation. The AAC system operating with Al2O3-SiO2/PAG nanolubricants has a lower temperature cycling frequency than the AAC system with the original PAG lubricant, representing less energy consumed. In addition, the AAC system with hybrid nanolubricants was performed with lower power consumption and significantly higher cooling capacity than the original system. The present simulation confirmed the feasibility of hybrid nanolubricants for application in an AAC system with a thermostatic switch.