A state of art review on future low global warming potential refrigerants and performance augmentation methods for vapour compression based mobile air conditioning system.

The use of vapor compression system-based air-conditioning units is predominant in conventional fossil-fueled and electric vehicles. Mobile air-conditioning (MAC) units play a significant role in direct and indirect CO2 emissions from vehicles. Refrigerant and component efficiency are the major factors that determine CO2 emissions from air-conditioning units. Therefore, it is essential to enhance the performance of MAC systems using environmentally friendly refrigerants that satisfy environmental requirements. In this study, we demonstrated the measures taken to minimize CO2 emissions by replacing high global warming potential HFC-134a, charge optimization methods, and performance enhancement strategies. HFO-1234yf could be better alternative for retrofitting HFC-134a, although it exhibited a slightly poor performance with mid-flammability. Mixtures of hydrocarbon-based refrigerants are suitable for secondary loop applications, and R-744 is the best option in cold climates. During charge optimization, the subcooling and superheating plateau methods were mostly adopted. To enhance system performance, most researchers have used variable displacement compressors, efficient microchannel evaporators, integrated received drier condensers, and suction line heat exchangers. Recently, Nano-seeded lubricants have been used in some MAC applications; however, further research is required on the condensation and evaporation aspects. The present review could be very helpful for researchers and manufacturers in developing MAC systems with lower CO2 emissions. [ABSTRACT FROM AUTHOR]