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Current Air Conditioning (AC) system uses hydrofluorocarbons (HFC) as refrigerant to transfer heat from cabin and cool the passengers. However, most refrigerants used today have severe environmental effects due to high global warming potential leading to global warming effects. Montreal Protocol and Kigali amendment calls for all nations to reduce refrigerant usage and transport sector being one of the main consumer of refrigerant, regulations regarding refrigerant usage and emission are becoming more stringent day by day. In this paper, a novel air-cycle refrigeration system has been designed and also tested for passenger vehicle applications. Automobile industry in developed countries has pivoted to R1234yf refrigerant for the most part, and has also rolled out R744 refrigerant for mass production to limited extent, which are in much lower Global warming potential (GWP) range than R134a.

In present day passenger cars, Mobile Air Conditioning (MAC) system is one of the essential features due to rise in overall ambient temperatures and comfort expectation of customers. During the development of MAC system, the focus is on cooling capacity of system for maintaining in-cabin temperatures. However, parameters like solar radiation, air velocities at occupant, relative humidity, metabolic rate and clothing of occupants also influence occupant’s thermal comfort and normally not considered in design of the MAC system. Subjective method is used to evaluate thermal comfort inside vehicle cabin which depends mainly on human psychology. To better understand the effect and minimize the human psychological factors a large sample of people are required. That process of evaluating the comfort inside the vehicle cabin is not only time consuming but also impractical.