Design and Development of a Novel Air-Cycle Refrigeration System for Passenger Vehicles

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. The aim is to achieve passenger comfort using air as heat transfer medium and power input either from the engine exhaust air of an ICE vehicle or a secondary air compressor. The effect of performance of various components like heat exchangers and turbo machinery on the air-cycle system is also analyzed in the present study. It was found that the pressure ratio of the cycle and the expander efficiency play a very important role in the overall performance of the cycle and significant cooling can be achieved without refrigerant.