Performance of High Pressure Air Cycle in Comparison With Synthetic and Natural Vapor Compression Refrigeration Cycles

Concerning the use of HFCs as substitutes for CFCs and HCFCs a major concern in applications with remarkable leakages of refrigerant is its contribution to global warming. Therefore, the attention has been drawn to the use of natural working fluids, like carbon dioxide, hydrocarbons, water and air. Air had been already used in the range of air conditioning technology. Air as refrigerants is standard in air conditioning of airplanes and also in the Inter-City-Express 3 of the German Railways. A research project of air cycle technology for transport refrigeration had been already reported by FKW at the Purdue Conference of 1996. In order to apply high pressure equipment as developed recently for transcritical carbon dioxide systems the singlestage high pressure air cycle process has been investigated theoretically as an alternative solution to conventional vapor compression systems with HFC-refrigerants and even to CO2-systems. An evaluation of the high pressure air cycle system has been done concerning their energetic and volumetric performances.