The air cycle refrigeration system used in Chinese train air conditioning engineering is investigated. The effects of possible
parameters affecting system performance are examined through sensitive analysis of the thermodynamic model. The results show
that, the pressure ratio should be in the range of 2-2.5, the COP will be in the range of 1-1.2, and the cold air distribution system
can be used. To increase the COP, higher efficiencies of compressors, expanders and heat exchangers are expected.