Thermodynamic analysis of low temperature refrigeration system with ammonia/carbon dioxide

Studied is a kind of ammonia/carbon dioxide two stage low temperature refrigeration system using exnergy analytic methods. The exergy loss of each part changing with the mean temperature is present at certain condensing temperature. The exergy efficiency of the system is simulated and analyzed by changing the mean temperature of the evaporator-condenser and the temperature of the condenser. It shows that evaporator and compressors are the maifi exergy loss parts; there exists an optimum mean temperature in evaporator-condenser to maximize the; exergy efficiency, and the maximal exergy efficiency of the system exists a peak point with heightening the condensing temperature.