Performance of super-critical CO₂ refrigeration cycle

The ideal super-critical refrigeration cycle of CO₂ is analyzed. For a given outlet temperature of the cooler, there is an optimum cooling pressure that maximizes the coefficient of performance (COP). When the COP reaches a maximum, the correlation between the cooler outlet temperature and cooling pressure can be expressed by a simple formula. The system COP can be improved by raising the evaporation temperature or enhancing the suction super-heat degree for low cooling pressure and elevating the cooler outlet temperature. When the evaporator and cooler outlet temperatures are high, a decrease in the heat transfer temperature difference of the regenerator can improve the specific cooling capacity and COP. The results can be used to guide the design and operation of super-critical CO₂ refrigeration system.