Theoretical evaluation of trans-critical CO2 systems in supermarket refrigeration. Part II: System modifications and comparisons of different solutions

The performance of CO2 refrigeration systems strongly depends on the operating conditions. The specific characteristics of low critical temperature and high operating pressure limit its applications and imply the implementation of different control strategies. This study compares the performance of different CO2 system solutions for supermarket refrigeration with R404A system. Some possible modifications and improvements on the CO2 system have been investigated. The COP of the investigated CO2 system solution can be improved by about 3–7% along the ambient temperature range of 10–40 °C. The annual energy consumption calculations in three different climates; cold, moderate and hot, show that the centralized trans-critical CO2 system is good solution for cold climates whereas the NH3–CO2 cascade system has the lowest energy consumption in hot climates. Both systems proved to be good alternatives to R404A DX system for supermarket refrigeration.