A thermodynamic analysis of various ejector expansions in R-744 trans-critical cycles at warm weather condition.

Refrigeration and air conditioning addresses fundamental human requirement in the fields like food conservation, health care and thermal comfort worldwide. Major research is currently focused towards improving the cycle efficiency of natural refrigerants as they have much lower GWP and ODP. Transcritical R-744 cycle is a promising refrigeration cycle using natural refrigerant. In this study, five different configurations of ejector expansion R-744 trans-critical cycle are identified from literature. Thermodynamic analysis of each are carried out using constant pressure mixing model assuming equivalent cooling load and warm weather operating condition. Performance parameters such as COP, entrainment ratio, pressure recovery and exergy destruction rate are compared for the various cycles by varying motive nozzle inlet condition and evaporator condition. Study clearly brings out relative merits of ejector expansion cycles in improving COP at warm weather operating condition.