Thermodynamic analysis of a novel multi-target temperature transcritical CO2 ejector-expansion refrigeration cycle with vapor-injection

In the present paper, a multi-target temperature ejector-expansion subcooler vapor-injection refrigeration cycle is proposed in order to improve the performance of natural fluid CO2 refrigeration cycles. A thermodynamics model to simulate a two-phase ejector cycle integrating a vapor-injection is first established from the energetic and exergetic perspectives. The behavior of the new cycle is then analyzed, and the adjustment direction of the cooling capacity and the evaporating temperature is pointed out. Furthermore, the new cycle is also compared with the subcooler vapor-injection refrigeration cycle and the ejector-expansion refrigeration cycle. The obtained results show that the behavior of the evaporators is affected by the bypass mass ratio and the entrainment ratio, and the two parameter determines the direction of adjusting the cooling capacity distribution and the evaporating temperature. The COP of the new cycle is about 17.9-29.4% and 2.8-7.8% higher than that of subcooler vapor-injection refrigeration cycle and ejector-expansion refrigeration cycle; the exergy efficiency of new cycle is about 14-28.2% and 3.7-11.3% higher than that of subcooler vapor-injection refrigeration cycle and ejector -expansion refrigeration cycle; and it is also found that the performance of the new cycle is improved more significantly under low cooling temperature and high ambient temperature conditions.

Automated summary

A multi-target temperature ejector-expansion subcooler vapor-injection refrigeration cycle is proposed to improve the performance of natural fluid CO2 refrigeration cycles. A thermodynamics model is established to simulate the new cycle, and the results show that the new cycle has higher COP and exergy efficiency compared to traditional cycles, with more significant performance improvement under low temperature and high ambient temperature conditions.