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 (MTES) refrigeration cycle is proposed in order to improve the performance of natural fluid CO2 refrigeration cycles. In this respect, 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 MTES cycle is then analyzed, and the adjustment direction of the cooling capacity and the evaporating temperature is pointed out. Furthermore, the METS cycle is also compared with the subcooler vapor-injection refrigeration cycle (SRC) and the ejector-expansion refrigeration cycle (ERC). The obtained results show that the behavior of the evaporators is affected by the bypass mass ratio (R) and the entrainment ratio (ω), and the two parameter determines the direction of adjusting the cooling capacity distribution and the evaporating temperature. The COP of the MTES cycle is about 25% and 6% higher than that of SRC cycle and ERC cycle; the exergy efficiency of MTES cycle is about 21% and 8% higher than that of SRC cycle and ERC cycle; and it is also found that the performance of the MTES cycle is improved more significantly under low cooling temperature and high ambient temperature conditions