A novel transcritical CO2 refrigeration cycle with two ejectors

In recent years, CO2 is being revisited as a fully environmentally friendly and safe refrigerant. However, basic CO2 transcritical refrigeration cycle suffers from large expansion loss due to high pressure difference between gas cooler and evaporator. Then, it is crucial to find effective and economic way to reduce the expansion loss. Here, a novel cycle with two ejectors is proposed for the first time. Compared with conventional ejector-expansion CO2 cycle with only one ejector, this novel cycle with two ejectors is able to recover more expansion loss, thus improving the system performance further. A computational model is designed to simulate the double ejector CO2 cycle. Simulation results show its high system COP. Effects of parameters, such as ejector nozzle efficiency, gas cooler pressure, entrainment ratios of the two ejectors, gas cooler outlet temperature, on the cycle performance are also analyzed by using the computational model.

► We propose a novel CO2 transcritical cycle with two ejectors for the first time.
► This cycle can further recover expansion loss compared with single-ejector one.
► We model this new cycle and analyze its thermodynamic characteristics.
► Numerical results show much higher COP of the double ejector cycle than basic and single ejector one.