Study of the performances of an ejector refrigeration cycle using CO2-based mixtures in subcritical and transcritical mode

Authors: Chaabane Abdou, Hakim Madani, Abdelmalek Hasseine

Volume 10, Issue 3, Paper No. 100304


  The negative impact of actual refrigerants on the environment urged conduct to search for new refrigerants with low global warming potential (GWP). CO2 is one of the promising alternatives; however, its thermodynamic properties impose a transcritical cycle that has a low energy efficiency. In the present study, a simulation program was developed to investigate the performances of an ejector refrigeration cycle working with three CO2-based mixtures: (CO2+R290), (CO2+R1234yf), and (CO2+R600a) according to subcritical mode and (CO2+R116) under transcritical mode. The addition of other pure compounds to CO2 displaces the critical point and modifies the phase equilibrium lines resulting in a reduction in operating pressures and an increase in the energy efficiency of the refrigeration cycle. Simulation results showed that the Suction Nozzle Pressure Drop (SNPD) has a significant impact on the performance of the cycle and has no effect on the entrainment ratio of the ejector. Moreover, it was found that there is an optimal SNPD which gives maximum COP and pressure recovery. It was also noticed that the maximum performance of the refrigeration cycle with a subcritical ejector depends on the evaporation and the condenser temperatures.

Keywords: CO2, Binary mixtures, Ejector, Subcritical cycle, Transcritical cycle, Numerical Simulation.

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