Thermodynamic comparison of ejector cooling cycles. Ejector characterisation by means of entrainment ratio and compression efficiency

Most of the energy consumed in cooling cycles comes from fossil fuels, whose reserves are becoming depleted. The aim of this article is to show the potential benefits of using ejectors in cooling systems to improve its energetic efficiency. A review of different configurations of ejector cooling systems has been carried out for being compared against a conventional compressor cycle. The same cooling capacity and working conditions were imposed by using refrigerants R134a, R1234yf and R600a. The results showed that the Coefficient of Performance could increase up to 26%. Ejectors have been characterised by correlations of entrainment ratio and a new definition of ejector compression efficiency. Those correlations have been obtained by means of a pseudo-one dimensional method of ejector analysis. Ejector cooling systems were proven to be a potential alternative to conventional vapour compression cycles.