Irreversibility distribution and characteristics within an ejector using zeotropic mixtures in the ejector refrigeration system

As energy crises and climate change intensify, ejector refrigeration systems using zeotropic mixtures offer potential for lower evaporation temperature and higher system performance. However, low ejector performance remains a key barrier. Reducing irreversibility inside the ejector is crucial, yet its characteristics with zeotropic mixtures are not understood. This work studies irreversibility characteristics within an R134a/R32 ejector using a two-dimensional numerical model coupling with direct entropy analysis method. Effects of primary flow and secondary flow mass fractions, primary flow and secondary flow temperatures, and ejector back pressure on entrainment ratio and four types of entropy generation are studied. Results show that turbulent dissipation entropy generation significantly contributes to the overall entropy generation. There exists an optimal entrainment ratio 0.401 as MF_R32,p equals 0.2, and direct dissipation entropy generation mainly occurs in the divergent part of the nozzle and in the mixing chamber. Mass transfer entropy generation primarily occurs where the primary and secondary flow meet and mix, it is the second most important factor affecting ejector performance as MF_R32,s equals 0.9, reaching 22.56%. Turbulent dissipation entropy generation reaches its minimum value 2.351 W·K⁻¹ at critical point. Results obtained in this work can be theoretical guidance for improving ejector performance using zeotropic mixtures and facilitate the application of ejector refrigeration systems with zeotropic mixtures.