Thermodynamic Analysis of a Marine-Type ORC Waste Heat Recovery System Using Zeotropic Mixtures of HCFO and HFO Refrigerants

This study aims to investigate the energetic and exergetic performance of an exhaust gas-driven recuperative ORC waste heat recovery system using zeotropic mixtures. Working fluids with zero ozone depletion potential and very low global warming potential (<10), including R1234ze (Z), R1336mzz (Z), R1224yd (Z), and R1233zd (E), are selected and mixed in various compositions. The effects of temperature glide, mass fraction, and evaporation pressure on thermodynamic performance are explored. Results show that using mixtures instead of pure fluids can enhance thermal and exergy efficiency by 5.1% to 9.4%, with a 7.2% reduction in exergy destruction when using an R1336mzz (Z)/R1233zd (E) (0.9/0.1) mixture.