Thermodynamic Modeling and Simulation of an Organic Rankine Cycle-Ejector Heat Pump-Based Trigeneration System Using a Zeotropic Mixture

Abstract

To solve the problem of low thermal efficiency of the organic Rankine cycle (ORC) and to enhance the coefficient of performance (COP) of ejector refrigeration cycle, an ORC combined with an ejector heat pump-based combined cooling, heat and power system using a zeotropic working fluid mixture is proposed in this paper. Utilization of zeotropic mixtures could improve the thermodynamic performance of ORC systems owing to superior fits of the temperature profiles of the working fluid and the heat source/sink. A thermodynamic model is built to predict the performance of the proposed trigeneration system using butane/propane zeotropic mixture. The model was validated with data obtained from the open literature. It was then applied to investigate and optimize the effect of a wide range of parameters on system performance. A detailed parametric analysis was then performed to assess the influence of generator temperature and entrainment ratio on the system’s heating, cooling and power efficiencies, exergy and thermal efficiencies, and COP. The analysis also examined the effect of mass fraction on the system’s power and cooling efficiencies. The results disclosed that for the zeotropic butane/propane mixture with mass fractions of 0.5/0.5, a generator temperature of 75°C and entrainment ratio of 0.5 produced a net power output of 136.3 kW, with a power efficiency of 4.6 %, a heating efficiency of 95.4%, a cooling efficiency of 42.9%, and a COP of 1 .43. With such thermodynamic analysis, the study demonstrated that the proposed system is feasible.