Validation and analysis of organic rankine cycle dynamic model using zeotropic mixture

Abstract Organic Rankine cycle (ORC) is being researched widely in the application for waste heat recovery and renewable energy utilization. The ORC using zeotropic mixtures (MORC) attracts much attention for better match in heat transfer. The system with fluctuant heat source often faces safety and efficiency challenges and this drives the development of dynamic research. Modeling methods including finite volume (FV) and moving boundary (MB) can well predict the dynamic behavior of system with pure fluids, but the situation with zeotropic mixtures are unclear because of composition shift. In this case, this paper establishes the dynamic model of MORC by these two methods separately and compares the simulation with experiment. Results indicate that both methods have similar high accuracy and ignoring composition shift in MORC dynamic simulation is acceptable. The study on dynamic characteristics shows the system response speed of ORC with R134a/R245fa tends to increase with mass fraction of R134a. The system response speed is fastest with the disturbance of fluid mass flowrate comparing to exhaust temperature and flowrate. This work contributes to provide abundant reference for dynamic modeling of MORC and lay a foundation for the subsequent control design.