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

Cai, Jinwen, Shu, Gequn, Tian, Hua, Wang, Xuan, Wang, Rui, Shi, Xiaolei
Energy 2020 v.197 pp. 117003
dynamic models, renewable energy sources, temperature, waste heat recovery
Organic Rankine cycle (ORC) is being widely researched in the application of waste heat recovery and renewable energy utilization. The ORC using zeotropic mixtures (MORC) attracts much attention owing to the ability to match better in heat transfer. The system with fluctuant heat source often encounters challenges of safety and efficiency and this issue 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 effect. 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 the composition shift effect in MORC dynamic simulation could be acceptably ignored. The following study on dynamic characteristics shows the response speed of ORC system with R134a/R245fa tends to increase with mass fraction of R134a. The system response speed with the disturbance of fluid mass flowrate is the fastest 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.