Numerical Evaluation of Equation of State Sensitivity in Energy Conversion Systems

Improving energy efficiency by minimizing waste heat losses has become a critical objective in industrial and transportation applications. Organic Rankine Cycles (ORCs) offer an effective solution for converting low-grade thermal energy into useful power. However, the accuracy of ORC performance predictions depends heavily on the thermodynamic property models, particularly the choice of equation of state. This study investigates how different equations of state models influence key thermodynamic predictions in an ORC operating with R245fa and high-temperature waste heat. A range of equations of state formulations are evaluated, from simplified ideal gas models to more complex real-fluid models. The results showed that the choice of equation of state can have a noticeable impact on the predicted cycle performance (up to 7.14% in some cases), highlighting the importance of accurate fluid property modeling when designing ORC systems. The sensitivity analysis indicated that minor variations in enthalpy values (±1%) can result in a 3–4% alteration in net power output, highlighting the need for precise property modeling in Organic Rankine Cycle design.