Today the Organic Rankine Cycle (ORC) is considered as one of the most promising technologies to recover the power from low-grade heat resources.In order to realize a high performance ORC turbine,the Computational Fluid Dynamics (CFD) is extensively used to simulate the internal flow in the aerodynamic design.But due to the high non-ideality of the working fluid,it is crucial to take the real gas effect into consideration.In the present study,an accurate and reliable method of the perfect gas approximation for an organic working fluid (R245fa) is developed.At first,the effectiveness of a perfect gas approximation is examined in two-dimensional CFD simulations of a convergent-divergent nozzle.Then the accuracy of the perfect gas approximation,definition of suitable non-dimensional performance parameters and effective conversion method between the different gas models are studied in three-dimensional CFD simulations of an ORC radial-inflow turbine.
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