The influence of cubic real-gas equations of state in the supersonic regime of dense gases

Real-gas effects should be considered in ORC expanders, particularly in a supersonic flow. This study deals with the numerical evaluation of cubic real gas models in a supersonic R245fa flow over a wedge-shaped cascade. The NIST Refprop real gas model was selected as a benchmark model, and four other cubic real gas equations of state (EoS) were evaluated with respect to the reference model. The four cubic real gas EoS are studied. The results show that the Peng-Robison EoS is the most accurate model with an average error of less than 1.1 % for Mach number prediction for 3 different sections, and its computational cost is 39 % lower than NIST. However, the Aungier-Redlich-Kwong EoS model shows better performance accuracy and the computational cost with an average error of 1.7 % for Mach number prediction and a 17 % computational cost lower than NIST. Therefore, using this model is recommended for modeling R245fa in the supersonic regime.