Fast and accurate CO2 properties calculation algorithm for massive numerical simulations of supersonic two-phase ejectors

Fang, Yu [UCL] De Lorenzo, Marco [Compressor Controls Corporation] Lafon, Philippe [French National Centre for Scientific Research, CNRS · IMSIANot specified] Poncet, Sébastien [Université de Sherbrooke] Bartosiewicz, Yann [UCL] Nesreddine, Hakim [Laboratoire des technologies de l'énergie, Canada]

This work presents a look-up table method to compute the thermodynamic properties of CO2. It is motivated by the massive employment of this fluid in the industrial domain, especially in the ejector-expansion cycle. Computational Fluid Dynamics (CFD) simulations have been used in the past to investigate two-phase ejector flows. CO2 exhibits then large property variations due to phase transition. As a result, it cannot be accurately modelled by a general analytical Equation of State (EoS), such as Peng-Robinson EoS and Perfect gas EoS, etc. Hence, a tabulated EoS is developed here based on the Span-Wagner (EoS), covering the temperature range from 217 to 800 K and pressures up to 50 MPa. Supercritical, liquid, vapor and liquid-vapor states are all included in this tabulated EoS. Besides, the density and the internal energy are chosen as two independent inputs to compute the other properties. The method is designed to be coupled with the system of equations in its conservative form which is a usual formulation for compressible solvers. Through two validation cases, the proposed tabulated EoS shows good performances in terms of accuracy and efficiency, making it suitable for future massive CFD simulations.