A generalized Kiselev crossover approach applied to Soave–Redlich–Kwong equation of state

Abstract

Three different variants of the crossover Soave-Redlich-Kwong equation of state are applied to describe the equilibrium behaviour of 72 common fluids -27 hydrocarbons (including the first 10 n-alkanes), 36 halogenated refrigerants, 5 cryogenics (fluorine, oxygene, nitrogene, argon and carbon monoxide) and 4 other industrially important inorganic fluids (carbon dioxide, sulfur dioxide, nitrous oxide and sulfur hexafluoride). The model contains six compound dependent parameters; two of them (a 0 and b of the classical part) are adjusted to reproduce the critical temperature and the critical pressure. Within the first approach (model A), the remaining four parameters -the softness of dispersion interactions m and three parameters of the crossover part (G i , d 1 and v 1 ) -are optimized to reproduce the coexistence densities and the saturation pressure over the whole vapor-liquid region and also the pressure along the critical-and one supercritical isotherms. In the second model (model B), mutual relation between two of the crossover parameters is employed (v 1 = v 1 (G i )) and distersion softness m is expressed as a qudratic function of acentric factor ω. Using these two constrains, the crossover parameter G i (and also v 1 ) becomes correlated to rectlinear diameter r d or 1 critical compression factor Z c . It is also found, that the crossover parameter d 1 has a minor effect on the equilibrium properties. In the third model (model C), this parameter is omitted and the remaining parameters are estimated from knowledge of critical properties (a 0 and b), acentric factor (m) and rectlinear diameter (G i ). The overall quality of model C -which requires only the knowledge of the critical properties, acentric factor and rectlinear diameter -is worse compared to the two models with fitted parameters. However, it is superior to classical cubic equations of state as for the liquid coexistence densities and superior to equations optimized to reproduce the liquid densities (PCSAFT, CPA) as for the description in the critical region. The model C is applied to describe the equilibrium behaviour of two compounds not included in the parametrization, hexafluoropropene (HFO1216) and hexafluoropropene oxide (HFPO), with acceptable quality.

Prediction of thermodynamic properties of refrigerant fluids with a new three-parameter cubic equation of state

“…The density in the critical region is well represented by using the NEoS, compared to the other EoSs considered in this work. However, this prediction could be better by combining the NEoS with a renormalization group theory [44], [45], using a crossover approach [46], [47] or the White's recursive method [48]. Such a study will be carried out in a future work.…”

Modeling the Critical and Phase Equilibrium Properties of Pure Fluids and Mixtures with the Crossover Cubic-Plus-Association Equation of State

“…The classical values for these two exponents are 0.5 and 3.0, while the ones obtained in our calculations are 0.370 and 4.668, respectively, which are closer to the universal values 0.326 and 4.8. 44 (a)…”

Vapor–liquid equilibrium and molecular simulation data for carbon dioxide (CO2) + trans-1,3,3,3-tetrafluoroprop-1-ene (R-1234ze(E)) mixture at temperatures from 283.32 to 353.02 K and pressures up to 7.6 MPa

“…It is right that the evolution of binary interaction parameters with temperature is better described by SAFT type models, but it is well known that SAFT type models are not good to calculate critical point [41]. It is still possible to correct the predicting capability of SAFT type models with crossover theory [42] [43].…”