Comparing the predictive ability of two- and three-parameter cubic equations of state in calculating specific heat capacity, Joule – Thomson coefficient, inversion curve and outlet temperature from Joule – Thomson valve

Abstract

In this study, six cubic equations of state (CEoSs) were used to predict the Joule-Thomson coefficient (JTC), specific heat capacity (SHC), inversion curve (IC) and outlet temperature of the Joule-Thomson (JT) valve parameters. The accuracy of each CEoS was evaluated from the comparison of experimental data with obtained results. Of the six CEoSs, three-paramter CEoSs— Esmaeilzadeh and Roshanfekr (ER), Harmen and Knapp (HK), and Patel and Teja (PT)— were more accurate than two-paramter equations— Nasrifar and Moshfeghian (NM), Peng-Robinson (PR), and Soave-Redlich-Kwong (SRK). Ironically, original SRK showed the optimum accuracy in estimation of JTC. In addition, the Joule-Thomson inversion curves (JTIC) were plotted for pure gases. Most of the CEoSs showed reasonable prediction on low-temperature branch of JTIC, but only original SRK and PT CEoSs estimated well at high-temperature branch. For two-parameter CEoSs, the effect of employing different α-functions and adding volume translation factor were also examined. The error analysis showed that the accuracy of original PR CEoS was significantly improved when volume translation factor was included as a third parameter. In addition, the SRK-Twu88 and PR-Twu91 CEoSs showed higher accuracy in prediction of SHC as compared to original SRK and original PR.