| Abstract
| - In a preceding project, functional forms for “short” Helmholtz energy equations of state for typical nonpolar andweakly polar fluids and for typical polar fluids were developed using simultaneous optimization. In this work,the coefficients of these short forms for the equations of state have been fitted for the fluids acetone, carbonmonoxide, carbonyl sulfide, decane, hydrogen sulfide, 2-methylbutane (isopentane), 2,2-dimethylpropane(neopentane), 2-methylpentane (isohexane), krypton, nitrous oxide, nonane, sulfur dioxide, toluene, xenon,hexafluoroethane (R-116), 1,1-dichloro-1-fluoroethane (R-141b), 1-chloro-1,1-difluoroethane (R-142b), octafluoropropane (R-218), 1,1,1,3,3-pentafluoropropane (R-245fa), and fluoromethane (R-41). The 12 coefficients ofthe equations of state were fitted to substance specific data sets. The results show that simultaneously optimizedfunctional forms can be applied to other fluids out of the same class of fluids for which they were optimizedwithout significant loss of accuracy. The high numerical stability of the functional forms resulted in successfulfits for fluids that previously could not be described by accurate empirical equations of state. For R-41, it isshown that the accuracies can be increased further by fitting the temperature exponents in addition to the coefficientsof the equation of state, provided that highly accurate experimental data are available. Typical uncertainties ofproperties calculated using the new equations are 0.2 % in density, 1 % to 2 % in heat capacity and liquid-phasespeed of sound, and 0.2 % in vapor pressure. Where data are available, uncertainties in vapor-phase sound speedsare generally less than 0.1 %.
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