Ideal Gas Heat Capacity and Critical Properties of HFE-Type Engineering Fluids: Ab Initio Predictions of Cpig, Modeling of Phase Behavior and Thermodynamic Properties Using Peng-Robinson and Volume-Translated Peng-Robinson Equations of State

Hydrofluoroethers (HFEs) represent a new generation of promising engineering fluids for heat transfer or cleaning applications. In this work, quantum chemistry calculations (qcc) were employed to obtain ideal gas heat capacities, C-p(ig), for the selected HFEs and comparisons were made against the group contribution (GC) methods by Rihani and Doraiswamy, Yoneda, and Joback. Comparison between B3LYP/6-31++ G(d,p) density functional theory (DFT) and Hartree-Fock (HF) methods showed that HF method provides better representation of the available experimental gas-phase speed of sound data for HFE-7000. Critical properties and acentric factors of the selected HFEs were optimized and compared to the other reported values. The Peng-Robinson equation of state (PR EoS) combined with the C-p(ig) correlation, allowing calculation of the ideal gas Helmholtz free energy, was used to model a complete set of thermodynamic properties of the five selected HFEs; namely HFE-7000, HFE-7100, HFE-7200, HFE-7300, and HFE-7500. The volume-translated (VT) PR EoS was also tested as an alternative. The accuracy of PR EoS for representing the phase behavior and caloric properties of the selected HFEs was analyzed based on the comparison with nearly 3500 experimental data points and a preliminary multiparameter EoS available for HFE-7000. Although relatively simple, but still widely used, PR EoS was found to provide reasonable vapor-liquid predictions for HFEs and, as such, can be used effectively in the design of their various applications. In addition, a vapor pressure correlation and the critical compressibility factor were analyzed from the view of application on various alternative refrigerants such as HFEs and hydrofluoroolefines. [GRAPHICS] .

Automated summary

This study utilized quantum chemistry calculations to investigate Hydrofluoroethers (HFEs), optimizing and comparing their ideal gas heat capacities and critical properties. The results indicate that the Peng-Robinson equation of state performs well in simulating the thermodynamic properties of HFEs and can be effectively used in the design of various applications.