First principles predictions of thermophysical properties of refrigerant mixtures

Abstract

Prediction of the phase behavior of acetonitrile and methanol with ab initio pair potentials. II. The mixture J. Chem. Phys. 116, 7637 (2002) We present pair potentials for fluorinated methanes and their dimers with CO 2 based on ab initio potential energy surfaces. These potentials reproduce the experimental second virial coefficients of the pure fluorinated methanes and their mixtures with CO 2 without adjustment. Ab initio calculations on trimers are used to model the effects of nonadditive dispersion and induction. Simulations using these potentials reproduce the experimental phase-coexistence properties of CH 3 F within 10% over a wide range of temperatures. The phase coexistence curve of the mixture of CH 2 F 2 and CO 2 is reproduced with an error in the mole fractions of both phases of less than 0.1. The potentials described here are based entirely on ab initio calculations, with no empirical fits to improve the agreement with experiment.

Vapor Liquid Equilibria of Hydrofluorocarbons Using Dispersion-Corrected and Nonlocal Density Functionals

“…[52][53][54][55][56][57][58][59][60][61][62] Furthermore, previous systems considered for FPMC had hydrogen bonding (water and methanol) and dispersion interactions (methane) as the dominant interactions. 42,43 HFCs selected here belong to a different class as these molecules, in addition to dispersion interactions, will have significant permanent dipole-dipole interactions, where upon thermal averaging, the leading order term goes as r −6 .…”

“…The aim of the present work is to assess the accuracy of KS-DFT by using different models that can account for dispersion interactions (PBE-D3, BLYP-D3, and rVV10) for predicting the vapor liquid coexistence curves (VLCC) of hydrofluoromethanes via FPMC simulations. We selected hydrofluoromethanes as hydrofluorocarbons (HFCs) are extensively used as a refrigerant in refrigerators and air conditioning units, fire suppression agents, propellant in the metered dose inhalers, etching agents, and blowing agent purposes. , The atmospheric concentration of HFCs is rapidly increasing and causing great environmental concern due to their greenhouse potential. , Due to their technological and environmental relevance, HFCs have been the focus of a number of experimental − and simulation studies. − Furthermore, previous systems considered for FPMC had hydrogen bonding (water and methanol) and dispersion interactions (methane) as the dominant interactions. , HFCs selected here belong to a different class as these molecules, in addition to dispersion interactions, will have significant permanent dipole–dipole interactions, where upon thermal averaging, the leading order term goes as r –6…”

Calculation of Partition Functions and Free Energies of a Binary Mixture Using the Energy Partitioning Method: Application to Carbon Dioxide and Methane

“…Free energy can be used to predict the vapor–liquid equilibrium properties and many other thermodynamic properties, including critical phenomena and pVT data for single phases. Of particular interest to us are mixtures that contain carbon dioxide (CO 2 ). − Systems of CO 2 in multicomponent mixtures with light paraffins are important to the natural gas industry, since it has become common practice to process gas streams with moderate to high levels of CO 2 . Supercritical CO 2 is a novel solvent that has attracted much attention .…”

Density of States Partitioning Method for Calculating the Free Energy of Solids

“…Of particular interest to us are systems that contain carbon dioxide (CO 2 ). ,− While the fluid phase of CO 2 has been extensively studied in molecular simulation, its solid phase has received rather less attention. In this paper, we apply our new DOS partitioning method together with the cage model to calculate the free energy of CO 2 cubic phase I, commonly known as dry ice.…”