Vapor–liquid equilibrium of copolymer+solvent mixtures: Thermodynamic modeling by two theoretical equations of state

2006 ◽  
Vol 246 (1-2) ◽  
pp. 52-63 ◽  
Author(s):  
Pedro F. Arce ◽  
Silvana Mattedi ◽  
Martín Aznar
Keyword(s):  
Thermodynamic Modeling ◽  
Equations Of State ◽  
Solvent Mixtures ◽  
Liquid Equilibrium ◽  
Vapor Liquid Equilibrium ◽  
Vapor Liquid

VAPOR–LIQUID EQUILIBRIUM MODELING FOR MIXTURES OF HFC-32 + ISOBUTANE AND HFC-32 + HFO-1234ze(E)

2011 ◽  
Vol 19 (02) ◽  
pp. 93-97 ◽  
Author(s):  
RYO AKASAKA
Keyword(s):  
Free Energy ◽  
Helmholtz Free Energy ◽  
Equations Of State ◽  
Dew Point ◽  
Working Fluid ◽  
Liquid Equilibrium ◽  
Vapor Liquid Equilibrium ◽  
Equilibrium Modeling ◽  
Independent Variables ◽  
Vapor Liquid

Vapor–liquid equilibrium (VLE) have been successfully modeled for the binary mixtures of difluoromethane (HFC-32) + isobutane and difluoromethane + trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)). These mixtures are considered as possible replacements for conventional refrigerants far from negligible global warming potential (GWP). A multifluid approach explicit in the Helmholtz free energy forms the basis of the model. The independent variables are the temperature, density, and composition. Accurate published equations of state for pure HFC-32, isobutane, and HFO-1234ze(E) are incorporated to calculate the Helmholtz free energy of each component. Typical uncertainties of bubble- and dew-point pressures calculated using the model are within 2%. Although adjustable parameters of the model are determined only from experimental VLE data, it is highly probable that the model reasonably predicts other thermodynamic properties such as enthalpy and heat capacities. Therefore, the model allows practical design and simulation of refrigeration systems using the mixtures as a working fluid.

scholarly journals Comparison of Cubic-Plus-Association and Soave-Redlich-Kwong equations of state for prediction of vapor-liquid equilibrium of Fischer-Tropsch reaction mixture

2019 ◽  
Vol 25 (1) ◽  
pp. 67-76
Author(s):  
Ljiljana Zivanic ◽  
Marko Stamenic ◽  
Branislav Todic ◽  
Dragomir Bukur ◽  
Nikola Nikacevic
Keyword(s):  
Liquid Phase ◽  
Equations Of State ◽  
Space Velocity ◽  
Computational Time ◽  
Feed Ratio ◽  
Process Conditions ◽  
Liquid Equilibrium ◽  
Fischer Tropsch ◽  
Vapor Liquid Equilibrium ◽  
Vapor Liquid

Predictions of vapor liquid equilibrium for Fischer-Tropsch mixtures were compared using the classical Soave-Redlich-Kwong (SRK) and cubic-plus-association (CPA) equations of state. The performance of the two equations of state was evaluated based on comparison with results from eight sets of experimental runs in which different process conditions (pressure, reactants feed ratio, space velocity) were used. Flash calculations were used to determine the phase split at defined process conditions, whereas the phase equilibrium was defined utilizing the concept of equal fugacities in the vapor and the liquid phase for all components. A total of 75 components were considered in the reaction mixture: CO, H2, H2O, CO2, C1-C57 paraffins and C2-C15 olefins. All calculations were performed in MATLAB. The results showed that both equations of state had similar performance regarding the hydrocarbons, whereas CPA gave better results with inorganic components and SRK with prediction of the composition of the liquid phase. Computational time for CPA was substantially (100 times with the CPU used) higher than that for SRK. Overall, the use of CPA did not improve VLE prediction for FTS systems significantly enough to be recommended for use in FTS reactor models.

Renormalization Group Theory Applied to the CPA Equation of State: Impacts on Phase Equilibrium and Derivative Properties

2019 ◽  
Author(s):  
Gabriel Silva ◽  
Charlles Abreu ◽  
Frederico W. Tavares
Keyword(s):  
Renormalization Group ◽  
Equation Of State ◽  
Thermodynamic Properties ◽  
Chemical Engineering ◽  
Equations Of State ◽  
Thermodynamic Description ◽  
Critical Conditions ◽  
Liquid Equilibrium ◽  
Vapor Liquid Equilibrium ◽  
Vapor Liquid

Calculation of thermodynamic properties such as vapor-liquid phase behavior with equations of state is largely and successfully employed in chemical engineering applications.<br>However, in the proximities of the critical point, the different density-fluctuation scales inherent to critical phenomena introduce significant changes in these thermodynamic properties, with which the classical equations of state are not prepared to deal.<br>Aiming at correcting this failure, we apply a renormalization-group methodology to the CPA equation of state in order to improve the thermodynamic description in the vicinity of critical points.<br>We use this approach to compute vapor-liquid equilibrium of pure components and binary mixtures, as well as derivative properties such as speed of sound and heat capacity.<br>Our results show that this methodology is able to provide an equation of state with the correct non-classical behavior, thus bringing it in consonance with experimental observation of vapor-liquid equilibrium and derivative properties in near-critical conditions.

Vapor liquid equilibrium modeling of alkane systems with Equations of State: “Simplicity versus complexity”

2006 ◽  
Vol 240 (2) ◽  
pp. 127-139 ◽  
Author(s):  
Epaminondas C. Voutsas ◽  
Georgia D. Pappa ◽  
Kostis Magoulas ◽  
Dimitrios P. Tassios
Keyword(s):  
Equations Of State ◽  
Liquid Equilibrium ◽  
Vapor Liquid Equilibrium ◽  
Equilibrium Modeling ◽  
Vapor Liquid
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