Present status of the group contribution equation of state VTPR and typical applications for process development

Schmid, Bastian; Gmehling, Jürgen

doi:10.1016/j.fluid.2016.06.042

Cited by 15 publications

(11 citation statements)

References 18 publications

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“…They called it Chain-FV and using diverse ways to get the Cparameter, for example, as r/q (ratio of the vdW volume over area), they obtained improved results over the Flory−Huggins and the free-volume model of Elbro et al 80 for activity coefficients of alkanes, solid−liquid equilibrium calculations, and against molecular simulation data. When C = 1, the model results to the same "comb-FV" term proposed by Elbro et al 68 and also implied in the van der Waals equation. There are no rigorous approaches to predict the C-parameter, and different (rather similar values) have been proposed in the literature in models which use this parameter, like the UNIFAC-FV model by Oishi and Prausnitz 81 and the Flory equation of state.…”

Section: Journal Of Chemical and Engineering Datasupporting

confidence: 75%

“…This approach was popular at the start with models such as MHV1/MHV2 (Dahl and Michelsen 89 ) and PSRK (Gmehling 90 ), but it turned out that poor results are obtained for sizeasymmetric systems due to "changing in the wrong direction" the combinatorial-free volume term of the equation of state. These problems were corrected by semiempirical approaches such as LCVM (Boukouvalas et 68 Moreover, the MHV1/PSRK/MHV2 models are only "approximate zero reference pressure" models as the approximations introduced essentially change the reference pressure to an approximate zero one (see Kontogeorgis and Coutsikos, 50 for details). Thus, we believe that the infinite pressure Huron−Vidal approach is the most promising way forward (the approach also used in the Wong−Sandler and VTPR models).…”

Section: Journal Of Chemical and Engineering Datamentioning

confidence: 99%

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Taking Another Look at the van der Waals Equation of State–Almost 150 Years Later

2019

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The van der Waals (vdW) equation of state has long fascinated researchers and engineers, largely because of its simplicity and engineering flexibility. At the same time as vdW and other equations of state (EoS) have been proposed, at first mostly used for petrochemical applications, solution theories in the form of activity coefficient models have been developed, focusing on the accurate representation of the liquid phase, of interest to the chemical industry. For both the van der Waals (and other cubic EoS) and the activity coefficient models we can identify size and energy terms, although different terminologies have been used (e.g., combinatorial-free volume, entropic, excess entropy or repulsive terms on one side and “residual”, energetic, excess energy or attractive contributions on the other side). These definitions are not necessarily identical, as it will be shown here, and the identification of distinct separable contributions in thermodynamic models is not always straightforward. Moreover, the different traditions lead sometimes to confusion as to the actual range of applicability of these models, and it may be useful to consider them (EoS and activity coefficient models) together. While much has been written about the van der Waals equation of state, a particular insight is obtained when the model is expressed in terms of excess Gibbs energy and activity coefficient expressions. We show that such a transformation, analysis of the distinct size and energy terms of vdW and comparison to classical solution theories, provides insight into the physical meaning, capabilities, and limitations of the model, including the associated mixing and combining rules used. We will discuss how this analysis of the vdW and subsequent equations of state, such as the Soave-Redlich-Kwong and Peng-Robinson, have enhanced our understanding of the actual applicability range of the models in terms of size effects or excess properties. The analysis reveals that the capabilities of the vdW and in general of the vdW-type cubic equations of state are possibly more significant than traditionally considered, and that the task of more advanced models in trying to “beat them (the cubic EoS)”, may be more difficult than previously anticipated.

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Section: Journal Of Chemical and Engineering Datasupporting

confidence: 75%

Section: Journal Of Chemical and Engineering Datamentioning

confidence: 99%

Taking Another Look at the van der Waals Equation of State–Almost 150 Years Later

2019

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“…Due to the broad spectrum of modeling approaches that have been considered for blends containing halogenated olefins, any survey will be necessarily incomplete. Equation of state approaches have included group-contribution volume translated Peng-Robinson (GC-VTPR), − perturbed-chain polar SAFT, , cubic plus association (CPA), , and predictive Peng-Robinson (PPR78). , With very few exceptions, insufficient detail is provided in the literature to verify the performance of the proposed equations of state. While these models can in many cases provide adequate representation of the vapor–liquid equilibrium (especially the cubic equations of state), simultaneously representing all thermodynamic properties with a consistent model formulation is challenging.…”

Section: Modelsmentioning

confidence: 99%

Survey of Data and Models for Refrigerant Mixtures Containing Halogenated Olefins

et al. 2021

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We survey existing data for refrigerant blends containing halogenated olefins (hydrofluoroolefins (HFO), hydrochlorofluoroolefins (HCFO), and hydrochloroolefins (HCO)) in the open literature. The data are primarily taken from the NIST SOURCE database and are presented in graphical form to demonstrate the relative coverage of the data. The primary conclusion is that blends containing halogenated olefins remain only sparsely measured in experiments, and some classes of data (e.g., speed-of-sound data) are particularly sparse for blends containing halogenated olefins. The second part of this study compares the thermodynamic models in NIST REFPROP against the experimental data sets and identifies systems (of which there are many) for which refitting of the thermodynamic model is required.

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“…Furthermore, the calculation of surface area fraction θ and group mole fraction X is given in Equations (13) and (14). The relative van der Waals group surface areas Q for the individual subgroups were either adopted from the PSRK model or adjusted for the VTPR model [5,16].…”

Section: Calculation Of Excess Enthalpy Using Vtpr Eosmentioning

confidence: 99%

“…The required pure component properties and the parameter for VTPR EOS were saved in an Excel file, which allows to use an extension of the program for other components in future. The data were retrieved from [1,12,13,16,19].…”

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confidence: 99%

Prediction of Excess Enthalpy Using Volume-Translated Peng–Robinson Equation of State

et al. 2021

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In this work volume-translated Peng–Robinson group contribution equation of state was used to calculate excess enthalpies. Four model systems were selected with the purpose to compare experimental and predicted enthalpy values at different temperatures. After the calculations were performed in Matlab software, results were verified with free software tool of Dortmunder Datenbank (DDB). In a next step, the mixing process and interaction forces were described on the basis of the sign and course of enthalpy values. The endothermic behavior of three systems could be well predicted, while for the most polar system, predictions were less precise. Furthermore, the discrepancy between experimental data from the literature and predicted values was discussed to evaluate the accuracy of the selected model. Lowest mean deviations (<75 J/mol and <15% at all temperatures) could be stated for alkane/benzene mixtures, while highest deviations could be again observed for the most polar mixture. Although the magnitude of deviations was in agreement with the literature, it could be shown that the selected temperature is of major importance for the quality of predictions. Furthermore, a review of different literature values for the n-hexane/benzene system could reveal that the reliability of experimental data has to be carefully checked.

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Present status of the group contribution equation of state VTPR and typical applications for process development

Cited by 15 publications

References 18 publications

Taking Another Look at the van der Waals Equation of State–Almost 150 Years Later

Taking Another Look at the van der Waals Equation of State–Almost 150 Years Later

Survey of Data and Models for Refrigerant Mixtures Containing Halogenated Olefins

Prediction of Excess Enthalpy Using Volume-Translated Peng–Robinson Equation of State

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