Results 121 to 130 of about 404 (171)
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Modeling electrolyte solutions with the extended universal quasichemical (UNIQUAC) model
Pure and Applied Chemistry, 2005Abstract The extended universal quasichemical (UNIQUAC) model is a thermodynamic model for solutions containing electrolytes and nonelectrolytes. The model is a Gibbs excess function consisting of a Debye–Hückel term and a standard UNIQUAC term. The model only requires binary ion-specific interaction parameters.
KAJ Thomsen
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A phase stability analysis of the combinatorial term of the UNIQUAC model
Chemical Engineering Science, 1999The conditions for the onset of liquid-phase instability in the combinatorial contribution of UNIQUAC are discussed. A peculiar and non-physical aspect of this predicted instability is that it is independent of temperature. It is recognized that by renormalizing the r and q parameters, this type of phase transition can be prevented.
Charlles R A Abreu +2 more
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A new predictive UNIQUAC for modeling of wax formation in hydrocarbon fluids
Fluid Phase Equilibria, 2006A new UNIQUAC based predictive local composition model is here compared against predictive Wilson and predictive modified UNIQUAC on their abilities to predict wax formation. For that purpose a very large database of phase equilibrium data of both synthetic and real hydrocarbon fluids, at both low and high pressures, will be used.
João A P Coutinho +2 more
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On the derivation and extension of the uniquac equation
Fluid Phase Equilibria, 1978Abstract The UNIQUAC equation is derived by phenomenological arguments based on a two-fluid theory. This derivation is free of the inconsistencies which arise when a lattice one-fluid theory is used to derive UNIQUAC or any other local-composition equation.
G. Maurer, J.M. Prausnitz
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On the combinatorial part of the UNIFAC and UNIQUAC models
The Canadian Journal of Chemical Engineering, 1980AbstractThe excess Cibbs energy of liquid mixtures may be predicted using group contribution models (f.ex. UNIFAC and ASOG), or it may be correlated using molecular models such as UNIQUAC. Group contribution models and the UNIQUAC model contain a combinatorial contribution which accounts for size‐ and shape‐effects and a residual contribution which ...
I. Kikic +3 more
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A modified extended UNIQUAC model for proteins
Fluid Phase Equilibria, 2004A modification of the extended UNIQUAC model is proposed for the description of the non-ideality of protein solutions. Here, the Staverman–Guggenheim combinatorial contribution used in extended UNIQUAC model is replaced by the Flory–Huggins term to take into account the size differences between the protein and solvent.
João A.P. Coutinho +1 more
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Fluid Phase Equilibria, 1991
Abstract The temperature effect on mutual solubility data for 81 binary systems has been studied by means of UNIQUAC and extended UNIQUAC models. The energy parameters of the models are expressed by a quadratic function of temperature. Among the systems studied 61 systems have an upper critical point, 14 systems have a closed partial miscibility and ...
Isamu Nagata +2 more
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Abstract The temperature effect on mutual solubility data for 81 binary systems has been studied by means of UNIQUAC and extended UNIQUAC models. The energy parameters of the models are expressed by a quadratic function of temperature. Among the systems studied 61 systems have an upper critical point, 14 systems have a closed partial miscibility and ...
Isamu Nagata +2 more
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On the temperature dependence of the UNIQUAC/UNIFAC models
Chemical Engineering Science, 1980Abstract Local composition models for the description of the properties of liquid mixtures do not in general give an accurate representation of excess Gibbs energy and excess enthalpy simultaneously. The introduction of temperature dependent interaction parameters leads to considerable improvements of the simultaneous correlation.
S. Skjold-Jørgensen +2 more
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UNIQUAC parameters determined by molecular mechanics
Fluid Phase Equilibria, 1994Abstract Interaction parameters for the UNIQUAC method have successfully been determined for three alkane/ alkane and three alkane/ ketone systems by means of a Molecular Mechanics method called the Consistent Force Field. In this method parameters optimized from experimental structural and spectroscopic data for the pure components are used, but no ...
Svava Ósk Jónsdóttir +2 more
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On the concentration dependence of the UNIQUAC/UNIFAC models
Chemical Engineering Science, 1982Abstract The UNIQUAC/UNIFAC models can not in general represent vapor-liquid and liquid-liquid equilibria simultaneously with satisfactory results. Recent modifications of the models take into account association and solvation effects by means of chemical theory.
Steen Skjold-Jørgensen +2 more
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