Self consistent equations for calculating ideal gas heat capacity, enthalpy and entropy. III. Coal chemicals

Rehman, Zia ur; Lee, L.L.

doi:10.1016/0378-3812(85)87009-6

Cited by 15 publications

(3 citation statements)

References 2 publications

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“…THERMFIT uses Marquardt's method37 to determine the parameters Bu B2, |, 2, and 3. This equation is similar in principle to that of Lee et al [33][34][35] By constraining the coefficients (f?,) to sum to the number of vibrational modes (j), however, the HOE has fewer parameters than that of Lee. These parameters also retain physical significance.…”

Section: Estimation Of Molecular and Radical Thermodynamic Propertiesmentioning

confidence: 95%

“…27 The comparable version of Lee's equation (three-term) is designed to represent both vibrational and electronic contributions and contains seven parameters. 35 It should be noted that electronic contributions are typically negligible for most polyatomic species, and the term in Lee's equation that is designed to represent electronic contributions actually represents vibrational contributions. This results in reduced physical significance for the parameters.…”

Section: Estimation Of Molecular and Radical Thermodynamic Propertiesmentioning

confidence: 99%

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THERM: a computer code for estimating thermodynamic properties for species important to combustion and reaction modeling

Ritter

1991

J. Chem. Inf. Comput. Sci.

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A computer package has been developed called THERM, an acronym for THermodynamic property Estimation for Radicals and Molecules. THERM is a versatile computer code designed to automate the estimation of ideal gas phase thermodynamic properties for radicals and molecules important to combustion and reaction-modeling studies. Thermodynamic properties calculated include heat of formation and entropies at 298 K and heat capacities from 300 to 1500 K. Heat capacity estimates are then extrapolated to above 5000 K, and NASA format polynomial thermodynamic property representations valid from 298 to 5000 K are generated. This code is written in Microsoft Fortran version 5.0 for use on machines running under MSDOS. THERM uses group additivity principles of Benson and current best values for bond strengths, changes in entropy, and loss of vibrational degrees of freedom to estimate properties for radical species from parent molecules. This ensemble of computer programs can be used to input literature data, estimate data when not available, and review, update, and revise entries to reflect improvements and modifications to the group contribution and bond dissociation databases. All input and output files are ASCII so that they can be easily edited, updated, or expanded. In addition, heats of reaction, entropy changes, Gibbs free-energy changes, and equilibrium constants can be calculated as functions of temperature from a NASA format polynomial database.

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Section: Estimation Of Molecular and Radical Thermodynamic Propertiesmentioning

confidence: 95%

Section: Estimation Of Molecular and Radical Thermodynamic Propertiesmentioning

confidence: 99%

THERM: a computer code for estimating thermodynamic properties for species important to combustion and reaction modeling

Ritter

1991

J. Chem. Inf. Comput. Sci.

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“…The corresponding expressions for each equation using each mixing rule are reported by Yanaki (1988). The enthalpy departure expressions were used with ideal gas enthalpy difference expressions reported by Rehman and Lee (1985) in calculating enthalpy differences.…”

Section: Equations Usedmentioning

confidence: 99%

Comparison of cubic- and hard-sphere-based equations of state for associating fluid mixtures

Yanaki¹,

Yesavage²

1990

Ind. Eng. Chem. Res.

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Comparison of Cubicand Hard-Sphere-Based Equations of State for Associating Fluid Mixtures Recently obtained enthalpy and phase behavior data at elevated pressures and temperatures for both pure fluids and binary and ternary mixtures of m-cresol, quinoline, and tetralin, combined with phase behavior data for mixtures of methanol, n-pentane, and acetone, were used to compare variations of perturbed hard sphere (PHS) equations of state for mixtures with a typical cubic equation of state, a modified Soave-Redlich-Kwong (SRK) equation, for estimating properties of these highly nonideal systems. By fitting pure fluid vapor pressures, attractive terms, a(T), were determined for the PHS equations of state, which are much more consistent with the original temperature-independent attractive parameters as suggested by van der Waals. Experimentally determined binary interaction parameters resulted in comparable phase behavior fits and predictions for both equations. However, the PHS equations of state yielded much more accurate predictions of ternary enthalpy differences than the

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Molecular density of states from estimated vapor phase heat capacities

Bozzelli

Chang

Dean

1997

Int. J. Chem. Kinet.

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Heat capacity data between 298 and 1500K are used to derive a reduced set of apparent vibrational frequencies that can be used for estimation of molecular density of states, (E). Estimates for a number of molecule and radical species, using a reduced set of three frequencies with noninteger degeneracies, are shown to compare favorably to direct count methods, which require specification of the complete frequency set. Use of the reduced set of three frequencies leads to significant improvement in calculations of (E)/Q as compared to similar calculations which use only a single geometric-or arithmetic-mean frequency approximation. Since vapor phase heat capacity data of molecules and radicals can be estimated accurately by a group additivity formalism, this approach provides a method to estimate (E) for use in calculations of pressure effects in unimolecular and chemical activation reaction systems. The accuracy of the (E)/Q distributions obtained from heat capacity data makes this a viable method for those cases where the complete frequency distribution is not known. It is especially valuable for those cases where contributions to (E) from internal rotors or low frequency vibrations such as inversions are not well known. This approach is useful for quantum RRK or inverse Laplace transform calculations of k(E) since no assignment of transition state properties is necessary. The reduced frequency set can also be combined with ⌬H f (298) and S(298) to provide a compact data set to describe thermodynamic properties at any temperature.

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Self consistent equations for calculating ideal gas heat capacity, enthalpy and entropy. III. Coal chemicals

Cited by 15 publications

References 2 publications

THERM: a computer code for estimating thermodynamic properties for species important to combustion and reaction modeling

THERM: a computer code for estimating thermodynamic properties for species important to combustion and reaction modeling

Comparison of cubic- and hard-sphere-based equations of state for associating fluid mixtures

Molecular density of states from estimated vapor phase heat capacities

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