Benedict - Webb - Rubin equation

Other pressure—volume—temperature (PVT) relationships may be found in the Hterature ie, Benedict, Webb, Rubin equations of state (4—7) the Benedict, Webb, Rubin, Starling equation of state (8) the Redlich equation of state (9) and the Redlich-Kwong equation of state (10). 

An example of a more complex equation that exhibits better accuracy is the Benedict-Webb-Rubin equation ... 

Benedict/Webb/Rubin Equation of State The BWR equation of state with Z as the dependent variable is written... 

As discussed in Sec. 4, the icomplex function of temperature, pressure, and equilibrium vapor- and hquid-phase compositions. However, for mixtures of compounds of similar molecular structure and size, the K value depends mainly on temperature and pressure. For example, several major graphical ilight-hydrocarbon systems. The easiest to use are the DePriester charts [Chem. Eng. Prog. Symp. Ser 7, 49, 1 (1953)], which cover 12 hydrocarbons (methane, ethylene, ethane, propylene, propane, isobutane, isobutylene, /i-butane, isopentane, /1-pentane, /i-hexane, and /i-heptane). These charts are a simplification of the Kellogg charts [Liquid-Vapor Equilibiia in Mixtures of Light Hydrocarbons, MWK Equilibnum Con.stants, Polyco Data, (1950)] and include additional experimental data. The Kellogg charts, and hence the DePriester charts, are based primarily on the Benedict-Webb-Rubin equation of state [Chem. Eng. Prog., 47,419 (1951) 47, 449 (1951)], which can represent both the liquid and the vapor phases and can predict K values quite accurately when the equation constants are available for the components in question. 

Benedict-Webb-Rubin equation 252. 256-7 benzene, vapor pressure 260-1 benzene + I, 4-dimethylbenzene mixture, phase equilbria 420-2, 424... 

Benedict equation of etate phys chem An empirical equation relating pressures, temperatures, and volumes for gases and gas mixtures superseded by the Benedict-Webb-Rubin equation of state. ben-3,dikt i kwa-zhsn 3v stat ... 

The van der Waals equation is not a particularly accurate tool for prediction of compressibility Z, but it is the first theory to illuminate the nature of the attractive and repulsive forces that lead to departure from the perfect gas law. There are many more accurate equations of state that use more parameters, including the Benedict-Webb-Rubin equation, the Redlich-Kwong equation, and the Peng-Robinson equation. The compressibility factor can also be expanded into the virial form... 

PREDICTIONS BY CORRELATIONS 1 81 And the Benedict-Webb-Rubin equation has many more parameters ... 

The development of mixture rules will be discussed in detail in connection with the Benedict-Webb-Rubin equation of state. 

These methods make use of available experimental knowledge combined with correlation techniques that may or may not be partially based on molecular concepts. They range from methods that are completely empirical to ones in which there is significant input from statistical mechanics (see Fig. 2). As an example of an approach that is almost fully empirical, one can cite the many modifications of the Benedict-Webb-Rubin equation of... 

Benedict/Webb/Rubin equation of state, 84 Bernoulli equation, 217-218 Bubble point, 307, 309, 365, 454 Bubble-point calculations, 307-316, 381-393, 482-486, 490-493... 

The Benedict-Webb-Rubin equation has eight empirical constants and gives accurate predictions for vapor and liquid-phase hydrocarbons. It can also be used for mixtures of light hydrocarbons with carbon dioxide and water (Benedict et al., 1951). 

The analytical equations of state used to compute the pressure-volume-temperature relationships are generally one of the following three classes, viz. virial equations of state, cubic equations of state and the Benedict-Webb-Rubin equation or modifications thereof. 

Because the solubility of acrylamide (JEL), water ( ), and the surfactants in ethane or propane is low, the viscosity of the continuous phase was taken to be that of the pure fluid. The viscosity of the various ethane/propane mixtures was calculated using a reduced-density correlation developed by Dean and Stiel (IQ.), which is reported to be accurate to within 2 to 4% for light hydrocarbon mixtures. The density of the ethane/propane mixtures was either calculated via a modified Benedict-Webb-Rubin equation of state (11.) or, in some cases, measured using a Mettler-Paar DMA-512 vibrating tube densimeter. The densimeter was thermostated via a circulating water bath to within 0.01 C, and calibrated using water and propane at the ten ratures of interest. 

The values in these tables were generated from the NIST REFPROP software (Lemmon, E. W., McLinden, M. O., and Huber, M. L., NIST Standard Reference Database 23 Reference Fluid Thermodynamic and Transport Properties—REFPROP, National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, Md., 2002, Version 7.1). The primary source for the thermodynamic properties is Outcalt, S. L., and McLinden, M. O., A Modified Benedict-Webb-Rubin Equation of State forthe Thermodynamic Properties of R152a (1,1-Difluoroethane), /. Phys. Chem. Ref. Data 25(2) 605-636,1996. Validated equations for the viscosity and thermal conductivity are not currently available for this fluid. 

More recently, Ustinov and coworkers [72, 73] developed a thermodynamic approach based on an equation of state to model the gas adsorption equilibrium over a wide range of pressure. Their model is based on the Bender equation of state, which is a virial-like equation with temperature dependent parameters based on the Benedict-Webb-Rubin equation of state [74]. They employed the model [75, 76] to describe supercritical gas adsorption on activated carbon (Norit Rl) at high temperature, and extended this treatment to subcritical fluid adsorption taking into account the phase transition in elements of the adsorption volume. They argued that parameters such as pore volume and skeleton density can be determined directly from adsorption measurements, while the conventional approach of He expansion at room temperature can lead to erroneous results due to the adsorption of He in narrow micropores of activated carbon. 

Table 14-4 The Benedict-Webb-Rubin equation of state6,7...

CONSTANTS AND MODIFICATIONS OF THE BENEDICT-WEBB-RUBIN EQUATION OF STATE... 

D. S. Viswanath and G.-J. Su Generalized Thermodynamic Properties of Real Gases, Part II. Generalized Benedict-Webb-Rubin Equation of State for Real Gases, AIChE J., 11(2) 205 (1965). 

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