Wilke-Chang model

It was shown that the modified Wilke-Chang model was applicable for experiments which span a range of Pa between 3 and 30 and a temperature range between 267 and 307 °C. An important finding was that even at Pn < 30, the mass transport of EG is the rate-determining step in PET synthesis. 

Modelling diffusion coefficients The Wilke-Chang model is... 

Therefore, the difference between chemical classes appears to be important. The results show that for sugars, observed values are smaller than predicted this applies to all models given herein. Before considering this further, we should consider whether this problem (or a similar one) exists within the Wilke-Chang model [3]. 

Effective diffusivities were used for the calculation of the mass-transfer coefficients. In contrast to the binary Maxwell-Stefan diffusivities, the effective diffusivities were calculated via available procedures in ASPEN Custom Modeler , whereas the Wilke-Chang model was used for the liquid phase and Chapman-Enskog-Wilke-Lee model for the vapor phase [94]. In the full model, computationally intensive matrix operations for the Maxwell-Stefan equations are necessary. The model has been further extended to consider the presence of liquid-liquid separation [110, 111]. 

In order to solve the mathematical model for the emulsion hquid membrane, the model parameters, i. e., external mass transfer coefficient (Km), effective diffu-sivity (D ff), and rate constant of the forward reaction (kj) can be estimated by well known procedures reported in the Hterature [72 - 74]. The external phase mass transfer coefficient can be calculated by the correlation of Calderback and Moo-Young [72] with reasonable accuracy. The value of the solute diffusivity (Da) required in the correlation can be calculated by the well-known Wilke-Chang correlation [73]. The value of the diffusivity of the complex involved in the procedure can also be estimated by Wilke-Chang correlation [73] and the internal phase mass transfer co-efficient (surfactant resistance) by the method developed by Gu et al. [75]. 

Some compound class-specific outliers are described, and an explanation of why they are predicted incorrectly is given. The interpretation of the results shows that there are serious inadequacies in the development of prior models such as the Wilke-Chang equation. 

This relationship is clearly related to equation (15.18) in particular. The term in log is of note. In the original reference [3] very limited justification for its inclusion was made. Furthermore, the values of quoted in Reference [3] were obtained from then unpublished work, and effectively have the nature of an empirical correction, which in itself is not a major problem in the utility of the model. However, when the work was published the values of the parameter were quite different [12], yet this error in the Wilke-Chang equation has not been corrected in the literature, to the authors knowledge. 

The diffusion coefficient in Eq. 4 was therefore dependent on DP. Numerical values were estimated as follows. For short chains, where the diffusivity was inversely proportional to DP, i.e., Dg = a/DP, the constant "a" was determined from the Wilke-Chang (17) model compound diffusivity where DP = 1. For longer polymers, where Dg = b/DP2 the scaling coefficient "b" was obtained by matching with a/ DP at DP = 200. 

This model is useful strictly for incompressible fluids only, but for small pressure changes it may be used for gas networks as well. The equations for general network simulation are based on eqn (1) and eqn (2) and a variety of models analogous to eqn (3). It goes beyond the scope of this paper to elaborate on networks with loops, this is dealt with in details by for example Mach (1), Gay and Preece (2,3) and Carnahan and Wilkes (4). A variety of... 

New models for the prediction of molecular diffusion coefficients are described, and compared to previously established ones. These are based on solute molecular size, solvent viscosity solvent molecular size, and temperature. The data set of diffusion coefficients used was primarily the one developed by Wilke and Chang and upon which their commonly used diffusion model is based (A.I.Ch.E. Journal, 1 (1955), 264). 

Though foe amount of gas changes during foe oxidation of foe sulfide concentrates in foe sintering process, it was ignored in fois model for sinq)lification. However, foe increase in foe H2O gas caused by drying was taken into consideration. The value of foe viscosity was evaluated with Wilke s equation for a mixed gas of N2-O2-H2O. 

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