Tyn and Calus equation

For predicting diffusivities in binaiy polar or associating liquid systems at high solute dilution, the method of Wilke and Chang defined in Eq. (2-156) can be utilized. The Tyn and Calus equation (2-152) can be used to determine the molar volume of the solute at the normal boiling point. Errors average 20 percent, with occasional errors of 35 percent. The method is not considered to be accurate above a solute concentration of 5 mole percent. 

Basically, DESIGNER can use different physical property packages that are easy to interchange with commercial flowsheet simulators. For the case considered, the vapor-liquid equilibrium description is based on the UNIQUAC model. The liquid-phase binary diffusivities are determined using the method of Tyn and Calus (see Ref. 72) for the diluted mixtures, corrected by the Vignes equation (57), to account for finite concentrations. The vapor-phase diffusion coefficients are assumed constant. The reaction kinetics parameters taken from Ref. 202 are implemented directly in the DESIGNER code. 

The following equation of Miller (1980), based on the earlier correlations of Rackett (1970) and Tyn and Calus (1975), is recommended in preference to a few others that have been proposed, for example, Myers, 1979 More and Capparelli, 1980 Joback, 1984 Ambrose, 1976 (specific to alkanols) ... 

The compilations of CRC (1-2), Daubert and Danner (3), TRC (11-12), and Yaws (15-33) were used extensively for liquid density. Estimates of liquid density were primarily based on Schroeder correlation (9, group contribution), Le Bas method (9, group contribution), and Tyn-Calus equation (9, critical volume). 

In case of infinite dilution of solute 1 in solvent 2 a diffusion coefficient can be estimated in many ways [6]. They are all characterized by individual rules for single substances, limited application ranges, and input parameters that are hardly accessible. The Tyn/Calus equation is a good compromise between accuracy and... 

The limitations and individual exception rules of the Tyn/Calus equation are as... 

Silva and Macedo [Ind. Eng. Chem. Res. 37,1490 (1998)] measured diffusivities of ethers in C02 under supercritical conditions and compared them to the Wilke-Chang [Eq. (5-218)], Tyn-Calus [Eq. (5-219)], Catchpole-King [Eq. (5-210)], and their own equations. They found that the Wilke-Chang equation provided the best fit. 

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