Acentric factor viscosity

An overview of some basic mathematical techniques for data correlation is to be found herein together with background on several types of physical property correlating techniques and a road map for the use of selected methods. Methods are presented for the correlation of observed experimental data to physical properties such as critical properties, normal boiling point, molar volume, vapor pressure, heats of vaporization and fusion, heat capacity, surface tension, viscosity, thermal conductivity, acentric factor, flammability limits, enthalpy of formation, Gibbs energy, entropy, activity coefficients, Henry s constant, octanol—water partition coefficients, diffusion coefficients, virial coefficients, chemical reactivity, and toxicological parameters. 

Table 1 gives the components present in the crude DDSO and their properties critical pressure (Pc), critical temperature (Tc), critical volume (Vc) and acentric factor (co). These properties were obtained from hypothetical components (a tool of the commercial simulator HYSYS) that are created through the UNIFAC group contribution. The developed DISMOL simulator requires these properties (mean free path enthalpy of vaporization mass diffusivity vapor pressure liquid density heat capacity thermal conductivity viscosity and equipment, process, and system characteristics that are simulation inputs) in calculating other properties of the system, such as evaporation rate, temperature and concentration profiles, residence time, stream compositions, and flow rates (output from the simulation). Furthermore, film thickness and liquid velocity profile on the evaporator are also calculated. 

Here is the fluid s critical pressure in atm, is the fluid s critical temperature in Kelvins, and u) is the fluid s acentric factor as defined in Poling et al. (2001). With these parameters, the kinetic theory reproduces the viscosities of the 14 investigated normal fluids with a RMS deviation of 2.13 percent. 

These two bulk properties (TBP data/°API) are then used to calculate other constants such as molecular weight (MW), the pseudo-critical temperature (T ) and pressure (P ), respectively, and the pseudo-acentric factor (m). The other properties generally measured are the kinematic viscosities at 100°F (—311 K) and 200°F (—366 K), respectively, and the Reid Vapor Pressure (RVP) (mainly for the gasoline range cut, defined as the vapor pressure exerted by the cut at 100 °F (—311 K)). All of the above-measured properties and the calculated constants are generally... 

At low and moderate pressures, the viscosity of a gas is nearly independent of pressure and can be correlated for engineering purposes as a function of temperatnre only. Eqnations have been proposed based on kinetic theory and on corresponding-states principles these are reviewed in The Properties of Gases and Liquids [15], which also inclndes methods for extending the calculations to higher pressures. Most methods contain molecular parameters that may be fitted to data where available. If data are not available, the parameters can be estimated from better-known quantities such as the critical parameters, acentric factor, and dipole moment. The predictive accuracy for gas viscosities is typically within 5%, at least for the sorts of small- and medinm-sized, mostly organic, molecules used to develop the correlations. 

The calculation of diffusion, viscosity and thermal diffusion coefficients, requires a knowledge of the values of the LENNARD-JONES parameters a and e/kg. Tables XIV.3 give these values for a few species. Other compilations in the literature allow the values of supplementary species to be obtained. However, it is useful to have correlations between these properties and other properties of the molecules most frequently tabulated, which is especially true of the critical pressure and temperature (p and T ) and of the PITZER ((o) acentric factor, which constitutes a macroscopic... 

Six methods are recommended by Reid et al. (1987) for the estimation of thermal conductivity of nonpolar compounds. These include the corresponding-states methods of Chung et al. (1984, 1988), Ely Hanley (1983) and Hanley (1976). The third method (Roy Thodos 1968, 1970) is recommended for polar as well as nonpolar compounds. Topical errors for nonpolar compounds are 5 to 7%, with higher errors expected for polar compounds. Both the Chung and Ely-Hanley methods correlate the Eucken factor, fy, = XMlriCv, with other variables such as C (heat capacity), Tr and 0) (acentric factor). Thus the viscosity is required to use these correlations. The Roy-Thodos correlation requires only the critical temperature and the pressure, and employs a group contribution method to account for the effect of internal degrees of freedom. 

---