of viscosity given by the present correlation and the values computed by Dean and Stiel's (3)equations. This may be attributed to inherent errors in the method of determination of the pseudocritical constants (3). In Figure 1, a regular trend is noticed between the limits of the two pure components. This clearly brings out the effect of mixture composition on viscosity of the Freon-12-Freon-22 vapor mixture system.
CONCLUSIONThe present correlation facilitates design of engineering systems, as viscosity information on pure Freon-12 and Freon-22 vapors and their mixtures may be obtained readily. The determination of viscosity, however, requires an accurate knowledge of the temperature-dependence of viscosity at zero density. For engineering purposes, it may be convenient to use the atmospheric viscosity values. These atmospheric viscosity values may be calculated for pure components by the correlation of Witzell and Johnson (20) and for mixtures by Herning and Zipperer's (4) equation or by Wilke's (19) equation.