Page 43 - Bird R.B. Transport phenomena

28 Chapter 1 Viscosity and the Mechanisms of Momentum Transport

EXAMPLE 1.4-1 Compute the viscosity of CO at 200, 300, and 800 К and 1 atm.
2
Computation of the SOLUTION
Viscosity of a Pure
Gas at Low Density Use Eq. 1.4-14. From Table E.I, we find the Lennard-Jones parameters for CO 2 to be е/к =
190 К and о- = 3.996 A. The molecular weight of CO 2 is 44.01. Substitution of M and a into
Eq. 1.4-14 gives

/x = 2.6693 X 10 (1.4-17)

in which JX [ = ] g/cm • s and T [ = ] K. The remaining calculations may be displayed in a table.

Viscosity (g/cm • s)
ПК) кТ/г Vf Predicted Observed 11

200 1.053 1.548 14.14 1.013 X 10" 4 1.015 X Ю" 4
300 1.58 1.286 17.32 1.494 x 10" 4 1.495 X 10' 4
800 4.21 0.9595 28.28 3.269 X 10" 4

Experimental data are shown in the last column for comparison. The good agreement is to be
expected, since the Lennard-Jones parameters of Table E.I were derived from viscosity data.

EXAMPLE 1.4-2 Estimate the viscosity of the following gas mixture at 1 atm and 293 К from the given data on
the pure components at the same pressure and temperature:
Prediction of the
Viscosity of a Gas
Molecular
Mole
Mixture at Low Species a fraction, x weight, M Viscosity, /x a
• s)
(g/cm
Density a a
l.CO 0.133 44.01 1462 X 10~ 7
2
2.O 0.039 32.00 2031 X 10~ 7
2
3.N 0.828 28.02 1754 X 10" 7
2
SOLUTION Use Eqs. 1.4-16 and 15 (in that order). The ailculations can b
3
a p MJM, „, a /fAu Ф а/ 3

1. 1 1.000 1.000 1.000
2 1.375 0.720 0.730 0.763
3 1.571 0.834 0.727

2. 1 0.727 1.389 1.394
2 1.000 1.000 1.000 1.057
3 1.142 1.158 1.006
3. 1 0.637 1.200 1.370
2 0.876 0.864 0.993 1.049
3 1.000 1.000 1.000

11 H. L. Johnston and K. E. McCloskey, /. Phys. Chem., 44,1038-1058 (1940).