Page 99 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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fi L is the liquid viscosity at 20°C;
3
p L is the liquid density in kg/m .
The diffiisivity of some gases dissolved in water is given in Table 3 A.
For determination of the diffiisivity at temperature t (in °C), the
following equation can be used

A. = D LX[l + 0.02(t-20)J. (5A)

For calculation of the diffiisivity of dilute solution, the following
equation is proposed:

M T
D =7.4x ltr" & ) rf . (6A)
/g
L
1 06
iooojiy
Here Mis the mol mass of the solvent;
V- mol volume of the diffusing substance;
fi L - liquid viscosity, Pa.s;
/?- parameter which takes into account the association of the solvent molecule.
Its value for different solvents is given below.

The value of /?:
For water 2.6
For methanol 1.9
Forethanol 1.5
For non-associated such as benzene, ether, heptane and so on, 0 = 1.

Table 3 A. Diffiisivily of some gases in water at 20°C
9
2
9
2
Gas D,2o.l0 m /s Gas D/ 3n.l0 m /s
co 2 1.8 H 2 5.3
N 20 1.8 N 2 1.9
1.6 2.1
Ci 2 Oj
H 2 S 1.6 NH 3 1.8
HC1 2.3