Page 98 - Packed bed columns for absorption, desorption, rectification and direct heat transfer
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The diffusivity of liquid D L can be calculated using the approximate
equation:
/ 10 I / /
2
D L = T w, — + — , m /s, (3A)
where ft - is the viscosity in Pa.s;
VA and Fg- mol volume of the dissolved substance and the solvent;
MA and M a- mol mass of the dissolved substance and the solvent;
A and B- coefficients depending on the property of the dissolved substance and
the solvent. Their values for some substances are given below.
The value of A for some substances dissolved in water:
For gasses 1
Forethanol 1.24
For methanol 1.19
For acetic acid 1.27
The value of B:
For water 4.7
For ethanol 2.0
For methanol 2.0
For acetone 1.15
For non-associated 1.0
The diffusivity of a gas in liquid can be calculated from its value
Di2o for 20°C by the equation
(4A)
where the temperature coefficient h can be determined by the empirical
equation:
"
