Page 303 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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1
where k La h is the liquid-side volumetric mass transfer coefficient in h' and L h
2
3
the liquid superficial velocity in m /(m h).
Equation (201) is obtained using experimental data for absorption of
oxygen in water and is valid only for this system. It shows that the volumetric
mass transfer coefficient does not depend on the packing specific area, but only
on the packing height. The authors [140] find, for example, that the volumetric
mass transfer coefficient for Raschig rings 100x100 mm is equal to that for
tubes with diameter 50 mm and height 100 mm, though the specific surface area
of the tubes is 1.9 times larger.
To obtain an equation for calculation of the liquid-side mass transfer
coefficient, it must be taken into account that the mass transfer rate for these
packings depend also on the mixing of the liquid on the horizontal surface
between the neighbour rows. It is easy to calculate that the area of this surface
2
per m cross-section of the column is equal to (1-e). Having in mind the
influence of e and processing the experimental data for different packings,
presented in Table 29, the following two equations are proposed [97]:

04
s
OI
Sh t = 0.01Q19Re¥- \S4 &af .(a.h)- 033E M Z9 (202)
and
66+0 4(i E)
0? J5(1 s}
s
Sh = 0.0026.R4 - - .S4 .G4 -° - x
t
(203)
Equation (202) fits the experimental data to an average accuracy of
3.4%. The maximal deviation is 14.5%. The respective data for equation (203)
are 3.5% and 22%. Only 6 of all 114 points in equation (202) have deviations
more than 10%.
Equation (203) fits the experimental data to an average accuracy of
3.5%. The maximal deviation is 22% and only 6 of the experimental points have
deviations more than 10%.
A comparison between the experimental data for the packings presented
in Table 29 and the line calculated by Eq. (202) is represented in Fig. 63.