Page 79 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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experimentally determined to take into account the different way for the gas
phase due to different form of the packings. As geometrical factors for some
structured packings also the maximal and the minimal free cross-section can be
also used.

1.6.1.2. Pressure drop of irrigated packing
The irrigated liquid affects the pressure drop as follows:
1. By occupying a part of the free cross-section of the packing and thus
increasing the gas velocity;
2. By smoothing the rough surface of the packing or its edges;
3. Due to the velocity of its free surface, it increases the relative gas
velocity essential for the pressure drop.
It is practically impossible to take into account in the form of the
equation all the above mentioned phenomena. That is why the equations take
directly into account only the first one. The rest of them influence through the
proper determined experimental constants.
Using a simple model of irrigated parallel tubes Zhavoronkov, Aerov
and Umnik [29] offered the equation:

AP= **" . . (259)
(1-Af

where A is a dimensionless value related to the liquid holdup. Theoretically,
when having one vertical pipe with surface folly wetted by a film of equal
thickness, the value of A is equal to the liquid holdup.
A can be presented formally [30] as a sum of two values:

A = A 0+M, (260)

where Ag is the value of A under the loading point and AA - the increasing of A
over the loading point.
The types of equations for describing Ao and AA [30,31] are:

(261)
A o = f(Re L,Fy L,Ed,e,l l...JJ t

M = f(-^-,^^,^ 1Eo,sJ,.J n), (262)
gd h g L