Page 135 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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2.1,2.5.2, Methods based on determination of the holdup
The method [1, 16, 24] is based on the acceptance that the whole
quantity of liquid in the packing is distributed in the form of a liquid film, and
the thickness s of this film can be determined by the theoretical equation:

S=3 (42)

where L { is the ratio of the liquid superficial velocity to the wetted perimeter of
2
the packing in 1 m cross-section equal to a w;
3
ju L is the liquid dynamic viscosity in Pa.s, and p L is its density in kg/m .
Otherwise, at these conditions the liquid holdup can be determined by
the equation:

H d = a ws (43)

where s is the thickness of the liquid film on the packing.
From Eq. (42) and (43) it follows:

(44)

or

(45)
a w=H d

The disadvantage of this method is that equation (42) is theoretically
obtained only for a vertical film and hence it is only an approximation for the
real packings.

2.1.2.5.3. Method using sublimation of naphthalene
According to this method [25, 26] the packing elements are made of
naphthalene or are covered with it by immersing in melted naphthalene. The
experiments are carried out by sublimating the naphthalene in two steps, first