Page 173 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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The equation presented by Kast [30] takes into account that plotted in
double logarithmic coordinates the relation of the pressure drop is not exactly a
straight line. The equation is as follows:

Ws =K w.(64/Re G+2.6/Re^), (16)

where K w is the so called way factor depending on the packing type and taking
into account the ratio of the average way of the gas phase in the packing to its
height.
In Table 4 the values of this constant for different types of packings are
presented.
For practical calculation of the pressure drop Billet [177] proposed the
equation

„ = <VG. (")

where F G = w o y/? G is the factor of vapour (gas) velocity. The experimental
constants Cj and e , presented in Table 5 for some highly effective packings,
depend on the packing construction. Billet [177] mentioned that they depend
also on the column diameter. The comparison of experimental data for different
packings shows that this dependence is very weak and can be neglected. It must
be mentioned also that the constants take into account the influence of the
packing dimensions and especially of the void fraction B. That is why they have
different values for packings made of different materials which determine also
the value of e, The data are obtained for system air-water at 1 bar, temperature
293 K in a column of 300 mm in diameter with a packing size 50 mm.
Billet [177] noted that his equation for calculating the pressure drop
was tested on different systems for 3300 experimental points both for dry and
irrigated packings.