Page 208 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

198

(65,

and

e°/Gaf
H =41.SRe°/Gaf s s (66)
d0

where d p is the nominal size of the packing in m.
Using results obtained by weighing, Gildenblat [66-68] proposes the
equation for random Raschig rings:

H =4.83xl0'^\^fj (67)
d0

The data published in [42-44] are also in a good agreement with these
equations.
The data of Gildenblat [66-68] obtained for random and arranged
packings show that at low liquid superficial velocity for a given dimension of
the packing the liquid holdup of the arranged packing is higher. At higher liquid
superficial velocity it is lower then that of the random packing. This can be
explained by the fact that the wetted surface area of the arranged packing is
larger than this of the random type which leads to higher holdup at lower liquid
superficial velocity. With increasing of the liquid superficial velocity the
difference in the wetted area of the two types of packings is not so great. This
and also the fact that in case of arranged packing with vertical walls the gravity
force acts in the direction of the moving liquid, and in case of random packing
only with a component in the liquid flow direction can explain the results of
Gildenblat [66-68]
Because the liquid holdup and the value A in Eqs. (259) and (260), from
Chapter 1, are very similar values, it is to be expected that it is easy to obtained
a good correlation between them. So Zhavoronkov [76] offered the equation:

- t (68)
tp