Page 228 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

218

(96)

where ex is in mN/m.
Using data from [83, 87] for the wetted surface area of Raschig rings
with diameters from 15 to 35 mm, the following equation was proposed [102]:

L / ( (97)
a

where Eotvos number Eo d = — is defined with the packing diameter,
XT
_ 4.L
a.u L '
The maximal error of the equation is 20%.
There are many investigations and different equations for calculating
the effective surface area of random packings given in the literature [87-95].
The first of them are proposed by Semmelbauer [93]. They are as follows:

for Raschig rings

s
4SS
^- = 0.00608•Re° l Eo°- ; (98)
a

for Berl saddles

4SS 05
^- = 0.00755Re° L Ed . (99)
a

In both cases Edtvos number is defined with the specific surface area

The disadvantage of the equations of Semmelbauer [103] is that using
Rei without any experimented data for the liquid viscosity, they predict too great
influence of this value. It must be mentioned that according to the dimensional
analysis the equations ought to have four instead of three terms.