Page 221 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

211

300

200
f

100 I
80
• RSR extrapolate
• RSR No.0.8 PP
eo
6 8 10 20 40 80 80 100 200

Fig. 23. Comparison of the effective surface of RSR No 0.6 of plastic with extrapolated data for
the same packing of metal.

The comparison shows that the effective surface area of metal RSR is
between 12% and 43% higher. The lower % is at higher liquid superficial
velocity.
In Fig. 24 a comparison of the metal RSR and IMTP with practically
the same specific surface area is presented. The first pair is RSR No 0.7 and
2
3
IMTP 40, with specific surfaces 175 and 171 m /m respectively. The second
2
one is RSR No 1.5 and IMTP 50, with specific surfaces 105.8 and 107.7 m /m\
The comparison shows that the effective surface of the RSR is about 15 %
higher. This difference is connected with the different form of the two packings
and mostly with the special forming of the end lamellas of the IMTP so that
each of these lamellas consists practically of two perpendicular lamellas. The
surface of these complicated end lamellas is about 28.8 to 49 % of the whole
surface of the packing depending on the size of the packing elements. In case of
RSR all lamellas are simple. The flowing of the liquid in the two cases is
different. To explain easier this difference, let us consider the results of
investigations [242] carried out for modelling the leakage of the liquid phase in
packings. It was found that at the bottom part of an irrigated well wettable
vertical plate, a long liquid drop is formed. Its height is about 5 mm in case of
irrigation with water. It means that the bottom part of the vertical plate is fully
wetted due to capillary forces. Simple experiments show also that narrow, well
wettable lamellas on which the liquid is flowing are completely wetted on both
sides with moving liquid. The reason is that because of the capillary forces, the
liquid cannot break away from the lamellas. If a given lamella is replaced by a