Page 282 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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calculated with account of AA differs considerably from the pressure drop
calculated without AA, In [34 and 160] AA is determined so that it affects the
total pressure drop, while in Eq. (176) it affects only the local pressure drop. It
is obvious that the value of IQ, used in the proposed equation should exceed the
value of Kf, determined in [160]. The lower limit of this value, supposing that
the losses caused by friction are negligible, can be obtained having in mind that
according to Eq, (259) from Chapter 1, and Eq. (46), K& is a cube root of the
ratio of the pressure drop calculated with account of AA to that without
accounting for AA at the point where AA begins to influence the pressure drop.
The power in the proposed Eq. (176) is 6.8 in contrast to 3 in [34, 160]. Then
the lower limit of JT A is:

1.03 6s/3 = 1.0693.

If the friction losses are taken into account, the calculated Kf, value is
higher and depends on the ratio of friction losses to local pressure drop.

Fig. 55 represents Kf, plotted versus the group values for

all packings listed in Table 26 were calculated using Eqs. (176)-(180). Its
average value is 1.10.
As it should be expected, packings with long channels and thin walls,
i.e. packings with relatively lower local pressure drop in comparison to friction
losses, have the highest values of Kf, (see Fig. 55).
The experimental data fit fairly well to the line calculated with IQ, -1.1.
It proves that it is not necessary to account for the additional effects associated
with the local pressure drop to friction loss ratio.

0.4 0.6 1.0 4.0 6.0 10.0 20.0 40.0

I )
Fig. 55. X* value as a function of for all paekinp (see Table 26 for symbols).
J
I