Page 65 - Packed bed columns for absorption, desorption, rectification and direct heat transfer
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G = K Ga eH.AC Gm> (205)
where
AC G3
G = K L.a e.H.AC Lav, (207)
where
AC,,-AC,,
-^- (208)
In Ll
AC L2
It is worth emphasizing that the condition for obtaining equations (200),
(202), (206) and (208) is that both the equilibrium constant and the overall mass
transfer coefficient can be considered constant over the whole height H of the
packing. It is easy to see that the flow rates of the liquid and of the gas phase
have to be constant too.
1,5.4.2,2, Piston flow model with height of a mass transfer twit
Other values often used instead of the mass transfer coefficient and the
average driving force are the height of a mass transfer unit and the number of
mass transfer units. To definite them, let us proceed from equations (194) and
(198) and from the equation of the mass balance of the apparatus. From these
equations it follows:
(209)
K ¥.a e AY av
or
H = HTU OY.NTU OY, (210)
