Page 67 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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is the height of one mass transfer unit, calculated for the liquid phase, and

^ (217)

is the overall number of mass transfer units in the apparatus calculated for the
liquid phase.
The number of the mass transfer units and the height of a mass transfer
unit can be defined also for any equilibrium equation.
From the equation

= K Ya e(Y-Y )Jh (218)

it follows:

(219)
K Y.a € Y-Y

or after integration

H = #- • C'T^ T = HTU or.NTU m . (220)

I.e. in the general case the number of mass transfer units for the gas phase is
defined by the equation

0 j v
A/77/ — l
m r
<, Y - Y

For the concentrations given for the liquid phase it can be written:

dG = G xdY = K xa e(X* -X).dh (222)