Page 53 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

48

z>O,0 f=O, C L=C Lb, (152)

z=O t0 r^O,Ci=Cf u. (153)

Where z is the distance from the interface (current coordinate), and Cy,
is the concentration in the liquid bulk.
Integrating Eq. (149) at the boundary conditions (150) to (153) the
following equation is obtained:

(154)

2
where G is the mass of the transferred substance per unit of interfece in mol/m ,
2
2
or kg An and F- the mass transfer area in m .
From Eq. (150) it is easy to see that with increasing of time the mass
transfer rate decreases.
The average mass flux N^av can be obtained by integration of Eq. (154)
taking into account the distribution of the elements by time of exposure.

(155)

Hereupon, the partial mass transfer coefficient for the liquid phase can be
obtained as:

(156)

where/is a function depending on the distribution of the contact time.
Higbie [18] has taken the contact time constant for all elements. For this
case