Page 80 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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4L
where Re L = is the Reynolds number for the liquid phase;
a.v L
:
Fr L = — — Froude number for the liquid phase;
g

Ed=—*z— -EStvos number;
a a
3
p L - liquid phase density in kg/m ;
2
v h - liquid phase kinematic viscosity in m /s;
In equation (262) the viscosities of both phases are omitted because at
developed turbulence the effect of the viscous forces is negligible.
In case of a fully wetted packing, like some packings with vertical
walls, Ed can also be omitted.

1.6.2. Liquid holdup

As already mentioned the value of A is closely connected with the
liquid holdup. The last can also be divided, some formally, into two parts;

H d=H d0+AH d, (263)

where Hat is the holdup under the loading point and AH d - its increase over this
point because of the forces between the gas and the liquid phase. The equations
for these two parts are similar to the equations for A and Ad, namely:

H d0 = f(Re L,Fr L.E6,e,l r.JJ, (264)

— f( 1 ~,——iEd,e,l,....L). (265)

1.6,3. Effective staface area

The effective surface area a e is the surface of the interface between the
3
gas and the liquid phases per 1 m of the packing volume. It is a sum of the
effective wetted surface of the packing and the surface of the jets and drops