Page 171 - Packed bed columns for absorption, desorption, rectification and direct heat transfer
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£ - coefficient which characterizes the type of the packing;
w = —— - real gas velocity in m/s;
s
w 0 - gas velocity determined for the column cross-section in m/s;
e - bed void fraction (free packing volume, equal to its free cross-section);
3
pa- gas density in kg/m ;
4e
d h = hydraulic diameter of the packing in m;
a
3
2
a- packing specific surface area, m /m .
Eq. (6) can be written also as follows:
AP B = ffl™ " . (7)
" 8e 3
The coefficient f takes into account the pressure drops both from
friction of the gas on the packing surface and from changing of its direction and
velocity of moving trough the packing.
Ergun [104] proposed the equation
VE=-Z- + *-75, (8)
where the dimensionless pressure drop (friction factor ys E ) is defined as
(9>
' • HI- . *p '
or:
3
H WE G ° e D a (10)
The Reynolds number Re 0 is given by the expression:
