mass transfer in multiphase systems - Greenleaf University

MASS TRANSFER IN MULTIPHASE SYSTEMS: VOLATILE ORGANIC COMPOUND
REMOVAL IN THREE-PHASE SYSTEMS
k
s
M
(49)
2
L t
Similarly for the liquid and gas:
i
i
N k C C k p p
(50)
A L A A G A A
k
k
L
G
L
(51)
t
m
(52)
2
atmL t
Further complicating mass transfer calculations is the convention to use coefficients in terms of inverse
time, 1/t for use in mass transfer rates as opposed to fluxes. Much of the liquid-phase mass transfer
literature has many correlations for this conversion. The idea is to apply an area of mass transfer such
that:
i
A L A A
k A C C
(53)
In moles or mass per time. However, in use of the partial differential equations rates are similar and
commensurate with chemical kinetics, i.e., rate in moles or mass per unit volume per time. Therefore, the
standard usage is to find the area per unit volume or mass, a = A/V (L 2 /L 3 ). The single-phase coefficients
then become:
2
M
* L
ka 1/
s
t
2
Lt M
(54)
2
L L
ka L
* 1/ t
3
t L
(55)
2
m L
kGa * * RT 1/ t
2 3
atmL t L
(56)
The same were applied to the overall coefficients. However some manipulation has to occur in order to
ensure equivalent areas or area averages are being accounted for in different phases, e.g.,
1 1
oa
K 1 1 1 1
L
aave
k k a k k a k a k aH
D s s D sL s L G A
(57)
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