
into a number of discrete layers with homogeneous properties
throughout. The situation is illustrated in Figure 6.48 for the case
of three sections with uniform liquid concentrations c
1
(t), c
2
(t), and
c
3
(t). The liquid concentration in the reservoir is c
R
(t).
Equations expressing the conservation of coffee extract in each
homogeneous section are
Section 1: w(t)c
R
(t) w(t)c
1
(t) þ (Dz)AaK
m
[c
s
c
1
(t)]E
0,1
(t)
¼ H
L
Dz
d
dt
c
1
(t)(6:294)
Section 2: w(t)c
1
(t) w(t)c
2
(t) þ (Dz)AaK
m
[c
s
c
2
(t)]E
0,2
(t)
¼ H
L
Dz
d
dt
c
2
(t)(6:295)
Section 3: w(t)c
2
(t) w(t)c
3
(t) þ (Dz)AaK
m
[c
s
c
3
(t)]E
0,3
(t)
¼ H
L
Dz
d
dt
c
3
(t)(6:296)
The third term in Equati ons 6.294 through 6.296 accounts for ...