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302 Chapter 6

6 2
1 9.807m (ISOxKT ) !!! 2 (897-1000) kg 1 m-s
v d = — ————— ———————— ————————— ————
18 1 s 2 1 1m 3 7X10" 4 kg
3
3
= - 1.804xlO~ m/s (-5.91x10 ~ ft/s)
The negative sign means that the oil drops move upward instead of downward.
From Equation 6.15.24, D = D. Substituting into the equation for V, given
H L
above,
v L = 8V L /7iD H 2

but from Equation 6.15.2, VD = V and from Equation 6.15.3, V = V. Therefore,
L D L
3
8 (1.405x10" ) m 3 1 1
3
3
V D = —————————— ——— —————— = 2.421xlO~ m/s (7.94xlO~ ft/s)
2
1 s 3.124 (1.219) m 2
From Equations 6.15.8 and 6.15.9, the settling length,
3
v DD 2.421xlO~ m 1.219m 1 s
L s = —— = ———————— ———— ———————— = 0.8180m (2.68 ft/s)
2 s i 1.804xlO~ 3 m
2 v d
From Equation 6.15.10, the dispersion layer thickness is

H D = 0.1 D = 0.1 (1.219) = 0.1219 m (0.400 ft)

From Equations 6.15.11, the interfacial area required for coalescence,

2V D t R

H D
The residence time for the oil drops in the dispersion layer is 5 min and from
Equation 6.15.2 V D =V L. Therefore, the interfacial area is
3
2 (1.405x10~ ) m 3 300s
2
2
A,= —————————— ————— = 6.916m (0.642 ft )
1 s 0.1219m
and from Equation 6.15.12, the dispersion length is

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