Environmental Engineering Reference
In-Depth Information
Fig. 4.8
Concept of holdup
This surprising result may be grasped more easily by reference to Fig.
4.8
. Two
conveyer belts are transporting barrels. One travels a constant speed of
V
w
transport-
ing water and the other travels faster, at a speed of
V
w
+
V
s
, transporting oil. On both
belts, one barrel is placed every minute. At the other end, one barrel of each is
offloaded each minute. So the “production” of oil and water is equal on the two
belts. However, someone unaware of the difference in speed of the two belts could
conclude that the system was “producing” more water than oil since there are more
barrels of water on the left belt than barrels of oil on the right belt. The gradio-
manometer tool, for example, just measures liquid density and has no knowledge of
flow rates or slip velocities. Proper interpretation of the average density requires
computation of the holdup.
Question #4.2
y
w
Pipe area = 200 cm
2
Slip velocity = 10 cm/s
Total flow rate = 4,800 cc/s
Water cut = 50 %
(a) Find
y
w
.
(b) If
ˁ
o
= 0.6 g/cc and
ˁ
w
= 1.0 g/cc, what will be the density of the flowing
mixture?
Search WWH ::
Custom Search