Page 118 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

104 Applied Process Design for Chemical and Petrochemical Plants

Val- of Cl

Pressure Drop per 100 feet Pipe:
APioo = CiCzV = -
- c1 c2
P
cz = - =APiooP
Apt00 = APiooP
c1=- - APioo
c2v c2 c1 v c1
C1 = Discharge Factor from Chart
C, = Size Factor, from Table 2-1 1

For AP>40% Pi, do not use this method.
For AP between 10% and 40% of P1, use average for
For AP<lO% Pi, use v at Pi or Pz.
APioo = Psi, pressure drop per 100' pipe. k
-
V = Specific Volume, cu ft/lb.
Note: For quick estimates; not as accurate as friction
loss calculations

Figure 2-31. Simplified flow formula for compressible fluids. By permission, Crane Co., Technical Paper #470, 1957. Also see 1976 edition.

6. Calculate pressure drop, hP/100 ft (or use Figure 2-34). ing pipe size. Consider reducing losses through
items in step 5 above. Recheck other pipe sizes as
may be indicated.
0.000336 fW2
AP/lOOfeet = (2-77)
pd5
Example 2-8 Pressure Drop for Vapor System
0.000000726 fTS, (s' )2
-
- (2 - 77A)
P'd5 The calculations are presented in Figure 2-35, Line
7. Total pressure drop, AP total Size Specification Sheet.
Figure 2-36 is convenient when using Dowtherm vapor.
= (L + Leq) (AP/lOO) + Item 5 (2-57)
8. If total line or system drop is excessive, examine the Alternate Solution to Compressible Flow Problems
portion of drop due to pipe friction and that due to
other factors in the system. If the line drop is a small There are several good approaches to recognizing the
portion of the total, little will be gained by increas- effects of changing conditions on compressible flow [44,47].