Page 125 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Fluid Flow 109

AVERAGE PRESSURE -LB. PER SQ. IN. ABSOLUTE
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0. 2! s • q'° � ci Of i
• q q
PRESSURE LOSS IN Le. PER SQ. INCH PER 100 FEET
Based on Babcock Formula: P = 0.000131 (I+ d ;!}
3 6)
Figure 2-32. Steam flow chart. (By permission, Walworth Co. Note: use for estimating only (this author).)
The maximum possible velocity of a compressible fluid P' = pressure, Psi abs (Psia)
in a pipe is sonic (speed of sound) velocity, as: �· = sonic or critical velocity of flow of a gas, ft/sec
V 1 = specific volume of fluid, cu ft/lb at T and P'
0.000001959f (q'h) 2Sg 2 g = acceleration of gravity= 32.2 ft/per/sec
or, �p I l 00 ft = (2- 78)
d''p Thus the maximum flow in a pipe occurs when the veloc-
ity at the exit becomes sonic. The sonic location may be
where k = ratio of specific heat for gas or vapor al constant
pressure other than the exit, can be at restrictive points in the sys-
R = individual gas constant = MR/M = 1544/M tem, or at control/ safety relief valves.
M = molecular weight
MR = universal gas constant = 1544 Shock waves travel at supersonic velocities and exhibit
T = temperature of gas, R, = ( 460 + °F) a near discontinuity in pressure, density, and tempera-