Page 123 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

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PRESSURE BOSS IN LB. PER Sa. INCH PER 100FEET
Based on Babcock Formula : P 2 0.0001 31 (I 4- $f

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: -
v, = sonic or critical velocity of flow of a gas, ft/sec
VI = specific volume of fluid, cu ft/lb at T and P’
g = acceleration of gravity = 32.2 ft/per/sec
0.000001959f (qi) 2sg2
or, BPI lG0 ft = - (2-78)
d5 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 at 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
a near discontinuity in pressure, density, and tempera-
T = ternper:ature of gas, R, = (460 + OF)