Page 131 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Fluid Flow 115

Table 2-14 For flow of gases and vapors through nozzles and orifices:
Typical Ratios of Specific Heats, k
Compound k = <;,/ Cv __ � (2-48)
Air 1.40
Ammonia 1.29
Argon 1.67 where � = ratio of orifice throat diameter to inlet diameter
Carbon Dioxide 1.28 C' = flow coefficient for nozzles and orifices (see Fig-
Carbon Monoxide 1.41 ures 2-17 and 2-18), when used as per ASME speci-
Ethylene 1.22 fication for differential pressure
Hydrochloric acid 1.40 p = fluid density, lb/ cu ft
Hydrogen 1.40 A = cross-sectional flow area, sq ft
Methane 1.26
Methyl Chloride 1.20 Note: .jhe use ofC' eliminates the calculation of velocity of
Nitrogen 1.40
4
Oxygen 1.40 approach. The flow coefficient C' is C' = Cd/ � 1 - � > 'f/
Sulfur dioxide 1.25 Cd = discharge coefficient for orifices or nozzles [3].
For compressible fluids flowing through nozzles and ori-
fices use Figures 2-17 and 2-18, using hL or f1P as differen-
tial static head or pressure differential across taps located
one diameter upstream at 0.5 diameters downstream from
Figures 2-38A and 2-388 are based on the perfect gas the inlet face of orifice plate or nozzle, when values of Care
laws and for sonic conditions at the outlet end of a pipe. taken from Figures 2-17 and 2-18 [3]. For any fluid:
For gases/vapors that deviate from these laws, such as
steam, the same application will yield about 5% greater
1
flow rate. For improved accuracy, use the charts in Figures q = C'A ([2g (144) l1P]/p) 1 2, cu ft/sec flow (2-48)
2-38A and 2-38B to determine the downstream pressure
when sonic velocity occurs. Then use the fluid properties Note for liquids f1P is upstream gauge pressure.
at this condition of pressure and temperature in: For estimating purposes for liquid flow with viscosity
similar to water through orifices and nozzles, the follow-
ing can be used [53]:
v, = � kgRT, ft/sec= (kg (144)P'V)l/ 2 (2-85)

Q = 19.636 c' d / .i; /----
to determine the flow rate at this condition from: ( : �
� I
1
v = q/A = 183.3q/d 2 = 0.0509W/(d 2 )(p) (2-91)
do
where - is greater than 0.3 (2- 92)
d = internal diameter of pipe, in. d
A= cross section of pipe, sq ft
q = cu ft/sec at flowing- conditions d
02
T = temperature, R Q = 19.636 c' d {h where - is less than 0.3 (2 - 93)
0
k = ratio of specific heats di
P' = pressure, psi abs
02
W = flow, lbs/hr or [3], '"' = 157.6d C' � hLp 2
v = velocity, mean or average, ft./sec = 1891 d 0 C -y l1Pp (2-94)
2
,�
These conditions are similar to flow through orifices, where Q = liquid flow, gpm
nozzles, and venturi tubes. Flow through nozzles and ven- d, = diameter of orifice or nozzle opening, in.
turi devices is limited by the critical pressure ratio, re = di = pipe inside diameter in which orifice or nozzle is
downstream pressure/upstream pressure at sonic condi- installed, in.
tions (see Figure 2-38C). h' L = differential head at orifice, ft liquid
C' = flow coefficient (see Figure 2-39 for water and
For nozzles and venturi meters, the flow is limited by crit- Figure 2-18 and 2-19 for vapors or liquids)
ical pressure ratio and the minimum value of Y to be used. (text continued on page 118)