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Compressors, Pumps, and Turbines 221

(392 °F). For low temperatures, Moens [22] reported a temperature as low as -162
°C (-260 °F).
Compressor Sizing
Table 5.7 lists the equations for the sizing a centrifugal compressor and Table 5.8
outlines the calculation procedure. The equations listed in Table 5.7 assumes three
stages of compression. Equation 5.7.1 in Table 5.8 sums up the work for three
stages of compression, where z is the average of the inlet and outlet compressibil-
ity factors. Equations 5.7.1 to 5.7.3 can be adjusted to include more or less stages
of compression. The other equations remain the same. To determine the stages of
compression and the number of intercoolers, first assume one stage of compres-
sion, and then check if the discharge-temperature limit is exceeded. If it is, then
assume two stages of compression with intercooling after the first stage, and again
check if the temperature limit is exceeded. Repeat the process until the gas tem-
perature is below the maximum acceptable value after each stage of compression.
The discharge temperature can be calculated from Equation 5.14, which was dis-
cussed earlier. If R = c - c, is substituted into Equation 5.14, the result is Equa-
p v
tion 5.7.6 in Table 5.7,

Table 5.7 Summary of Equations for Sizing a Compressor

n i)/n
n i)/n
ZR'T,' r v - ( p 4 V -
fp
2
W PN = ————— I I — I - 1 + 1 ————————I - 1
(n-l)/n L (.Pi') lP2-0.1P2 av )
n 1)/n
( P 6' Y - 1
+ I ———————— I -1 I (5.7.1)

for two stages of compression:

P 2 P 4
P,' P 2 -0.1P 2 07

for three stages of compression:
P 6'
P 4
_ _ _________ fc 1 -5\
(P./.JJ
07
P 3 P 4 -0.1P 4
P 2/P,=P 4/P 3 (5.7.4)

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