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Gas Movers and Compressors
• Fans
• Centrifugal blowers and compressors
• Rotary blowers and compressors
• Reciprocating compressors
• Ejectors
• Discharge pressure > 2 bara = compressor
Gas Movers and Compressors
• Where are they needed?
Gas Movers and Compressors
• Where are they needed?– utility air, steam– high pressure reactor;– refrigeration– heat pumps– feed to furnaces
• Question: When is redundancy necessary?
Fans
• Low pressure (ca 101 kPa) and low P (1-15 kPa)
• High volume flow to 500 std m3/s
• Efficiencies of 65-80%• Variety of materials• Four types
Centrifugal Fan
Centrifugal Compressors
• Pressure to 700 atm, 1.2-1.4 compression ratio/stage
• Up to 8 stages per casing
• Volume flow to 200 std m3/s
• Efficiencies of 70-80%
• Favored choice for P < 15 atm
What is the compression ratio?
Outlet pressure/inlet pressure
Axial Compressors• Pressures to 14 atm• Compression ratio 1.4
per stage, up to 15 stages/casing
• High volume flow to 300 std m3/s
• Efficiencies of 80-85%• Expensive, inflexible
operation• Base loads, utilities
Rotary Compressors• Medium pressure (to 10
atm) and compression ratio to 4!
• Low volume flow to 20 std m3/s
• Efficiencies of 60-80%• Good for constant volume
delivery• Four types listed in UlrichSliding vane compressor
Reciprocating Compressors
• Pressure to 3000 atm, compression ratio=4/stage
• Up to 8 stages per casing
• Efficiencies of 60-80%
• Expensive, but commonly used for high-pressure applications
All of this information is summarized in one table:consider the first half in detail
Radial Fans Axial Fans CentrifugalCompressors
Summary:Selection of Equipment
• Fans are for low P (101 kPa), low P (1-15 kPa)
• Blowers (centrifugal and rotary) are for moderate pressures, up to 1 MPa
• Compressors operate at 0.01 to 30 MPa depending on type
• Turbo-expanders are like compressors running in reverse for power recovery
Summary: Selection
• Select based on:– range of application– location– cost– service
Costing of Fans and Compressors
• What is the size basis?
For fans, the volumetric flow: P is low
For compressors, power or shaft work: must be considered
Fans
Blo
wer
s an
d C
omp
ress
ors
Mot
ors
Compressor Calculations
/
w m vdp
w w
fp
p
s f i
1
2
Fluid Powerfor costing
Shaft Powerfor driver
Non-ideal fluids:
m
whh
ww
hhmw
sSinTexit
iconstSfs
SinSexitconstSf
in
inin
,,
,
,,,
/
)(
Compressor Calculations (cont)
Ideal Gas:
vp
kk
f
CCk
p
p
kM
kRTmw
/
1)1(
//)1(
1
21
Temperature increases with compression compression ratio p2/p1 < 4 for each stage
Example Compressor
• Hydrogen compressor, from 1 MPa at 25 C to 20 MPa
• Flow rate of 0.123 kg/s
• What is the bare module cost?