This document calculates the efficiency of a rotary screw compressor at a nitrogen PSA plant. It defines the polytropic coefficient and uses the ideal gas law to determine compressor power based on suction and discharge parameters. The compressor power, electrical power input, and assumed mechanical losses are used to calculate the compressor efficiency in two different ways, both resulting in an efficiency of approximately 60%.

1. Calculating Rotary Screw Compressor Efficiency at N2 PSA
Polytropic Coefficient is defined by
n
1n
P1
P2
T1
T2
eq1
see Ref_1.pdf
Suction Parameters Discharge Parameters
K27331T1
bar1P1 K273161T2
bar7.4P2
min
3
m
10.6Q
solve ,neq1
n
1.2164n Gas Constant for air
Kkg
J
287.1RCompressor Power is defined by
Rearrangement of ideal gas law
see Ref_1.pdfsee Ref_1.pdf
1
n
1n
P1
P2
1n
P1
Qn
Power
s
kg
0.2024
T1
R
QP1
QM
see Ref_2.pdf
1n
T1
T2
RQM
n
Powerother
W42472.249eval PowerPower W42472.1547Powerother
Compressor Electrical Parameters
Observed Parameters Assumed Parameters Assumed 5% Mechanical Losses
A134RunningLoad 0.85cosΦ 0.95MechanicalEff
V403Volt 0.9MotorEff
MotorEffcosΦRunningLoadVolt1.732RunningElectricalPower
eval RunningElectricalPowerRunningElectricalPower
W71551.57RunningElectricalPower
Compressor Efficiency%
1st solution
100
Power
PowerMechanicalEffRunningElectricalPower
CompressorEff
60.0433eval CompressorEffCompressorEff
2nd solution
100
Powerother
Powerother
MechanicalEffRunningElectricalPower
CompressorEff
60.0437eval CompressorEffCompressorEff
12 Dec 2017 21:46:45 - Compressor_Power_PSA.sm
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