A compressor is equipment to raise the pressure of a compressible fluid. Work is required as an input to the compressor in this process. User can calculate theoretical energy consumption through the calculation below.
Formula of adiabatic compression
W = Pi*Vi*(k/(k-1))*[(Pe/Pi)^((k-1)/k)-1]
Where,
W : fluid or gas power (Watt)
Vi : inlet or suction flow (m3/s, actual condition)
Pe : exit or discharge pressure (N/m2)
ηc : compressor efficiency
Example of adiabatic compression
If an adiabatic compressor compresses 5,000 m3/hr of atmospheric air to 10 barg, how much energy will it consume (adiabatic efficiency η = 75%, ratio of specific heats k = 1.4)?
Pi : inlet or suction pressure (N/m2)
k : ratio of specific heats = cp/cv ()
Vi = 5,000 m3/hr = 1.389 m3/s
k = 1.4
Pi = 0 barg = 101,325 Pa
Pe = 10 barg = 1,101,325 Pa
η = 75%
W = Pi*Vi*(k/(k-1))*[(Pe/Pi)^((k-1)/k)-1]/η
W = 101,325*1.389*1.4/(1.4-1)*((1,101,325/101,325)^((1.4-1)/1.4)-1)/0.75 =
Pe = 10 barg = 1,101,325 Pa
η = 75%
W = Pi*Vi*(k/(k-1))*[(Pe/Pi)^((k-1)/k)-1]/η
W = 101,325*1.389*1.4/(1.4-1)*((1,101,325/101,325)^((1.4-1)/1.4)-1)/0.75 =
641,832 W = 642 kW
