Horsepower required to Compress Air

The horsepower required to adiabatic compression of air can be calculated with the calculator below:

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Theoretical horsepower required to compress one cubic foot of free air (atmospheric pressure) for single-staged, two-staged and three-staged compressors are indicated in the diagram below. In general - plus 15-20% friction.

• 1 cfm (ft³ /min) = 1.7 m³ /h = 0.47 l/s = 28.3 l/min
  
• 1 psi (lb/in²) = 6894.8 Pa (N/m²) =  6.895 10^-2 bar
• 1 hp = 745.7 W

The power required for adiabatic (process without transfer of heat) compression of air can be expressed as

HP = [144 N P₁ V k / (33000 (k - 1))] [(P₂/ P₁ ) ^{(k - 1)/(N k)} - 1]                                (1)

where

HP = horsepower

N = number of compression stages

k = 1.41 = adiabatic expansion coefficient

P₁ = absolute initial atmospheric pressure (psi) (14.7 psi at sea level)

P₂= absolute final pressure after compression (psi)

V = volume of air at atmospheric pressure - standard or free air (scfm, ft³ /min)

• adiabatic compression (or expansion) takes place without transmission of heat

Temperature ^oC
K
^oF

Length m
km
in
ft
yards
miles
naut miles

Area m²
km²
in²
ft²
miles²
acres

Volume m³
liters
in³
ft³
us gal

Weight kg_f
N
lbf

Velocity m/s
km/h
ft/min
ft/s
mph
knots

Pressure Pa
bar
mm H₂O
kg/cm²
psi
inches H₂O

Flow m³/s
m³/h
US gpm
cfm