KEVOS® MAKEOS · Pneumatics
Air Compressor Staging Check (Power and Discharge Temperature)
Should this air compressor be single- or two-stage: how much power does each take, what discharge temperature does each reach, and does the chosen arrangement stay within the temperature limit?
Comparison of single-stage and two-stage compression with perfect intercooling: pressure ratio, adiabatic and shaft power for one and two stages (as the compressor power tool), the best intermediate pressure √(p₁ p₂), the ideal adiabatic discharge temperature for each case (as the gas compression process tool) and the actual temperature allowing for the adiabatic efficiency, the power saved by staging, and the discharge temperature of the chosen arrangement against your limit.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Air delivery (as free air) | m³/min | Air delivered, as free air at inlet conditions. |
| Inlet pressure (absolute) | bar | Absolute pressure at the inlet. |
| Discharge pressure (gauge) | bar | Gauge pressure at discharge. |
| Inlet temperature | °C | Air temperature at the inlet (and after the intercooler). |
| Ratio of specific heats | Ratio of specific heats (1.4 for air). | |
| Adiabatic (overall) efficiency | % | Adiabatic efficiency used to turn ideal power and temperature rise into actual values. |
| Arrangement to check | choice | Arrangement whose discharge temperature is checked. |
| Largest discharge temperature | °C | Highest discharge temperature for the lubricant, valves and piping (your value from the maker). |
Method and formulas
- r = p₂(abs) ÷ p₁; adiabatic power = s k ÷ (k − 1) p₁ Q [r^((k−1)/(s k)) − 1] for s stages; shaft = adiabatic ÷ efficiency (as the compressor power tool).
- Best intermediate pressure p_i = √(p₁ p₂) (equal ratio per stage, intercooled to inlet temperature).
- Ideal discharge T = T₁ r_s^((k−1)/k) (as the gas compression process tool); actual T = T₁ + (ideal rise) ÷ efficiency.
- Example: one stage needs 63.475 kW and reaches 334.89 °C; two stages need 54.165 kW and reach 154.36 °C, saving 14.666%.
Limitations
- Perfect intercooling to inlet temperature; real intercoolers leave a temperature approach.
- Ideal-gas, steady-flow model; oil-flooded screw compressors control discharge temperature by injection.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose between single- and two-stage compressors
- Check discharge temperature for oil and valve life
- Estimate the power saved by an intercooler
Who it is for
- Plant engineers
- Energy managers
- Maintenance engineers
What you get
- Pressure ratio and best intermediate pressure
- Power for one and two stages and the saving
- Discharge temperatures and the check
Interpreting the result
- Above a pressure ratio of about 4–5 per stage, discharge temperatures rise fast: staging protects valves and oil as well as saving power.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3032–3041. Topic reference; no source tables or recommended settings are reproduced.
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Open the Air Compressor Staging Check (Power and Discharge Temperature) calculator
