KEVOS® MAKEOS · Pneumatics
Gas Compression and Expansion Process
What final volume, temperature and work result from compressing or expanding this gas?
Final volume and temperature and the work for isothermal, adiabatic or polytropic compression or expansion of a gas between two absolute pressures.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Process | choice | How heat is exchanged during the process. |
| Initial pressure (absolute) | bar | Absolute starting pressure (1.013 bar at sea level for free air). |
| Initial volume | L | Starting volume. |
| Initial temperature | °C | Starting temperature. |
| Final pressure (absolute) | bar | Absolute final pressure. |
| Ratio of specific heats k | k = cp/cv (1.4 for air and nitrogen). | |
| Polytropic exponent n | Polytropic exponent for the polytropic process (between 1 and k for cooled compressors). |
Method and formulas
- p₁V₁ⁿ = p₂V₂ⁿ, with n = 1 (isothermal), k (adiabatic) or as entered.
- T₂ = T₁ (p₂/p₁)^((n − 1)/n) (kelvin).
- Work (closed system): isothermal p₁V₁ ln(p₂/p₁); otherwise (p₂V₂ − p₁V₁) ÷ (n − 1).
- Example: adiabatic compression of 100 L of air from 1.013 to 8 bar abs ends at 255.92 °C in 22.853 L.
Limitations
- Ideal gas; real compressors also have valve losses and leakage.
- Closed-system (non-flow) work; for steady-flow compressor work see the compressor power tool.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Estimate discharge temperature of a compressor
- Find work and volume for an air spring or accumulator
- Compare isothermal and adiabatic behaviour
Who it is for
- Process engineers
- Maintenance engineers
- Design engineers
What you get
- Final volume
- Final temperature
- Work done on (or by) the gas
Interpreting the result
- High adiabatic temperatures show why compressors need intercooling and aftercooling.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3032–3041. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
