Inputs
Example Data Table
Sample field readings for a portable site compressor.
| Scenario | Inlet Pressure (bar abs) | Discharge Pressure (bar abs) | Inlet Temp (°C) | Flow (m³/min) | Power (kW) |
|---|---|---|---|---|---|
| Morning commissioning | 1.013 | 7.0 | 25 | 1.8 | 18.5 |
| Midday heat load | 1.013 | 7.0 | 35 | 1.7 | 19.2 |
| After filter service | 1.013 | 7.0 | 28 | 1.85 | 18.1 |
Formula Used
Power-based method (ideal-gas, isentropic):
- Pressure ratio: r = P₂ / P₁
- Isentropic discharge temperature: T₂s = T₁ · r^((k−1)/k)
- Mass flow at inlet: ṁ = (P₁ · Q) / (R · T₁) (air: R = 287.05 J/(kg·K))
- Specific work: wₛ = cₚ · (T₂s − T₁), where cₚ = kR/(k−1)
- Ideal power: Ẇideal = ṁ · wₛ
- Isentropic efficiency: ηis = Ẇideal / Ẇmeasured
- Overall efficiency: ηoverall = ηis · ηmech (optional)
Temperature-based method:
- Compute T₂s from pressures as above.
- Isentropic efficiency: ηis = (T₂s − T₁) / (T₂ − T₁)
- Overall efficiency: ηoverall = ηis · ηmech (optional)
How to Use This Calculator
- Select a method: power-based when you know inlet flow and measured power.
- Choose units, then enter absolute inlet and discharge pressures.
- Enter inlet temperature; for temperature method, also enter discharge temperature.
- Use k ≈ 1.4 for air unless you have better data.
- Optionally enter mechanical efficiency to estimate overall performance.
- Press Calculate, then export CSV or PDF for site records.
Accurate compressor efficiency checks help plan reliable site operations.