Centrifugal Compressor - Required Polytrophic Horsepower

This application uses initial impeller speed and final impeller rotational speed to determine final flow rate, compression head and final shaft Horsepower (HP). One drawback is the difficulty to determine efficiency which is based on the ratio of specific heat for the gas being used in the compressor.

𝐻𝑃 − Adiabatic Compressor Horsepower

𝑄 − Gas Flow Rate[MMSCFD]

𝑇₁ − Suction Temperature[°𝑅]

𝑇₂ − Discharge Temperature[°𝑅]

Z₁ − Compressibility of Gas at Suction Conditions

Z₂ − Compressibility of Gas at Discharge Conditions

𝑧_𝑎𝑣𝑔 − Average Compressibility Factor

𝑘 =  − Specific Heat Ratio

𝑛_𝑝 − Compressor Polytropic Efficiency

𝑃₁ − Gas Suction Pressure[psia]

𝑃₂ − Gas Discharge Pressure[psia]

CNGA/GPSA Compressibility Factor Approximation

𝑍 − Compressibility Factor

𝑃 − Pressure(psi)

𝑇_𝑓 − Gas Flowing Temperature[°𝑅]

This approximation will produce results sufficiently accurate for preliminary calculations.

Brake Horsepower

𝑛_𝑚 − Mechanical Efficency 𝑛_𝑚 = 0.95/0.98

 

Input Parameters

1. To create a new case, click the “Add Case” button
2. Select the Centrifugal Compressor – Required Polytropic Horsepower application from the Pipeline Compressor module.
3. Enter Case Name, Location, Date and any necessary notes.
4. Fill out all required fields.
5. Make sure the values you are inputting are in the correct units.
6. Click the CALCULATE button.

• Base Pressure(psi)
• Base Temperature(°F)
• Suction Pressure(psi)
• Suction Temperature(°F)
• Discharge Pressure(psi)
• Capacity/Required Flow Rate(ft/sec.)
• Gas Specific Heat Ratio
• Gas Specific Gravity (Relative to air)
• Adiabatic Efficiency (0.75 – 0.79)
• Mechanical Efficiency (0.95 – 0.98)
• Polytropic Efficiency
• Z1 – Compressibility Factor at Suction Conditions
• Z2 – Compressibility Factor at Discharge Conditions

 

Outputs/Reports

1. View the results.
2. If an input parameter needs to be edited be sure to hit the CALCULATE button after the change.
3. To SAVE, fill out all required case details then click the SAVE button.
4. To rename an existing file, click the SAVE As button. Provide all case info then click SAVE.
5. To generate a REPORT, click the REPORT button.
6. The user may export the Case/Report by clicking the Export to Excel/PowerPoint icon.
7. To delete a case, click the DELETE icon near the top of the widget.

• Polytropic Exponent
• Discharge Temperature(°F)
• Zavg – Average Compressibility Factor
• Adiabatic Head (ft lbf/lbm)
• Adiabatic GHP per Unit of the Flowrate(HP/MMSCFD)
• GHP – Adiabatic Gas Horsepower(HP)
• BHP – Adiabatic Brake Horsepower(HP)
• ACFM – Actual Flow Rate for Sizing(ft³/min)

Related Links