Reciprocating Compressor - Cylinder/Equivalent Capability & Horsepower

This application uses a positive displacement compressor model to deliver gases at high pressures. With piston displacement reciprocating compressors, often final outlet temp could be a concern.

Piston Displacement

Single-Acting Piston Compression on the Outer End Only:

Single-Acting Piston Compression on the Crank End Only:

Double-Acting Piston Compression (Other than Tail Rod Type):

Double-Acting Piston Compression (With a Tail Rod):

𝑃𝐷 − Piston Displacement[ft³/min]

𝑠 – Stroke[𝑖𝑛]

𝑛 − Rotational Speed[rpm]

𝐷 − Cylinder Inside Diameter[in]

𝑑 − Piston Rod Diameter [in]

Reciprocating Compressor Volumetric Efficiency 

𝑉𝐸−Volumetric Efficiency[%]

𝐴 − Effect of Leakage, Losses, etc.[%]

𝐿_𝑢 − Effect due to Lack of Lubrication[%]

𝑟 − Compression Ratio[𝑃₂/𝑃₁]

𝐶−Cylinder Clearance as a Percent of Cylinder Volume[%]

𝑧_𝑠 − Compressibility Factor at Suction Conditions

𝑧_𝑑 − Compressibility Factor at Discharge Conditions

𝑘 − Adiabatic/Isentropic Exponent[𝑐_𝑝/𝑐_𝑣]

In practice for normal operation

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.

Reciprocating Compressor Horsepower

𝑄 − Suction Capacity[SCFM]

𝑃₁ − Gas Suction Pressure(psi)

𝑛 − Compressor Efficiency

𝑘 =  −Specific Heat Ratio

𝑟 − Compression Ratio [𝑃₂/𝑃₁]

Ideal Discharge Temperature

𝑇_{2(𝑖𝑑𝑒𝑎𝑙)} − Ideal Discharge Temperature[°R]

𝑇₁ − Suction Temperature[°R]

𝑟 − Compression Ratio [P₂/P₁]

𝑘 − 𝐴diabatic/Isentropic Exponent 

Theoretical Discharge Temperature

𝑇₂ = 𝑇₁ + ∆𝑇_{𝑖𝑑𝑒𝑎𝑙}

𝑇₂ − Theoretical Discharge Temperature[°R]

Actual Discharge Temperature

𝑇₂ = 𝑇₁ + ∆𝑇_{𝑎𝑐𝑡𝑢𝑎𝑙}

𝑇₂ − Actual Discharge Temperature[°R]

𝑛_𝑎 − Adiabatic (Isentropic)Efficiency

Input Parameters

1. To create a new case, click the “Add Case” button
2. Select the Reciprocating Compressor – Cylinder/Equivalent Capability & 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)
• Select Piston Acting Compressor Type
• Bore/Cylinder Inside Diameter(in)
• Stroke/Travel Length of Piston(in)
• Rotational Speed(rpm)
• Cylinder Clearance (%)
• Piston Rod Diameter(in)
• Suction Pressure(psi)
• Suction Temperature(°F)
• Discharge Pressure(psi)
• Gas Specific Heat Ratio
• Gas Specific Gravity (Relative to air)
• Compressor Mechanical Efficiency (0.95 – 0.98)
• 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.

• Piston Displacement(ft³/min)
• Discharge Temperature(°F)
• Z1 – Compressibility Factor at Suction
• Z2 – Compressibility Factor at Discharge
• Volumetric Efficiency (%)
• Cylinder Capacity(ft³/min)
• Equivalent Capacity(MMSCFD)
• Cylinder Brake Horsepower Required(HP)

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