Design Calculators - Mechanical

This calculator estimates the ideal (adiabatic or polytropic) and actual power required for a compressor, based on gas properties, pressures, inlet temperature, flow rate, and compressor efficiency.

Key Inputs:

• Unit System: Select Metric (kPa, m³/min, °C, kW) or Imperial (psi, ft³/min, °F, HP).
• Gas Type: Choose common gases to auto-populate the Specific Heat Ratio (\(k\)), Molar Mass (\(M\)), and a suggested Polytropic Exponent (\(n\)).
• Calculation Type: Select 'Adiabatic (Isentropic)' for ideal constant-entropy compression, or 'Polytropic' for a more realistic process including heat transfer.
• Inlet Pressure (\(P_1\)): The absolute pressure at the compressor's suction.
• Inlet Temperature (\(T_1\)): The absolute temperature of the gas at the compressor's suction.
• Discharge Pressure (\(P_2\)): The absolute pressure at the compressor's discharge.
• Inlet Volumetric Flow Rate (\(Q_1\)): The volumetric flow rate of the gas at inlet conditions.
• Specific Heat Ratio (\(k\)): The ratio of specific heats (\(C_p/C_v\)) for the gas (for adiabatic calculation).
• Molar Mass (\(M\)): The average mass of one mole of the gas mixture.
• Polytropic Exponent (\(n\)): An empirical exponent describing the actual compression process (for polytropic calculation). Typically \(1 < n < k\).
• Inlet Compressibility Factor (\(Z_1\)): Accounts for real gas deviation from ideal gas law at inlet conditions. Defaults to 1.0 for ideal gas.
• Compressor Efficiency (\(\eta_{comp}\)): The overall isentropic/polytropic efficiency of the compressor, as a percentage.
• Mechanical Efficiency (\(\eta_{mech}\)): The efficiency of the mechanical drive system (e.g., motor, gears) transferring power to the compressor shaft, as a percentage.

Calculated Outputs:

• Pressure Ratio (\(P_2/P_1\)): The ratio of discharge to inlet pressure.
• Specific Gas Constant (\(R_{specific}\)): The gas constant for the specific gas, derived from universal gas constant and molar mass.
• Mass Flow Rate (\(\dot{m}\)): The mass of gas flowing per unit time.
• Ideal (Isentropic/Polytropic) Discharge Temperature (\(T_{2,ideal}\)): The theoretical temperature of the gas at discharge.
• Ideal Power (\(P_{ideal}\)): The theoretical power required for the chosen ideal compression process.
• Actual Power (Brake Power) (\(P_{actual}\)): The mechanical power required at the compressor shaft, accounting for both compressor efficiency and mechanical efficiency.