GIFSQ Tools · Module 06 — Bakery, Pasta, Breakfast Cereals & Snacks · Tool 117 of 500
Calculate the specific mechanical energy (SME) of an extrusion run from screw speed, torque and throughput.
Try sample values — fills the form with the worked example below.
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Mechanical power (kW)
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SME (kWh/kg)
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SME (kJ/kg)
Equation: Mechanical power (kW) = 2π × screw speed (rpm) ÷ 60 × torque (N·m) ÷ 1000. SME (kWh/kg) = power (kW) ÷ throughput (kg/h). SME (kJ/kg) = SME (kWh/kg) × 3600.
Method: Standard extrusion engineering definition of specific mechanical energy (Harper, Extrusion of Foods, 1981; Riaz, Extruders in Food Applications, 2000). Torque is the shaft torque at the stated screw speed; throughput is the steady mass flow rate.
Assumptions: steady-state running at constant speed and throughput; torque is the net shaft torque, not the motor nameplate value.
Limitations: SME covers mechanical energy only — thermal energy from barrel heating and steam is not included; comparing SME across different extruders needs the same product and die.
Rounding: power and SME in kJ/kg to 2 decimal places; SME in kWh/kg to 4 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: Standard extrusion engineering definition of specific mechanical energy (Harper, Extrusion of Foods, 1981; Riaz, Extruders in Food Applications, 2000). Torque is the shaft torque at the stated screw speed; throughput is the steady mass flow rate.
Assumptions: steady-state running at constant speed and throughput; torque is the net shaft torque, not the motor nameplate value.
Limitations: SME covers mechanical energy only — thermal energy from barrel heating and steam is not included; comparing SME across different extruders needs the same product and die.
Rounding: power and SME in kJ/kg to 2 decimal places; SME in kWh/kg to 4 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: screw speed 300 rpm, torque 100 N·m, throughput 200 kg/h. Power = 2π × 300 ÷ 60 × 100 ÷ 1000 = 3.14 kW; SME = 3.14 ÷ 200 = 0.0157 kWh/kg (56.55 kJ/kg).
Enter values above to see results.
Typical SME for cereal extrusion: 0.05–0.30 kWh/kg (180–1080 kJ/kg). Snack pellets run lower; directly expanded cereals run higher. Tool 117 of 500 — GIFSQ
