When working with gases, especially compressed air, it is important to distinguish between physical flow (Q) and normalized flow (Qn), as they represent the same mass of air but under different reference conditions.

The tool allows you to enter the physical flow rate (Q) at the operating pressure

However, most users normally work with normalized flow (Qn) to avoid oversizing components

For this reason, even if you enter the flow in physical conditions, the software will automatically convert it into normalized flow (Qn) and use that value for all internal calculations, sizing, and checks

Physical flow (Q)

Q is the volumetric flow rate at the actual operating conditions, meaning at the real pressure and temperature in the system.

• Depends on operating pressure
• Depends on temperature
• Changes when pressure changes, even if air consumption (mass) stays the same

Example (compressed air):

If a pneumatic tool consumes air at 6 bar(g) and the measured flow at this pressure is 200 L/min, this value represents Q.

Normalized flow (Qn)

Qn is the volumetric flow rate converted to standard (normalized) conditions, typically:

• Pressure: 1.013 bar(a)
• Temperature: 0 °C or 20 °C (depending on the standard used)

Normalized flow represents the actual amount (mass) of air, independent of pressure.

Because of this, Qn is always higher than Q for compressed air systems.

Example (compressed air):