Flue Gas Velocity Pressure Calculator

The measurement behind stack flow testing

Velocity pressure represents the kinetic energy of moving flue gas, distinct from static pressure - this is the exact quantity a pitot tube measures during EPA Method 2 stack testing, used to back-calculate stack gas velocity for emissions flow rate reporting.

Worked example

For flue gas at 0.7 kg/m³ density moving at 15 m/s:

VP = 0.5 x 0.7 x 15² = 78.75 Pa

Frequently asked questions

How is this used in reverse during actual stack testing? Field pitot tubes measure velocity pressure directly, then this same formula is rearranged (v = sqrt(2 x VP / density)) to solve for velocity - this calculator demonstrates the forward direction, going from known density and velocity to expected velocity pressure.

Why does density matter so much here? At the same velocity, denser flue gas carries more kinetic energy and produces higher velocity pressure - this is why accurate flue gas density (accounting for actual temperature, moisture, and composition) is essential for correct stack flow measurements.