A Question About the Flow of Axial Fan

You don't need those two parameters also. Simply measure average gas velocity in the duct with the help of pitot and multiply it with duct cross section area to get the flow.

please let me know how to measure average gas velocity in the fan.

thanks for your answer.

1. Do a traverse across the duct with a pitot tube.
2. Install a vortex-shedding flowmeter.
3. Install a doppler-effect ultrasonic flowmeter.
4. Using the fan manufacturer's performance curve, measure the differential pressure across the fan and use it to find the operating point on the curve.
5. Etc.