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Help with duct flow rate testing

Help with duct flow rate testing

Help with duct flow rate testing

I haven't done this kind of testing before and would like to verify that I'm on the right track.

There is a duct system with many branches and in order to properly balance the system need to do some testing. I'm using an S type pitot tube with an inclined manometer. The duct is round and am taking (10) samples vertically and (10) horizontally based on a traverse set up for equal concentric areas. The tube and manometer are set up to read velocity pressure. At each duct I'm taking one temperature reading.

Velocity (ft/min) is calculated at each reading using velocity=4005 * sqrt(velocity pressure). All readings are then used to calculate the average velocity. Flow is calculated from average velocity * cross sectional area (sq.ft.)of duct. Then adjusting for temperature by multiplying by (530 / (T deg F + 460)) to get scfm.

Is this correct?

Thanks in advance for your help.

RE: Help with duct flow rate testing

Forgot to add in the Pitot Tube Correction Factor of 0.84. So velocity would be 4005 * 0.84 * sqrt(measured velocity pressure).

This is also assuming dry air.


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