Flow measurement in AHU

[juan2025]

Hello dear Members

We have a electronic velocity sensor located in a straight segment duct which send the velocity data to software and make a calculation for convert velocity to flow using the equation (Flow = Velocity * Area).
What kind of corrections have to do in order to obtain the real flow produced by the Air Handling Unit (AHU)? (All the sensors have beeen calibrated before)
What is the best way to measure the Flow in a AHU?

Thanks in advance for your help

Best Regards
Juan Ruiz

 

[235zzzo]

Hi Juan2025!

In order to help you, two questions:
-Your air duct, is it circular or rectangular?
-If you can, give some data about your anemometer device (I think, it is an anemometer).
Best Regards.
zzzo

 

[Islander]

...if your velocity sensor is reading feet per minute
of air flow..then it is simply..feet per minute x area of the duct=actual cfm output of ahu.

if your velocity sensor is reading pressure in inches h20...
then you have to calculate what your fpm is...

ex. anemomter reads at...05".
.05 x 4005(square rooted) x 4005 = 895.5 fpm.

then multiply the 895.5 x area of duct to get your cfm.

make sure your sensor location is...7xwidth of the duct downstream of any elbows/obstructions..and 3xwidth of duct upstream of any obstructions for best results.

best way to read flow is to have a test and balance guy read it...see if he can match with your sensor..I would not trust the sensor without having it checked this way.

also..density of air flow..(altitude..temp) can be a factor that has to be accounted for.