air flow metering

[LdPmtc]

what is the more practical ways of measuring air flow in ducts and at diffuser outlets
please let us have your oppinion?

 

[DrRTU]

1. Hire a certified test and balance contractor.

2. Standard flows in duct is best with a pitot traverse. How to measure flow

http://www.dwyer-inst.com/Products/AirMeas.cfm

3. Grilles are measured with a flow hood. Such as

http://buy.tsi.com/cgi-bin/ecom/prodline.pl?1284891242000&web=TSI&grp=AL&line=AB&lv=1

4. Smacna has an excellent testing and balance publication.

http://www.smacna.org/bookstore/index.cfm?fuseaction=search_results&cfid=10274787&cftoken=22426741

 

[sprinkler1000]

Balometer for measuring airflow in diffusers, pitot tube for measuring airflow in ducts.

See Alnor for balometers

 

[LdPmtc]

how practical is it use a pitot tube to determine duct velocity? my concern is if the pitot tube is not held 100% perpendicular with the air stream, how accurate is the velocity reading?

 

[berkshire]

It that concerns you, use a pot head pitot which is less sensitive to yaw angles.
B.E.

 

[KiwiMace]

An annubar is less sensitive to variations in the flow profile, in that it averages. Similar fundamentals to a pitot traverse, but can be used for permanent installation. Oft-used in VAV measuring stations.

Flow hood is the only good way for diffusers.

 

[LdPmtc]

what is your experience of using a hot wire anemometer for measuring inline duct velocity (instead of pitot tubes)?

 

[AnotherEllis]

For permanent installs for continuous monitoring I like to use Greenhecks's temperature compensating air flow measuring stations.

http://www.ellisconsultingengineers.com

 

[KiwiMace]

I have used hot wire anemometers in general site testing including duct traverses, but not against a standard.

They usually list in around 5% accuracy and are not as directional as a pitot. Gut feeling is that the hot RTD resistance measurement would be more robust than a low static dp, and thus more likely to be accurate between trips to the lab.

Quality means a lot with instruments though. You gets what you pays for.