Area of slot diffuser when calculate air flow during commissioning

[chaiwat]

Now I am commissioning air flow balance, How can calculate area of slot diffuser?

[r.bartlett]

contact manufacturer for free area.

[Brian_UK]

Make up an air collection hood and use that for measurements.

Don't forget to calibrate it against a proven/measured airflow.

[dougheret0]

r.bartlett is correct. The manufacturer will have a web site with diffuser technical catalogs and submittal sheets for free. Just google the manufacturer's name and the web site should be on the first search page. The engineering catalog will have all of the data on your diffuser, including free area, static and total pressure drop vs air flow, and throw vs air flow. You can usually download the catalog for future reference.

As Brian noted, you will need an airflow measurement hood, such as those made by Alnor, to measure the airflow and compare it to the design.