mechanical airflow formula

[ambrosia]

someone tell me the formula for calculating mechanical ventilation airflow, i dont like relying on an app and theyve removed the formula for calculating mechanical ventilation airflow from our books and exams. very frustraiting

i seem to remember it was some thing like; wind speed averaged over five points x surface area of the vent in meters x 3600 =m3 per hour. however the result comes out different from the app i'm using
ENGINEERING.com | Air Flow Conversion Calculator

thanks in advance

 

[ShaunCorbs]

@Last Plumber dong suppose you know off your head ?

 

[Last Plumber]

@Last Plumber dong suppose you know off your head ?

Not off top of my head Shaun but I could find out.

 

[Last Plumber]

someone tell me the formula for calculating mechanical ventilation airflow, i dont like relying on an app and theyve removed the formula for calculating mechanical ventilation airflow from our books and exams. very frustraiting

i seem to remember it was some thing like; wind speed averaged over five points x surface area of the vent in meters x 3600 =m3 per hour. however the result comes out different from the app i'm using
ENGINEERING.com | Air Flow Conversion Calculator

thanks in advance

If you take anemometer readings at the 5 points of a vent e.g. 4 corners and centre, add the readings then divide by 5 you 'll get the average (M/s).
Convert the free area of the vent to M/2
Times the free area in M/2 by the average M/s and that will give you the Air flow rate in M/s

Flow rate (Q) m3/s = V (m/s) x A (M2)

If you calculate the free area of the vent in mm2 or cm2 you need to remember to covert it to m2

I think this is the calculation you might be recalling but not sure if it's what you need the answer to??

 

[Last Plumber]

Example from book.
Measurements taken from the 5 points in M/s
1.7 + 3.4 + 2.9 + 3.6 + 4.2 = 15.8 M/s

15.8 divided by 5 point = 3.16 M/s average

So if the free area of a vent is 900 cm2 You divide that by 10000 to change it to M2

That gives 0.09 M2 x 3.16 = 0.2844 M 3/s

Hope this helps!

 

[ambrosia]

thanks guys