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Thread: Air change rate

09082013, 11:22 PM #1
Air change rate
Hi all,
I am hoping someone could offer some assistance. I was advised a fairly simple way of calculating the require air flow rate required to condition an area can determined by the following formula:
Room volume (m3) x Air changes = Air flow (l/s)
I was also advised to use a quantity of (10) for this 'air change'. (As an average).
Can anyone advise how you actually calculate this '10' air changes?
Thanks in advance for any assistance?

10082013, 12:07 AM #2
Re: Air change rate
Hmmm,
Some mix and match there...
If we start with the formula, then if you use m3 in the input the result will come out in m3 not litres.
And as for air changes in the formula, that must be desired air changes per hour and the result would therefore be per hour and not per second.
Your formula would therefore be: V(m3) x chances per hour = airflow (M3/hr), to get this in to l/s you have to divide it by 0.36. (1m3=1000l and there are 3600 seconds per hour)
Now, as different environments requires different amount of air changes I can't see any rule of thumb giving a value of 10 for the number of air changes.
However, it is normally considered that 10 l/s is the minimum amount of fresh air per person but that is a different way of calculating the fresh air requirement, bypassing the need to calculate air changes.
Any chance you mixed up the two ways of calculation?
Last edited by frank; 10082013 at 07:39 AM.

10082013, 12:17 PM #3
Re: Air change rate
Thanks for this. Yes, I made a mistake. I rechecked the formula: area(m2) x air changes = air flow (l/s). Unfortunately no one at my office can tell me why we use this 10 ACH, and say; not 8 or 12 etc? As I say, just very curious how to calculate this ACH.
Thanks

10082013, 12:30 PM #4
Re: Air change rate
http://www.engineeringtoolbox.com/ai...oomd_867.html
list of air change rates for different applications