[Bldg-sim] Negative pressure for EQ cr 5
Hopf, Johannes
johannes.hopf at dreso.com
Fri Oct 8 04:38:45 PDT 2010
Cheney, can you post the chapter in the ASHRAE Handbook of Fundamentals where
I can find the equation
Johannes
Von: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] Im Auftrag von Cheney
Gesendet: Mittwoch, 6. Oktober 2010 22:43
An: creations.deepa at gmail.com
Cc: Bldg-Sim
Betreff: Re: [Bldg-sim] Negative pressure for EQ cr 5
Hi Deepa,
My two cents.
For your question, you need to know:
1. the air volume in room and its pressure
2. To achieve 5Pa, how much more air should be introduced -
Higher pressure x air volume in room/atmospheric pressure
Now you get the number for the static condition... ;)
to maintain the pressure in a leaky room you have to pump in more air, right?
3. from the ASHRAE Handbook of Fundamentals:
Q = 2610 x A x (DP)1/2
* Q is the room leakage flow rate in cfm,
* 2610 is a conversion factor,
* A is the net open crack area of the room (generally not measurable), and
* DP is the differential pressure.
4. If you'd like to maintain certain pressure in the room, you need to supply
2+3 first. When the pressure is established in dynamic condition, you need to
supply only 3 to maintain the pressure you want.
This is only the theoretical calculation for your reference.
Cheers,
Cheney
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