[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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