[Bldg-sim] Negative pressure for EQ cr 5

Cheney chenyu73 at gmail.com
Wed Oct 6 13:43:24 PDT 2010

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,

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.
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