RE: [EnergyPlus_Support] Re: Actual Air flow ?

I think, it is just like the OA mixer box. Inlet air volume and exhaust (relief) air amount are equal.

When the inlet volume is small, the relief air is ignored. When the inlet temperature is different from the desired temperature zone temperature by a large value , one starts to think about pre-cooling and pre-heating using the return air.

No one will open a window in Winter and use AFN. When AFN is in use for natural ventilation, the exhaust air amount should equal to the inlet air amount, when all the five OA nodes are specified for one wind velocity..

For infiltration and ventilation objects, they are usually scheduled to reduce energy consumption, when the temperature difference between the inlet or outlet with the zone is large..

If the two windows are on the same wall, the AFN may not have net flow through them.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Tue, 3 Jul 2012 13:54:55 +0000
Subject: [EnergyPlus_Support] Re: Actual Air flow ?

Bidirectional flow is also calculated depending on what object you are using (AirflowNetwork models such two-directional flow, but only for vertical openings).

I think you may be right that only infiltration is considered in load calcs, but then exfiltration is usually less interesting (has very small impact on building energy usage). This is the case for TrnSys.

However,
the io ref states that exfiltration is better handled with an exhaust componant and that AFN can "16) Determine the impact of zone exhaust fans on air flows, pressures, air temperatures/humidity levels and energy consumption."

I've not checked the engineering ref on this.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "lisacng" <lisa.ng@...> wrote:
>
> Alberto, Oscar
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> Just to make things clear, "inside" and "outside" aren't inside the building and outside the building. It is the inside or outside face of the referenced surface (AirflowNetwork:MultiZone:Surface // Surface name // Leakage component name) where your leakage element is.
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> Also, in the same hour, you are seeing two different values for 1-->2 and 2-->1 in the same window because your time step is smaller than an hour. If you output detailed or timestep results, you will see that only one flow should have a value and the other is zero. The hourly output is an average of the timestep outputs. If using the hourly results is fine, then the flow of air is the difference of 1-->2 and 2-->1 and the direction is determined by which is greater.
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> It should be noted that EnergyPlus only uses the flow into a building from the outdoors to affect the load on a zone. Exfiltration (air leaving a building) and mixing of air between zones does not affect load calculations. Someone out there can correct me if I'm wrong.
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> Lisa Ng
> NIST
> IAQ & Ventilation Group
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, oscar hernandez <oscarhernandez_81@> wrote:
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> > Don't worry.
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> > If I remember, 1 to 2 is from outside to inside and 2 to 1 inside to outside. Look at the energyplus input output manual (airflow network) you have everything about that.
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> > Let me know if you need more help.
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> > Oscar.
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > From: ahneto@
> > Date: Sat, 30 Jun 2012 17:44:40 -0300
> > Subject: RE: [EnergyPlus_Support] Actual Air flow ?
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> > Dear Oscar,
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> > Sorry to bother you again but , regarding the air flow network, how do
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> > Thanks for your help.
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> > Alberto
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> > Citando oscar hernandez <oscarhernandez_81@>:
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> > > THe value 1 to 2 or 2 to 1 is the flow rate. You have to inside or
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> > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
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> > > From: ahneto@
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> > > Date: Fri, 29 Jun 2012 13:54:19 -0300
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> > > Subject: [EnergyPlus_Support] Actual Air flow ?
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> > > Dear Forum,
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> > > I modeling a room with the AirFlowNetwork object. I would like to
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> > > When I set as output variable AirflowNetwork Mass Flow Rate from Node
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> > > exterior window, the difference between these two variables will give
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> > > the actual flow rate and the direction will be set verifiying which
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> > > Regards,
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> > > Alberto Hernandez Neto
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