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[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:
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> 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
>
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> --- 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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> > I know the direction (from inside to outside and vice versa) of the
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> > flow in the window?
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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 outside.
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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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> > > confirm the following:
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> > > When I set as output variable AirflowNetwork Mass Flow Rate from Node
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> > > 1 to 2 and AirflowNetwork Mass Flow Rate from Node 2 to 1 for a
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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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> > > variable is greater?
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> > > Regards,
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> > > Alberto Hernandez Neto
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