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Re: [EnergyPlus_Support] Re: How do you disable modulation of opening factors?
I think you might actually get better behavior if you change the timestep in
hour to be 4 or 6 rather than 1. Beyond that, if the open windows are able to
cool the zone in one HVAC timestep, then it appears there is too much cooling
available for the current conditions (either the windows are too large, or the
outdoor temperature is too cold. Perhaps with a little experimenting, you can
determine a lower outdoor temperature limit below which the windows should not
be opened? Then you could report the outdoor temperatures for a year and
create an hourly venting schedule to disable the windows when it is too cold
out? You can use SCHEDULE:FILE:COMMA to pull in an hourly schedule. Just
trying to think of a solution here.
I will add some additional vent control options to the wish list as well.
Mike
On 7 Sep 2006 at 15:16, colotupper wrote:
> Thanks for explaining that!
>
> It's a little strange that the decision of whether or not to open the
> windows occurs on a minute by minute basis (this is how it appeared
> when I output in detailed mode). It would be nice if there was a
> control that could force the windows to be either open or closed for
> at least a half an hour (or something other time chunk) to avoid the
> unrealistic modelling of windows being opened and closed every minute
> based on temperature conditions.
>
> Also, I am trying to model cross ventilation, but the opposite windows
> are not always opening at the same times. Is there any way to model
> ventilation with temperature control and force the windows to open
> simultaneously? I am guessing this has to be done with the constant
> control mode and a schedule, but then the windows are opened
> regardless of the outdoor air temperatures.
>
> Thanks,
>
> Kendra
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Lixing Gu <gu@...> wrote:
> >
> > Kendra:
> >
> > What you have done is right to make all opening factors either 0 or 1.
> > Output results are also right at "timestep" report frequency.
> >
> > There are two timesteps used in EnergyPlus: zone time step and
> system time
> > step. The zone time step is your input from the TIMESTEP IN HOUR
> object. The
> > system time step is used internally and is determined by zone
> temperature
> > difference between previous timestep and current timestep. If the
> difference
> > is more than 0.3C, the system time step is shorter than the zone
> time step.
> > The AirflowNetwork model is performed at the system timestep level.
> If you
> > use "detailed" reprt frequency, you can see opening factors are
> either 0 or
> > 1.0. When "timestep" reprot frequncey is used, the opening factors
> are gived
> > as an average value over a zone timestep when system time step <
> zone time
> > step. That is why you see opening factors vary between 0 and 1.0.
> >
> > Please let me know if you have more concerns.
> >
> > Lixing Gu
> > Florida Solar Energy Center
> >
> > ----- Original Message -----
> > From: "colotupper" <kendra.tupper@...>
> > To: <EnergyPlus_Support@xxxxxxxxxxxxxxx>
> > Sent: Wednesday, September 06, 2006 9:12 PM
> > Subject: [EnergyPlus_Support] How do you disable modulation of opening
> > factors?
> >
> >
> > >I am simulating Natural Ventilation with Airflow Networks and my
> > > Ventilation Control Mode = Temperature. I want to have only 2
> > > conditions: closed windows (opening factor = 0) and open windows
> > > (opening factor = 1). I have set Limit Value on Multiplier for
> > > Modulating Venting Open Factor = 1, and all opening factors equal to 1
> > > as well.
> > >
> > > For some reason, when i output hourly results, my Opening Factor and
> > > Opening Factor Multiplier for Venting Modulation vary between 0
> and 1.
> > >
> > > I read past messages about this problem and tried changing my
> > > timesteps and reporting frequency, but this had no effect. Right now,
> > > I have my timestep set to 1 and my report frequency set to timestep.
> > > I also tried letting all of the fields default to disable the
> > > modulation, but this had no impact either.
> > >
> > > I am going to post this file - if anyone has any suggestion, I would
> > > greatly appreciate it!
> > >
> > > Thanks,
> > >
> > > Kendra
> > >
> > >
> > >
> > >
> > >
> > >
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>
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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