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Re: [EnergyPlus_Support] Re: Mixing objects assumptions
Your last point is correct, if you use exhaust fans you "might" get
unbalanced flows but you will have a lower return air flow than you
expect. Use the mixing object to move air from the first zone (any zone
you choose) to your zone. Remember to make up the amount of air in the
first zone using another mixing object or infiltration.
anarui.oliveira wrote:
>
> I find the documentation isn't completely clear to me on this point.
>
> So, if I have a zone which, in reality, has only forced exhaust, and
> which receives air by pressure difference from an adjacent zone, what
> would be the best way to model it, for the purpose of heat balance
> and thermal loads calculation?
>
> If I use just the mixing and infiltration objects, is it actually as
> if I was continuously increasing the zone air volume? Should I add a
> mixing object to extract the correspondent airflow to some dummy zone?
>
> If I implement an exhaust fan, since the mixing object does not use
> inlet nodes, I suppose I'll get unbalanced flow errors?...
>
> Thanks again,
> Ana.
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com>, "Edwin Lee"
> <leeed2001@...> wrote:
> >
> > There is also a cross-mixing object, which is described in the
> > documentation, that simulates air exchange between two zones, and
> therefore
> > affects both zones energy balance.
> >
> > On Mon, Apr 28, 2008 at 9:36 AM, Richard Raustad <RRaustad@...>
> > wrote:
> >
> > > When mixing objects are used, the user is responsible for
> accurately
> > > predicting the air flow into and out of a zone. Only air entering
> a zone
> > > is used in the heat balance. Infiltration and mixing (into a
> zone) are
> > > included in the heat balance predict step (mi and minf in Eng.
> Ref. Eq 2
> > > and 5) Supply air entering a zone is included in the heat balance
> > > correct step (msys in Eng. Ref. Eq 5). The return air leaving the
> zone
> > > is assumed to be balanced based on the supply and exhaust node
> mass flow
> > > rates (mixing and infiltration are not included here). You can
> read more
> > > about the assumptions for balanced flow in the text near these
> equations
> > > in the Engineering Reference.
> > >
> > >
> > > anarui.oliveira wrote:
> > > >
> > > > Hi, everyone.
> > > >
> > > > I think I've read this somewhere, but I can't find it now:
> > > >
> > > > - When doing the heat Balance for a Zone Air volume that is
> receiving
> > > > air with a mixing object, does E+ assume that an equal amount
> of air is
> > > > withdrawn from that zone, for heat balance purposes?
> > > >
> > > > Thank you in advance,
> > > > Ana Rui.
> > > >
> > > >
> > >
> > > --
> > > Richard A. Raustad
> > > Senior Research Engineer
> > > Florida Solar Energy Center
> > > University of Central Florida
> > > 1679 Clearlake Road
> > > Cocoa, FL 32922-5703
> > > Phone: (321) 638-1454
> > > Fax: (321) 638-1439 or 1010
> > > Visit our web site at: http://www.fsec.ucf.edu
> <http://www.fsec.ucf.edu>
> > >
> > > UCF - From Promise to Prominence: Celebrating 40 Years
> > >
> > >
> > >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
--
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL 32922-5703
Phone: (321) 638-1454
Fax: (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu
UCF - From Promise to Prominence: Celebrating 40 Years
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