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[EnergyPlus_Support] Re: Should I model the plenum?
Dear Alan,
Perfect! I had forgotten about that field. Thanks for responding.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Alan Jackson"
<alan.jackson@...> wrote:
>
> JV
>
>
>
> With regards to the second item, have you looked into the lights field:
> return air fraction? I believe this is what you are looking for.
>
>
>
> -
>
> alan
>
>
>
> ________________________________
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of JV Dirkes II
> Sent: Friday, April 25, 2008 9:45 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: Should I model the plenum?
>
>
>
> Dear E+ Forum,
>
> I am deciding whether to model a return plenum in a new project and
> have reviewed some of the old discussions in the Forum. It seems that
> the consensus is "Don't bother with the plenum".
>
> However, I have not seen a discussion that addresses the heat added by
> lighting which is suspended in the ceiling. Since a significant
> portion of suspended lighting is added to the plenum in a suspended
> ceiling design, the fan sizing is affected, and that's of interest to
> me.
>
> If I decide to model the plenum, is there a way to assign a fraction
> of the lighting energy to two different zones (the below-ceiling zone
> and above-ceiling zone)? My best thought so far is to create a Lights
> object for the below-ceiling zone and an Equipment object for the
> above-ceiling zone, giving each of them the appropriate amount of
> Watts and an identical schedule.
>
> So....
> 1) Any opinions regarding the need to model return plenums in order to
> capture the lighting energy in the return air stream (and not the zone)?
> 2) Does E+ have a means to add lighting energy to a return plenum in a
> more elegant manner than my "best thought"?
>
> Thanks!
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> , fred buhl <wfbuhl@>
> wrote:
> >
> > For calculating building energy consumption, modeling the plenums as
> > separate zones is generally
> > not very important. There are cases where it will be important: 1
> story
> > building with a large roof area
> > and considerable outside air. For a multi-story office building it
> isn't
> > important.
> >
> > Fred Buhl
> >
> > Michael J. Witte wrote:
> >
> > >Should you model plenums? It depends largely on the specific goals
> of the
> > >analysis.
> > >
> > >If you decide to ignore the plenums, you must make the conditioned
> zones tall
> > >enough to include the plenum height so that the total area of
> exterior wall is
> > >accounted for.
> > >
> > >If you choose to model the plenums, then the plenum is modeled as a
> thermal
> > >zone.
> > >
> > >With EP-Quick it may be possible to create two buildings - one that
> is 7
> > >stories with a floor-to-floor height of the conditioned space only,
> and then
> > >another which is 7 stories with a floor-to-floor height of the
> plenum space
> > >only, and then mix the two together. All of the surface
> coordinates should be
> > >OK except for the z values which could be easily modified to stack
> thing up
> > >correctly. Note that the plenum floors will come out of EP-Quick
> as multiple
> > >zones, but these can be combined into a single zone simply be
> reassigning the
> > >interior environment for the plenum surfaces and deleting the extra
> interior
> > >surfaces that would be created in the plenum. Well, it may not be
> a real
> > >simple task, but it is doable.
> > >
> > >Mike
> > >
> > >
> > >On 1 Sep 2006 at 21:25, kir kumar wrote:
> > >
> > >
> > >
> > >>Dear Mike,
> > >> I have got a huge building with 7 floors, each floor is having
> a plenum.
> > >>All the return air from the zones enters the plenum before
> entering the air
> > >>handling unit in the mechanical room and this happens for every
> floor. One
> > >>side of the air handling unit sucks the return air from the
> plenum and sends
> > >>fresh air from its other end into the supply duct as supply air to
> the
> > >>zones.
> > >> My questions are
> > >> 1. Should I model plenum as a separate zone?( I am actually
> using ep quick
> > >>to build my zones but unfortunately ep-quick does not have the
> capability of
> > >>building plenums)
> > >> 2. Should I just ignore the plenum and treat it as return air
> duct which
> > >>carries return air from zones to the air handler in mechanical room?
> > >>
> > >>Can any one help me with those questions?
> > >> thanks in advance,
> > >>kiran
> > >>
> > >>
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> > >
> > >========================================================
> > >Michael J. Witte, GARD Analytics, Inc.
> > >EnergyPlus Testing and Support
> > >EnergyPlus-Support@
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