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[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, 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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