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[EnergyPlus_Support] Re: No interzonal wall?
Thanks,
Great answer. This information should be saved and linked to the E+
help files.
Ben
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
<mjwitte@...> wrote:
>
> Unfortunately, there is no good solution to modeling this case.
Here is a
> (long) answer laying out some of the issues.
>
> Mike
>
> It is extremely difficult to model the interactions between
thermal zones which
> are connected by a large opening. If the zones are controlled to
the same
> conditions, then there is little to be gained by making them
interact, so you
> could neglect any connections between the zones. In fact, if this
is the case,
> you might consider combining the spaces into a single thermal
zone. If you
> expect the zones to have significantly different temperatures
and/or
> humidities, then use one of the following options. If they are
modeled as
> separate zones, EnergyPlus models only what is explicitly
described in the
> input file, so simply leaving a void (no surfaces) between two
zones will
> accomplish nothing - the two zones will not be connected. The
main
> interactions which occur across the dividing line between two
zones which are
> fully open to each other are:
>
> 1. Convection or airflow, which will transfer both sensible heat
and moisture.
> Some modelers use MIXING (one-way flow) or CROSS MIXING (two-way
flow) to move
> air between the zones, but the user must specify airflow rates and
schedules
> for this flow, and it cannot be automatically linked to HVAC
system operation.
> Other modelers use AirFlowNetwork with large vertical openings
between the
> zones as well as other openings and cracks in the exterior
envelope to provide
> the driving forces. It can also be connected with the HVAC system
(for limited
> system types). This requires a much higher level of detailed
input and should
> be used only if the detailed specification data is available. If
the two zones
> are controlled to similar conditions, this effect could be safely
neglected.
>
> 2. Solar gains and daylighting. The only way to pass solar and
daylight from
> one zone to the next is through a window or glass door described
as a
> subsurface (Surface:HeatTransfer:Sub) on an interzone wall
surface. Note that
> all solar is diffuse after passing through an interior window.
>
> 3. Radiant (long-wave thermal) transfer. There is currently no
direct radiant
> exchange between surfaces in different thermal zones. Windows in
EnergyPlus
> are opaque to direct radiant exchange, so an interzone window will
not behave
> any differently than an opaque interzone surface for this aspect.
However, a
> large interzone surface (opaque or window) would result in some
indirect
> radiant exchange since the interzone surface will exchange
directly with
> surfaces in zone A and in zone B. The surface thermal resistance
should be low
> in order to most closely approximate this effect.
>
> 4. Conduction. If an interzone surface is place between the two
zones, it will
> conduct sensible heat between the two zones. Using a low thermal
resistance
> helps to move radiant exchange between the zones.
>
> 5. Visible and thermal radiant output from internal gains. These
gains will
> not cross zone boundaries. But again, they will impact any
interzone surfaces,
> so some of the energy may move across to the next zone.
>
>
>
> On 17 Apr 2007 at 7:04, benteqman wrote:
>
> > Hi all,
> > I am hoping this will be straight forward to answer. How do you
model
> > to zones which do not have a wall between them? Should I leave
the
> > imaginary surface out, or should I define it by a wall with a
full size
> > window with miniscual heat transfer properties?
> >
> > If there is signicant daylighting, defining the imaginary
surface a
> > wall would block this out..
> > I look forward to a response.
> > Regards
> > Ben
> >
> >
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> >
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
> > Attachments are not allowed -- please post any files to the
appropriate folder
> > in the Files area of the Support Web Site.
> >
> > EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf
under the
> > Documentation link and press the "search" button.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
>
>
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@...
>
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