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Re: [EnergyPlus_Support] No interzonal wall?
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@xxxxxxxx
The primary EnergyPlus web site is found at:
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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.
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