Re: [EnergyPlus_Support] "Air-Wall" between Surfaces

["Michael J. Witte" <mjwitte@xxxxxxxx>]

This is difficult to answer.  One of the tenets in EnergyPlus is that 
conditions within a zone are uniform.  Yes, you can divide an open space into 
multiple zones.  The difficult thing is how to model the interaction between 
the zones when they are open to each other.  If the input contains no interzone 
surfaces, mixing, or COMIS objects connecting the zones, they will not interact 
with each other in EnergyPlus.  We know of no credible method of modeling this 
interaction outside of using a CFD program.  You must add some type of surface 
or airflow from one zone to another to provide a heat-transfer mechanism.  
There are four options in EnergyPlus for modeling the interaction between zones 
which are open to each other:

1.  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.

2. Some modelers define fictitious "air walls"  with no mass and a certain 
resistance to account for heat transfer through open doorways, etc., but it is 
difficult to know what resistance to use.  This will transfer only sensible 
heat, no moisture.

3. Some modelers use MIXING (one-way flow) or CROSS MIXING (two-way flow) to 
move air between the zones, but it is difficult to know what flow rate to use.  
This will transfer both sensible heat and moisture.

4. One could define a COMIS network with large vertical openings between the 
zones as well as other openings and cracks in the exterior envelope to provide 
the driving forces.  This requires a much higher level of detailed input and 
should be used only if the detailed specification data is available.  This 
approach does not include any flow induced by the HVAC systems.

Mike


On 23 Feb 2004, at 9:53, markus_gmeinder wrote:

> Another question:
> How can I build an "Air-Wall" between 2 zones? In my case The Wall 
> between conservatory and livingroom (wall between zone1 and zone2)?
> I built the Walls and connected it with the "OutsideFaceEnvironment 
> Object". When I delete both walls how know the zones about each 
> other?
> Thank you very much
> Markus
> 
> 
> 
> The primary EnergyPlus web site is found at:
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> 
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> 
>  -- please post any files to the appropriate folder in the Files are of the
>  Support Web Site.
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
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> 
> 
> 



========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx



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