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Re: [EnergyPlus_Support] Modelling natural cross-ventilation using COMIS module


Here are some comments from someone familiar with COMIS regarding 
your input file.  There are still some questions which need to be 
resolved, but perhaps these comments will help you make some progress.

Mike Witte


1. There is an airflow link between the small exhaust zone with the 
larger cube through the floorExhaust, but it's modeled just as a 
crack rather than as a larger opening.  

2. Although this is not explained in the documentation, from the best I can 
piece together, for COMIS Surface Data for interior links (walls), the 
external node number should be left blank to allow the program to read it
automatically from the OtherZoneSurface information. I think the creator of the
test file figured that out and did this for floorExhaust.

3. Energyplus defines a interior wall twice, but only one is needed 
for the COMIS link. The user in this case has a floorExhaust sitting 
on top of a much larger roof. floorExhaust is input with roof as the 
OtherzZoneSurface, but roof is input with ExteriorEnvironment as the 
outside face environment.  If part of the roof is exposed to the 
exterior environment and part is exposed to the exhaust stack, then 
the roof must be divided into two surfaces, one for each outside 

4. I tried to add another node for the roof, but got stuck in the COMIS 
documentation on what to put for the site wind condition, which seems to
imply vertical facades. 

5. I also wanted to change the floorExhaust to a large horizontal opening,
assuming that the creator wanted to model an exhaust duct driven by the stack
effect. Here, too, there isn't any guidelines in the COMIS manual on how to
input a large horizontal, rather than vertical, opening.


On 13 Jun 2002, at 11:47, colin harris wrote:

> Hi,
> I am evaluating using Energy Plus for modelling natural cross-ventilation 
> for a hospital building. The basic strategy will be to cross ventilate the 
> rooms, with air coming in from windows and exhausted through a stack in the 
> roof. I am trying to do a very simple model of this using E+ and the COMIS 
> module. I have modelled one zone with a window in the south face, and 
> another zone on top of this to for the stack.
> The problem is that i am not sure how to link the 2 zones together?
> Also, i have seen that there is a passive stack component in COMIS 3.0, 
> will this become available in the E+ COMIS module?
> Kind regards
> Colin Harris.

EnergyPlus Testing and Support      

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