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Re: [EnergyPlus_Support] COMIS questions

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] COMIS questions
From: "Michael J. Witte" <mjwitte@xxxxxxxx>
Date: Fri, 9 Jan 2004 08:05:21 -0600
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On 5 Jan 2004, at 14:32, Ian Doebber wrote:

> Two questions:
> 
> 1) Have the increase in the Significant Figures for the intermediate COMIS file
> been applied to Energy Plus such that if I redownload it from the E+ web site I
> can enter in Air Mass Flow Coefficient to five decimal points.  If this fix has
> not been uploaded yet, is there a way I can do this fix on my own.

If you redownload today, you will get the same version you already have, 
1.1.1.012.  New changes, including this one, will become available in the next 
official release which is scheduled for April 2004.  There is no way for you to 
implement this change on your own without becoming a licensed developer and 
modifying the source code yourself.

> 
> 2) Currently, my COMIS infiltration for the Washington DC weather is dominated
> by Wind Effects.  I am wondering if the way I have my COMIS program set up
> minimizes the Stack Effects or whether COMIS in general for DC weather
> emphasizes wind as the main source of infiltration.  If it is due to the way I
> have COMIS set up, how would I change my program to have more stack infiltration
> such as altering my ceiling vs wall leakage areas.
> 

The balance between stack and wind driven infiltration is affected by wind 
speeds, temperature differences, and opening characteristics including size, 
orientation, and height.  I have little experience with COMIS, but my intuitive 
feel is that wind-driven infiltration will nearly always dominate unless the 
weather is very calm or the building has a tall profile.  Perhaps others with 
more experience in this area can offer some guidance.  This is a situation 
where sensitivity tests would be very useful in helping you understand what 
parameters in your model are the primary drivers.

Mike



> Thanks
> Ian
> 
>   ----- Original Message ----- 
>   From: Joe Huang 
>   To: EnergyPlus_Support@xxxxxxxxxxxxxxx 
>   Sent: Saturday, December 13, 2003 4:30 AM
>   Subject: Re: [EnergyPlus_Support] EnergyPlus/COMIS error: MATRIX SINGULAR FOR
>   ZONE #2
> 
> 
>   Ming,
> 
>   I have repeated your steps with the example file and found that this error
>   (MATRIX SINGULAR FOR ZONE #2) was occuring due to your third change where you
>   reduced the Air Mass Flow Coefficient from 0.001 to 0.0001.  The problem is
>   caused by the intermediate COMIS input file (eplusout.cif) not being written
>   to the sufficient level of precision, so that the input 0.0001 appeared as
>   0.000, i.e., interpeted as a flow coefficient of 0.  I solved the problem by
>   increasing the precision for writing the flow coefficient and exponents from
>   three decimal points (F10.3) to five decimal points (F10.5). I will upload
>   that fix to the EnergyPlus server on Monday.  Until the correction makes it
>   into the compiled code on the server, please keep the flow coefficients and
>   exponent at above 0.001.  Even after the fix is implemented, you need to keep
>   them at above 0.00001.
> 
>   Joe
>   ----- Original Message -----
>   From: "waspoorboy" <mingsbox@xxxxxxxxxxxxxx>
>   To: <EnergyPlus_Support@xxxxxxxxxxxxxxx>
>   Sent: Tuesday, December 09, 2003 11:20 AM
>   Subject: [EnergyPlus_Support] EnergyPlus/COMIS error: MATRIX SINGULAR FOR ZONE
>   #2
> 
> 
>   > To reproduce this problem,
>   > I took example file 3zvent.idf
>   > #1: Delete all cracks. [only two window and one door left]
>   > #2: Remove East_Zone from COMIS ZONE DATA
>   > #3: Change the Air Mass Flow Coeff from 0.001 to 0.0001
>   > #4: Execute EnergyPlus and Fatal error will be there.
>   >
>   > COMIS AIR FLOW:OPENING,
>   > WiOpen1,  !- Name
>   > 0.001,  !- Air Mass Flow Coefficient When Window or Door Is Closed
>   > 0.667,  !- Air Mass Flow Exponent When Window or Door Is Closed
>   >
>   > Is this problem solvable ?
>   > Thanks,
>   > Ming
>   >
>   >
>   >
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx


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 are of the Support Web Site.




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References:
- [EnergyPlus_Support] COMIS questions
  - From: Ian Doebber

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