Re: [EnergyPlus_Support] Severe Geometry & Fatal Airflow Network Iterations Errors

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

Regarding the view factor area, the MAIN zone description has internal mass 
with an area of 333 m2, and the total area of the other surfaces in the zone is 
338 m2.  The EnergyPlus view factor calculation struggles to define an 
enclosure when the area of one surface is equal to or greater than the sum of 
the areas of the other surfaces.  In this case, it is very close and happens to 
fail.  Splitting the one large internal mass surface into two smaller ones 
eliminates the view factor error.

Mike


On 24 Sep 2006 at 8:50, Kristin Field wrote:

> If anyone could help me with the following errors I've been 
> receiving, I would be *very* grateful.
> 
> Background: My file, which I'll upload shortly (titled 
> BAB_Baltimore_092306.idf), is supposed to represent a simple 30'x30' 
> house that's 16' tall with a 4-sided, unconditioned attic on top (2 
> triangles and 2 rectangles).  The attic peak is at 23.5'.  This house 
> should have typical DX cooling and furnace heating, with natural 
> ventilation when weather permits.  I have attempted to implement a 
> simple airflow network model with several cracks for infiltration and 
> operable windows/doors for natural ventilation.  To the greatest 
> extent possible, I followed the simple house airflow network example 
> file with EP-V1.3.0.
> 
> First (Severe) Error: I get the following geometry error after having 
> experimented with several different view factor combinations and 
> after thoroughly reviewing what seem to be logical vertices to me.
> 
> "View factors not complete. Probably bad surface descriptions in 
> zone="MAIN ZONE". Enforced reciprocity has tolerance (ideal is 0.0)
> =3.0292E-002. Enforced value is not within normal convergence 
> tolerance (<.0001)."
> 
> Second (Fatal) Error: I get this message after EP aborts following 
> the "Initializing HVAC" line in the command prompt window.  I have 
> also tried several combinations of new values for the parameters it 
> suggests - including increasing and decreasing them by several orders 
> of magnitude.  No effect except increased processing time in some 
> cases.  The audit file doesn't tell me anything.  I actually wonder 
> if the first error is influencing EP's ability to converge here.
> 
> "Too many iterations (SOLVZP) in AirflowNetwork simulation
> AirflowNetwork: SOLVER, Changing values for initialization flag, 
> Relative airflow convergence, Absolute airflow convergence, 
> Convergence acceleration limit or Maximum Iteration Number may solve 
> the problem. Occurrence info: Occurrence info=STERLING VA USA TMY2-
> 93738 WMO#=724030, 01/01 01:00 - 02:00
> AirflowNetwork: SOLVER, The previous error causes termination."
> 
> Any ideas/help appreciated - thanks!
> 
> --Kristin Field
> 
> 
> 
> 
> 
> 
> 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.idf and press the
> "search" button.
>  
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 


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





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