Re: [EnergyPlus_Support] Ground temperature-Convergence has NOT been gained.

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

In the BldgProps object, "ConvTol: Convergence Tolerance" (the last field) is 
defined in the Auxiliary Programs doc as "specifies the convergence tolerance 
used to control the iteration. When the temperature change of all nodes is less 
than the convergence value, iteration ceases."  Also, in the BldgProps object, 
the first field "Number of years to iterate" limits the number of years the 
Slab program repeats.  To achieve convergence, you can increase the tolerance 
(not recommended) or increase the number of years.  You can set the number of 
years to a large number, becuase it will stop when convergence is reached, and 
then you can check the output to see how many years were simulated.

Is a nonconverged answer incorrect?  In most cases it is incorrect, but that 
depends on what you seek to model.  When a new building is built in a site that 
was previously open land, it takes a number of years for the soil to "warm up" 
to a periodic steady-state.  For the EnergyPlus simulation, a nonconverged 
solution will produce heat flows to the ground that represent the warmup period 
for the new construction.  This may be of interest to some modelers.  However, 
most users want a converged periodic steady-state result.

Mike

On 27 Oct 2005, at 3:01, wnstot wrote:

> Mike:
> Thank you very much!
> I calculated the ground temperater with the "Slab.exe", but at the last 
> line of the outputfile (*.gtp) there are the following words:
> "Convergence has NOT been gained."
> Does this mean my calcution is wrong? Or how to correct it?
> 
> Could you give me a help? Thanks!
> 
> Lei
> 
> 
> 
> 
> 
> 
> 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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