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Re: [EnergyPlus_Support] what can i do for convergence the result ?



Dr, Li 

I have been having similar issues, and had attempted to help with the issues Mohammad is by editing his file and sending it back to him, so think that we may have the same issues..

Currently I have a small building working, but for a large model am having convergence issues, ie the model takes hours to run and then does not show savings, and produces many convergence warnings.   

The issues I am having with the full building are in finding the correct convergence settings, but from reading the E+ documentation it is difficult for me to figure out a group of settings that allow the model to run without the convergence issues. I had it work yesterday, but then adjusted and saved-- so lost my working version. This is a good thing, because I want to know why it is working, not just that it is doing so. 

If you could please provide some insight to my assumptions below, such as if assumption #1 or #2 is the correct interpretation, and an answer to the following question that would be great. 

Field: Loads Convergence Tolerance Value/Field: Temperature Convergence Tolerance Value = value in Celsius for the difference in temperatures from previous iteration.

Assumptions: (not sure if number 1 or 2 is correct)
  1. Smaller may be better as it would represent less difference
  2. Larger may be better as it would provide a greater window of difference

Field: Inside Face Surface Temperature Convergence Criteria
Assumption: Lower values may further increase stability at the expense of longer runtimes, Higher values may decrease runtimes but lead to possible instabilities.

Question:

Here is a link to a visualisation of the working Energy Plus model for a small building: https://docs.google.com/spreadsheet/ccc?key=0Ag7cD5ZV9QwRdGdmMThETElEaGJNWUQ3ZGU1MEZRcEE

Thanks


On Thu, Mar 8, 2012 at 1:30 PM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:
 

What values were you comparing?
 
How do you match your experimental values to the simulated values?
 
Did you have modified current data weather file?
 
How do you mount your thermometers for temperature measurement?
 
Use real weather data measured at site is easy to say and difficult to obtain and insert into the EPW file.
 

 Dr. Li  

 
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: salehsnjsaadi404@xxxxxxxxx
Date: Thu, 8 Mar 2012 11:33:50 -0800
Subject: Re: [EnergyPlus_Support] what can i do for convergence the result ?


 
Does the simulation underestimate or overestimate your experimental results?

You might need to consider the infiltration in your model. try to use simple convective heat transfer coefficient algorithm.

Use real weather data measured at site.  

what is the uncertainty in your measurements equipment. ? your results need to be within 1 deg difference. (3-4) degree difference is large.

regards,


From: Mohammad Kheradmand <mohammadkheradmand@xxxxxxxxx>
To: "EnergyPlus_Support@xxxxxxxxxxxxxxx" <EnergyPlus_Support@xxxxxxxxxxxxxxx>
Sent: Thursday, March 8, 2012 11:06 AM
Subject: [EnergyPlus_Support] what can i do for convergence the result ?

 
I simulate my model for coldest and hottest a day of August, for comparing results between experimental and simulation results, i got reasonable result for hottest day(almost 4-5 degree differences ), but for coldest day i have difference almost 10-12 degree ...what is my problem?

regards






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Jeremiah D. Crossett
CleanTech Analytics
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www.cleantechanalytics.com


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