Sorry for the late response.
I am not really interested in the convergence level warning, if the calculation can continue with diverging and crash. Because we are calculating for temperature values and have a set convergence not met per step in temperature, it is not a severe problem.
I joined in the discussion, because suddently the following question showed up.
"Does the simulation underestimate or overestimate your experimental results? "
"what is the uncertainty in your measurements equipment. ?"
My curiousity was "how you can compared the measured value with the TMY simulated value."
4-5 (hottest day) or 10-12 (coldest day in August) in degree difference may not be related to convergience at all.
I mentioned the mounting of thermomters, because:
Can you comment on the problems? Solar radiation, convection, conduction, etc on the tape. Tape colour, tape thickness, to name a few more.
I was after the measurement technique, rather than the EPlus definition.
On the simulation of large or small buildings, the convergence may not be the reason for simulation speed. Many building surfaces are not correctly defined and the errors ignored.
I think, that is more likely the cause of the problem.
Improper use of infiltration and ventilation objects can be the other cause, because the moisture and temperature of the input air are not design controlled.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeremiah@xxxxxxxxxxxxxxxxxxxxxx
Date: Thu, 8 Mar 2012 14:49:25 -0800
Subject: Re: [EnergyPlus_Support] what can i do for convergence the result ?
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)
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.
--
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The primary EnergyPlus web site is found at:
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I am not really interested in the convergence level warning, if the calculation can continue with diverging and crash. Because we are calculating for temperature values and have a set convergence not met per step in temperature, it is not a severe problem.
I joined in the discussion, because suddently the following question showed up.
"Does the simulation underestimate or overestimate your experimental results? "
"what is the uncertainty in your measurements equipment. ?"
My curiousity was "how you can compared the measured value with the TMY simulated value."
4-5 (hottest day) or 10-12 (coldest day in August) in degree difference may not be related to convergience at all.
I mentioned the mounting of thermomters, because:
Someody simply tape a thermal junction on the outside wall with a digital temperature display, and call it the temperature of the exterior surface of the wall in EPlus.
Can you comment on the problems? Solar radiation, convection, conduction, etc on the tape. Tape colour, tape thickness, to name a few more.
I was after the measurement technique, rather than the EPlus definition.
On the simulation of large or small buildings, the convergence may not be the reason for simulation speed. Many building surfaces are not correctly defined and the errors ignored.
I think, that is more likely the cause of the problem.
Improper use of infiltration and ventilation objects can be the other cause, because the moisture and temperature of the input air are not design controlled.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeremiah@xxxxxxxxxxxxxxxxxxxxxx
Date: Thu, 8 Mar 2012 14:49:25 -0800
Subject: 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)
- Smaller may be better as it would represent less difference
- 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:
- Could this reference to stability be the cause convergence issues, and if so would it make since for me to use the lowest possible value?
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
Jeremiah D. Crossett
CleanTech Analytics
503-688-8951
This document may contain valuable information proprietary to CleanTech Analytics which is private and confidential. It may not be shared, copied, stored or transmitted in any form without the prior written consent of CleanTech Analytics
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to 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 currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
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