[TRNSYS-users] TRNBuild Error

David Bradley bradley at tess-inc.com
Tue Nov 29 05:37:23 PST 2005

   Unfortunately, I am not sure that there is a simple workaround to your 
problem. The algorithm that TRNBuild uses to choose the coefficients to 
describe the wall does not work for very thick or in some cases, very high 
capacitance walls. The only solution that I can think of off hand is to 
write your own model for the very thick wall (probably using a method 
similar to the way that storage tanks and the rock bed thermal storage 
models are written). This model could then be attached to a Type56 boundary 
wall that represents the inside surface of your wall. Your wall model would 
take the inside wall surface temperature (calculated by Type56) and would 
return the temperature at the interface between the Type56 boundary wall 
and the wall in your model.
   If you would like to send me your .bui file, I would be happy to take a 
look at it and comment if there are other possible workarounds to your problem.
Kind regards,

At 08:23 11/25/2005, Dimitris Anastaselos wrote:
>Hi all!!
>I would like to model very thick walls. In the case I am working I have 
>walls around 6m! For this case, TRNSYS (i.e. TRNBuild) cannot calculate 
>the transfer coefficients. I have created new walls with 40cm thickness 
>and keeping the U-value constant by changing the thermal conductivity.
>When I save the project, the following message is shown:
>Error creating the wall transfer function coefficient:
>Stability criteria not fullfield
>Check layer definition (thickness, ratio of conductivity/density)
>Please check the INF-file for further information
>When I check the INF-file the same message is shown: Stability criteria 
>not fullfield
>I have changed the TIMEBASE from 1 to 2 but the problem still remained.
>The same was when I set TIMEBASE=3 or 4 or 5 or 6. Only when the TIMEBASE 
>is 7 the problem is solved but then the following message is shown:
>* *
>Error creating the wall transfet function coefficients:
>Unable to find a root after indication that a root exists.
>Maybe the timebase is too small.
>Please, check the INF-file for further information
>* *
>If I set the TIMEBASE around 100 the above message still remain.
>What can I do to work around this problem?
>Anastaselos Dimitris
>Dipl. Mechanical Engineer
>Laboratory of Heat Transfer and
>Environmental Engineering
>Aristotle University Thessaloniki
>Box 483 54124 Thessaloniki, GREECE
>Tel: + 30 2310 996048
>Fax: + 30 2310 996012
>e-mail: jimanas at aix.meng.auth.gr
>URL: http://aix.meng.auth.gr
>TRNSYS-users mailing list
>TRNSYS-users at engr.wisc.edu

Thermal Energy System Specialists (TESS), LLC
David BRADLEY                           2916 Marketplace Drive - Suite 104
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