[LBNL-THERM] heat flux greater than maximum tolerance puzzle

[R K]

Hi

I am trying to replicate a Kingspan model in Therm for a simple flat roof.  The model has worked fine when I created a BC which had Hc=6.  U=0.2189 and isotherms visible.

The Kingspan model uses Hc=25 and so I applied a new BC outside home with this but keep getting heat flux greater than maximum tolerance error stating results may not be valid.  In fact no U is calculated and no isotherms shown.  I then adjusted Hc for this new BC to 6 thinking that it should then work as it then mirrors the previous BC which works.  However, it still gives same error and fails to generate U or isotherms.

This seems very strange.  I tried changing tolerance in preferences but still could not get the new BC to work and yet the old BC (identical) works fine.

So then I changed Hc to 25 for the old BC and it worked without error giving me U=0.2251.  Apparently 25 is very high but in the end it doesnt change the U by that much.

So I think I now have a valid result but am puzzled why the model could not handle a new BC.  I checked with Chatgpt and it suggested changing mesh fineness setting that I dont think exists in v7.8,

So a few hours wasted going in circles.  I would be interested to know if anyone can shed light on this strange behaviour and if there is a fix as Chatgpt isnt helpful and there is no manual to refer to.

Rupert