[TRNSYS-users] User-defined CHTC: pane temperature calculation diverging

[Sarah Leenknegt]

Dear TRNSYS-user,

I have the following problem. I am trying to input a CHTC-correlation in the building model. I am using the input value recall to get the surface and air temperature of one timestep before. I can calculate the CHTC and plot it with an online plotter, but whenever I try to use it as an input, a get the "pane temperature calculation is diverging" warnings from the start of the simulation and the simulation stops. The CHTC is non-zero and positive, and for now, the equation used is simply max(1,2*abs(surftemp-airtemp)). If I calculate a variable CHTC without using the surface and air temperature, the simulation runs without error. 

I have used TRNSYS3D to make my one-zone model, including one window facing south-west (TURN = -45°) and 4 air nodes. I am using the detailed radiation model, so all air nodes are combined into one zone. Viewfactors and insolation matrix are generated without problem. I have gone back to the most basic simulation, using only the idf imported in a 3D building project standard template, with a standard Meteonorm Uccle climate. 

Following recommendations in previous posts, I have set the CHTC at the window to the standard fixed values for inside and outside. I have also checked if something went wrong when drawing the window in sketch-up, but I do not see any lines that shouldn't be there. Changing to a different glazing doesn't help either.

Can anyone give me some help as to what else I can try? I have done this before without problems, but it is the first time I try it with trnsys3D.
Please answer to me privately as well, as I am not subscribed to the mailing list. 

Kind regards,

Sarah

--
ir. - arch. Sarah Leenknegt,
Afdeling Bouwfysica, Dept. Burgerlijke Bouwkunde,
Faculteit Ingenieurswetenschappen, KULeuven,
Kasteelpark Arenberg 40 - bus 2447, 3001 Heverlee, België

sarah.leenknegt at bwk.kuleuven.be
tel. 016 321347