[TRNSYS-users] Type 56 , active Layers Error

[Philippe Goffin <goffin@arch.ethz.ch>]

Dear all

I'm receiving following error:
Specific fluid mass flow of active layer in surface 5 below minimum value of 10.04 kg/m^2*h. Please increase the minimum mass flow rate or use the autosegmentation feature of ...

I saw that this error was already reported in '08 (https://www-old.cae.wisc.edu/pipermail/trnsys-users/2008/003947.html), but apparently the cause wasn't really known. 

Anyway the strange thing is that TrnBuild, in the "Definition Active Layer" says that the "min allowed inlet mass flowrate" is 10.79 kg/h. Trnsys in its error message says 10.04 kg/m^2*h. The real minimal mass flowrate that ever under all possible conditions happens in my simulation is 12 kg/m^2*h, but most time it's 18.75 kg/m^2*h (that's for sure, I did some experiments, outputting the mass flow rate)

So, I decided nevertheless to autosegment it, for fun I created 6 segments by choosing the "desired min. allo. in. mass flowrate" accordingly (e.g. 1 kg/m^2*h). Now the strange thing is that the simulation works for some time after eventually crashing down. But the super strange thing is that my "Entering load temperature (=Tel)" spikes from 25°C to 65°C in the first iteration, e.g. it = i-1, pump is not active, Tel = 20°C, then for it=i the HP goes on, and Tel is 65°C. Without segmenting the active layer it would be 25°C.

As far as I understand, segmenting shouldn't influence the entering load temperature, how and why does it spike this strong in the first iteration and why do I actually get this error ??? Am I getting something completely wrong ?

Thanks for any advice, help.

Philippe