[TRNSYS-users] TRNflow: problems with airflows

[Inge Brems]

Hello TRNSYS-users,

I am making a master thesis about the evaluation of demand controlled ventilation in school buildings. To evaluate the indoor air improvement and energy safe of CO2 controlled ventilation I am making use of TRNSYS 16 and TRNflow to modulate an air duct network. 

First I modulated a simple classroom and corridor (2 zones) with a duct from the classroom and a duct from the corridor to an extraction duct that leads to the extraction fan (mechanical extraction ventilation). The fan speed factor can be controlled by the CO2-concentration in the classroom and by the population of the classroom. When I use a constant ventilation flow or a constant base ventilation, there is no problem. When I use the population or the CO2-concentration to control the extraction fan, I get a different air flow distribution over the classroom and corridor after a couple weeks, and again a different distribution a couple weeks further, the total air flow trough the extraction duct stays the same, its just different distributed over classroom and corridor. 

An other problem occurred when I modulate, for the simple model classroom and corridor, balanced ventilation (mechanical extraction and pulsion). The constant ventilation flow and constant base ventilation are simulated without problem, but when I for example control the fan speed factor by the population, it simply stops running after a couple hours (for example 24 h). When the time step in TRNSYS (first it was 10s) is changed it stops running on a different hour (for example 500h). It doesn’t give an error or warning in the list- or logfile, it just stops running. On a different computer it stops running on the same moment.

Does anybody know the cause of these problems, I already tried to use test data instead of fans, but the problem stays.

Best regard and thanks in advance.

Inge
Student KULeuven
Belgium