Hi all,
I am modeling a hot water system with a tempering valve (step 1 : a fraction of the cold flow is sent to the heat source to be heated up, step 2 : the other is mixed with the resulting hot flow). However, in my case, I can't use the built-in component "tempering valve". Indeed, another hot flow is added between step 1 and 2 so the component equations are not valid anymore. Yet, I haven't found any satisfactory method to handle this. Here is what I have tried out :
- The flow diverter parameter Y (step 1) is set by user-provided equations (equations box), function of temperatures and flow rates in the loop + set temperature
--> convergence problems
- The flow diverter parameter Y (step 1) is set by a controller (PID or iterative). However, when the set temperature is reached, tracking error tends to 0 and so does the control signal (connected directly to the valve opening Y). It is not the solution at a given time step. Controller output should not be linked direcly to the valve opening (but to its derivative I guess).
--> stability problems (it oscillated around the set temperature)
Do you have any idea how to solve this simple problem?
Please let me know if I am not clear enough.
Thanks in advance,
Regards,
Damien CASETTA
INSA Lyon / Génie Energétique et Environnement
ENERTECH / Cabinet SIDLER
26160 Félines sur Rimandoule
Tél & Fax : 04 75 90 18 54