[TRNSYS-users] Cold water tank & Convergence Problems

[Santeri Siren <santeri.siren1@gmail.com>]

Dear Trnsys users,


Description of my project:

I have a Trnsys simulation project where I have created a closed flow circuit that models a chiller equipped cooling system with a cold water tank (2 inputs & 2 outputs). On the other side of the tank are the chiller and a pump and on the other side are the load and another pump. The chiller is set to cool the water flow to 7 C. The tank is used for buffering purposes. The chiller side pump is controlled by an on/off controller that is set to keep the tank temperature between certain values. The pump on the load side is set to maintain a constant flow.


Description of the problem:

The system works perfectly in a static situation when both pumps have constant water flows.

The on/off controller seems to cause problems. Covergence Warnings start to appear when I use the controller to keep the tank temperature at the wanted value. Also all the temperatures get weird values (not infinite). Even the chiller doesnt keep the water flow at 7 C anymore (although it has more than enough capacity).
If I try to use a variable speed pump and iterative feedback controller instead, the same thing happens.

I have no idea why controlling the tank temperature is so difficult and causes these problems. I hope some one could help me with this.

Best regards.
Santeri Siren.