[TRNSYS-users] Cold water tank & Convergence Problems

[Santeri Siren]

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.
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