PID Control Issue in Dynamic Heat Exchanger Simulation (DWSIM 9.0.5)

[fabriziorosichini]

Hello everyone,
I’m Fabrizio and I’m working on a dynamic simulation in DWSIM (v9.0.5). I have a heat exchanger where water (25°C) should cool hot air from 430.77°C to 100°C.

I set up a PID controller with the outlet air temperature as the controlled variable (set point 100°C) and the valve opening as the manipulated variable. However, the valve does not seem to affect the water flow rate. I then tried using a specification block to link the flow rate to the valve opening, which improved results, but even after tuning the PID, the air temperature drops too much.

Both simulation files are attached. I’m looking for guidance on:
1)Controlling the water flow without a specification block.
2)Understanding why the temperature control fails in the second file.

Thanks in advance for any help!

Best regards,
Fabrizio
PID issue.zip