Heaters and coolers in Dynamics Mode

[svidille]

Hi, Dan and everybody else

This is (again) Simone. Motivated by the hold-up necessity for the controllers, I started checking why I was getting issues with the heaters and coolers in the simulation circuit.

The concept that I have from other simulators is: if you select pressures in the boundaries, no matter what happens, those pressures are fixed (a crash may happen, but still the pressures will be fixed). In the case of the attached simulations, I fixed pressures but they vary when I run the simulation.

The best I could get is using calculation rates of 1 for controllers, pressure-flow solver and flash calculations and 500 ms as step size.
All other integrators crash for different reasons. Even though, the results don´t seem correct.

In the beginning, I though that maybe it could be a problem of the pressure drop specification in the cooler, from the steady-state, so I left this spec blank. By the end, it seems it is necessary to include a zero in this spec and not leave it blank (not sure, could you clarify, please?).

Again, I suppose the question is the same: what is the concept of fixing boudary pressures in the dynamics simulation in DWSIM?

Coolers_heaters_test - copia.zip

Thanks so much,
Best wishes,
Simone