Differential equation for a temperature-operated valve
Hi everybody,
I hope I can get some answers here, notwithstanding the fact that I am actually asking more than just a MathCAD question. I tried to put up a MathCAD-framework in order to explain my problem.
I wish to compute numerically the flow passing through a temperature-operated valve, of which I know (from supplier datasheet and measures on site),
1) the time constant tau (assuming that it is first order linear system)
2) the law giving the flow as a function of the temperature f(T) in quasi static behavior (dT/dt=0)
and I assume a certain transient of temperature, T=T(t)
A lot of time ago, when I was young 
and still remembered "Control Theory 1", I would have solved this problem imediatly (maybe!). Now I am a little out of training 
. Can someone point me to the answer, or eventually if not, to the right forum where to ask for help? Or even to some appropriate literature?
Sorry if I am out of subject, I looked for a MathCAD-forum on Control Theory but it does not seem to exist, so I just posted here.
Best regards
Claudio