Hi!
I'd like to model a closed hydraulic cycle as one can find in the Modelica Standard Library/Fluid/Examples/HeatingSystem. With the heating system as well as with my (minimalistic example) I've got the same problem: The system is overdetermined.
As one can find the HeatingSystem as a "bad example" in the following lecture
http://www.modprod.liu.se/MODPROD2011/1 … delica.pdf
I guess this is a well known problem, but I don't really get the point.
My example is:
1. a pump
model Erzeuger
  Rohrflansch w,k;
  parameter Real a,b,c;
equation
  w.p = k.p + a * k.Vp ^ 2 + b * k.Vp + c;
end Erzeuger;
2. a resistence
model Verbraucher
  Rohrflansch w,k;
  parameter Real rho;
  parameter Real d_i;
  parameter Real zeta;
equation
  k.p = w.p - rho / 2 * ((w.Vp * 4) / 3.14 * d_i ^ 2) ^ 2 * zeta;
end Verbraucher;
3. they are connected with a
connector Rohrflansch
  Real p;
  flow Real Vp;
end Rohrflansch;

The whole system is:
model System
  Verbraucher verbraucher1(rho = 1000, d_i = 0.06, zeta = 0.5);
  Erzeuger erzeuger1(a = -740741, b = -19630, c = 1070);
equation
  connect(verbraucher1.w,erzeuger1.w);
  connect(verbraucher1.k,erzeuger1.k);
end System;

Can anybody give me a hint what the problem is all about?

With kind Regards
Elisabeth

Technical University of Dresden
Faculty of Mechanical Science and Engineering
Institute of Power Engineering
Professorship of Building Engineering and Heat Supply
Dipl.-Ing. Elisabeth Eckstädt