Hi!
I still haven'tr solved the following issue:
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.
You can find the HeatingSystem as a "bad example" in the following lecture, so I guess this is a well known problem, but I don't really get the point.
http://www.modprod.liu.se/MODPROD2011/1 … delica.pdf

My example is:

1. a pump
model producer
  pipe_flange w,k;
  parameter Real a,b,c;
equation
  w.p = k.p + a * k.Vp ^ 2 + b * k.Vp + c;
end producer;

2. a resistence
model consumer
  pipe_flange 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 consumer;

3. they are connected with a
connector pipe_flange
  Real p;
  flow Real Vp;
end pipe_flange;

The whole system is:
model System
  consumer consumer1(rho = 1000, d_i = 0.06, zeta = 0.5);
  producer producer1(a = -740741, b = -19630, c = 1070);
equation
  connect(consumer1.w,producer1.w);
  connect(consumer1.k,producer1.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