modelExample2

Information

This example demonstrates that the use of the parameter from_dp can be important for reducing the size of algebraic loops in hydraulic circuits with many pressure drop components connected in series and a pump setting the pressure head.

If from_dp=true, we obtain:
Sizes of nonlinear systems of equations: {7}
Sizes after manipulation of the nonlinear systems: {5}
If from_dp=false, we obtain:
Sizes of nonlinear systems of equations: {7}
Sizes after manipulation of the nonlinear systems: {1}

This can have a large impact on computational speed.

Following script can be used in Dymola to compare the CPU times.

cpuOld=OutputCPUtime;
evaluateOld=Evaluate;
OutputCPUtime:=true;
simulateModel("BuildingSystems.Fluid.Examples.Performance.Example2(from_dp.k=false)", stopTime=10000, numberOfIntervals=10, method="dassl", resultFile="Example2");
simulateModel("BuildingSystems.Fluid.Examples.Performance.Example2(from_dp.k=true)", stopTime=10000, numberOfIntervals=10, method="dassl", resultFile="Example2");
createPlot(id=1, position={15, 10, 592, 421}, range={0.0, 10000.0, -0.01, 25}, autoscale=false, grid=true);
plotExpression(apply(Example2[end-1].CPUtime), false, "from_dp=false", 1);
plotExpression(apply(Example2[end].CPUtime), false, "from_dp=true", 1);
OutputCPUtime=cpuOld;
Evaluate=evaluateOld;


See Jorissen et al. (2015) for a discussion.

References

• Filip Jorissen, Michael Wetter and Lieve Helsen.
  Simulation speed analysis and improvements of Modelica models for building energy simulation.
  Submitted: 11th Modelica Conference. Paris, France. Sep. 2015.

Parameters

Components

Contents

Name	Description
Medium

Revisions

• January 22, 2016, by Michael Wetter:
  Corrected type declaration of pressure difference. This is for #404.
• July 14, 2015, by Michael Wetter:
  Revised documentation.
• May 20, 2015, by Filip Jorissen:
  First implementation.