.BuildingSystems.Fluid.FixedResistances.Validation.PlugFlowPipes.PlugFlowAIT

Information

The example contains experimental data from a real district heating network.

The pipes' temperatures are not initialized. Therefore, results of outflow temperature before approximately the first 10000 seconds should not be considered.

Note that these three models are identical, except for the pipe model that is used:

• The model BuildingSystems.Fluid.FixedResistances.Validation.PlugFlowPipes.MSLAIT uses the pipe model from the Modelica Standard Library, with a fine discretization. See the parameter nNodes.
• The model BuildingSystems.Fluid.FixedResistances.Validation.PlugFlowPipes.MSLAIT2Nodes uses the same model as above, but sets nNodes=2.
• The model BuildingSystems.Fluid.FixedResistances.Validation.PlugFlowPipes.PlugFlowAIT uses the plug flow model BuildingSystems.Fluid.FixedResistances.PlugFlowPipe.

This comparison between different discretization levels and pipe models is made to check the influence of the discretization and pipe model on computation time and simulation accuracy.

Test bench schematic

Calibration

To calculate the length specific thermal resistance R of the pipe, the thermal resistance of the surrounding ground is added, which yields

R=1/(0.208)+1/(2   lambda_g   Modelica.Constants.pi)   log(1/0.18),

where the thermal conductivity of the ground lambda_g = 2.4 W/(m K).

Contents

Name	Description
Medium

Revisions

• March 7, 2020, by Michael Wetter:
  Replaced measured data from specification in Modelica file to external table, as this reduces the computing time.
  This is for #1289.
• May 15, 2019, by Jianjun Hu:
  Replaced fluid source. This is for #1072.
• July 4, 2016 by Bram van der Heijde:
  Added parameters to test the influence of allowFlowReversal and the presence of explicit volumes in the pipe.
• January 26, 2016 by Carles Ribas:
  First implementation.