modelMSLAIT2Nodes

Smaller discretisation. Validation pipe against data from Austrian Institute of Technology with standard library components
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Extends from Modelica.Icons.Example (Icon for runnable examples).

Information

The example contains experimental data from a real district heating network. This data is used to validate this library's plug flow pipe model in Buildings.Fluid.FixedResistances.Validation.PlugFlowPipes.PlugFlowAIT.

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

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.

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

Test bench schematic

Schematic of test district heating network

Calibration

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

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

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

Parameters

TypeNameDefaultDescription
BooleanallowFlowReversalfalse= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
RealR1/(2*kIns*Modelica.Constants.pi)*log(0.18/0.0899) + 1/(2*2.4*Modelica.Constants.pi)*log(2/0.18)Thermal resistance per unit length of main pipes
RealR801/(2*0.024*Modelica.Constants.pi)*log(0.07/0.0337) + 1/(2*2.4*Modelica.Constants.pi)*log(2/0.07)Thermal resistance per unit length of service pipes
Modelica.Units.SI.ThermalConductivitykIns0.024Heat conductivity
Modelica.Units.SI.LengthdIns0.045Thickness of pipe insulation
Modelica.Units.SI.Diameterdiameter0.089Outer diameter of pipe
Modelica.Units.SI.MassFlowRatem_flow_nominal1Nominal mass flow rate, used for regularization near zero flow
Modelica.Units.SI.TimetauHeaTra6500Time constant for heat transfer, default 20 minutes

Components

TypeNameDefaultDescription
Fluid.Sources.MassFlowSource_TPoint1
Fluid.Sources.MassFlowSource_TPoint4Substation 4
Fluid.Sources.MassFlowSource_TPoint3Substation 3
Fluid.Sources.MassFlowSource_TPoint2Substation 2
Modelica.Blocks.Sources.CombiTimeTableDataReaderRead measurement data
Data.PipeDataAIT151218pipeDataAIT151218Measurement data from AIT
Modelica.Blocks.Sources.RealExpressionm_flow_p3Mass flow rate for substation 3
Modelica.Blocks.Sources.RealExpressionm_flow_p4Mass flow rate for substation 4
Modelica.Blocks.Sources.RealExpressionm_flow_p2Mass flow rate for substation 2
Modelica.Blocks.Sources.RealExpressionT_p1Inlet temperature
Buildings.Fluid.Sources.Boundary_pTExcludedBranchMass flow sink for excluded branch
Buildings.HeatTransfer.Sources.PrescribedTemperatureprescribedTemperatureVariable environment temperature
Modelica.Fluid.Pipes.DynamicPipepip0Pipe 0
Modelica.Fluid.Systemsystem
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip0.nNodes]res0Thermal resistances for elements of pipe 0
Modelica.Thermal.HeatTransfer.Components.ThermalCollectorcol0Combine heat flows to one
Modelica.Fluid.Pipes.DynamicPipepip1Pipe 1
Modelica.Thermal.HeatTransfer.Components.ThermalCollectorcol1Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip1.nNodes]res1Thermal resistances for elements of pipe 1
Modelica.Fluid.Pipes.DynamicPipepip2Pipe 2
Modelica.Thermal.HeatTransfer.Components.ThermalCollectorcol2Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip2.nNodes]res2Thermal resistances for elements of pipe 2
Modelica.Fluid.Pipes.DynamicPipepip3Pipe 3
Modelica.Thermal.HeatTransfer.Components.ThermalCollectorcol3Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip3.nNodes]res3Thermal resistances for elements of pipe 3
Modelica.Fluid.Pipes.DynamicPipepip4Pipe 4
Modelica.Thermal.HeatTransfer.Components.ThermalCollectorcol4Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip4.nNodes]res4Thermal resistances for elements of pipe 4
Modelica.Fluid.Pipes.DynamicPipepip5Pipe 5
Modelica.Thermal.HeatTransfer.Components.ThermalCollectorcol5Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip5.nNodes]res5Thermal resistances for elements of pipe 5
Fluid.Sensors.TemperatureTwoPortsenTem_p2Temperature sensor
Fluid.Sensors.TemperatureTwoPortsenTem_p3Temperature sensor
Fluid.Sensors.TemperatureTwoPortsenTemIn_p2Temperature sensor
Fluid.Sensors.TemperatureTwoPortsenTem_p1Temperature sensor
Fluid.Sensors.TemperatureTwoPortsenTem_p4Temperature sensor
Modelica.Blocks.Logical.SwitchswitchDecide if mass flow rate is below measurement noise threshold or not
Modelica.Blocks.Sources.RealExpressionm_flow_zeroDefault value when mass flow rate is below measurement noise threshold
Modelica.Blocks.Logical.LessThresholdlessThresholdMeasurement noise threshold
Fluid.Sources.MassFlowSource_TPoint5Low flow bypass of substation 4
Modelica.Blocks.Logical.Switchswitch1Decide if mass flow rate is below measurement noise threshold or not

Contents

NameDescription
Medium

Revisions

  • April 29, 2026, by Michael Wetter:
    Changed configuration of table to cause the parameters to be evaluated, as this leads to more efficient code.
    This is for IBPSA, #2111.
  • 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.
  • November 28, 2016 by Bram van der Heijde:
    Remove pipVol.
  • August 24, 2016 by Bram van der Heijde:
    Implement validation with MSL pipes for comparison, based on AIT validation.
  • 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.