modelMSLAIT

Validation pipe against data from Austrian Institute of Technology with standard library components

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 IBPSA.Fluid.FixedResistances.PlugFlowPipe in IBPSA.Fluid.FixedResistances.Validation.PlugFlowPipes.PlugFlowAIT. This model compares its performance with the original Modelica Standard Library pipes, using one discretization element per unit length of pipe. For a coarser discretization, please refer to MSLAIT2Nodes.

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

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

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 lambda_g Modelica.Constants.pi) log(1/0.18)

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

Parameters

Type	Name	Default	Description
Boolean	allowFlowReversal	false	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Modelica.Units.SI.ThermalResistance	R	1/(2kInsModelica.Constants.pi)log(0.18/0.0899) + 1/(22.4Modelica.Constants.pi)log(2/0.18)	Thermal resistance of main pipes
Modelica.Units.SI.ThermalResistance	R80	1/(20.024Modelica.Constants.pi)log(0.07/0.0337) + 1/(22.4Modelica.Constants.pi)log(2/0.07)	Thermal resistance of service pipes
Modelica.Units.SI.ThermalConductivity	kIns	0.024	Heat conductivity of pipe insulation material
Modelica.Units.SI.Length	dIns	0.045	Thickness of pipe insulation
Modelica.Units.SI.Diameter	diameter	0.089	Outer diameter of pipe
Modelica.Units.SI.MassFlowRate	m_flow_nominal	1	Nominal mass flow rate, used for regularization near zero flow
Modelica.Units.SI.Time	tauHeaTra	6500	Time constant for heat transfer, default 20 minutes

Components

Type	Name	Description
Fluid.Sources.MassFlowSource_T	Point1	Mass flow source
Fluid.Sources.MassFlowSource_T	Point4	Substation 4
Fluid.Sources.MassFlowSource_T	Point3	Substation 3
Fluid.Sources.MassFlowSource_T	Point2	Substation 2
Modelica.Blocks.Sources.CombiTimeTable	DataReader	Read measurement data
Data.PipeDataAIT151218	pipeDataAIT151218	Record with measurement data
Modelica.Blocks.Sources.RealExpression	m_flow_p3	Mass flow rate for substation 3
Modelica.Blocks.Sources.RealExpression	m_flow_p2	Mass flow rate for substation 2
Modelica.Blocks.Sources.RealExpression	T_p1	Inlet temperature
IBPSA.Fluid.Sources.Boundary_pT	ExcludedBranch	Mass flow sink for excluded branch
Modelica.Thermal.HeatTransfer.Sources.PrescribedTemperature	prescribedTemperature	Variable environment temperature
Modelica.Fluid.Pipes.DynamicPipe	pip0	Pipe 0
Modelica.Fluid.System	system
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip0.nNodes]	res0	Thermal resistances for pipe 0
Modelica.Thermal.HeatTransfer.Components.ThermalCollector	col0	Combine heat flows to one
Modelica.Fluid.Pipes.DynamicPipe	pip1	Pipe 1
Modelica.Thermal.HeatTransfer.Components.ThermalCollector	col1	Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip1.nNodes]	res1	Thermal resistances for pipe 1
Modelica.Fluid.Pipes.DynamicPipe	pip2	Pipe 2
Modelica.Thermal.HeatTransfer.Components.ThermalCollector	col2	Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip2.nNodes]	res2	Thermal resistances for pipe 2
Modelica.Fluid.Pipes.DynamicPipe	pip3	Pipe 3
Modelica.Thermal.HeatTransfer.Components.ThermalCollector	col3	Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip3.nNodes]	res3	Thermal resistances for pipe 3
Modelica.Fluid.Pipes.DynamicPipe	pip4	Pipe 4
Modelica.Thermal.HeatTransfer.Components.ThermalCollector	col4	Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip4.nNodes]	res4	Thermal resistances for pipe 4
Modelica.Fluid.Pipes.DynamicPipe	pip5	Pipe 5
Modelica.Thermal.HeatTransfer.Components.ThermalCollector	col5	Combine heat flows to one
Modelica.Thermal.HeatTransfer.Components.ThermalResistor[pip5.nNodes]	res5	Thermal resistances for pipe 5
Fluid.Sensors.TemperatureTwoPort	senTem_p2	Temperature sensor
Fluid.Sensors.TemperatureTwoPort	senTem_p3	Temperature sensor
Fluid.Sensors.TemperatureTwoPort	senTemIn_p2	Temperature sensor
Fluid.Sensors.TemperatureTwoPort	senTem_p1	Temperature sensor
Fluid.Sensors.TemperatureTwoPort	senTem_p4	Temperature sensor
Fluid.Sources.MassFlowSource_T	Point5	Mass flow sink for substation 4 in case of low flow rates
Modelica.Blocks.Sources.RealExpression	m_flow_p4	Measured mass flow rate for substation 4
Modelica.Blocks.Logical.Switch	switch	Switch to avoid mass flow rate measurement noise on substation with flow standstill.
Modelica.Blocks.Sources.RealExpression	m_flow_zero	Default value when mass flow rate is below noise threshold
Modelica.Blocks.Logical.LessThreshold	lessThreshold	Check if mass flow rate is lower than 0.001
Modelica.Blocks.Logical.Switch	switch1	If flow is lower than measurement noise threshold, bypass temperature sensor

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.
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.