modelPipe
Pipe with 1D discretisation along flow direction
Extends from BuildingSystems.Fluid.Interfaces.LumpedVolumeDeclarations (Declarations for lumped volumes), BuildingSystems.Fluid.Interfaces.PartialTwoPortInterface (Partial model with two ports and declaration of quantities that are used by many models), BuildingSystems.Fluid.Interfaces.TwoPortFlowResistanceParameters (Parameters for flow resistance for models with two ports).
Information
Model of a straight pipe with flow resistance and optional heat storage.
This model can be used for modeling the heat exchange between the pipe and environment.
The model consists of a flow resistance
BuildingSystems.Fluid.FixedResistances.FixedResistanceDpM
and nNodes mixing volumes
BuildingSystems.Fluid.MixingVolumes.MixingVolume.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nNodes | 1 | Number of volume segments |
| Boolean | useMultipleHeatPorts | false | = true to use one heat port for each segment of the pipe, false to use a single heat port for the entire pipe |
| Dynamics › Conservation equations | |||
| Modelica.Fluid.Types.Dynamics | energyDynamics (from LumpedVolumeDeclarations) | Modelica.Fluid.Types.Dynamics.DynamicFreeInitial | Type of energy balance: dynamic (3 initialization options) or steady state |
| Modelica.Fluid.Types.Dynamics | substanceDynamics (from LumpedVolumeDeclarations) | energyDynamics | Type of independent mass fraction balance: dynamic (3 initialization options) or steady state |
| Modelica.Fluid.Types.Dynamics | traceDynamics (from LumpedVolumeDeclarations) | energyDynamics | Type of trace substance balance: dynamic (3 initialization options) or steady state |
| Advanced › Dynamics | |||
| Modelica.Fluid.Types.Dynamics | massDynamics (from LumpedVolumeDeclarations) | energyDynamics | Type of mass balance: dynamic (3 initialization options) or steady state, must be steady state if energyDynamics is steady state |
| Initialization | |||
| Medium.AbsolutePressure | p_start (from LumpedVolumeDeclarations) | Medium.p_default | Start value of pressure |
| Medium.Temperature | T_start (from LumpedVolumeDeclarations) | Medium.T_default | Start value of temperature |
| Medium.MassFraction[Medium.nX] | X_start (from LumpedVolumeDeclarations) | Medium.X_default | Start value of mass fractions m_i/m |
| Medium.ExtraProperty[Medium.nC] | C_start (from LumpedVolumeDeclarations) | fill(0, Medium.nC) | Start value of trace substances |
| Medium.ExtraProperty[Medium.nC] | C_nominal (from LumpedVolumeDeclarations) | fill(1E-2, Medium.nC) | Nominal value of trace substances. (Set to typical order of magnitude.) |
| Dynamics | |||
| Real | mSenFac (from LumpedVolumeDeclarations) | 1 | Factor for scaling the sensible thermal mass of the volume |
| Assumptions | |||
| Boolean | allowFlowReversal (from PartialTwoPort) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Nominal condition | |||
| Modelica.Units.SI.MassFlowRate | m_flow_nominal (from PartialTwoPortInterface) | Nominal mass flow rate | |
| Modelica.Units.SI.PressureDifference | dp_nominal (from TwoPortFlowResistanceParameters) | Pressure difference | |
| Advanced | |||
| Modelica.Units.SI.MassFlowRate | m_flow_small (from PartialTwoPortInterface) | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow |
| Boolean | useExternalHeatSource | false | = true to transfer the volume temperature to the outer interface (heatPort) |
| Advanced › Diagnostics | |||
| Boolean | show_T (from PartialTwoPortInterface) | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Boolean | computeFlowResistance (from TwoPortFlowResistanceParameters) | true | =true, compute flow resistance. Set to false to assume no friction |
| Boolean | from_dp (from TwoPortFlowResistanceParameters) | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance (from TwoPortFlowResistanceParameters) | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM (from TwoPortFlowResistanceParameters) | 0.1 | Fraction of nominal flow rate where flow transitions to laminar |
| Modelica.Units.SI.ReynoldsNumber | ReC | 4000 | Reynolds number where transition to turbulent starts |
| Geometry | |||
| Modelica.Units.SI.Length | length | Length of the pipe | |
| Modelica.Units.SI.Length | diameter | sqrt(4*m_flow_nominal/rho_default/v_nominal/Modelica.Constants.pi) | Pipe diameter (without insulation) |
| Modelica.Units.SI.Length | thicknessIns | Thickness of insulation | |
| Material | |||
| Modelica.Units.SI.ThermalConductivity | lambdaIns | Heat conductivity of insulation | |
| Heat transfer | |||
| Modelica.Units.SI.SurfaceCoefficientOfHeatTransfer | alpha_in | 1000.0 | Heat transfer coefficient pipe inside |
| Modelica.Units.SI.SurfaceCoefficientOfHeatTransfer | alpha_out | 3.0 | Heat transfer coefficient pipe outside |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.Interfaces.FluidPort_a | port_a (from PartialTwoPort) | Fluid connector a (positive design flow direction is from port_a to port_b) | |
| Modelica.Fluid.Interfaces.FluidPort_b | port_b (from PartialTwoPort) | Fluid connector b (positive design flow direction is from port_a to port_b) | |
| Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a | heatPort | Single heat port that connects to outside of pipe wall (default, enabled when useMultipleHeatPorts=false) | |
| Modelica.Fluid.Interfaces.HeatPorts_a[nNodes] | heatPorts | Multiple heat ports that connect to outside of pipe wall (enabled if useMultipleHeatPorts=true) |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.MassFlowRate | m_flow (from PartialTwoPortInterface) | port_a.m_flow | Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) |
| Modelica.Units.SI.PressureDifference | dp (from PartialTwoPortInterface) | port_a.p - port_b.p | Pressure difference between port_a and port_b |
| Medium.ThermodynamicState | sta_a (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow))) else Medium.setState_phX(port_a.p, noEvent(inStream(port_a.h_outflow)), noEvent(inStream(port_a.Xi_outflow))) | Medium properties in port_a |
| Medium.ThermodynamicState | sta_b (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow))) else Medium.setState_phX(port_b.p, noEvent(port_b.h_outflow), noEvent(port_b.Xi_outflow)) | Medium properties in port_b |
| BuildingSystems.Fluid.FixedResistances.HydraulicDiameter | res | Flow resistance | |
| BuildingSystems.Fluid.MixingVolumes.MixingVolume[nNodes] | vol | Volume for pipe fluid | |
| Modelica.Thermal.HeatTransfer.Components.ThermalConductor[nNodes] | conPipWal | Thermal heat transfer through pipe wall | |
| Modelica.Thermal.HeatTransfer.Components.ThermalCollector | colAllToOne | Connector to assign multiple heat ports to one heat port | |
| Modelica.Thermal.HeatTransfer.Components.ThermalCollector[nNodes] | thermalCollector1 |
Revisions
-
May 13, 2021, by Christoph Nytsch-Geusen:
Thermal heat transfer calculation through pipe walls extendend with internal and external convective heat transfer coefficients. -
June 1, 2015, by Christoph Nytsch-Geusen:
Adaptation from the Builings to the BuildingSystms library. -
October 8, 2013, by Michael Wetter:
Removed parametershow_V_flow. -
September 13, 2013 by Michael Wetter:
Replacednominalwithdefaultvalues as they are computed using the default Medium values. -
February 15, 2012 by Michael Wetter:
Changed base class from which the model extends. Propagated parameters of volume to the top if this model. -
February 12, 2012 by Wangda Zuo:
First implementation.