modelPipe
Pipe model. Extends form Clara TubeBundle_L1_TML component
Extends from ClaRa.Components.VolumesValvesFittings.Pipes.PipeFlowVLE_L1_TML (Simple tube model based on transmission line equations. Can choose between Modelica and ClaRa Delay implementation.).
Information
Purpose of model
A transmission line model of a pipe featuring an analytical energy balance. Therefore, the accuracy of the model doesn't depend on the number of states. Only a linear pressure loss can be considered. It was designed to simulate pipes with a higher length while avoiding too many states. The same effect can be achieved with the plug-flow concept described in the SinglePipe_L2. It is recommended to use the SinglePipe_L2 model for such use cases. The model was extended from the ClaRa library.
Level of detail, physical effects considered, and physical insight
- Dynamic energy balance (analytical)
- Linear pressure loss
- No reverse flow possible
Limits of validity
Flow reversal is not supported. A quadratic pressure loss model can't be considered.
Interfaces
inlet:fluidPortIn
outlet: fluidportOut
heat: heat port
eye
Remarks for Usage
When this model is used for modelling a district heating network, non-linear systems of equations might occur.
References
This model was extended from the ClaRa library.
Version History
The model was documented by Jan Westphal (j.westphal@tuhh.de) in January 2025
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Length | length (from PipeFlowVLE_L1_TML) | 10 | |Geometry|Length of the pipe |
| Modelica.Units.SI.Length | diameter_i (from PipeFlowVLE_L1_TML) | 0.5 | |Geometry|Inner diameter of the pipe |
| Modelica.Units.SI.Length | z_in (from PipeFlowVLE_L1_TML) | 0.1 | |Geometry|height of inlet above ground |
| Modelica.Units.SI.Length | z_out (from PipeFlowVLE_L1_TML) | 0.1 | |Geometry|height of outlet above ground |
| Integer | N_tubes (from PipeFlowVLE_L1_TML) | 1 | |Geometry|Number Of parallel pipes |
| Modelica.Units.SI.Area | A_cross (from PipeFlowVLE_L1_TML) | Modelica.Constants.pi/4*diameter_i^2*N_tubes | cross area of volume elements |
| Real | S (from PipeFlowVLE_L1_TML) | Modelica.Constants.pi*diameter_i*N_tubes | Shape factor of pipe wall for heat conduction |
| Integer | N_cv (from PipeFlowVLE_L1_TML) | 1 | |Discretisation|number of subdivisions of tube wall |
| Integer | N_wall (from PipeFlowVLE_L1_TML) | N_cv | number of subdivisions for wall temperature |
| Modelica.Units.SI.Length[N_wall] | Delta_x (from PipeFlowVLE_L1_TML) | ones(N_wall)*length/N_wall | Length of heated wall section |
| Integer | N_temp (from PipeFlowVLE_L1_TML) | 2*N_wall + 1 | number of tempratures to be computed |
| Boolean | useConstantMediaData (from PipeFlowVLE_L1_TML) | false | |Media Data|Use of constant media data |
| Modelica.Units.SI.MassFlowRate | m_flow_nom (from PipeFlowVLE_L1_TML) | 10 | |Physical Effects|Linear Pressure Loss|Nominal mass flow w.r.t. all parallel tubes |
| Modelica.Units.SI.Pressure | Delta_p_nom (from PipeFlowVLE_L1_TML) | 1e3 | |Physical Effects|Linear Pressure Loss|Pressure loss over pipe length length at nominal mass flow w.r.t. all parallel tubes |
| Modelica.Units.SI.Pressure | Delta_p_grav_start (from PipeFlowVLE_L1_TML) | rho_start*g_n*(z_out - z_in) | Pressure loss over pipe length length at nominal operation point |
| Boolean | adiabaticWall (from PipeFlowVLE_L1_TML) | true | |Physical Effects|Heat Transfer|set true if pipe is adiabatic |
| Modelica.Units.SI.Frequency | F (from PipeFlowVLE_L1_TML) | (Delta_p_nom*A_cross)/(m_flow_nom*length) | Friction coefficient |
| Boolean | useHomotopy (from PipeFlowVLE_L1_TML) | simCenter.useHomotopy | |Initialisation|Model Settings|True, if homotopy method is used during initialisation |
| Modelica.Units.SI.SpecificEnthalpy | h_start (from PipeFlowVLE_L1_TML) | TILMedia.VLEFluid.MixtureCompatible.Functions.liquidSpecificEnthalpy_pTxi(medium, p_start, simCenter.T_amb_start) | |Initialisation|Initial Medium Properties|Initial averaged fluid specific enthalpy |
| Modelica.Units.SI.Pressure | p_start (from PipeFlowVLE_L1_TML) | (p_in_start + p_out_start)/2 | |Initialisation|Initial Medium Properties|Initial averaged fluid pressure |
| Modelica.Units.SI.Pressure | p_in_start (from PipeFlowVLE_L1_TML) | simCenter.p_amb_start | |Initialisation|Initial Medium Properties|Initial inlet pressure |
| Modelica.Units.SI.Pressure | p_out_start (from PipeFlowVLE_L1_TML) | simCenter.p_amb_start | |Initialisation|Initial Medium Properties|Initial outlet pressure |
| Modelica.Units.SI.Density | rho_start (from PipeFlowVLE_L1_TML) | TILMedia.VLEFluid.MixtureCompatible.Functions.density_phxi(medium, p_start, h_start) | Initial fluid density |
| Boolean | showExpertSummary (from PipeFlowVLE_L1_TML) | simCenter.showExpertSummary | |Summary and Visualisation||True, if an extended summary shall be shown, else false |
| Boolean | showData (from PipeFlowVLE_L1_TML) | false | |Summary and Visualisation||True, if a data port containing p,T,h,s,m_flow shall be shown, else false |
| Boolean | useClaRaDelay (from PipeFlowVLE_L1_TML) | simCenter.useClaRaDelay | |Expert Settings|Delay Function|True for using ClaRa delay implementation / false for built in Modelica delay |
| Real | kappa (from PipeFlowVLE_L1_TML) | 1.25 | |Expert Settings|Transmission Line Settings|TML pFrequency approximation |
| Real | f_ps (from PipeFlowVLE_L1_TML) | 0.01 | |Expert Settings|Transmission Line Settings|Speed factor for pseudo state fluid properties averaging |
| Integer | numDelays (from PipeFlowVLE_L1_TML) | N_wall + N_temp + 13 | |
| Modelica.Units.SI.Pressure | p_L_init (from PipeFlowVLE_L1_TML) | Initial pressure at outlet: p_out = p_in_init + dp_L | |
| Modelica.Units.SI.Pressure | p_0_init (from PipeFlowVLE_L1_TML) | Initial pressure at inlet: p_in = p_out_init + dp_0 | |
| Modelica.Units.SI.VolumeFlowRate | V_flow_start (from PipeFlowVLE_L1_TML) | Initial volume flow at inlet | |
| Media Data | |||
| TILMedia.VLEFluid.Types.BaseVLEFluid | medium (from PipeFlowVLE_L1_TML) | simCenter.fluid1 | Medium in the component |
| Modelica.Units.SI.SpecificHeatCapacity | cp_const (from PipeFlowVLE_L1_TML) | 4200 | Constant heat capacity in pipe |
| Modelica.Units.SI.Density | rho_const (from PipeFlowVLE_L1_TML) | 985 | Constant fluid density in pipe |
| Modelica.Units.SI.Velocity | a_const (from PipeFlowVLE_L1_TML) | 1500 | Constant speed of sound in pipe |
| Physical Effects › Heat Transfer | |||
| Real | alpha (from PipeFlowVLE_L1_TML) | 10 | |
| Summary and Visualisation | |||
| Boolean | contributeToCycleSummary (from PipeFlowVLE_L1_TML) | simCenter.contributeToCycleSummary | True if component shall contribute to automatic efficiency calculation |
| Boolean | heatFlowIsLoss (from PipeFlowVLE_L1_TML) | true | True if negative heat flow is a loss (not a process product) |
| Expert Settings › Delay Function | |||
| Real | MaxSimTime (from PipeFlowVLE_L1_TML) | simCenter.MaxSimTime | Maximum time for simulation, must be set for Modelica delay blocks with variable delay time if simCenter.useClaRaDelay==true |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| ClaRa.Basics.Interfaces.FluidPortIn | inlet (from PipeFlowVLE_L1_TML) | Inlet port | |
| ClaRa.Basics.Interfaces.FluidPortOut | outlet (from PipeFlowVLE_L1_TML) | Outlet port | |
| ClaRa.Basics.Interfaces.HeatPort_a[N_wall] | heat (from PipeFlowVLE_L1_TML) | ||
| ClaRa.Basics.Interfaces.EyeOut | eye (from PipeFlowVLE_L1_TML) |