modelSimplePipe
Extends from AixLib.Fluid.Interfaces.PartialTwoPort (Partial component with two ports).
Information
This model represents a pipe using a simple approach and consists of a HydraulicDiameter and n volume elements to approximate the thermal wave propagation. The heat transfer through the pipe wall is modeled with a CylindricHeatTransfer and can be deactivated. This model can be used if a heat flow or heat transfer to the pipe has to be modeled and the thermal mass of the fluid cannot be neglected. Since the pipe is discretized in n elements, this model should only be used, if the dead time of the thermal wive propagation can be neglected. With an increasing number of elements (nNodes) the wave propagation becomes more realistic. However, the simulation time will increase as well.
For long pipes, the model PlugFlowPipe can be used (the heat transfer in the PlugFlowPipe can cause problems for small volume flows ).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nNodes | 2 | Spatial segmentation |
| Modelica.Units.SI.Length | dh | Inner/hydraulic diameter (assuming a round cross section area) | |
| Modelica.Units.SI.Length | length | Pipe length | |
| Real | fac | 1 | Factor to take into account flow resistance of bends etc., fac=dp_nominal/dpStraightPipe_nominal |
| Assumptions | |||
| Boolean | allowFlowReversal (from PartialTwoPort) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Material | |||
| Boolean | withHeattransfer | true | True, if heat transfer to ambient |
| Real | ReC | 2300 | Reynolds number where transition to turbulent starts |
| Modelica.Units.SI.Height | roughness | 2.5e-5 | Average height of surface asperities (default: smooth steel pipe) |
| Modelica.Units.SI.ThermalConductivity | lambda | 370 | Heat conductivity of pipe material |
| Modelica.Units.SI.SpecificHeatCapacity | c | 1600 | Specific heat capacity of pipe material |
| Modelica.Units.SI.Density | rho | 1000 | Density of pipe material |
| Modelica.Units.SI.Length | thickness | 0.001 | Pipe wall thickness |
| Advanced | |||
| Modelica.Units.SI.MassFlowRate | m_flow_small | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
| Initialization | |||
| Modelica.Units.SI.Temperature | T_start | Medium.T_default | Initialization temperature at pipe inlet |
| Medium.AbsolutePressure | p_start | Medium.p_default | Start value of pressure |
| Nominal condition | |||
| Modelica.Units.SI.MassFlowRate | m_flow_nominal | Nominal mass flow rate | |
| Dynamics › Equations | |||
| Modelica.Fluid.Types.Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamics.DynamicFreeInitial | Type of energy balance: dynamic (3 initialization options) or steady state |
| Modelica.Fluid.Types.Dynamics | massDynamics | energyDynamics | Type of mass balance: dynamic (3 initialization options) or steady state |
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.Fluid.Interfaces.HeatPorts_a[nNodes] | heatPorts |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| HydraulicDiameter | res | Pressure drop calculation for this pipe | |
| MixingVolumes.MixingVolume[nNodes] | vol | ||
| Utilities.HeatTransfer.CylindricHeatTransfer[nNodes] | PipeWall |
Revisions
- Mai 07, 2020, by Alexander Kümpel:
First implementation