modelPressDrop
Extends from Icons.Gas.Tube.
Information
The pressure drop across the inlet and outlet connectors is computed according to a turbulent friction model, i.e. is proportional to the squared velocity of the fluid. The friction coefficient can be specified directly, or by giving an operating point, or as a multiple of the kinetic pressure. The correction coefficient Kfc can be used to modify the friction coefficient, e.g. to fit some experimental operating point.
A small linear pressure drop is added to avoid numerical singularities at low or zero flowrate. The wnom parameter must be always specified; the additional linear pressure drop is such that it is equal to the turbulent pressure drop when the flowrate is equal to wnf*wnom (the default value is 1% of the nominal flowrate).
Modelling options
The actual gas used in the component is determined by the replaceable Medium package. In the case of multiple component, variable composition gases, the start composition is given by Xstart, whose default value is Medium.reference_X.
The following options are available to specify the friction coefficient:
- FFtype = 0: the hydraulic friction coefficient Kf is used directly.
- FFtype = 1: the hydraulic friction coefficient is specified by the nominal operating point (wnom,dpnom, rhonom).
- FFtype = 2: the pressure drop is K times the kinetic pressure.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Medium.MassFlowRate | wnom | Nominal mass flowrate | |
| SI.PressureDifference | dpnom | Nominal pressure drop | |
| ThermoPower.Choices.PressDrop.FFtypes | FFtype | ThermoPower.Choices.PressDrop.FFtypes.Kf | Friction factor type |
| Real | Kf | 0 | Hydraulic resistance coefficient (DP = Kf*w^2/rho) |
| Medium.Density | rhonom | 0 | Nominal density |
| SI.PerUnit | K | 0 | Kinetic resistance coefficient (DP=K*rho*velocity2/2) |
| SI.Area | A | 0 | Cross-section |
| SI.PerUnit | wnf | 0.01 | Fraction of nominal flow rate at which linear friction equals turbulent friction |
| SI.PerUnit | Kfc | 1 | Friction factor correction coefficient |
| Real | Kf_a | Actual hydraulic resistance coefficient | |
| Boolean | allowFlowReversal | system.allowFlowReversal | = true to allow flow reversal, false restricts to design direction |
| Initialisation | |||
| Medium.AbsolutePressure | pstart | 101325 | Start pressure value |
| Medium.Temperature | Tstart | 300 | Start temperature value |
| Medium.MassFraction[Medium.nX] | Xstart | Medium.reference_X | Start gas composition |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| FlangeA | inlet | ||
| FlangeB | outlet |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Medium.BaseProperties | gas | ||
| ThermoPower.System | system | System wide properties | |
| Medium.MassFlowRate | w | Mass flow rate in the inlet | |
| Medium.AbsolutePressure | pin | Inlet pressure | |
| Medium.AbsolutePressure | pout | Outlet pressure | |
| SI.PressureDifference | dp | Pressure drop |
Contents
| Name | Description |
|---|---|
 Medium | |
 squareReg |
Revisions
- 19 Nov 2004
by Francesco Casella:
Adapted to Modelica.Media. - 5 Mar 2004
by Francesco Casella:
First release.
Kfnom removed, Kf can now be set directly.