modelEdgedOrifice
Extends from ThermofluidStream.Interfaces.SISOFlow.
Information
This orifice model computes the pressure loss of the fluid depending on the massflow or the massflow depending on a given pressure difference, some medium properties and the geometry of the orifice.
If the resistance coefficient of a real component is known, it is recommended to calibrate the model to this value varying the Darcy friciton parameter.
This component is an adaptation of ThickEdgedOrifice by Modelica to make it compatible with ThermofludiStream library.
The model is usable for both incompressible and compressible calculation up to at least Ma 0.3 at pipe outlet and one phase medium. The best performance is achieved when using steady state or slowly changing boundary conditions. Numerical stability is best by given mass flow rate and one given pressure boundary. When using two pressure boundaries deviations due to inertia have to be accepted. The Model is not valid for hydraulic shock calculation (sudden change of pressure or mass flow rate).
The pipe bend component is using the partial model SISOFlowBend implementing the common flow balances. For the calculation of pressure loss the function dp_thickEdgedOverall_DP by Modelica is implemented and extended by an additional input which allows the manual adjustment of the Darcy friction factor. (This was removed to increase the compatibility with Modelica.Fluid but may be added again) The input records dp_curvedOverall_IN_con & dp_thickEdgedOverall_IN_var are overwritten with the input parameters defining the orifice geometry and fluid properties. For more information on the underlying pressure loss function, click here. To improve the accuracy when compressible media are used, center state fluid properties (mean dynamic viscosity & mean density) are defined and refered to in the pressure loss function.
The following figure, a resistance coefficient charts representing the pressure loss model under common conditions is shown. (Currently not yet available)
[P. Jordan; HTWG Konstanz; 10/23]
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | assumeConstantMaterialProperties | true | = true, if constant density and dynamic viscosity is assumed (use '= false' e.g. for Ma > 0.3) |
| Modelica.Fluid.Dissipation.PressureLoss.Orifice.dp_thickEdgedOverall_IN_con | In_con | Input record constants | |
| Geometry | |||
| SI.Length | d_1 | Perimeter of pipe | |
| SI.Length | d_0 | Perimeter of vena contraction | |
| SI.Length | l_0 | Length of vena contraction | |
| Initialization › dp | |||
| ThermofluidStream.Utilities.Types.InitializationMethods | initdp | ThermofluidStream.Utilities.Types.InitializationMethods.none | Initialization method for dp |
| SI.Pressure | dp_0 | 0 | Initial value for dp |
| ThermofluidStream.Utilities.Units.MassFlowAcceleration | dp_acceleraton_0 | 0 | Initial value for der(dp) |
| Initialization | |||
| SI.Pressure | dp_smooth | 1 | Start linearisation for decreasing pressure loss |
| Advanced › Inertance | |||
| Boolean | computeL | true | = true, if inertance L is computed from the geometry |
| ThermofluidStream.Utilities.Units.Inertance | L_value | dropOfCommons.L | Inertance |
| Advanced | |||
| Medium.Density | rho_min | dropOfCommons.rho_min | Minimal input density |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Medium.Density | rho | Mean density | |
| Medium.DynamicViscosity | mu | Mean dynamic viscosity | |
| Modelica.Fluid.Dissipation.PressureLoss.Orifice.dp_thickEdgedOverall_IN_var | In_var | Input record variables | |
| SI.ReynoldsNumber | Re | d_0*abs(m_flow)/A_0/mu | Reynoldsnumber at vena contraction |