modelEdgedBend
Extends from Interfaces.SISOFlowBend.
Information
This pipe bend 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 pipe bend.
The pressure loss of the model refers to a flowpath length l = 5*d_hyd upstream as well as downstream of the edge. If the adjacent components are pipes, these must be adjusted accordingly.
Note that the results may differ from actual values. Due to complex flow behavior in pipe bends, widely applicable formulas are approximations only. If the pressure drop coefficient of a real component is known, it is recommended to calibrate the model to this value using the roughness parameter.
This component is an adaptation of EdgedBend 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_edgedOverall_DP by Modelica is implemented. The input records dp_edgedOverall_IN_con & dp_edgedOverall_IN_var are overwritten with the input parameters defining the pipe bend 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 2 figures, resistance coefficient charts representing the pressure loss model under common conditions are 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) |
| Geometry | |||
| SI.Length | d | Diameter | |
| SI.Angle | delta | Bending angle (5° <= delta <= 180°) | |
| Roughness | |||
| ThermofluidStream.Processes.Internal.Material | material | ThermofluidStream.Processes.Internal.Material.other | Material of pipe |
| SI.Length | ks | Roughness of pipe | |
| Advanced | |||
| StateSelect | dpStateSelect | StateSelect.default | State select for pressure difference dp |
| ThermofluidStream.Utilities.Units.Inertance | L_value | dropOfCommons.L | Inertance |
| Boolean | computeL | true | Compute L from r and l |
| Medium.Density | rho_min | dropOfCommons.rho_min | Minimal density |
| Initialization › Pressure difference | |||
| ThermofluidStream.Utilities.Types.InitializationMethods | initdp | ThermofluidStream.Utilities.Types.InitializationMethods.none | Initialization method for pressure difference dp |
| SI.Pressure | dp_0 | 0 | Initial value for pressure difference dp |
| ThermofluidStream.Utilities.Units.MassFlowAcceleration | dp_acceleraton_0 | 0 | Initial value for der(dp) |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Medium.Density | rho | Mean density | |
| Medium.DynamicViscosity | mu | Mean dynamic viscosity |