modelDP
Extends from ThermoCycle.Icons.Water.PressDrop.
Information
The DP model is a lumped model that computes a punctual pressure drop.
The assumptions for this model are:
- Incompressible fluid for computing the pressure drop
- No thermal energy losses to the ambient
The total pressure drop is computed as the sum of three different terms: a constant pressure difference (e.g. due to the static pressure head), a linear pressure drop (e.g. due to friction in a laminar flow) and a quadratic pressure drop (typical of turbulent flow):
Modelling options
In the General tab the following options are availabe:
- Medium: the user has the possibility to easly switch Medium.
- UseNom: If true, use the nominal conditions defined in the Nominal Conditions tab to compute the pressure drop characteristic (i.e. the parameters h, K and A)
In the Nominal condition tab the following option is availabe:
- use_rho_nom: If true, the density is considered constant during the whole simulation and equal to the nominal value.
In the Initialization tab the following options are availabe:
- constinit: If true, the pressure drop is considered constant at the beginning of the simulation to avoid oscillations.
- UseHomotopy: If true, the homotopy function is used to set the pressure drop to zero in the first initialization.
The parameter DELTAp_0 defines a limitation of the pressure drop below which the quadratic expression is replaced by a third order polynomial expression to avoid the non-physical infinite derivative at DELTAp=0.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | UseNom | false | Use Nominal conditions to compute pressure drop characteristics |
| Modelica.SIunits.Length | h | 0 | Static fluid head (dp = h * rho * g) |
| Real | k | 0 | Coefficient for linear pressure drop (dp = k * V_dot) |
| Modelica.SIunits.Area | A | 10e-5 | Valve throat area for quadratic pressure drop (dp = 1/A?*M_dot?/(2*rho)) |
| Modelica.SIunits.Pressure | DELTAp_0 | 500 | Pressure drop below which a 3rd order interpolation is used for the computation of the flow rate in order to avoid infinite derivative at 0 |
| Nominal Conditions | |||
| Modelica.SIunits.MassFlowRate | Mdot_nom | 0.1 | Nominal mass flow rate |
| Modelica.SIunits.Pressure | p_nom | 1e5 | Nominal pressure |
| Modelica.SIunits.Temperature | T_nom | 423.15 | Nominal temperature |
| Modelica.SIunits.Density | rho_nom | Medium.density_pT(p_nom, T_nom) | Nominal density |
| Modelica.SIunits.Pressure | DELTAp_stat_nom | 0 | Nominal static pressure drop |
| Modelica.SIunits.Pressure | DELTAp_lin_nom | 0 | Nominal linear pressure drop |
| Modelica.SIunits.Pressure | DELTAp_quad_nom | 0 | Nominal quadratic pressure drop |
| Boolean | use_rho_nom | false | Use the nominal density for the computation of the pressure drop (i.e it depends only on the flow rate) |
| Initialization | |||
| Modelica.SIunits.Pressure | DELTAp_start | DELTAp_stat_nom + DELTAp_lin_nom + DELTAp_quad_nom | Start Value for the pressure drop |
| Modelica.SIunits.Time | t_init | 10 | if constinit is true, time during which the pressure drop is set to the constant value DELTAp_start |
| Boolean | constinit | false | if true, sets the pressure drop to a constant value at the beginning of the simulation in order to avoid oscillations |
| Boolean | UseHomotopy | false | if true, uses homotopy to set the pressure drop to zero in the first initialization |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.SIunits.Length | h_ok | ||
| Real | k_ok | ||
| Modelica.SIunits.Area | A_ok | ||
| Modelica.SIunits.Density | d_fl | ||
| Medium.Density | rho | ||
| Modelica.SIunits.Pressure | p_fl | ||
| Medium.SpecificEnthalpy | h_fl | ||
| Modelica.SIunits.Pressure | DELTAp | ||
| Modelica.SIunits.Pressure | DELTAp_quad | Quadratic pressure drop | |
| Modelica.SIunits.Pressure | DELTAp_lin | Linear pressure drop | |
| Modelica.SIunits.Pressure | DELTAp_stat | Static pressure drop | |
| Modelica.SIunits.MassFlowRate | Mdot | ||
| Modelica.SIunits.Time | t_change | 5 | time during which the transition of the weighting factor function happens |
| Modelica.SIunits.MassFlowRate | Mdot_0 | Nominal mass flow rate | |
| Interfaces.Fluid.FlangeA | InFlow | ||
| Interfaces.Fluid.FlangeB | OutFlow |
Contents
| Name | Description |
|---|---|
| Medium |