NominalTurbulentPipeFlowNominalTurbulentPipeFlow: Quadratic turbulent flow in circular tubes for given nominal values |
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Information
This information is part of the Modelica Standard Library maintained by the Modelica Association.
This model defines the pressure loss assuming turbulent flow for
specified dp_nominal and m_flow_nominal.
It takes into account the fluid density of each flow segment and
obtains appropriate pathLengths_nominal values
for an inverse parameterization of the
TurbulentPipeFlow
model. Per default the upstream and downstream densities are averaged with the setting useUpstreamScheme = false,
in order to avoid discontinuous pathLengths_nominal values in the case of flow reversal.
The geometry parameters crossAreas, diameters and roughnesses do
not effect simulation results of this nominal pressure loss model.
As the geometry is specified however, the optionally calculated Reynolds number as well as
m_flows_turbulent and dps_fg_turbulent become meaningful
and can be related to m_flow_small and dp_small.
Optional Variables if show_Res
| Type | Name | Description |
|---|---|---|
| ReynoldsNumber | Res[n] | Reynolds numbers of pipe flow per flow segment |
| MassFlowRate | m_flows_turbulent[n-1] | mass flow rates at start of turbulent region for Re_turbulent=4000 |
| AbsolutePressure | dps_fg_turbulent[n-1] | pressure losses due to friction and gravity corresponding to m_flows_turbulent |
Parameters (18)
| m |
Value: n - 1 Type: Integer Description: Number of flow segments |
|---|---|
| n |
Value: 2 Type: Integer Description: Number of discrete flow volumes |
| nParallel |
Value: Type: Real Description: Number of identical parallel flow devices |
| g |
Value: system.g Type: Acceleration (m/s²) Description: Constant gravity acceleration |
| allowFlowReversal |
Value: system.allowFlowReversal Type: Boolean Description: = true, if flow reversal is enabled, otherwise restrict flow to design direction (states[1] -> states[n+1]) |
| momentumDynamics |
Value: system.momentumDynamics Type: Dynamics Description: Formulation of momentum balance |
| m_flow_start |
Value: system.m_flow_start Type: MassFlowRate (kg/s) Description: Start value of mass flow rates |
| p_a_start |
Value: Type: AbsolutePressure (Pa) Description: Start value for p[1] at design inflow |
| p_b_start |
Value: Type: AbsolutePressure (Pa) Description: Start value for p[n+1] at design outflow |
| useUpstreamScheme |
Value: false Type: Boolean Description: = false to average upstream and downstream properties across flow segments |
| use_Ib_flows |
Value: momentumDynamics <> Types.Dynamics.SteadyState Type: Boolean Description: = true to consider differences in flow of momentum through boundaries |
| Re_turbulent |
Value: 4000 Type: ReynoldsNumber Description: Start of turbulent regime, depending on type of flow device |
| show_Res |
Value: false Type: Boolean Description: = true, if Reynolds numbers are included for plotting |
| from_dp |
Value: momentumDynamics >= Types.Dynamics.SteadyStateInitial Type: Boolean Description: = true, use m_flow = f(dp), otherwise dp = f(m_flow) |
| dp_nominal |
Value: Type: AbsolutePressure (Pa) Description: Nominal pressure loss (only for nominal models) |
| m_flow_nominal |
Value: Type: MassFlowRate (kg/s) Description: Nominal mass flow rate |
| m_flow_small |
Value: if system.use_eps_Re then system.eps_m_flow * m_flow_nominal else system.m_flow_small Type: MassFlowRate (kg/s) Description: Within regularization if |m_flows| < m_flow_small (may be wider for large discontinuities in static head) |
| m_flow_turbulent |
Value: if system.use_eps_Re then 0.1 * m_flow_nominal else system.m_flow_small Type: MassFlowRate (kg/s) Description: Turbulent flow starting from |m_flows| > m_flow_turbulent (may be wider for large discontinuities in static head) |
Inputs (9)
| pathLengths |
Type: Length[m] (m) Description: Lengths along flow path |
|---|---|
| states |
Type: ThermodynamicState[n] Description: Thermodynamic states along design flow |
| vs |
Type: Velocity[n] (m/s) Description: Mean velocities of fluid flow |
| crossAreas |
Type: Area[n] (m²) Description: Cross flow areas at segment boundaries |
| dimensions |
Type: Length[n] (m) Description: Characteristic dimensions for fluid flow (diameters for pipe flow) |
| roughnesses |
Type: Roughness[n] (m) Description: Average height of surface asperities |
| dheights |
Type: Length[n - 1] (m) Description: Height(states[2:n]) - Height(states[1:n-1]) |
| pathLengths_internal |
Default Value: pathLengths_nominal Type: Length[n - 1] (m) Description: pathLengths used internally; to be defined by extending class |
| Res_turbulent_internal |
Default Value: Res_turbulent_nominal Type: ReynoldsNumber[n - 1] Description: Re_turbulent used internally; to be defined by extending class |
Components (2)
 |
system |
Type: System Description: System properties |
|---|---|---|
 |
states |
Type: ThermodynamicState[n] Description: Thermodynamic states along design flow |