modelNominalLaminarFlow
NominalLaminarFlow: Linear laminar flow for given nominal values
Extends from Modelica.Fluid.Pipes.BaseClasses.FlowModels.PartialStaggeredFlowModel (Base class for momentum balances in flow models).
Information
This model defines a simple linear pressure loss assuming laminar flow for
specified dp_nominal and m_flow_nominal.
Select show_Res = true to analyze the actual flow and the lengths of a pipe that would fulfill the
specified nominal values for given geometry parameters crossAreas, dimensions and roughnesses.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | m (from PartialDistributedFlow) | 1 | Number of flow segments |
| SI.ReynoldsNumber | Re_turbulent (from PartialStaggeredFlowModel) | 4000 | Start of turbulent regime, depending on type of flow device |
| SI.AbsolutePressure | dp_nominal | Nominal pressure loss | |
| SI.MassFlowRate | m_flow_nominal | Mass flow rate for dp_nominal | |
| Internal interface | |||
| Integer | n (from PartialStaggeredFlowModel) | 2 | Number of discrete flow volumes |
| Internal interface › Geometry | |||
| Real | nParallel (from PartialStaggeredFlowModel) | Number of identical parallel flow devices | |
| Internal interface › Static head | |||
| SI.Acceleration | g (from PartialStaggeredFlowModel) | system.g | Constant gravity acceleration |
| Internal interface › Assumptions | |||
| Boolean | allowFlowReversal (from PartialStaggeredFlowModel) | system.allowFlowReversal | = true, if flow reversal is enabled, otherwise restrict flow to design direction (states[1] -> states[n+1]) |
| Modelica.Fluid.Types.Dynamics | momentumDynamics (from PartialStaggeredFlowModel) | system.momentumDynamics | Formulation of momentum balance |
| Internal interface › Initialization | |||
| Medium.MassFlowRate | m_flow_start (from PartialStaggeredFlowModel) | system.m_flow_start | Start value of mass flow rates |
| Medium.AbsolutePressure | p_a_start (from PartialStaggeredFlowModel) | Start value for p[1] at design inflow | |
| Medium.AbsolutePressure | p_b_start (from PartialStaggeredFlowModel) | Start value for p[n+1] at design outflow | |
| Advanced | |||
| Boolean | useUpstreamScheme (from PartialStaggeredFlowModel) | true | = false to average upstream and downstream properties across flow segments |
| Boolean | use_Ib_flows (from PartialStaggeredFlowModel) | momentumDynamics <> Types.Dynamics.SteadyState | = true to consider differences in flow of momentum through boundaries |
| Diagnostics | |||
| Boolean | show_Res (from PartialStaggeredFlowModel) | false | = true, if Reynolds numbers are included for plotting |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Medium.ThermodynamicState | states (from PartialStaggeredFlowModel) | Thermodynamic states along design flow | |
| SI.Velocity | vs (from PartialStaggeredFlowModel) | Mean velocities of fluid flow | |
| SI.Area | crossAreas (from PartialStaggeredFlowModel) | Cross flow areas at segment boundaries | |
| SI.Length | dimensions (from PartialStaggeredFlowModel) | Characteristic dimensions for fluid flow (diameters for pipe flow) | |
| Modelica.Fluid.Types.Roughness | roughnesses (from PartialStaggeredFlowModel) | Average height of surface asperities | |
| SI.Length | dheights (from PartialStaggeredFlowModel) | Height(states[2:n]) - Height(states[1:n-1]) | |
| Modelica.Fluid.System | system (from PartialDistributedFlow) | System properties | |
| SI.Length | pathLengths (from PartialDistributedFlow) | Lengths along flow path | |
| Medium.MassFlowRate | m_flows (from PartialDistributedFlow) | Mass flow rates between states | |
| SI.Momentum | Is (from PartialDistributedFlow) | Momenta of flow segments | |
| SI.Force | Ib_flows (from PartialDistributedFlow) | Flow of momentum across boundaries | |
| SI.Force | Fs_p (from PartialDistributedFlow) | Pressure forces | |
| SI.Force | Fs_fg (from PartialDistributedFlow) | Friction and gravity forces | |
| Medium.Density | rhos (from PartialStaggeredFlowModel) | if use_rho_nominal then fill(rho_nominal, n) else Medium.density(states) | |
| Medium.Density | rhos_act (from PartialStaggeredFlowModel) | Actual density per segment | |
| Medium.DynamicViscosity | mus (from PartialStaggeredFlowModel) | if use_mu_nominal then fill(mu_nominal, n) else Medium.dynamicViscosity(states) | |
| Medium.DynamicViscosity | mus_act (from PartialStaggeredFlowModel) | Actual viscosity per segment | |
| SI.Pressure | dps_fg (from PartialStaggeredFlowModel) | Pressure drop between states | |
| SI.ReynoldsNumber | Res (from PartialStaggeredFlowModel) | Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber(vs, rhos, mus, dimensions) | Reynolds numbers |
| Medium.MassFlowRate | m_flows_turbulent (from PartialStaggeredFlowModel) | {nParallel*(crossAreas[i] + crossAreas[i + 1])/(dimensions[i] + dimensions[i + 1])*mus_act[i]*Re_turbulent for i in 1:n - 1} | Start of turbulent flow |
| SI.Length | pathLengths_nominal | {(dp_nominal/(n - 1) - g*dheights[i])*Modelica.Constants.pi*((dimensions[i] + dimensions[i + 1])/2)^4*rhos_act[i]/(128*mus_act[i])/(m_flow_nominal/nParallel) for i in 1:n - 1} | Lengths resulting from given nominal values for circular tubes |