modelWallFrictionAndGravity
Extends from Modelica.Fluid.Interfaces.PartialTwoPortTransport (Partial element transporting fluid between two ports without storage of mass or energy).
Information
This model describes pressure losses due to wall friction in a pipe and due to gravity. It is assumed that no mass or energy is stored in the pipe. Correlations of different complexity and validity can be selected via the replaceable package WallFriction (see parameter menu below). The details of the pipe wall friction model are described in the UsersGuide. Basically, different variants of the equation
dp = λ(Re,Δ)*(L/D)*ρ*v*|v|/2
are used, where the friction loss factor λ is shown in the next figure:
By default, the correlations are computed with media data at the actual time instant. In order to reduce non-linear equation systems, parameter use_nominal provides the option to compute the correlations with constant media values at the desired operating point. This might speed-up the simulation and/or might give a more robust simulation.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| SI.Length | length | Length of pipe | |
| SI.Diameter | diameter | Inner (hydraulic) diameter of pipe | |
| SI.Area | crossArea | Modelica.Constants.pi*diameter*diameter/4 | Inner cross section area |
| SI.Length | height_ab | 0.0 | Height(port_b) - Height(port_a) |
| Modelica.Fluid.Types.Roughness | roughness | 2.5e-5 | Absolute roughness of pipe (default = smooth steel pipe) |
| Boolean | use_nominal | false | = true, if mu_nominal and rho_nominal are used, otherwise computed from medium |
| SI.DynamicViscosity | mu_nominal | Medium.dynamicViscosity(Medium.setState_pTX(Medium.p_default, Medium.T_default, Medium.X_default)) | Nominal dynamic viscosity (e.g., mu_liquidWater = 1e-3, mu_air = 1.8e-5) |
| SI.Density | rho_nominal | Medium.density_pTX(Medium.p_default, Medium.T_default, Medium.X_default) | Nominal density (e.g., rho_liquidWater = 995, rho_air = 1.2) |
| Assumptions | |||
| Boolean | allowFlowReversal (from PartialTwoPort) | system.allowFlowReversal | = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
| Advanced | |||
| Medium.AbsolutePressure | dp_start (from PartialTwoPortTransport) | 0.01*system.p_start | Guess value of dp = port_a.p - port_b.p |
| Medium.MassFlowRate | m_flow_start (from PartialTwoPortTransport) | system.m_flow_start | Guess value of m_flow = port_a.m_flow |
| Medium.MassFlowRate | m_flow_small (from PartialTwoPortTransport) | if system.use_eps_Re then system.eps_m_flow*system.m_flow_nominal else system.m_flow_small | Small mass flow rate for regularization of zero flow |
| Boolean | show_Re | false | = true, if Reynolds number is included for plotting |
| Boolean | from_dp | true | = true, use m_flow = f(dp), otherwise dp = f(m_flow) |
| Advanced › Diagnostics | |||
| Boolean | show_T (from PartialTwoPortTransport) | true | = true, if temperatures at port_a and port_b are computed |
| Boolean | show_V_flow (from PartialTwoPortTransport) | true | = true, if volume flow rate at inflowing port is computed |
| Nominal operating point | |||
| SI.MassFlowRate | m_flow_nominal | if system.use_eps_Re then system.m_flow_nominal else 1e2*system.m_flow_small | Nominal mass flow rate |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.Interfaces.FluidPort_a | port_a (from PartialTwoPort) | Fluid connector a (positive design flow direction is from port_a to port_b) | |
| Modelica.Fluid.Interfaces.FluidPort_b | port_b (from PartialTwoPort) | Fluid connector b (positive design flow direction is from port_a to port_b) |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.System | system (from PartialTwoPort) | System wide properties | |
| Medium.MassFlowRate | m_flow (from PartialTwoPortTransport) | Mass flow rate in design flow direction | |
| SI.Pressure | dp (from PartialTwoPortTransport) | Pressure difference between port_a and port_b (= port_a.p - port_b.p) | |
| SI.VolumeFlowRate | V_flow (from PartialTwoPortTransport) | m_flow/Modelica.Fluid.Utilities.regStep(m_flow, Medium.density(state_a), Medium.density(state_b), m_flow_small) | Volume flow rate at inflowing port (positive when flow from port_a to port_b) |
| Medium.Temperature | port_a_T (from PartialTwoPortTransport) | Modelica.Fluid.Utilities.regStep(port_a.m_flow, Medium.temperature(state_a), Medium.temperature(Medium.setState_phX(port_a.p, port_a.h_outflow, port_a.Xi_outflow)), m_flow_small) | Temperature close to port_a, if show_T = true |
| Medium.Temperature | port_b_T (from PartialTwoPortTransport) | Modelica.Fluid.Utilities.regStep(port_b.m_flow, Medium.temperature(state_b), Medium.temperature(Medium.setState_phX(port_b.p, port_b.h_outflow, port_b.Xi_outflow)), m_flow_small) | Temperature close to port_b, if show_T = true |
| SI.ReynoldsNumber | Re | Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber_m_flow(m_flow, noEvent(if m_flow > 0 then mu_a else mu_b), diameter) | Reynolds number of pipe flow |
Contents
| Name | Description |
|---|---|
 WallFriction |