Package Modelica.Fluid.Pipes.BaseClasses.WallFrictionDifferent variants for pressure drops due to pipe wall friction
Package Modelica.Fluid.Pipes.BaseClasses.WallFriction
This package provides functions to compute pressure losses due to wall friction in a pipe. Every correlation is defined by a package that is derived by inheritance from the package WallFriction.PartialWallFriction. The details of the underlying pipe wall friction model are described in the UsersGuide. Basically, different variants of the equation
dp = λ(Re,D)*(L/D)*ρ*v*|v|/2
are used, where the friction loss factor λ is shown in the next figure:
Extends from Modelica.Icons.Package (Icon for standard packages).
| Name | Description |
|---|---|
Detailed … | Pipe wall friction for laminar and turbulent flow (detailed characteristic) |
Laminar … | Pipe wall friction for laminar flow in circular tubes (linear correlation) |
LaminarAndQuadraticTurbulent … | Pipe wall friction for laminar and turbulent flow in circular tubes (simple characteristic) |
NoFriction … | No pipe wall friction, no static head |
PartialWallFriction … | Partial wall friction characteristic (base package of all wall friction characteristics) |
QuadraticTurbulent … | Pipe wall friction for turbulent flow in circular tubes (simple characteristic, mu not used) |
TestWallFrictionAndGravity | Pressure loss in pipe due to wall friction and gravity (only for test purposes; if needed use Pipes.StaticPipe instead) |
Model Modelica.Fluid.Pipes.BaseClasses.WallFriction.TestWallFrictionAndGravity
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,D)*(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.
Extends from Modelica.Fluid.Interfaces.PartialTwoPortTransport (Partial element transporting fluid between two ports without storage of mass or energy).
| Type | Name | Default | Description |
|---|---|---|---|
Boolean | allowFlowReversal | system.allowFlowReversal | = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
AbsolutePressure | dp_start | dp_fric_nominal + system.g * height_ab * rho_nominal | Guess value of dp = port_a.p - port_b.p |
MassFlowRate | m_flow_start | system.m_flow_start | Guess value of m_flow = port_a.m_flow |
MassFlowRate | m_flow_small | if system.use_eps_Re then system.eps_m_flow * m_flow_nominal else system.m_flow_small | Small mass flow rate for regularization of zero flow |
Boolean | show_T | true | = true, if temperatures at port_a and port_b are computed |
Boolean | show_V_flow | true | = true, if volume flow rate at inflowing port is computed |
Length | length | Length of pipe | |
Diameter | diameter | Inner (hydraulic) diameter of pipe | |
Area | crossArea | 0.25 * (Modelica.Constants.pi * diameter * diameter) | Inner cross section area |
Length | height_ab | 0 | Height(port_b) - Height(port_a) |
Roughness | roughness | 2.5e-5 | Absolute roughness of pipe (default = smooth steel pipe) |
MassFlowRate | m_flow_nominal | if system.use_eps_Re then system.m_flow_nominal else 100 * system.m_flow_small | Nominal mass flow rate |
Boolean | use_nominal | false | = true, if mu_nominal and rho_nominal are used, otherwise computed from medium |
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) |
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) |
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) |
| Type | Name | Description |
|---|---|---|
FluidPort_a | port_a | Fluid connector a (positive design flow direction is from port_a to port_b) |
FluidPort_b | port_b | Fluid connector b (positive design flow direction is from port_a to port_b) |