WOLFRAM SYSTEMMODELER

TestWallFrictionAndGravity

Pressure loss in pipe due to wall friction and gravity (only for test purposes; if needed use Pipes.StaticPipe instead)

Wolfram Language

In[1]:=
SystemModel["Modelica.Fluid.Pipes.BaseClasses.WallFriction.TestWallFrictionAndGravity"]
Out[1]:=

Information

This information is part of the Modelica Standard Library maintained by the Modelica Association.

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:

PipeFriction1.png

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 (17)

allowFlowReversal

Value: system.allowFlowReversal

Type: Boolean

Description: = true to allow flow reversal, false restricts to design direction (port_a -> port_b)

dp_start

Value: dp_fric_nominal + system.g * height_ab * rho_nominal

Type: AbsolutePressure (Pa)

Description: Guess value of dp = port_a.p - port_b.p

m_flow_start

Value: system.m_flow_start

Type: MassFlowRate (kg/s)

Description: Guess value of m_flow = port_a.m_flow

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: Small mass flow rate for regularization of zero flow

show_T

Value: true

Type: Boolean

Description: = true, if temperatures at port_a and port_b are computed

show_V_flow

Value: true

Type: Boolean

Description: = true, if volume flow rate at inflowing port is computed

length

Value:

Type: Length (m)

Description: Length of pipe

diameter

Value:

Type: Diameter (m)

Description: Inner (hydraulic) diameter of pipe

crossArea

Value: Modelica.Constants.pi * diameter * diameter / 4

Type: Area (m²)

Description: Inner cross section area

height_ab

Value: 0.0

Type: Length (m)

Description: Height(port_b) - Height(port_a)

roughness

Value: 2.5e-5

Type: Roughness (m)

Description: Absolute roughness of pipe (default = smooth steel pipe)

m_flow_nominal

Value: if system.use_eps_Re then system.m_flow_nominal else 1e2 * system.m_flow_small

Type: MassFlowRate (kg/s)

Description: Nominal mass flow rate

use_nominal

Value: false

Type: Boolean

Description: = true, if mu_nominal and rho_nominal are used, otherwise computed from medium

mu_nominal

Value: Medium.dynamicViscosity(Medium.setState_pTX(Medium.p_default, Medium.T_default, Medium.X_default))

Type: DynamicViscosity (Pa·s)

Description: Nominal dynamic viscosity (e.g., mu_liquidWater = 1e-3, mu_air = 1.8e-5)

rho_nominal

Value: Medium.density_pTX(Medium.p_default, Medium.T_default, Medium.X_default)

Type: Density (kg/m³)

Description: Nominal density (e.g., rho_liquidWater = 995, rho_air = 1.2)

show_Re

Value: false

Type: Boolean

Description: = true, if Reynolds number is included for plotting

from_dp

Value: true

Type: Boolean

Description: = true, use m_flow = f(dp), otherwise dp = f(m_flow)

Connectors (2)

port_a

Type: FluidPort_a

Description: Fluid connector a (positive design flow direction is from port_a to port_b)

port_b

Type: FluidPort_b

Description: Fluid connector b (positive design flow direction is from port_a to port_b)

Components (3)

system

Type: System

Description: System wide properties

state_a

Type: ThermodynamicState

Description: state for medium inflowing through port_a

state_b

Type: ThermodynamicState

Description: state for medium inflowing through port_b