PartialGenericPipeFlow

GenericPipeFlow: Pipe flow pressure loss and gravity with replaceable WallFriction package

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. 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.

By default, the correlations are computed with media data at the actual time instant. In order to reduce non-linear equation systems, the parameters use_mu_nominal and use_rho_nominal provide 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)

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 to allow flow reversal, false restricts 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: true 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)

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	Type: Length[n - 1] (m) Description: pathLengths used internally; to be defined by extending class
Res_turbulent_internal	Default Value: Re_turbulent * ones(n - 1) Type: ReynoldsNumber[n - 1] Description: Re_turbulent used internally; to be defined by extending class