WOLFRAM SYSTEMMODELER

DetailedPipeFlow

DetailedPipeFlow: Detailed characteristic for laminar and turbulent flow

Wolfram Language

In[1]:=
SystemModel["Modelica.Fluid.Pipes.BaseClasses.FlowModels.DetailedPipeFlow"]
Out[1]:=

Information

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

This component defines the complete regime of wall friction. The details are described in the UsersGuide. The functional relationship of the friction loss factor λ is displayed in the next figure. Function massFlowRate_dp() defines the "red curve" ("Swamee and Jain"), where as function pressureLoss_m_flow() defines the "blue curve" ("Colebrook-White"). The two functions are inverses from each other and give slightly different results in the transition region between Re = 1500 .. 4000, in order to get explicit equations without solving a non-linear equation.

PipeFriction1.png

Additionally to wall friction, this component properly implements static head. With respect to the latter, two cases can be distinguished. In the case shown next, the change of elevation with the path from a to b has the opposite sign of the change of density.

PipeFrictionStaticHead_case-a.png

In the case illustrated second, the change of elevation with the path from a to b has the same sign of the change of density.

PipeFrictionStaticHead_case-b.png

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

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

Default Value: pathLengths

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

Components (2)

system

Type: System

Description: System properties

states

Type: ThermodynamicState[n]

Description: Thermodynamic states along design flow

Extended by (4)

FlowModel

Modelica.Fluid.Pipes.BaseClasses.PartialTwoPortFlow

Wall friction, gravity, momentum flow

FlowModel

Modelica.Fluid.Pipes.BaseClasses.PartialStraightPipe

Wall friction, gravity, momentum flow

FlowModel_2

Modelica.Fluid.Examples.HeatExchanger.BaseClasses.BasicHX

Characteristic of wall friction

FlowModel_1

Modelica.Fluid.Examples.HeatExchanger.BaseClasses.BasicHX

Characteristic of wall friction