Modelica.Fluid.Fittings

Adaptors for connections of fluid components and the regulation of fluid flow

Information

This sublibrary contains models and functions providing pressure loss correlations. All models in this library have the property that no mass and no energy is stored in the component. Therefore, none of the models have a state.

All functions are continuous and have a finite, non-zero, smooth, first derivative. The functions are all guaranteed to be strict monotonically increasing. The mentioned properties guarantee that a unique inverse of every function exists. Note, the usual quadratic pressure loss correlation

The two mentioned problems are solved in this package by approximating the characteristics around zero mass flow rates with appropriate polynomials. The monotonicity is guaranteed using results from:

Fritsch F.N. and Carlson R.E. (1980):
Monotone piecewise cubic interpolation. SIAM J. Numerc. Anal., Vol. 17, No. 2, April 1980, pp. 238-246

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name Description
Modelica.Fluid.Fittings.Bends Bends Flow models for bends
Modelica.Fluid.Fittings.Orifices Orifices Flow models for orifices
Modelica.Fluid.Fittings.GenericResistances GenericResistances Flow models for generic resistances
Modelica.Fluid.Fittings.SimpleGenericOrifice SimpleGenericOrifice Simple generic orifice defined by pressure loss coefficient and diameter (only for flow from port_a to port_b)
Modelica.Fluid.Fittings.SharpEdgedOrifice SharpEdgedOrifice Pressure drop due to sharp edged orifice (for both flow directions)
Modelica.Fluid.Fittings.AbruptAdaptor AbruptAdaptor Pressure drop in pipe due to suddenly expanding or reducing area (for both flow directions)
Modelica.Fluid.Fittings.MultiPort MultiPort Multiply a port; useful if multiple connections shall be made to a port exposing a state
Modelica.Fluid.Fittings.TeeJunctionIdeal TeeJunctionIdeal Splitting/joining component with static balances for an infinitesimal control volume
Modelica.Fluid.Fittings.TeeJunctionVolume TeeJunctionVolume Splitting/joining component with static balances for a dynamic control volume
Modelica.Fluid.Fittings.BaseClasses BaseClasses Base classes used in the Fittings package (only of interest to build new component models)

Modelica.Fluid.Fittings.SimpleGenericOrifice Modelica.Fluid.Fittings.SimpleGenericOrifice

Simple generic orifice defined by pressure loss coefficient and diameter (only for flow from port_a to port_b)

Information

This pressure drop component defines a simple, generic orifice, where the loss factor ζ is provided for one flow direction (e.g., from loss table of a book):

Δp = 0.5*ζ*ρ*v*|v|
   = 8*ζ/(π^2*D^4*ρ) * m_flow*|m_flow|

where

Since the pressure loss factor zeta is provided only for a mass flow from port_a to port_b, the pressure loss is not correct when the flow is reversing. If reversing flow only occurs in a short time interval, this is most likely uncritical. If significant reversing flow can appear, this component should not be used.

Extends from Modelica.Fluid.Interfaces.PartialTwoPortTransport (Partial element transporting fluid between two ports without storage of mass or energy), Modelica.Fluid.Interfaces.PartialLumpedFlow (Base class for a lumped momentum balance).

Parameters

NameDescription
replaceable package MediumMedium in the component
diameterDiameter of orifice [m]
zetaLoss factor for flow of port_a -> port_b
use_zeta= false to obtain zeta from dp_nominal and m_flow_nominal
Custom Parameters
pathLengthLength flow path [m]
Nominal operating point
m_flow_nominalMass flow rate for dp_nominal [kg/s]
dp_nominalNominal pressure drop [Pa]
Assumptions
allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Dynamics
momentumDynamicsFormulation of momentum balance
Advanced
dp_startGuess value of dp = port_a.p - port_b.p [Pa]
m_flow_startGuess value of m_flow = port_a.m_flow [kg/s]
m_flow_smallSmall mass flow rate for regularization of zero flow [kg/s]
use_Re= true, if turbulent region is defined by Re, otherwise by m_flow_small
from_dp= true, use m_flow = f(dp) else dp = f(m_flow)
Diagnostics
show_T= true, if temperatures at port_a and port_b are computed
show_V_flow= true, if volume flow rate at inflowing port is computed

Connectors

NameDescription
port_aFluid connector a (positive design flow direction is from port_a to port_b)
port_bFluid connector b (positive design flow direction is from port_a to port_b)

Modelica.Fluid.Fittings.SharpEdgedOrifice Modelica.Fluid.Fittings.SharpEdgedOrifice

Pressure drop due to sharp edged orifice (for both flow directions)

Information

Extends from BaseClasses.QuadraticTurbulent.BaseModel (Generic pressure drop component with constant turbulent loss factor data and without an icon).

Parameters

NameDescription
replaceable package MediumMedium in the component
dataLoss factor data
lengthLength of orifice [m]
diameterInner diameter of pipe (= same at port_a and port_b) [m]
leastDiameterSmallest diameter of orifice [m]
alphaAngle of orifice [deg]
Nominal operating point
m_flow_nominalNominal mass flow rate [kg/s]
Assumptions
allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
dp_startGuess value of dp = port_a.p - port_b.p [Pa]
m_flow_startGuess value of m_flow = port_a.m_flow [kg/s]
m_flow_smallSmall mass flow rate for regularization of zero flow [kg/s]
use_Re= true, if turbulent region is defined by Re, otherwise by m_flow_small
from_dp= true, use m_flow = f(dp) else dp = f(m_flow)
Diagnostics
show_T= true, if temperatures at port_a and port_b are computed
show_V_flow= true, if volume flow rate at inflowing port is computed
show_Re= true, if Reynolds number is included for plotting

Connectors

NameDescription
port_aFluid connector a (positive design flow direction is from port_a to port_b)
port_bFluid connector b (positive design flow direction is from port_a to port_b)

Modelica.Fluid.Fittings.AbruptAdaptor Modelica.Fluid.Fittings.AbruptAdaptor

Pressure drop in pipe due to suddenly expanding or reducing area (for both flow directions)

Information

Extends from BaseClasses.QuadraticTurbulent.BaseModelNonconstantCrossSectionArea (Generic pressure drop component with constant turbulent loss factor data and without an icon, for non-constant cross section area).

Parameters

NameDescription
replaceable package MediumMedium in the component
dataLoss factor data
diameter_aInner diameter of pipe at port_a [m]
diameter_bInner diameter of pipe at port_b [m]
Nominal operating point
m_flow_nominalNominal mass flow rate [kg/s]
Assumptions
allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
m_flow_startGuess value of m_flow = port_a.m_flow [kg/s]
m_flow_smallSmall mass flow rate for regularization of zero flow [kg/s]
Diagnostics
show_T= true, if temperatures at port_a and port_b are computed
show_V_flow= true, if volume flow rate at inflowing port is computed
show_Re= true, if Reynolds number is included for plotting
show_totalPressures= true, if total pressures are included for plotting
show_portVelocities= true, if port velocities are included for plotting

Connectors

NameDescription
port_aFluid connector a (positive design flow direction is from port_a to port_b)
port_bFluid connector b (positive design flow direction is from port_a to port_b)

Modelica.Fluid.Fittings.MultiPort Modelica.Fluid.Fittings.MultiPort

Multiply a port; useful if multiple connections shall be made to a port exposing a state

Information

This model is useful if multiple connections shall be made to a port of a volume model exposing a state, like a pipe with ModelStructure av_vb. The mixing is shifted into the volume connected to port_a and the result is propagated back to each ports_b.

If multiple connections were directly made to the volume, then ideal mixing would take place in the connection set, outside the volume. This is normally not intended.

Parameters

NameDescription
replaceable package Medium 

Connectors

NameDescription
replaceable package Medium 
port_a 
ports_b[nPorts_b] 

Modelica.Fluid.Fittings.TeeJunctionIdeal Modelica.Fluid.Fittings.TeeJunctionIdeal

Splitting/joining component with static balances for an infinitesimal control volume

Information

This model is the simplest implementation for a splitting/joining component for three flows. Its use is not required. It just formulates the balance equations in the same way that the connect semantics would formulate them anyways. The main advantage of using this component is, that the user does not get confused when looking at the specific enthalpy at each port which might be confusing when not using a splitting/joining component. The reason for the confusion is that one examines the mixing enthalpy of the infinitesimal control volume introduced with the connect statement when looking at the specific enthalpy in the connector which might not be equal to the specific enthalpy at the port in the "real world".

Extends from Modelica.Fluid.Fittings.BaseClasses.PartialTeeJunction (Base class for a splitting/joining component with three ports).

Parameters

NameDescription
replaceable package MediumMedium in the component

Connectors

NameDescription
port_1 
port_2 
port_3 

Modelica.Fluid.Fittings.TeeJunctionVolume Modelica.Fluid.Fittings.TeeJunctionVolume

Splitting/joining component with static balances for a dynamic control volume

Information

This model introduces a mixing volume into a junction. This might be useful to examine the non-ideal mixing taking place in a real junction.

Extends from Modelica.Fluid.Fittings.BaseClasses.PartialTeeJunction (Base class for a splitting/joining component with three ports), Modelica.Fluid.Interfaces.PartialLumpedVolume (Lumped volume with mass and energy balance).

Parameters

NameDescription
replaceable package MediumMedium in the component
VMixing volume inside junction [m3]
Custom Parameters
fluidVolumeVolume [m3]
Assumptions
Dynamics
energyDynamicsFormulation of energy balance
massDynamicsFormulation of mass balance
Initialization
p_startStart value of pressure [Pa]
use_T_start= true, use T_start, otherwise h_start
T_startStart value of temperature [K]
h_startStart value of specific enthalpy [J/kg]
X_start[Medium.nX]Start value of mass fractions m_i/m [kg/kg]
C_start[Medium.nC]Start value of trace substances

Connectors

NameDescription
port_1 
port_2 
port_3 
Automatically generated Thu Oct 1 16:07:58 2020.