Package with base classes for Buildings.Fluid
Information
This package contains base classes that are used to construct the models in
Buildings.Fluid.
Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).
Package Content
| Name |
Description |
| IndexMassFraction
|
Computes the index of a substance in the mass fraction vector Xi |
 PartialResistance
|
Partial model for a hydraulic resistance |
 PartialThreeWayResistance
|
Flow splitter with partial resistance model at each port |
 FlowModels
|
Flow models for pressure drop calculations |
Computes the index of a substance in the mass fraction vector Xi
Information
This block computes the index that the subtance with name
substanceName has in the mass fraction vector X.
If the medium model has no component called substanceName,
then the block writes an error message and terminates the simulation.
This block is used for example to obtain the index of the subtance 'water'
to obtain the water vapor concentration, or to measure any other mass fraction.
Parameters
| Type | Name | Default | Description |
|---|
| replaceable package Medium | Modelica.Media.Interfaces.Pa... | Medium model |
| String | substanceName | "" | Name of species substance |
Connectors
| Type | Name | Description |
|---|
| replaceable package Medium | Medium model |
Modelica definition
block IndexMassFraction
replaceable package Medium =
Modelica.Media.Interfaces.PartialCondensingGases ;
parameter String substanceName="" ;
protected
parameter Integer i_x(fixed=false) ;
initial algorithm
i_x :=-1;
for i
in 1:Medium.nXi
loop
if Modelica.Utilities.Strings.isEqual(string1=Medium.substanceNames[i],
string2=substanceName,
caseSensitive=false)
then
i_x :=i;
end if;
end for;
assert(i_x > 0, "Substance '" + substanceName + "' is not present in medium '"
+ Medium.mediumName + "'.\n"
+ "Change medium model to one that has '" + substanceName + "' as a substance.");
end IndexMassFraction;
Partial model for a hydraulic resistance
Information
Partial model for a flow resistance, possible with variable flow coefficient.
Models that extend this class need to implement an equation that relates
m_flow and dp, and they need to assign the parameter
m_flow_turbulent.
See for example
Buildings.Fluid.FixedResistances.FixedResistanceDpM for a model that extends
this base class.
Extends from Buildings.Fluid.Interfaces.PartialTwoPortInterface (Partial model transporting fluid between two ports without storing mass or energy).
Parameters
| Type | Name | Default | Description |
|---|
| replaceable package Medium | PartialMedium | Medium in the component |
| MassFlowRate | m_flow_turbulent | | Turbulent flow if |m_flow| >= m_flow_turbulent [kg/s] |
| Nominal condition |
| MassFlowRate | m_flow_nominal | | Nominal mass flow rate [kg/s] |
| PressureDifference | dp_nominal | | Pressure drop at nominal mass flow rate [Pa] |
| Assumptions |
| Boolean | allowFlowReversal | true | = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
| Advanced |
| MassFlowRate | m_flow_small | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
| Diagnostics |
| Boolean | show_T | false | = true, if actual temperature at port is computed |
Connectors
| 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) |
Modelica definition
partial model PartialResistance
extends Buildings.Fluid.Interfaces.PartialTwoPortInterface(
show_T=false,
dp(start=0,
nominal=
if dp_nominal_pos > Modelica.Constants.eps
then dp_nominal_pos
else 1),
m_flow(
nominal=
if m_flow_nominal_pos > Modelica.Constants.eps
then m_flow_nominal_pos
else 1),
final m_flow_small = 1E-4*
abs(m_flow_nominal));
parameter Boolean from_dp = false ;
parameter Modelica.SIunits.PressureDifference dp_nominal(displayUnit="Pa") ;
parameter Boolean homotopyInitialization = true ;
parameter Boolean linearized = false ;
parameter Modelica.SIunits.MassFlowRate m_flow_turbulent(min=0) ;
protected
parameter Medium.ThermodynamicState sta_default=
Medium.setState_pTX(T=Medium.T_default, p=Medium.p_default, X=Medium.X_default);
parameter Modelica.SIunits.DynamicViscosity eta_default=
Medium.dynamicViscosity(sta_default) ;
final parameter Modelica.SIunits.MassFlowRate m_flow_nominal_pos =
abs(m_flow_nominal) ;
final parameter Modelica.SIunits.PressureDifference dp_nominal_pos(displayUnit="Pa") =
abs(dp_nominal) ;
equation
port_a.h_outflow =
if allowFlowReversal
then inStream(port_b.h_outflow)
else Medium.h_default;
port_b.h_outflow =
inStream(port_a.h_outflow);
port_a.m_flow + port_b.m_flow = 0;
port_a.Xi_outflow =
if allowFlowReversal
then inStream(port_b.Xi_outflow)
else Medium.X_default[1:Medium.nXi];
port_b.Xi_outflow =
inStream(port_a.Xi_outflow);
port_a.C_outflow =
if allowFlowReversal
then inStream(port_b.C_outflow)
else zeros(Medium.nC);
port_b.C_outflow =
inStream(port_a.C_outflow);
end PartialResistance;
Flow splitter with partial resistance model at each port
Information
Partial model for flow resistances with three ports such as a
flow mixer/splitter or a three way valve.
If energyDynamics ≠ Modelica.Fluid.Types.Dynamics.SteadyState,
then at the junction of the three flows,
a mixing volume will be present. This will introduce a dynamic energy and momentum
balance, which often breaks algebraic loops.
The time constant of the mixing volume is determined by the parameter tau.
Extends from Buildings.Fluid.Interfaces.LumpedVolumeDeclarations (Declarations for lumped volumes).
Parameters
| Type | Name | Default | Description |
|---|
| replaceable package Medium | PartialMedium | Medium in the component |
| PartialTwoPortInterface | res1 | redeclare Buildings.Fluid.In... | Partial model, to be replaced with a fluid component |
| PartialTwoPortInterface | res2 | redeclare Buildings.Fluid.In... | Partial model, to be replaced with a fluid component |
| PartialTwoPortInterface | res3 | redeclare Buildings.Fluid.In... | Partial model, to be replaced with a fluid component |
| Dynamics |
| Equations |
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Dynamics | massDynamics | energyDynamics | Type of mass balance: dynamic (3 initialization options) or steady state |
| MassFlowRate | mDyn_flow_nominal | | Nominal mass flow rate for dynamic momentum and energy balance [kg/s] |
| Real | mSenFac | 1 | Factor for scaling the sensible thermal mass of the volume |
| Nominal condition |
| Time | tau | 10 | Time constant at nominal flow for dynamic energy and momentum balance [s] |
| Initialization |
| AbsolutePressure | p_start | Medium.p_default | Start value of pressure [Pa] |
| Temperature | T_start | Medium.T_default | Start value of temperature [K] |
| MassFraction | X_start[Medium.nX] | Medium.X_default | Start value of mass fractions m_i/m [kg/kg] |
| ExtraProperty | C_start[Medium.nC] | fill(0, Medium.nC) | Start value of trace substances |
| ExtraProperty | C_nominal[Medium.nC] | fill(1E-2, Medium.nC) | Nominal value of trace substances. (Set to typical order of magnitude.) |
| Advanced |
| Boolean | from_dp | true | = true, use m_flow = f(dp) else dp = f(m_flow) |
| PortFlowDirection | portFlowDirection_1 | Modelica.Fluid.Types.PortFlo... | Flow direction for port_1 |
| PortFlowDirection | portFlowDirection_2 | Modelica.Fluid.Types.PortFlo... | Flow direction for port_2 |
| PortFlowDirection | portFlowDirection_3 | Modelica.Fluid.Types.PortFlo... | Flow direction for port_3 |
Connectors
| Type | Name | Description |
|---|
| FluidPort_a | port_1 | First port, typically inlet |
| FluidPort_b | port_2 | Second port, typically outlet |
| FluidPort_a | port_3 | Third port, can be either inlet or outlet |
Modelica definition
partial model PartialThreeWayResistance
extends Buildings.Fluid.Interfaces.LumpedVolumeDeclarations(
final mSenFac=1);
Modelica.Fluid.Interfaces.FluidPort_a port_1(
redeclare package Medium =
Medium,
m_flow(min=
if (portFlowDirection_1 == Modelica.Fluid.Types.PortFlowDirection.Entering)
then 0.0
else -Modelica.Constants.inf,
max=
if (portFlowDirection_1== Modelica.Fluid.Types.PortFlowDirection.Leaving)
then 0.0
else Modelica.Constants.inf)) ;
Modelica.Fluid.Interfaces.FluidPort_b port_2(
redeclare package Medium =
Medium,
m_flow(min=
if (portFlowDirection_2 == Modelica.Fluid.Types.PortFlowDirection.Entering)
then 0.0
else -Modelica.Constants.inf,
max=
if (portFlowDirection_2 == Modelica.Fluid.Types.PortFlowDirection.Leaving)
then 0.0
else Modelica.Constants.inf)) ;
Modelica.Fluid.Interfaces.FluidPort_a port_3(
redeclare package Medium=
Medium,
m_flow(min=
if (portFlowDirection_3==Modelica.Fluid.Types.PortFlowDirection.Entering)
then 0.0
else -Modelica.Constants.inf,
max=
if (portFlowDirection_3==Modelica.Fluid.Types.PortFlowDirection.Leaving)
then 0.0
else Modelica.Constants.inf)) ;
parameter Modelica.SIunits.Time tau=10 ;
parameter Modelica.SIunits.MassFlowRate mDyn_flow_nominal ;
parameter Boolean from_dp = true ;
parameter Modelica.Fluid.Types.PortFlowDirection portFlowDirection_1=Modelica.Fluid.Types.PortFlowDirection.Bidirectional ;
parameter Modelica.Fluid.Types.PortFlowDirection portFlowDirection_2=Modelica.Fluid.Types.PortFlowDirection.Bidirectional ;
parameter Modelica.Fluid.Types.PortFlowDirection portFlowDirection_3=Modelica.Fluid.Types.PortFlowDirection.Bidirectional ;
replaceable Buildings.Fluid.Interfaces.PartialTwoPortInterface res1
constrainedby Buildings.Fluid.Interfaces.PartialTwoPortInterface(
redeclare final package Medium =
Medium,
allowFlowReversal=portFlowDirection_1 == Modelica.Fluid.Types.PortFlowDirection.Bidirectional) ;
replaceable Buildings.Fluid.Interfaces.PartialTwoPortInterface res2
constrainedby Buildings.Fluid.Interfaces.PartialTwoPortInterface(
redeclare final package Medium =
Medium,
allowFlowReversal=portFlowDirection_2 == Modelica.Fluid.Types.PortFlowDirection.Bidirectional) ;
replaceable Buildings.Fluid.Interfaces.PartialTwoPortInterface res3
constrainedby Buildings.Fluid.Interfaces.PartialTwoPortInterface(
redeclare final package Medium =
Medium,
allowFlowReversal=portFlowDirection_3 == Modelica.Fluid.Types.PortFlowDirection.Bidirectional) ;
Buildings.Fluid.Delays.DelayFirstOrder vol(
redeclare final package Medium =
Medium,
final nPorts=3,
final tau=tau,
final m_flow_nominal=mDyn_flow_nominal,
final energyDynamics=energyDynamics,
final massDynamics=massDynamics,
final p_start=p_start,
final T_start=T_start,
final X_start=X_start,
final C_start=C_start,
final allowFlowReversal=true,
final prescribedHeatFlowRate=false)
if
have_controlVolume ;
protected
parameter Boolean have_controlVolume=
energyDynamics <> Modelica.Fluid.Types.Dynamics.SteadyState
or
massDynamics <> Modelica.Fluid.Types.Dynamics.SteadyState ;
Modelica.Fluid.Interfaces.FluidPort_a port_internal(
redeclare package Medium =
Medium)
if not have_controlVolume ;
equation
if portFlowDirection_1==Modelica.Fluid.Types.PortFlowDirection.Leaving
then
if not have_controlVolume
then
connect(res1.port_a, port_internal);
else
connect(res1.port_a, vol.ports[1]);
end if;
connect(port_1, res1.port_b);
else
if not have_controlVolume
then
connect(res1.port_b, port_internal);
else
connect(res1.port_b, vol.ports[1]);
end if;
connect(port_1, res1.port_a);
end if;
if portFlowDirection_2==Modelica.Fluid.Types.PortFlowDirection.Leaving
then
if not have_controlVolume
then
connect(res2.port_a, port_internal);
else
connect(res2.port_a, vol.ports[2]);
end if;
connect(port_2, res2.port_b);
else
if not have_controlVolume
then
connect(res2.port_b, port_internal);
else
connect(res2.port_b, vol.ports[2]);
end if;
connect(port_2, res2.port_a);
end if;
if portFlowDirection_3==Modelica.Fluid.Types.PortFlowDirection.Leaving
then
if not have_controlVolume
then
connect(res3.port_a, port_internal);
else
connect(res3.port_a, vol.ports[3]);
end if;
connect(port_3, res3.port_b);
else
if not have_controlVolume
then
connect(res3.port_b, port_internal);
else
connect(res3.port_b, vol.ports[3]);
end if;
connect(port_3, res3.port_a);
end if;
end PartialThreeWayResistance;
http://simulationresearch.lbl.gov/modelica
Buildings.Fluid.BaseClasses.PartialResistance
Buildings.Fluid.BaseClasses.PartialThreeWayResistance