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
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
"Computes the index of a substance in the mass fraction vector Xi"
replaceable package Medium =
Modelica.Media.Interfaces.PartialCondensingGases "Medium model";
parameter String substanceName
"Name of species substance";
protected
parameter Integer i_x(fixed=false)
"Index of substance";
initial algorithm
// Compute index of species vector that carries the substance name
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] |
| Pressure | dp_nominal | | Pressure drop at nominal mass flow rate [Pa] |
| Assumptions |
| Boolean | allowFlowReversal | system.allowFlowReversal | = 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
"Partial model for a hydraulic resistance"
extends Buildings.Fluid.Interfaces.PartialTwoPortInterface(
show_T=false,
m_flow(start=0, nominal=m_flow_nominal_pos),
dp(start=0, nominal=dp_nominal_pos),
final m_flow_small = 1E-4*
abs(m_flow_nominal));
parameter Boolean from_dp = false
"= true, use m_flow = f(dp) else dp = f(m_flow)";
parameter Modelica.SIunits.Pressure dp_nominal(displayUnit="Pa")
"Pressure drop at nominal mass flow rate";
parameter Boolean homotopyInitialization = true
"= true, use homotopy method";
parameter Boolean linearized = false
"= true, use linear relation between m_flow and dp for any flow rate";
parameter Modelica.SIunits.MassFlowRate m_flow_turbulent(min=0)
"Turbulent flow if |m_flow| >= m_flow_turbulent";
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)
"Dynamic viscosity, used to compute transition to turbulent flow regime";
protected
final parameter Modelica.SIunits.MassFlowRate m_flow_nominal_pos =
abs(m_flow_nominal)
"Absolute value of nominal flow rate";
final parameter Modelica.SIunits.Pressure dp_nominal_pos =
abs(dp_nominal)
"Absolute value of nominal pressure";
equation
// Isenthalpic state transformation (no storage and no loss of energy)
port_a.h_outflow =
inStream(port_b.h_outflow);
port_b.h_outflow =
inStream(port_a.h_outflow);
// Mass balance (no storage)
port_a.m_flow + port_b.m_flow = 0;
// Transport of substances
port_a.Xi_outflow =
inStream(port_b.Xi_outflow);
port_b.Xi_outflow =
inStream(port_a.Xi_outflow);
port_a.C_outflow =
inStream(port_b.C_outflow);
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 dynamicBalance=true, 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... | Formulation of energy balance |
| Dynamics | massDynamics | energyDynamics | Formulation of mass balance |
| Boolean | dynamicBalance | true | Set to true to use a dynamic balance, which often leads to smaller systems of equations |
| MassFlowRate | mDyn_flow_nominal | | Nominal mass flow rate for dynamic momentum and energy balance [kg/s] |
| 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) |
Connectors
Modelica definition
partial model PartialThreeWayResistance
"Flow splitter with partial resistance model at each port"
extends Buildings.Fluid.Interfaces.LumpedVolumeDeclarations;
outer Modelica.Fluid.System system
"System properties";
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 Boolean from_dp = true
"= true, use m_flow = f(dp) else dp = f(m_flow)";
replaceable Buildings.Fluid.Interfaces.PartialTwoPortInterface res1(
redeclare
package Medium = Medium, allowFlowReversal=true)
"Partial model, to be replaced with a fluid component";
replaceable Buildings.Fluid.Interfaces.PartialTwoPortInterface res2(
redeclare
package Medium = Medium, allowFlowReversal=true)
"Partial model, to be replaced with a fluid component";
replaceable Buildings.Fluid.Interfaces.PartialTwoPortInterface res3(
redeclare
package Medium = Medium, allowFlowReversal=true)
"Partial model, to be replaced with a fluid component";
protected
parameter Modelica.Fluid.Types.PortFlowDirection portFlowDirection_1=Modelica.Fluid.Types.PortFlowDirection.Bidirectional
"Flow direction for port_1";
parameter Modelica.Fluid.Types.PortFlowDirection portFlowDirection_2=Modelica.Fluid.Types.PortFlowDirection.Bidirectional
"Flow direction for port_2";
parameter Modelica.Fluid.Types.PortFlowDirection portFlowDirection_3=Modelica.Fluid.Types.PortFlowDirection.Bidirectional
"Flow direction for port_3";
public
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
dynamicBalance
"Fluid volume to break algebraic loop";
parameter Boolean dynamicBalance = true
"Set to true to use a dynamic balance, which often leads to smaller systems of equations";
parameter Modelica.SIunits.Time tau=10
"Time constant at nominal flow for dynamic energy and momentum balance";
parameter Modelica.SIunits.MassFlowRate mDyn_flow_nominal
"Nominal mass flow rate for dynamic momentum and energy balance";
equation
connect(port_1, res1.port_a);
connect(res2.port_a, port_2);
connect(res3.port_a, port_3);
connect(res1.port_b,vol. ports[1]);
connect(res2.port_b,vol. ports[2]);
connect(res3.port_b,vol. ports[3]);
if not dynamicBalance
then
connect(res1.port_b, res3.port_b);
connect(res1.port_b, res2.port_b);
end if;
end PartialThreeWayResistance;
Automatically generated Thu Jun 19 10:57:11 2014.
FlowModels
PartialResistance
PartialThreeWayResistance
Buildings.Fluid.BaseClasses.PartialResistance
Buildings.Fluid.BaseClasses.PartialThreeWayResistance