This package contains base classes that are used to construct the models in Buildings.Fluid.MixingVolumes.
Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).
| Name | Description |
|---|---|
 PartialMixingVolume
| Partial mixing volume with inlet and outlet ports (flow reversal is allowed) |
 PartialMixingVolumeWaterPort
| Partial mixing volume that allows adding or subtracting water vapor |
Buildings.Fluid.MixingVolumes.BaseClasses.PartialMixingVolume
If the model is operated in steady-state and has two fluid ports connected,
then the same energy and mass balance implementation is used as in
steady-state component models, i.e., the use of actualStream
is not used for the properties at the port.
For simple models that uses this model, see Buildings.Fluid.MixingVolumes.
Extends from Buildings.Fluid.Interfaces.LumpedVolumeDeclarations (Declarations for lumped volumes).
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Volume | V | Volume [m3] | |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| Dynamics | |||
| Equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Formulation of energy balance |
| Dynamics | massDynamics | energyDynamics | Formulation of mass balance |
| 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 | |||
| MassFlowRate | m_flow_small | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Assumptions | |||
| Boolean | allowFlowReversal | system.allowFlowReversal | = true to allow flow reversal in medium, false restricts to design direction (ports[1] -> ports[2]). Used only if model has two ports. |
| Heat transfer | |||
| Boolean | prescribedHeatFlowRate | false | Set to true if the model has a prescribed heat flow at its heatPort |
| Type | Name | Description |
|---|---|---|
| VesselFluidPorts_b | ports[nPorts] | Fluid inlets and outlets |
| HeatPort_a | heatPort | Heat port connected to outflowing medium |
partial model PartialMixingVolume
"Partial mixing volume with inlet and outlet ports (flow reversal is allowed)"
outer Modelica.Fluid.System system "System properties";
extends Buildings.Fluid.Interfaces.LumpedVolumeDeclarations;
parameter Modelica.SIunits.MassFlowRate m_flow_nominal(min=0)
"Nominal mass flow rate";
// Port definitions
parameter Integer nPorts=0 "Number of ports";
parameter Modelica.SIunits.MassFlowRate m_flow_small(min=0) = 1E-4*abs(m_flow_nominal)
"Small mass flow rate for regularization of zero flow";
parameter Boolean homotopyInitialization = true "= true, use homotopy method";
parameter Boolean allowFlowReversal = system.allowFlowReversal
"= true to allow flow reversal in medium, false restricts to design direction (ports[1] -> ports[2]). Used only if model has two ports.";
parameter Modelica.SIunits.Volume V "Volume";
parameter Boolean prescribedHeatFlowRate=false
"Set to true if the model has a prescribed heat flow at its heatPort";
Modelica.Fluid.Vessels.BaseClasses.VesselFluidPorts_b ports[nPorts](
redeclare each package Medium = Medium) "Fluid inlets and outlets";
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a heatPort
"Heat port connected to outflowing medium";
Modelica.SIunits.Temperature T "Temperature of the fluid";
Modelica.SIunits.Pressure p "Pressure of the fluid";
Modelica.SIunits.MassFraction Xi[Medium.nXi]
"Species concentration of the fluid";
Medium.ExtraProperty C[Medium.nC](nominal=C_nominal)
"Trace substance mixture content";
// Models for the steady-state and dynamic energy balance.
protected
Buildings.Fluid.Interfaces.StaticTwoPortConservationEquation steBal(
sensibleOnly = true,
redeclare final package Medium=Medium,
final m_flow_nominal = m_flow_nominal,
final allowFlowReversal = allowFlowReversal,
final m_flow_small = m_flow_small,
final homotopyInitialization = homotopyInitialization,
final show_V_flow = false) if
useSteadyStateTwoPort "Model for steady-state balance if nPorts=2";
Buildings.Fluid.Interfaces.ConservationEquation dynBal(
redeclare final package Medium = Medium,
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 C_nominal=C_nominal,
final fluidVolume = V,
m(start=V*rho_nominal),
U(start=V*rho_nominal*Medium.specificInternalEnergy(
state_start)),
nPorts=nPorts) if
not useSteadyStateTwoPort "Model for dynamic energy balance";
parameter Medium.ThermodynamicState state_start = Medium.setState_pTX(
T=T_start,
p=p_start,
X=X_start[1:Medium.nXi]) "Start state";
parameter Modelica.SIunits.Density rho_nominal=Medium.density(
Medium.setState_pTX(
T=T_start,
p=p_start,
X=X_start[1:Medium.nXi])) "Density, used to compute fluid mass";
////////////////////////////////////////////////////
final parameter Boolean useSteadyStateTwoPort=(nPorts == 2) and
prescribedHeatFlowRate and (
energyDynamics == Modelica.Fluid.Types.Dynamics.SteadyState) and (
massDynamics == Modelica.Fluid.Types.Dynamics.SteadyState) and (
substanceDynamics == Modelica.Fluid.Types.Dynamics.SteadyState) and (
traceDynamics == Modelica.Fluid.Types.Dynamics.SteadyState)
"Flag, true if the model has two ports only and uses a steady state balance";
Modelica.SIunits.HeatFlowRate Q_flow
"Heat flow across boundaries or energy source/sink";
// Outputs that are needed to assign the medium properties
Modelica.Blocks.Interfaces.RealOutput hOut_internal(unit="J/kg")
"Internal connector for leaving temperature of the component";
Modelica.Blocks.Interfaces.RealOutput XiOut_internal[Medium.nXi](each unit="1")
"Internal connector for leaving species concentration of the component";
Modelica.Blocks.Interfaces.RealOutput COut_internal[Medium.nC](each unit="1")
"Internal connector for leaving trace substances of the component";
equation
///////////////////////////////////////////////////////////////////////////
// asserts
if not allowFlowReversal then
assert(ports[1].m_flow > -m_flow_small,
"Model has flow reversal, but the parameter allowFlowReversal is set to false.
m_flow_small = " + String(m_flow_small) + "
ports[1].m_flow = " + String(ports[1].m_flow) + "
");
end if;
// actual definition of port variables
// If the model computes the energy and mass balances as steady-state,
// and if it has only two ports,
// then we use the same base class as for all other steady state models.
if useSteadyStateTwoPort then
connect(steBal.port_a, ports[1]);
connect(steBal.port_b, ports[2]);
connect(hOut_internal, steBal.hOut);
connect(XiOut_internal, steBal.XiOut);
connect(COut_internal, steBal.COut);
else
connect(dynBal.ports, ports);
connect(hOut_internal, dynBal.hOut);
connect(XiOut_internal, dynBal.XiOut);
connect(COut_internal, dynBal.COut);
end if;
// Medium properties
p = if nPorts > 0 then ports[1].p else p_start;
T = Medium.temperature_phX(p=p, h=hOut_internal, X=cat(1,Xi,{1-sum(Xi)}));
Xi = XiOut_internal;
C = COut_internal;
// Port properties
heatPort.T = T;
heatPort.Q_flow = Q_flow;
end PartialMixingVolume;
Buildings.Fluid.MixingVolumes.BaseClasses.PartialMixingVolumeWaterPort
The model is partial in order to allow a submodel that can be used with media
that contain water as a substance, and a submodel that can be used with dry air.
Having separate models is required because calls to the medium property function
enthalpyOfLiquid results in a linker error if a medium such as
Modelica.Media.Air.SimpleAir
is used that does not implement this function.
Extends from Buildings.Fluid.MixingVolumes.BaseClasses.PartialMixingVolume (Partial mixing volume with inlet and outlet ports (flow reversal is allowed)).
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Volume | V | Volume [m3] | |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| Dynamics | |||
| Equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Formulation of energy balance |
| Dynamics | massDynamics | energyDynamics | Formulation of mass balance |
| 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 | |||
| MassFlowRate | m_flow_small | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Assumptions | |||
| Boolean | allowFlowReversal | system.allowFlowReversal | = true to allow flow reversal in medium, false restricts to design direction (ports[1] -> ports[2]). Used only if model has two ports. |
| Heat transfer | |||
| Boolean | prescribedHeatFlowRate | false | Set to true if the model has a prescribed heat flow at its heatPort |
| Type | Name | Description |
|---|---|---|
| VesselFluidPorts_b | ports[nPorts] | Fluid inlets and outlets |
| HeatPort_a | heatPort | Heat port connected to outflowing medium |
| input RealInput | mWat_flow | Water flow rate added into the medium [kg/s] |
| input RealInput | TWat | Temperature of liquid that is drained from or injected into volume [K] |
| output RealOutput | X_w | Species composition of medium |
partial model PartialMixingVolumeWaterPort "Partial mixing volume that allows adding or subtracting water vapor" extends Buildings.Fluid.MixingVolumes.BaseClasses.PartialMixingVolume; // additional declarationsModelica.Blocks.Interfaces.RealInput mWat_flow(final quantity="MassFlowRate", final unit = "kg/s") "Water flow rate added into the medium"; Modelica.Blocks.Interfaces.RealInput TWat(final quantity="Temperature", final unit = "K", displayUnit = "degC", min=260) "Temperature of liquid that is drained from or injected into volume"; Modelica.Blocks.Interfaces.RealOutput X_w "Species composition of medium"; Modelica.SIunits.MassFlowRate mXi_flow[Medium.nXi] "Mass flow rates of independent substances added to the medium"; Modelica.SIunits.HeatFlowRate HWat_flow "Enthalpy flow rate of extracted water";end PartialMixingVolumeWaterPort;