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 Medium.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](unit="1")
"Internal connector for leaving species concentration of the component";
Modelica.Blocks.Interfaces.RealOutput COut_internal[Medium.nC](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;
// Only one connection allowed to a port to avoid unwanted ideal mixing
if not useSteadyStateTwoPort then
for i in 1:nPorts loop
assert(cardinality(ports[i]) == 2 or cardinality(ports[i]) == 0,"
each ports[i] of volume can at most be connected to one component.
If two or more connections are present, ideal mixing takes
place with these connections, which is usually not the intention
of the modeller. Increase nPorts to add an additional port.
");
end for;
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"; Medium.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;