Buildings.Fluid.FMI.ExportContainers

Package with containers to export thermofluid flow models

Information

This package contains containers that can be used, either with replaceable models or through object inheritance, to export HVAC models, HVAC systems and thermal zones. See the Buildings.Fluid.FMI.UsersGuide for instructions.

Extends from Modelica.Icons.Package (Icon for standard packages).

Package Content

Name	Description
HVACZone	Partial block to export an HVAC system that has no radiative component and that serves multiple zones as an FMU
HVACZones	Partial block to export an HVAC system that has no radiative component and that serves multiple zones as an FMU
PartialTwoPort	Partial block to be used as a container to export a thermofluid flow model with two ports
ReplaceableTwoPort	Container to export thermofluid flow models with two ports as an FMU
ThermalZone	Partial block to export a model of a thermal zone as an FMU
ThermalZones	Partial block to export a model of multiple thermal zones as an FMU
Examples	Collection of models that illustrate model use and test models
Validation	Collection of validation models

Buildings.Fluid.FMI.ExportContainers.HVACZone

Partial block to export an HVAC system that has no radiative component and that serves multiple zones as an FMU

Information

Model that is used as a container for an HVAC system that is to be exported as an FMU and that serves a single zone.

Typical use and important parameters

To use this model as a container for an FMU, extend from this model, rather than instantiate it, and add your HVAC system. By extending from this model, the top-level signal connectors on the right stay at the top-level, and hence will be visible at the FMI interface. The example Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.HVACZone shows how a simple HVAC system can be implemented and exported as an FMU. The example Buildings.Fluid.FMI.ExportContainers.Validation.RoomHVAC shows how such an FMU can be connected to a room model that has signal flow.

The conversion between the fluid ports and signal ports is done in the HVAC adapter hvacAda. This adapter has a vector of fluid ports called ports. The supply and return air ducts, including any resistance model for the inlet diffusor or exhaust grill, need to be connected to these ports. Also, if a thermal zone has interzonal air exchange or air infiltration, these flows need to be connected to ports. This model outputs at the port fluPor the mass flow rate for each flow that is connected to ports, together with its temperature, water vapor mass fraction per total mass of the air (not per kg dry air), and trace substances. These quantities are always as if the flow enters the room, even if the flow is zero or negative. If a medium has no moisture, e.g., if Medium.nXi=0, or if it has no trace substances, e.g., if Medium.nC=0, then the output signal for these properties are removed. These quantities are always as if the flow enters the room, even if the flow is zero or negative. Thus, a thermal zone model that uses these signals to compute the heat added by the HVAC system needs to implement an equation such as

Q_sen = max(0, ṁ_sup)   c_p   (T_sup - T_air,zon),

where Q_sen is the sensible heat flow rate added to the thermal zone, ṁ_sup is the supply air mass flow rate from the port fluPor (which is negative if it is an exhaust), c_p is the specific heat capacity at constant pressure, T_sup is the supply air temperature and T_air,zon is the zone air temperature. Note that without the max(·, ·), the energy balance would be wrong.

The input signals of this model are the zone radiative temperature. The the zone air temperature, the water vapor mass fraction per total mass of the air (unless Medium.nXi=0) and trace substances (unless Medium.nC=0) are obtained from the connector fluPor.backward. The outflowing fluid stream(s) at the port ports will be at the states obtained from fluPor.backward. All fluid streams at port ports are at the same pressure. For convenience, the instance hvacAda also outputs the properties obtained from fluPor.backward. These can be used to connect a controller. The properties are available for each flow path in fluPor.backward. For a thermal zone with mixed air, these are all equal, while for a stratified room model, they can be different.

See Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.HVACZone for a model that uses this model.

For models that multiple thermal zones connected to the HVAC system, use the model Buildings.Fluid.FMI.ExportContainers.HVACZones.

Assumption and limitations

The mass flow rates at ports sum to zero, hence this model conserves mass.

This model does not impose any pressure, other than setting the pressure of all fluid connections to ports to be equal. The reason is that setting a pressure can lead to non-physical system models, for example if a mass flow rate is imposed and the HVAC system is connected to a model that sets a pressure boundary condition such as Buildings.Fluid.Sources.Outside. Also, setting a pressure would make it impossible to use multiple instances of this model (one for each thermal zone) and build in Modelica an airflow network model with pressure driven mass flow rates.

The model has no pressure drop. Hence, the pressure drop of an air diffuser or of an exhaust grill needs to be modelled in models that are connected to ports.

Parameters

Connectors

Modelica definition

Buildings.Fluid.FMI.ExportContainers.HVACZones

Partial block to export an HVAC system that has no radiative component and that serves multiple zones as an FMU

Information

Model that is used as a container for an HVAC system that is to be exported as an FMU and that serves multiple zones.

Typical use and important parameters

To use this model as a container for an FMU, simply extend from this model, rather than instantiate it, and add your HVAC system. By extending from this model, the top-level signal connectors on the right stay at the top-level, and hence will be visible at the FMI interface. The example Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.HVACZones shows how a simple HVAC system that serves two rooms can be implemented and exported as an FMU. The example Buildings.Fluid.FMI.ExportContainers.Validation.RoomHVAC shows how such an FMU can be connected to a room model that has signal flow.

The following two parameters need to be assigned by the user: Set nZon to the number of thermal zones to which the FMU will be connected. Set nPorts to the largest number of fluid ports that the thermal zones has. For example, if nZon=2 and zone 1 has one inlet and one outlet (hence it has 2 ports), and zone 2 has one inlets and two outlets (hence it has 3 ports), then set nPorts=3. This will add more fluid ports than are needed for zone 1, but this causes no overhead if they are not connected.

The conversion between the fluid ports and signal ports is done in the HVAC adapter hvacAda. This adapter has a vector of fluid ports called ports. The supply and return air ducts, including any resistance model for the inlet diffusor or exhaust grill, need to be connected to these ports. Also, if a thermal zone has interzonal air exchange or air infiltration, these flows need to be connected to ports. This model outputs at the port fluPor the mass flow rate for each flow that is connected to ports, together with its temperature, water vapor mass fraction per total mass of the air (not per kg dry air), and trace substances. These quantities are always as if the flow enters the room, even if the flow is zero or negative. If a medium has no moisture, e.g., if Medium.nXi=0, or if it has no trace substances, e.g., if Medium.nC=0, then the output signal for these properties are removed. These quantities are always as if the flow enters the room, even if the flow is zero or negative. Thus, a thermal zone model that uses these signals to compute the heat added by the HVAC system need to implement an equation such as

Q_sen = max(0, ṁ_sup)   c_p   (T_sup - T_air,zon),

where Q_sen is the sensible heat flow rate added to the thermal zone, ṁ_sup is the supply air mass flow rate from the port fluPor (which is negative if it is an exhaust), c_p is the specific heat capacity at constant pressure, T_sup is the supply air temperature and T_air,zon is the zone air temperature. Note that without the max(·, ·), the energy balance would be wrong.

The input signals of this model are the radiative temperature of each zone. The the zone air temperatures, the water vapor mass fractions per total mass of the air (unless Medium.nXi=0) and trace substances (unless Medium.nC=0) are obtained from the connector fluPor.backward. The outflowing fluid stream(s) at the port ports will be at the states obtained from fluPor.backward. For any given i_zon ∈ {1, ..., n_zon}, for each i_ports ∈ {1, ..., n_ports} all fluid streams at port ports[izon, iports] are at the same pressure. For convenience, the instance hvacAda also outputs the properties obtained from fluPor.backward. These can be used to connect a controller. The properties are available for each flow path in fluPor.backward. For a thermal zone with mixed air, these are all equal, while for a stratified room model, they can be different.

See Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.HVACZones for a model that uses this model.

For models that only have one thermal zone connected to the HVAC system, use the simpler model Buildings.Fluid.FMI.ExportContainers.HVACZone.

Assumption and limitations

The mass flow rates at ports sum to zero, hence this model conserves mass for each thermal zone.

This model does not impose any pressure, other than, for any given i_zon ∈ {1, ..., n_zon} and for each j,k ∈ {1, ..., n_ports}, setting the pressure of ports[izon, j].p = ports[izon, k].p to be the same. The reason is that setting a pressure can lead to non-physical system models, for example if a mass flow rate is imposed and the HVAC system is connected to a model that sets a pressure boundary condition such as Buildings.Fluid.Sources.Outside. Also, setting a pressure would make it impossible to use multiple instances of this model (one for each thermal zone) and build in Modelica an airflow network model with pressure driven mass flow rates.

The model has no pressure drop. Hence, the pressure drop of an air diffuser or of an exhaust grill needs to be modelled in models that are connected to ports.

Parameters

Connectors

Modelica definition

Buildings.Fluid.FMI.ExportContainers.PartialTwoPort

Partial block to be used as a container to export a thermofluid flow model with two ports

Information

Partial model that can be used to export thermofluid flow models as an FMU. This model only declares the inlet and outlet ports, the medium and whether flow reversal is allowed.

See Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.ResistanceVolume for a block that extends this partial block.

Parameters

Connectors

Modelica definition

Buildings.Fluid.FMI.ExportContainers.ReplaceableTwoPort

Container to export thermofluid flow models with two ports as an FMU

Information

Block that serves as a container to export a thermofluid flow component. This block contains a replaceable model com that needs to be redeclared to export any model that has as its base class Buildings.Fluid.Interfaces.PartialTwoPort. This allows exporting a large variety of thermofluid flow models with a simple redeclare.

See for example Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.PressureDrop or Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.HeaterCooler_u for how to use this block.

Note that this block must not be used if the instance com sets a constant pressure. In such a situation, use Buildings.Fluid.FMI.ExportContainers.PartialTwoPort together with Buildings.Fluid.FMI.InletAdaptor and Buildings.Fluid.FMI.OutletAdaptor and set the pressure to be equal to the port p of Buildings.Fluid.FMI.OutletAdaptor.

Extends from Buildings.Fluid.FMI.ExportContainers.PartialTwoPort (Partial block to be used as a container to export a thermofluid flow model with two ports).

Parameters

Connectors

Modelica definition

Buildings.Fluid.FMI.ExportContainers.ThermalZone

Partial block to export a model of a thermal zone as an FMU

Information

Model that is used as a container for a single thermal zone that is to be exported as an FMU.

Typical use and important parameters

To use this model as a container for an FMU, extend from this model, rather than instantiate it, add your thermal zone and a vector of mass flow rate sensors. By extending from this model, the top-level signal connectors on the left stay at the top-level, and hence will be visible at the FMI interface.

• The vector of mass flow rate sensors is used to connect the thermal zone adapter and your thermal zone.
• The vector of mass flow rate sensors must have the size nPorts.
• All fluid ports of the mass flow rate sensor must be connected.
• If the vector of mass flow rate sensors is not used, and your themal zone has fluid ports which are autosized, then a direct connection between the thermal zone adpater theZonAda and your thermal zone will be rejected. The reason is because autosized fluid ports can only be connected to vector of ports whose sizes are literal.

The example Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.ThermalZone shows how a simple thermal zone can be implemented and exported as an FMU. The example Buildings.Fluid.FMI.ExportContainers.Validation.RoomHVAC shows how such an FMU can be connected to an HVAC system that has signal flow.

The conversion between the fluid ports and signal ports is done in the thermal zone adapter theZonAda. This adapter has a vector of fluid ports called ports[nPorts] which needs to be connected to the air volume of the thermal zone. At this port, air exchanged between the thermal zone, the HVAC system and any infiltration flow paths.

This model has input signals fluPor[nPorts], which carry the mass flow rate for each flow that is connected to ports, together with its temperature, water vapor mass fraction per total mass of the air (not per kg dry air), and trace substances. These quantities are always as if the flow enters the room, even if the flow is zero or negative. If a medium has no moisture, e.g., if Medium.nXi=0, or if it has no trace substances, e.g., if Medium.nC=0, then the output signal for these properties are removed. Thus, a thermal zone model that uses these signals to compute the heat added by the HVAC system need to implement an equation such as

Q_sen = max(0, ṁ_sup)   c_p   (T_sup - T_air,zon),

where Q_sen is the sensible heat flow rate added to the thermal zone, ṁ_sup is the supply air mass flow rate from the port fluPor (which is negative if it is an exhaust), c_p is the specific heat capacity at constant pressure, T_sup is the supply air temperature and T_air,zon is the zone air temperature. Note that without the max(·, ·), the energy balance would be wrong. Models in the package Buildings.ThermalZones.Detailed as well as the control volumes in Buildings.Fluid.MixingVolumes implement such a max(·, ·) function.

The zone air temperature, the water vapor mass fraction per total mass of the air (unless Medium.nXi=0) and trace substances (unless Medium.nC=0) can be obtained from the outupt connector fluPor.backward. These signals are the same as the inflowing fluid stream(s) at the port theAdaZon.ports[1:nPorts]. The fluid connector ports[nPorts] has a prescribed mass flow rate, but it does not set any pressure.

This model has a user-defined parameter nPorts which sets the number of fluid ports, which in turn is used for the ports fluPor and ports. All nPorts ports[1:nPorts] need to be connected as demonstrated in the example Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.ThermalZone.

The example Buildings.Fluid.FMI.ExportContainers.Validation.RoomHVAC shows conceptually how such an FMU can then be connected to a HVAC system that has signal flow.

Parameters

Connectors

Modelica definition

Buildings.Fluid.FMI.ExportContainers.ThermalZones

Partial block to export a model of multiple thermal zones as an FMU

Information

Model that is used as a container for a multiple thermal zones that are to be exported as an FMU.

Typical use and important parameters

To use this model as a container for an FMU, extend from this model, rather than instantiate it, add your thermal zones. For each thermal zone, add a vector of mass flow rate sensors. By extending from this model, the top-level signal connectors on the left stay at the top-level, and hence will be visible at the FMI interface.

• A vector of mass flow rate sensors is used to connect one element of the thermal zone adapter with one thermal zone.
• The size of the thermal zone adapter must be the same as the number of vectors of mass flow rate sensors.
• The vector of mass flow rate sensors must have the size nPorts.
• All fluid ports of the mass flow rate sensor must be connected.
• If mass flow rate sensors are not used, and your themal zone has fluid ports which are autosized, then a direct connection between an element of the thermal zone adpater theZonAda and your thermal zone will be rejected. The reason is because autosized fluid ports can only be connected to vector of ports whose sizes are literal.

The example Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.ThermalZones shows how multiple simple thermal zones can be implemented and exported as an FMU. The example Buildings.Fluid.FMI.ExportContainers.Validation.RoomHVAC shows how such an FMU can be connected to an HVAC system that has signal flow.

The conversion between the fluid ports and signal ports is done in the thermal zone adapter theZonAda[nZon]. This adapter has a vector of fluid ports called ports[nPorts] which needs to be connected to the air volume of the thermal zones. At this port, air exchanged between the thermal zones, the HVAC system and any infiltration flow paths.

This model has input signals fluPor[nZon, nPorts] which carry the mass flow rate for each flow that is connected to ports[1:nPorts] for the respective zone, together with its temperature, water vapor mass fraction per total mass of the air (not per kg dry air), and trace substances. These quantities are always as if the flow enters the respective room, even if the flow is zero or negative. If a medium has no moisture, e.g., if Medium.nXi=0, or if it has no trace substances, e.g., if Medium.nC=0, then the output signal for these properties are removed. Thus, a thermal zone model that uses these signals to compute the heat added by the HVAC system need to implement an equation such as

Q_sen = max(0, ṁ_sup)   c_p   (T_sup - T_air,zon),

where Q_sen is the sensible heat flow rate added to the thermal zone, ṁ_sup is the supply air mass flow rate from the port fluPor (which is negative if it is an exhaust), c_p is the specific heat capacity at constant pressure, T_sup is the supply air temperature and T_air,zon is the zone air temperature. Note that without the max(·, ·), the energy balance would be wrong. Models in the package Buildings.ThermalZones.Detailed as well as the control volumes in Buildings.Fluid.MixingVolumes implement such a max(·, ·) function.

For each zone, its air temperature, water vapor mass fraction per total mass of the air (unless Medium.nXi=0) and trace substances (unless Medium.nC=0) can be obtained from the outupt connector fluPor[1:nZon].backward. These signals are the same as the inflowing fluid stream(s) at the port theAdaZon[1:nZon].ports[1:nPorts]. The fluid connector ports[nPorts] has a prescribed mass flow rate, but it does not set any pressure.

This model has a user-defined parameter nPorts which sets the number of fluid ports, which in turn is used for the ports fluPor and ports. All zones must have the same number of fluid ports nPorts. All nPorts ports[1:nPorts] need to be connected as demonstrated in the example Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.ThermalZones.

The example Buildings.Fluid.FMI.ExportContainers.Validation.RoomHVAC shows conceptually how such an FMU can then be connected to a HVAC system that has signal flow.

Parameters

Connectors

Modelica definition