Adaptor that can be used to connect an HVAC system (with acausal ports) to input/output signals, which then can be exposed in an FMI interface.
The adaptor has a vector of fluid ports called ports.
The supply and return air ducts need to be connected to these ports.
Also, if a thermal zone has interzonal air exchange or air infiltration,
these flow paths also need 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
Qsen = max(0, ṁsup) cp (Tsup - Tair,zon),
where
Qsen is the sensible heat flow rate added to the thermal zone,
ṁsup is the supply air mass flow rate from
the port fluPor (which is negative if it is an exhaust),
cp is the specific heat capacity at constant pressure,
Tsup is the supply air temperature and
Tair,zon is the zone air temperature.
Note that without the max(·, ·) function, the energy
balance would be wrong.
The output signals of this model are 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).
These output connectors can be used to connect to a controller.
These values are obtained from the fluid stream(s) that flow into this component
at the port fluPor, e.g., from the connector
fluPor.backward.
Note that there are nPorts of these signals.
For a completely mixed room, they will all have the same value, but
for a room with non-uniform temperatures, they can have different values.
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 need to be modelled
in models that are connected to ports.
See Buildings.Fluid.FMI.ExportContainers.HVACZone for a model that uses this model.
| Name | Description |
|---|---|
| Medium | Medium in the component |
each.
quantity in CZon.