.Buildings.Fluid.FMI.ExportContainers.ThermalZones

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. For example, 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.

Contents

Revisions

• January 18, 2019, by Jianjun Hu:
  Limited the media choice to moist air. See #1050.
• September 20, 2016, by Thierry S. Nouidui:
  Revised documentation to explain the rationale of needing mass flow rate sensors.
• June 29, 2016, by Michael Wetter:
  Revised implementation and documentation.
• April 27, 2016, by Thierry S. Nouidui:
  First implementation.