.Buildings.ThermalZones.EnergyPlus_24_2_0.ThermalZone .Buildings.ThermalZones.EnergyPlus_24_2_0.ThermalZoneModel for a thermal zone that is implemented in EnergyPlus.
This model instantiates the FMU with the name
idfName and connects to the thermal zone with name
zoneName. The idfName needs to be
specified in an instance of Buildings.ThermalZones.EnergyPlus_24_2_0.Building
that is named building, and that is placed at this or
at a higher hierarchy-level of the model. If the FMU is already
instantiated by another instance of this model, it will use the
already instantiated FMU. Hence, for each thermal zone in an
EnergyPlus FMU, one instance of this model needs to be used. See
Buildings.ThermalZones.EnergyPlus_24_2_0.UsersGuide
for how zones are simulated that are declared in the EnergyPlus
input data file but not in Modelica.
If there are two instances that declare the same
zoneName and have in the model hierarchy the same
instance of Buildings.ThermalZones.EnergyPlus_24_2_0.Building,
then the simulation will stop with an error.
This model computes in Modelica the air energy, mass and species balance. Outside air infiltration needs to be modeled in Modelica, because any infiltration that the EnergyPlus model may specify is ignored. The convective heat transfer with the building fabric, the long-wave and the short-wave radiation are computed by EnergyPlus.
The zone uses a volume of air that is fully mixed. The size of
this volume, and its floor area, which is used to scale the heat
gains q_flow, are obtained from the EnergyPlus
model.
The zone has a fluid port fluPor that can be used
to connect one or several HVAC inlets, flow paths for air
infiltration and exfiltration, or for interzonal air exchange,
using for example models from Buildings.Airflow.Multizone.
The model also has a heat port heaPorAir that
connects to the sensible heat balance of the room air, and a heat
port heaPorRad that connects to the radiative heat
balance of the room inside surfaces. If heat is added to
heaPorRad.Q_flow, then this heat is sent to EnergyPlus
as if it were a radiant heat gain of the zone. The heat port
temperature heaPorRad.T is the radiant temperature of
the room. Hence, these two ports heatPorAir and
heaPorRad could be used to connect a radiator. Note,
however, that such a coupling is an approximation as the surface
temperature of the radiator will not be reflected in the radiative
temperature of the room. Also, read to section Notes about
modeling components that are connected to the radiative heat
port below.
The model has a parameter use_C_flow. If set to
true, then an input connector C_flow is
enabled, which allows adding trace substances to the room air. Note
that this requires a medium model that has trace substances
enabled.
If the EnergyPlus model computes internal heat gains such as
from people or equipment, then their sensible convective and latent
heat gains are automatically added to this room model, and the
radiant fraction is added to the EnergyPlus envelope and thus
treated correctly. In addition, if desired, radiant, convective and
latent heat gains in units of W/m2 can be added
using the input connector qGai_flow.
Similarly, if people are modeled in EnergyPlus (using the
EnergyPlus People object), and if the Modelica
Medium contains CO2 (e.g., if Medium.nC >
0 and there is a Medium.substanceName = "CO2"),
then the CO2 emitted by the people is automatically added to this
volume. However, the "Generic Contaminant" modeled in EnergyPlus is
not added to the air volume. (Because EnergyPlus does not declare
the name of the species or its molar mass and hence it cannot be
matched to species in Modelica or converted to emitted mass flow
rate.)
Also, note that while CO2 emitted from people simulated in
EnergyPlus is added automatically to the air balance of this model,
there is no CO2 added automatically for the heat gain specified
through the input connector qGai_flow. Hence, if
qGai_flow accounts for people and CO2 should be
modelled, then the CO2 emitted by the people specified in
qGai_flow needs to be added manually to the input
connector C_flow. (This manual addition is needed
because qGai_flow can also contain heat gains not
caused by people.)
Models in which a component is connected to the radiative heat
port heaPorRad may cause convergence problems during
the initialization of the simulation if that component computes the
radiative heat exchange heaPorRad.Q_flow based on the
temperature heaPorRad.T, and if the parameter
building.setInitialRadiativeHeatGainToZero is changed
from its default value true. It is therefore
recommended to leave the parameter
setInitialRadiativeHeatGainToZero at its default value
true. This sets the radiative heat flow rate sent from
Modelica to EnergyPlus to zero during the initialization of the
model, thereby avoiding a potential nonlinear system of equations
that may give convergence problems. This only affects the
initialization of the model but not the time integration, hence the
error should be small for typical models.
If you decide to set setInitialRadiativeHeatGainToZero =
false, you need to be aware of the following: If
setInitialRadiativeHeatGainToZero = false, then the
radiative heat gain from the model input is being used. If this
radiative heat gain depends on the radiative temperature that is an
output of the EnergyPlus model, a nonlinear equation is formed.
Because in EnergyPlus, computing the radiative temperature involves
an iterative solution, this can cause convergence problems due to
having two nested solvers, the outer being the Modelica solver that
solves for the radiative heat flow rate QGaiRad_flow,
and the innner being the EnergyPlus solver that solves for the
radiative temperature TRad. Hence, we recommend to
leave building.setInitialRadiativeHeatGainToZero =
true.
If you decide to set
building.setInitialRadiativeHeatGainToZero = false,
you may need to also tighten the tolerance of the EnergyPlus solver
by tightening building.relativeSurfaceTolerance, but
one cannot assure that the nested nonlinear equations converge.
Because a Modelica model does not have knowledge of the solver
tolerance, automatically tightening
building.relativeSurfaceTolerance as a function of the
Modelica solver tolerance is not possible.
| Name | Description |
|---|---|
 Medium |
Medium in the component |
setInitialRadiativeHeatGainToZero. This avoids a
nonlinear system of equation during the time integration for models
in which the radiative heat gain is a function of the room
radiative temperature, such as when a radiator is connected to the
room model.heaPorRad.