Model for an ideally mixed fluid volume and the ability to store mass and energy. The volume is fixed, and latent and sensible heat can be exchanged.
This model represents the same physics as
IBPSA.Fluid.MixingVolumes.MixingVolume, but in addition, it allows
adding or subtracting water to the control volume.
The mass flow rate of the added or subtracted water is
specified at the port mWat_flow.
Adding mWat_flow itself does not affect the energy balance
in this model. Hence, the enthalpy that is added or removed with the
flow of mWat_flow needs to be added to the heat port
heatPort.
To increase the numerical robustness of the model, the constant
prescribedHeatFlowRate can be set by the user.
This constant only has an effect if the model has exactly two fluid ports connected,
and if it is used as a steady-state model.
Use the following settings:
prescribedHeatFlowRate=true if the only means of heat transfer
at the heatPort is a prescribed heat flow rate that
is not a function of the temperature difference
between the medium and an ambient temperature. Examples include an ideal electrical heater,
a pump that rejects heat into the fluid stream, or a chiller that removes heat based on a performance curve.
If the heatPort is not connected, then set prescribedHeatFlowRate=true as
in this case, heatPort.Q_flow=0.
prescribedHeatFlowRate=false if there is heat flow at the heatPort
computed as K * (T-heatPort.T), for some temperature T and some conductance K,
which may itself be a function of temperature or mass flow rate.prescribedHeatFlowRate=false.
The parameter mSenFac can be used to increase the thermal mass of this model
without increasing its volume. This way, species concentrations are still calculated
correctly even though the thermal mass increases. The additional thermal mass is calculated
based on the density and the value of the function HeatCapacityCp
of the medium state state_default.
This parameter can for instance be useful in a pipe model when the developer wants to
lump the pipe thermal mass to the fluid volume. By default mSenFac = 1, hence
the mass is unchanged. For higher values of mSenFac, the mass will be scaled proportionally.
Set the parameter use_C_flow = true to enable an input connector for the trace substance flow rate.
This allows to directly add or subtract trace substances such as
CO2 to the volume.
See
IBPSA.Fluid.Sensors.Examples.PPM
for an example.
initialize_p to final so that it does not
appear as a user-selectable parameter. This is done because
initialize_p has been changed from a constant
to a parameter for
Buildings, issue 1013.
QSen_flow and
QLat_flow.sensibleOnly in steBal
as this constant is no longer used.
s to allow this model to also be used
with IBPSA.Media.Water.
i_w to avoid a warning in OpenModelica.
IBPSA.Fluid.MixingVolumes.BaseClasses.PartialMixingVolumeWaterPort.
mXi_flow[Medium.nXi]
to a scalar input connector mWat_flow
in the conservation equation model.
The reason is that mXi_flow does not allow
to compute the other components in mX_flow and
therefore leads to an ambiguous use of the model.
By only requesting mWat_flow, the mass balance
and species balance can be implemented correctly.
cardinality function.
Therefore, all input signals must be connected.
IBPSA.Fluid.Interfaces.