Buildings.Fluid.MixingVolumes.BaseClasses

Information

This package contains base classes that are used to construct the models in Buildings.Fluid.MixingVolumes.

Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).

Package Content

Name	Description
PartialMixingVolumeWaterPort	Partial mixing volume that allows adding or subtracting water vapor

Buildings.Fluid.MixingVolumes.BaseClasses.PartialMixingVolumeWaterPort

Information

This model represents the same physics as Modelica.Fluid.Vessels.Volume but in addition, it allows to connect signals for the water exchanged with the volume. The model is partial in order to allow a submodel that can be used with media that contain water as a substance, and a submodel that can be used with dry air. Having separate models is required because calls to the medium property function enthalpyOfLiquid results in a linker error if a medium such as Modelica.Media.Air.SimpleAir is used that does not implement this function.

Extends from Buildings.Fluid.MixingVolumes.MixingVolume (Mixing volume with inlet and outlet ports (flow reversal is allowed)).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Volume	V		Volume [m3]
Nominal condition
MassFlowRate	m_flow_nominal		Nominal mass flow rate [kg/s]
Dynamics
Equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Formulation of energy balance
Dynamics	massDynamics	energyDynamics	Formulation of mass balance
Initialization
AbsolutePressure	p_start	Medium.p_default	Start value of pressure [Pa]
Temperature	T_start	Medium.T_default	Start value of temperature [K]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]
ExtraProperty	C_start[Medium.nC]	fill(0, Medium.nC)	Start value of trace substances
ExtraProperty	C_nominal[Medium.nC]	fill(1E-2, Medium.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)
Advanced
MassFlowRate	m_flow_small	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	homotopyInitialization	true	= true, use homotopy method
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal in medium, false restricts to design direction (ports[1] -> ports[2]). Used only if model has two ports.
Heat transfer
Boolean	prescribedHeatFlowRate	false	Set to true if the model has a prescribed heat flow at its heatPort

Connectors

Type	Name	Description
VesselFluidPorts_b	ports[nPorts]	Fluid inlets and outlets
HeatPort_a	heatPort	Heat port connected to outflowing medium
input RealInput	mWat_flow	Water flow rate added into the medium [kg/s]
input RealInput	TWat	Temperature of liquid that is drained from or injected into volume [K]
output RealOutput	X_w	Species composition of medium

Modelica definition

partial model PartialMixingVolumeWaterPort 
  "Partial mixing volume that allows adding or subtracting water vapor"
  extends Buildings.Fluid.MixingVolumes.MixingVolume(
   steBal(
    sensibleOnly = false,
    final Q_flow = Q_flow + HWat_flow,
    final mXi_flow = mXi_flow),
   dynBal(
    final Q_flow = Q_flow + HWat_flow,
    final mXi_flow = mXi_flow));

 // additional declarations
  Modelica.Blocks.Interfaces.RealInput mWat_flow(final quantity="MassFlowRate",
                                                 final unit = "kg/s") 
    "Water flow rate added into the medium";
  Modelica.Blocks.Interfaces.RealInput TWat(final quantity="Temperature",
                                            final unit = "K", displayUnit = "degC", min=260) 
    "Temperature of liquid that is drained from or injected into volume";
  Modelica.Blocks.Interfaces.RealOutput X_w "Species composition of medium";
  Medium.MassFlowRate mXi_flow[Medium.nXi] 
    "Mass flow rates of independent substances added to the medium";
  Modelica.SIunits.HeatFlowRate HWat_flow 
    "Enthalpy flow rate of extracted water";

end PartialMixingVolumeWaterPort;