Buildings.Fluid.Humidifiers
Package with humidifier models
Information
Package with humidifiers.
Extends from Modelica.Icons.Package (Icon for standard packages).
Package Content
| Name | Description |
|---|---|
 Humidifier_u
|
Ideal humidifier or dehumidifier with prescribed water mass flow rate addition or subtraction |
 SprayAirWasher_X
|
Spray air washer with leaving water mass fraction as input |
 SteamHumidifier_X
|
Steam humidifier with leaving water mass fraction as input |
 Examples
|
Collection of models that illustrate model use and test models |
| Validation
|
Collection of validation models |
Buildings.Fluid.Humidifiers.Humidifier_u
Ideal humidifier or dehumidifier with prescribed water mass flow rate addition or subtraction
Information
Model for an air humidifier or dehumidifier.
This model adds (or removes) moisture from the air stream. The amount of exchanged moisture is equal to
ṁwat = u ṁwat,nom,
where u is the control input signal and
ṁwat,nom is equal to the parameter mWat_flow_nominal.
The parameter mWat_flow_nominal can be positive or negative.
If ṁwat is positive, then moisture is added
to the air stream, otherwise it is removed.
If the heat port heatPort is unconnected, then the enthalpy of the
air that flows through the device remains unchanged, e.g., the humidification
is adiabatic. To change the enthalpy of the air, add heat flow to the connector
heatPort.
Extends from Buildings.Fluid.Interfaces.TwoPortHeatMassExchanger (Partial model transporting one fluid stream with storing mass or energy).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| MassFlowRate | mWat_flow_nominal | Water mass flow rate at u=1, positive for humidification [kg/s] | |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dp_nominal | Pressure difference [Pa] | |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| 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 |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM | 0.1 | Fraction of nominal flow rate where flow transitions to laminar |
| Dynamics | |||
| Nominal condition | |||
| Time | tau | 30 | Time constant at nominal flow (if energyDynamics <> SteadyState) [s] |
| Equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Dynamics | massDynamics | energyDynamics | Type of mass balance: dynamic (3 initialization options) or steady state |
| 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 |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable package Medium | Medium in the component | |
| FluidPort_a | port_a | Fluid connector a (positive design flow direction is from port_a to port_b) |
| FluidPort_b | port_b | Fluid connector b (positive design flow direction is from port_a to port_b) |
| input RealInput | u | Control input [1] |
| output RealOutput | mWat_flow | Water added to the fluid [kg/s] |
| HeatPort_a | heatPort | Heat port for total heat exchange with the control volume |
Modelica definition
Buildings.Fluid.Humidifiers.SprayAirWasher_X
Spray air washer with leaving water mass fraction as input
Information
Model for a spray air washer with a prescribed outlet water vapor mass fraction in kg/kg total air.
This model forces the outlet water mass fraction at port_b to be
no lower than the
input signal X_wSet, subject to optional limits on the
maximum water vapor mass flow rate that is added, as
described by the parameter mWatMax_flow.
By default, the model has unlimited capacity.
The output signal mWat_flow ≥ 0 is the moisture added
to the medium if the flow rate is from port_a to port_b.
If the flow is reversed, then mWat_flow = 0.
The outlet specific enthalpy at port_b is increased by
the enthalpy of liquid water at 10°C times the mass of water that was added.
Therefore, the temperature of the leaving fluid is below the inlet temperature.
The outlet conditions at port_a are not affected by this model,
other than for a possible pressure difference due to flow friction.
If the parameter energyDynamics is different from
Modelica.Fluid.Types.Dynamics.SteadyState,
the component models the dynamic response using a first order differential equation.
The time constant of the component is equal to the parameter tau.
This time constant is adjusted based on the mass flow rate using
τeff = τ |ṁ| ⁄ ṁnom
where τeff is the effective time constant for the given mass flow rate ṁ and τ is the time constant at the nominal mass flow rate ṁnom. This type of dynamics is equal to the dynamics that a completely mixed control volume would have.
Optionally, this model can have a flow resistance.
Set dp_nominal = 0 to disable the flow friction calculation.
For a model that uses a control signal u ∈ [0, 1] and multiplies this with the nominal water mass flow rate, use Buildings.Fluid.Humidifiers.Humidifier_u
Limitations
This model only adds water vapor for the flow from
port_a to port_b.
The water vapor of the reverse flow is not affected by this model.
This model does not affect the enthalpy of the air. Therefore, if water is added, the temperature will decrease, e.g., the humidification is adiabatic.
Extends from Buildings.Fluid.HeatExchangers.BaseClasses.PartialPrescribedOutlet (Ideal heater, cooler, humidifier or dehumidifier with prescribed outlet conditions).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| MassFlowRate | mWatMax_flow | Modelica.Constants.inf | Maximum water mass flow rate addition (positive) [kg/s] |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dp_nominal | Pressure difference [Pa] | |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| 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 |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM | 0.1 | Fraction of nominal flow rate where flow transitions to laminar |
| Dynamics | |||
| Time | tau | 10 | Time constant at nominal flow rate (used if energyDynamics or massDynamics not equal Modelica.Fluid.Types.Dynamics.SteadyState) [s] |
| Equations | |||
| Dynamics | massDynamics | Modelica.Fluid.Types.Dynamic... | Type of mass balance: dynamic (3 initialization options) or steady state |
| Initialization | |||
| MassFraction | X_start[Medium.nX] | Medium.X_default | Start value of mass fractions m_i/m [1] |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a | Fluid connector a (positive design flow direction is from port_a to port_b) |
| FluidPort_b | port_b | Fluid connector b (positive design flow direction is from port_a to port_b) |
| input RealInput | X_w | Set point for water vapor mass fraction in kg/kg total air of the fluid that leaves port_b [1] |
| output RealOutput | mWat_flow | Water added to the fluid (if flow is from port_a to port_b) [kg/s] |
Modelica definition
Buildings.Fluid.Humidifiers.SteamHumidifier_X
Steam humidifier with leaving water mass fraction as input
Information
Model for a steam humidifier with a prescribed outlet water vapor mass fraction in kg/kg total air.
This model forces the outlet water mass fraction at port_b to be
no lower than the
input signal X_wSet, subject to optional limits on the
maximum water vapor mass flow rate that is added, as
described by the parameter mWatMax_flow.
By default, the model has unlimited capacity.
The output signal mWat_flow ≥ 0 is the moisture added
to the medium if the flow rate is from port_a to port_b.
If the flow is reversed, then mWat_flow = 0.
The outlet specific enthalpy at port_b is increased by
the enthalpy of steam at 100°C times the mass of steam that was added.
Therefore, the temperature of the leaving fluid is slightly above the inlet temperature.
The outlet conditions at port_a are not affected by this model,
other than for a possible pressure difference due to flow friction.
If the parameter energyDynamics is different from
Modelica.Fluid.Types.Dynamics.SteadyState,
the component models the dynamic response using a first order differential equation.
The time constant of the component is equal to the parameter tau.
This time constant is adjusted based on the mass flow rate using
τeff = τ |ṁ| ⁄ ṁnom
where τeff is the effective time constant for the given mass flow rate ṁ and τ is the time constant at the nominal mass flow rate ṁnom. This type of dynamics is equal to the dynamics that a completely mixed control volume would have.
Optionally, this model can have a flow resistance.
Set dp_nominal = 0 to disable the flow friction calculation.
For a model that uses a control signal u ∈ [0, 1] and multiplies this with the nominal water mass flow rate, use Buildings.Fluid.Humidifiers.Humidifier_u
Limitations
This model only adds water vapor for the flow from
port_a to port_b.
The water vapor of the reverse flow is not affected by this model.
Extends from Buildings.Fluid.HeatExchangers.BaseClasses.PartialPrescribedOutlet (Ideal heater, cooler, humidifier or dehumidifier with prescribed outlet conditions).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| MassFlowRate | mWatMax_flow | Modelica.Constants.inf | Maximum water mass flow rate addition (positive) [kg/s] |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dp_nominal | Pressure difference [Pa] | |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| 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 |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM | 0.1 | Fraction of nominal flow rate where flow transitions to laminar |
| Dynamics | |||
| Time | tau | 10 | Time constant at nominal flow rate (used if energyDynamics or massDynamics not equal Modelica.Fluid.Types.Dynamics.SteadyState) [s] |
| Equations | |||
| Dynamics | massDynamics | Modelica.Fluid.Types.Dynamic... | Type of mass balance: dynamic (3 initialization options) or steady state |
| Initialization | |||
| MassFraction | X_start[Medium.nX] | Medium.X_default | Start value of mass fractions m_i/m [1] |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a | Fluid connector a (positive design flow direction is from port_a to port_b) |
| FluidPort_b | port_b | Fluid connector b (positive design flow direction is from port_a to port_b) |
| input RealInput | X_w | Set point for water vapor mass fraction in kg/kg total air of the fluid that leaves port_b [1] |
| output RealOutput | mWat_flow | Water added to the fluid (if flow is from port_a to port_b) [kg/s] |
| output RealOutput | Q_flow | Heat flow rate added to the fluid (if flow is from port_a to port_b) [W] |