modelSteamHumidifier_X
Extends from IDEAS.Fluid.HeatExchangers.BaseClasses.PartialPrescribedOutlet.
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 IDEAS.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.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.MassFlowRate | mWatMax_flow | Modelica.Constants.inf | Maximum water mass flow rate addition (positive) |
| Initialization | |||
| Modelica.Units.SI.MassFraction[Medium.nX] | X_start | Medium.X_default | Start value of mass fractions m_i/m |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Interfaces.RealInput | X_w | Set point for water vapor mass fraction in kg/kg total air of the fluid that leaves port_b | |
| Modelica.Blocks.Interfaces.RealOutput | mWat_flow | Water added to the fluid (if flow is from port_a to port_b) | |
| Modelica.Blocks.Interfaces.RealOutput | Q_flow | Heat flow rate added to the fluid (if flow is from port_a to port_b) |
Revisions
-
March 8, 2022, by Michael Wetter:
Renamed parametermassDynamicstoenergyDynamicsfor consistency with other models. -
May 10, 2017, by Michael Wetter:
First implementation.