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 and τ is the time constant at the nominal mass flow rate nom. 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


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.


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