BuildingSystems.Fluid.Humidifiers.SteamHumidifier_X

# .BuildingSystems.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 BuildingSystems.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.

## Revisions

- March 8, 2022, by Michael Wetter:
  Renamed parameter `massDynamics` to `energyDynamics` for consistency with other models.
- May 10, 2017, by Michael Wetter:
  First implementation.

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