.Buildings.Fluid.Humidifiers.SprayAirWasher_X

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

τ_eff = τ |ṁ| ⁄ ṁ_nom

where τ_eff is the effective time constant for the given mass flow rate ṁ and τ is the time constant at the nominal mass flow rate ṁ_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

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.

Revisions

• March 8, 2022, by Michael Wetter:
  Renamed parameter massDynamics to energyDynamics for consistency with other models.
• December 14, 2018, by Michael Wetter:
  Restricted base class for medium to one that implements the function enthalpyOfLiquid.
  This is for #1057.
• May 3, 2017, by Michael Wetter:
  First implementation.