Engee documentation

Controlled Reservoir (MA)

Boundary conditions for a network of moist air at time-varying pressure, temperature, humidity and impurity gas levels.

blockType: AcausalFoundation.MoistAir.Elements.ControlledReservoir

controlled reservoir (ma)

Path in the library:

/Physical Modeling/Fundamental/Moist Air/Elements/Controlled Reservoir (MA)

Description

The Controlled Reservoir (MA) block sets the controlled boundary conditions in the humid air network. The volume of humid air inside the reservoir is assumed to be infinite. Therefore, the flow is assumed to be quasi-stationary. Humid air exits the reservoir at a given pressure, temperature, specific humidity and admixture gas mass fraction. The moist air enters the tank at tank pressure, but the temperature, specific humidity and mass fraction of impurity gas are determined by the upstream moist air network.

The pressure, temperature, moisture and impurity gas quantities in the tank are set by control signals at ports P, T, W/Tw and G respectively. The input signals are limited by their allowable ranges. For moisture quantity, the allowable range is from zero to saturation or 100% water vapour. For the amount of impurity gas, the allowable range is from zero to either the fraction remaining after water vapour or 100% impurity gas.

You can specify humidity as one of the options:

  • Relative humidity, φ

  • Specific humidity,

  • Molar fraction of water vapour,

  • Moisture coefficient,

  • Humidity thermometer temperature,

You can specify impurity gas as one of the options:

  • Mass fraction of impurity gas,

  • Molar fraction of impurity gases,

The amount of moisture and impurity gases are related to each other as follows:

φ

Where:

  • - pressure.

  • - is the universal gas constant.

The indices , and indicate the properties of dry air, water vapour and residual gases respectively. The lower index indicates the water vapour saturation level.

The block implicitly calculates the wet-bulb temperature using the following equation:

Where:

  • - temperature.

  • - is the wet-bulb temperature.

  • - specific humidity.

  • - mass fraction of impurity gases.

  • - saturation specific humidity at wet-bulb temperature.

  • - specific enthalpy of dry air.

  • - specific enthalpy of dry air at wet-bulb temperature.

  • - specific enthalpy of impurity gas.

  • - specific enthalpy of impurity gases at wet-bulb temperature.

  • - specific enthalpy of water vapour.

  • - specific enthalpy of water vapour at wet-bulb temperature.

  • - specific enthalpy of vaporisation of water vapour at wet-bulb temperature.

Ports

Non-directional

A - humid air port
`humid air

Humid air port, corresponds to the tank inlet.

Inlet

P - pressure, Pa
scalar

Input port that defines the pressure value in the tank.

T - temperature, K
scalar

Input port that defines the temperature value in the tank.

W - humidity
scalar

Input port defining the value of the reservoir moisture specification. The method of setting is defined by the Reservoir moisture specification parameter.

Dependencies

Used when Reservoir moisture specification is set to a value other than `Wet-bulb temperature'.

Tw - wet-bulb temperature specification, K
scalar

Input port that controls the wet tank thermometer temperature.

Dependencies

Used when the Reservoir moisture specification is set to Wet-bulb temperature.

G - level of impurity gases
scalar

Input port defining the value of the amount of impurity gases in the reservoir. The method of setting is defined by the Reservoir trace gas specification parameter.

Parameters

Reservoir moisture specification - method of moisture measurement
Relative humidity (by default) | Specific humidity | Water vapor mole fraction | Humidity ratio | Wet-bulb temperature

Sets the method of measurement:

  • Relative humidity - the signal on the W port is relative humidity.

  • Specific humidity - the signal on the W port is equal to specific humidity.

  • Water vapor mole fraction - signal on the W port is equal to molar fraction of humidity.

  • Humidity ratio - signal on the W port is equal to the humidity ratio.

  • Wet-bulb temperature - signal on the W port sets the wet-bulb temperature.

*Reservoir trace gas specification - method of measuring the amount of trace gases
Mass fraction (by default) | Mole fraction.

Sets the method of measuring trace gas composition:

  • Mass fraction - the signal on the G port is equal to the mass fraction of impurity gases.

  • Mole fraction - the signal on the G port is equal to the molar fraction of impurity gases.

Relative humidity at saturation - relative humidity above which condensation occurs
1.0 (By default).

Relative humidity above which condensation occurs. The amount of moisture must be less than the saturation level.

Cross-sectional area at port A - area normal to the direction of flow at the tank inlet
`0.01 m² (by default)

The cross-sectional area of the tank inlet in the direction normal to the wet air flow path.