Reservoir (MA)

Boundary conditions for a network of moist air at constant pressure, temperature, humidity and amount of impurity gases.

blockType: AcausalFoundation.MoistAir.Elements.Reservoir

Path in the library:

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

Description

The Reservoir (MA) unit is an infinite reservoir at fixed pressure, temperature, humidity and amount of impurity gases. The tank and its inlet can be at atmospheric or set pressure. Port A corresponds to the inlet of the tank. The volume of moist air inside the tank is assumed to be infinite, so the flow is assumed to be quasi-stationary.

Humid air enters and leaves the tank at the pressure specified for the tank, the other characteristics of the humid air (temperature, specific humidity and mass fraction of impurity gases) are determined by the direction of the humid air flow:

If the moist air leaves the tank, its temperature, specific humidity and mass fraction of impurity gases are equal to the corresponding parameters of the tank.
If humid air enters the tank, its temperature, specific humidity and mass fraction of impurity gases are determined by the previous network of humid air.

Humidity can be measured as one of the values:

Relative humidity, - relative humidity, parameters Reservoir relative humidity;
Specific humidity, - specific humidity, parameter Reservoir specific humidity;
Water vapor mole fraction, - molar fraction of water vapour, parameter Reservoir water vapor mole fraction;
Humidity ratio, - humidity coefficient, parameter Reservoir humidity ratio;
Wet-bulb temperature, - wet-bulb temperature, parameter Reservoir wet-bulb temperature.

You can specify the impurity gas as one of the following parameters:

Mass fraction, - mass fraction of impurity gas, parameter Reservoir trace gas mass fraction;
Mole fraction , - molar fraction of impurity gas, parameter Reservoir trace gas mole fraction.

The amounts of moisture and impurity gas are related to each other as follows:

where

- pressure;
- is the universal gas constant.

The subscripts , and denote the properties of dry air, water vapour and impurity gas, respectively. The subscript denotes water vapour at saturation.

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

where

- temperature;
- is the wet-bulb temperature;
- specific humidity;
- mass fraction of impurity gas;
- 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 gas at wet-bulb temperature;
- specific enthalpy of water vapour;
- specific enthalpy of water vapour at wet thermometer temperature;
- specific enthalpy of vaporisation of water vapour at wet thermometer temperature.

Ports

Conserving

# A — humid air port
humid air

Details

Moist air port, corresponds to the tank inlet.

Program usage name

port

Parameters

# Reservoir pressure specification — pressure setting method
Atmospheric pressure | Specified pressure

Details

Select the pressure setting method:

Atmospheric pressure - atmospheric pressure is used.
Specified pressure - the value of the parameter Reservoir pressure is used.

Values	`Atmospheric pressure` \| `Specified pressure`
Default value	`Atmospheric pressure`
Program usage name	`pressure_type`
Evaluatable	No

# Reservoir pressure — tank pressure
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar

Details

Sets the pressure in the tank. This pressure remains constant for the duration of the simulation.

Dependencies

To use this parameter, set the Reservoir pressure specification parameters to . Specified temperature.

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`101325.0 Pa`
Program usage name	`p_const`
Evaluatable	Yes

# Reservoir temperature specification — temperature setting method
Atmospheric temperature | Specified temperature

Details

Select the temperature setting method:

Atmospheric temperature - atmospheric temperature is used.
Specified temperature - the value of the parameter Reservoir temperature is used.

Values	`Atmospheric temperature` \| `Specified temperature`
Default value	`Atmospheric temperature`
Program usage name	`temperature_type`
Evaluatable	No

Details

Sets the temperature in the tank. This temperature remains constant for the duration of the simulation.

Dependencies

To use this parameter, set the Reservoir temperature specification parameters to . Specified temperature.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`293.15 K`
Program usage name	`T_const`
Evaluatable	Yes

# Reservoir moisture specification — moisture measurement method
Relative humidity | Specific humidity | Water vapor mole fraction | Humidity ratio | Wet-bulb temperature

Details

Sets the measurement method:

Relative humidity - moisture composition is set via relative humidity with the parameters Reservoir relative humidity.
Specific humidity - Moisture composition is set via specific humidity with the parameters Reservoir specific humidity.
Water vapor mole fraction - Moisture content is specified in terms of molar fraction of moisture using the parameters Reservoir water vapor mole fraction.
Humidity ratio - Moisture content is specified by the moisture content coefficient parameter Reservoir humidity ratio.
Wet-bulb temperature - Moisture content is given by the wet-bulb temperature with the parameters Reservoir wet-bulb temperature.

Values	`Relative humidity` \| `Specific humidity` \| `Water vapor mole fraction` \| `Humidity ratio` \| `Wet-bulb temperature`
Default value	`Relative humidity`
Program usage name	`moisture_type`
Evaluatable	No

# Reservoir relative humidity — relative humidity in the tank

Details

Sets the value of the relative humidity in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set the Reservoir moisture specification parameters to . Relative humidity.

Default value	`0.5`
Program usage name	`RH_const`
Evaluatable	Yes

# Reservoir specific humidity — specific humidity in the tank

Details

Sets the value of the specific humidity in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set the Reservoir moisture specification parameters to . Specific humidity.

Default value	`0.01`
Program usage name	`q_const`
Evaluatable	Yes

# Reservoir water vapor mole fraction — molar fraction of water vapour in the tank

Details

Enter the desired molar fraction of water vapour in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set the parameters Reservoir moisture specification to . Mole fraction.

Default value	`0.01`
Program usage name	`water_vapor_constant_mole_fraction`
Evaluatable	Yes

# Reservoir humidity ratio — tank moisture coefficient

Details

Sets the value of the relative humidity in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set the Reservoir moisture specification parameters to . Humidity ratio.

Default value	`0.01`
Program usage name	`constant_humidity_ratio`
Evaluatable	Yes

Details

Enter the temperature of the wet thermometer in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set the parameter Reservoir moisture specification to Wet-bulb temperature.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`287.0 K`
Program usage name	`Tw_const`
Evaluatable	Yes

# Reservoir trace gas specification — method of measuring the amount of impurity gases
Mass fraction | Mole fraction

Details

Sets the measurement method:

Mass fraction - mass fraction of impurity gases is set by the parameters Reservoir trace gas mass fraction.
Mole fraction - molar fraction of impurity gases is set by the parameters Reservoir trace gas mole fraction.

Values	`Mass fraction` \| `Mole fraction`
Default value	`Mass fraction`
Program usage name	`trace_gas_type`
Evaluatable	No

# Reservoir trace gas mass fraction — mass fraction of impurity gas in the tank

Details

Enter the desired mass fraction of impurity gas in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set the parameter Reservoir trace gas specification to . Mass fraction.

Default value	`0.001`
Program usage name	`x_g_const`
Evaluatable	Yes

# Reservoir trace gas mole fraction — molar fraction of impurity gas

Details

Enter the desired molar fraction of impurity gas in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set the parameter Reservoir trace gas specification to Mole fraction.

Default value	`0.001`
Program usage name	`trace_gas_constant_mole_fraction`
Evaluatable	Yes

# Relative humidity at saturation — Relative humidity above which condensation occurs

Details

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

Default value	`1.0`
Program usage name	`RH_saturation`
Evaluatable	Yes

# Cross-sectional area at port A — area normal to the flow direction at the tank inlet
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

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

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`0.01 m^2`
Program usage name	`port_area`
Evaluatable	Yes

Examples

Modelling the operation of a pneumatic actuator in a wet environment