Interface (G-MA)

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The boundary between the gas and wet air networks.

blockType: EngeeFluids.Interfaces.GasMoistAir

Path in the library:

/Physical Modeling/Fluids/Fluid Network Interfaces/Interface (G-MA)

Description

The unit Interface (G-MA) represents the connection between the gas network and the moist air network flows. Pressure, temperature and mass flow rate are equal at the boundary. The block does not transfer the fluid properties of each network across the boundary. To preserve the fluid properties, make sure the Gas Properties (G) block and the Moist Air Properties (MA) block have the same settings. When humid air leaves the MA port, the block assigns the Interface relative humidity and Interface trace gas mass fraction parameters or input values to it. However, when humid air enters the MA port, the unit stores the variable values in the humid air stream.

You can choose whether to keep the humidity and the amount of impurity gas at the boundary constant or set them using the W, Tw, and TG ports, respectively.

Mass and momentum conservation

The mass flow rate is stored:

where

- is the mass flow rate of gas into the port G;
- is the mass flow rate of moist air into port MA.

The unit maintains equal port pressures and temperatures such that:

Conservation of energy

Energy conservation at the boundary:

where

- energy flow to port G;
- energy flux to port MA;
- specific enthalpy at port G;
- specific enthalpy at port MA;
- flow rate at port G;
- flow rate at port MA.

For a given port cross-sectional area , the block defines and as:

where

- specific volume at port G;
- specific volume in the port MA:

The universal gas constant of the mixture at the boundary is a function of the liquid on both sides:

where

- is the specific gas constant of dry air;
- specific gas constant of water vapour;
- specific gas constant of impurity gases;
- specific humidity at the boundary. The unit determines this value when the flow leaves the MA port based on the parameters settings:
- When the Controlled moisture and trace gas checkbox is unchecked, the block calculates based on the method specified in parameter Interface moisture specification.
- When Controlled moisture and trace gas is checked, the block calculates based on the input value at port W or at port Tw.
- The mass fraction of the impurity gas at the boundary. The block determines this value when the flow exits port MA based on the parameters settings:
- When the Controlled moisture and trace gas checkbox is unchecked, the block calculates based on the value of the parameters Interface trace gas mass fraction or Interface trace gas mole fraction.
- When Controlled moisture and trace gas is checked, the block calculates based on the input value on the TG port.

Ports

Conserving

# G — gas port
gas

Details

A non-directional port associated with gas at the border.

Program usage name

gas_port

# MA — humid air port
`humid air

Details

A non-directional port associated with moist air at the boundary.

Program usage name

moist_air_port

Input

# TG — impurity gas
scalar

Details

A port that determines the fraction of impurity gas at the boundary.

Dependencies

To use this port, select the checkbox Controlled moisture and trace gas.

Data types	`Float64`.
Complex numbers support	No

# W — humidity, dimensionless
scalar

Details

A port that determines the humidity at the boundary.

Dependencies

To use this port, select the checkbox Controlled moisture and trace gas, and set the parameters Interface moisture specification to the value of Relative humidity, Specific humidity, Mole fraction or Humidity ratio.

Data types	`Float64`.
Complex numbers support	No

# Tw — temperature, K
scalar

Details

A port that determines the temperature from a wet thermometer at the boundary, in K.

Dependencies

To use this port, select the checkbox Controlled moisture and trace gas, and set the parameters Interface moisture specification to Wet-bulb temperature.

Data types	`Float64`.
Complex numbers support	No

Parameters

# Controlled moisture and trace gas — option for controlling moisture and impurity gas at the boundary

Details

If unchecked, the unit maintains a constant humidity and impurity gas at the boundary. If this checkbox is selected, the humidity and impurity gas are set via the W and TG ports.

Default value	`false (switched off)`
Program usage name	`controlled_moisture_and_trace_gas`
Evaluatable	Yes

# Interface moisture specification — moisture parameterization
Relative humidity | Specific humidity | Mole fraction | Humidity ratio | Wet-bulb temperature

Details

Choose how to calculate humidity: using relative humidity, specific humidity, molar fraction, humidity coefficient or wet-bulb temperature.

Values	`Relative humidity` \| `Specific humidity` \| `Mole fraction` \| `Humidity ratio` \| `Wet-bulb temperature`
Default value	`Relative humidity`
Program usage name	`moisture_type`
Evaluatable	Yes

# Interface relative humidity — relative humidity at the boundary

Details

The relative humidity at the boundary. The block uses this value to calculate the humidity.

Dependencies

To use this parameter, uncheck Controlled moisture and trace gas, and for the parameter Interface moisture specification on the Relative humidity.

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

# Interface trace gas specification — impurity gas parameterization
Mass fraction | Mole fraction

Details

Choose how to parameterise the impurity gas at the boundary: using mass fraction or molar fraction.

Values	`Mass fraction` \| `Mole fraction`
Default value	`Mass fraction`
Program usage name	`trace_gas_type`
Evaluatable	Yes

# Interface trace gas mass fraction — mass fraction of impurity gas at the boundary

Details

Mass fraction of impurity gas at the boundary.

Dependencies

To use this parameter, uncheck Controlled moisture and trace gas and set the Interface trace gas specification parameters to . Mass fraction.

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

# Relative humidity at saturation — relative humidity at saturation point

Details

Relative humidity at saturation point.

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

# Cross-sectional area at ports G and MA — cross-sectional area of the openings for gas and moist air
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

Cross-sectional area of the gas and moist air openings.

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

# Inputs outside valid range — option for monitoring or controlling input data outside the permissible range
Limit to valid values | Error

Details

Monitor or control invalid inputs. If the value is selected `Limit to valid values`is selected, the unit saturates the input values within the set limits. If the value is selected `Error`is selected, the simulation stops when the block receives invalid input values.

Values	`Limit to valid values` \| `Error`
Default value	`Limit to valid values`
Program usage name	`assert_action`
Evaluatable	Yes

# Interface trace gas mole fraction — molar fraction of impurity gas at the boundary

Details

Molar fraction of impurity gas at the boundary.

Dependencies

To use this parameter, uncheck Controlled moisture and trace gas, and set the Interface trace gas specification parameters to . Mole fraction.

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

# Interface specific humidity — specific humidity at the boundary

Details

The specific humidity at the boundary. The block uses this value to calculate the humidity.

Dependencies

To use this parameter, uncheck Controlled moisture and trace gas, and set the Interface moisture specification parameters to . Specific humidity.

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

# Interface water vapor mole fraction — molar fraction of water vapour at the boundary

Details

The molar fraction of water vapour at the interface. The block uses this value to calculate the moisture content.

Dependencies

To use this parameter, uncheck Controlled moisture and trace gas, and set the Interface moisture specification parameters to . Mole fraction.

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

# Interface humidity ratio — moisture coefficient at the boundary

Details

The moisture coefficient on the boundary. The block uses this value to calculate the moisture content.

Dependencies

To use this parameter, uncheck Controlled moisture and trace gas, and set the Interface moisture specification parameters to . Humidity ratio.

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

Details

The temperature of the wet thermometer at the interface. The block uses this value to calculate humidity.

Dependencies

To use this parameter, uncheck Controlled moisture and trace gas, and set the Interface moisture specification parameters 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