Moisture Source (MA)

Adding or removing moisture at a constant or variable flow rate.

blockType: AcausalFoundation.MoistAir.MoistureTraceGasSources.Moisture

Controlled Moisture Source (MA)

Path in the library:

/Physical Modeling/Fundamental/Moist Air/Moisture & Trace Gas Sources/Controlled Moisture Source (MA)

Moisture Source (MA)

Path in the library:

/Physical Modeling/Fundamental/Moist Air/Moisture & Trace Gas Sources/Moisture Source (MA)

Description

The Moisture Source (MA) unit is a constant or time-varying moisture source or absorber for a connected volume with humid air.

A positive or negative mass flow rate results in an increase or decrease of the moisture level respectively.

Moisture can be added in the form of water vapour or water.

For water vapour, the energy associated with the addition or removal of moisture is equal to:

where

- is the mass flow rate of water vapour given by the input scalar signal at port M or parameters Rate of added moisture;
- specific enthalpy of water vapour;
- is the temperature of the added water vapour, given by the input scalar signal at port T or parameters Temperature of added moisture. The unit uses this value to estimate the specific enthalpy of only the added moisture. The specific enthalpy of the removed moisture is determined from the temperature of the connected volume with humid air;
- is the temperature at port S, which is equal to the temperature of the connected volume with humid air.

For water, the energy associated with the addition or removal of moisture is equal to:

where is the specific enthalpy of vaporisation of water.

Ports

Conserving

# S — adding or removing moisture
moist air

Details

Humid air source port. Connect this port to the S port of the humid air final volume unit to add or remove moisture using the unit Controlled Moisture Source (MA).

Program usage name

source_port

Input

# M — mass flow rate, kg/s
scalar

Details

An input port that determines the mass flow rate of moisture through the source.

Dependencies

To use this port, select the Controlled source checkbox.

Data types	`Float64`.
Complex numbers support	No

# T — temperature, K
scalar

Details

An input port that determines the temperature of the added moisture. The unit uses this value to estimate the specific enthalpy of the added moisture only. The specific enthalpy of removed moisture is determined from the temperature of the connected moist air volume.

Dependencies

To use this port, select the checkbox Controlled source.

Data types	`Float64`.
Complex numbers support	No

Parameters

# Controlled source — whether the moisture flow rate and temperature are set by the input signal

Details

Determines how the flow rate and moisture temperature will be set:

If checked, the flow rate and moisture temperature are set via the M and T input ports.
If unchecked, the constant flow rate and moisture temperature are set using the parameters Rate of added moisture and Added moisture temperature specification respectively.

Default value	`—`
Program usage name	`controlled`
Evaluatable	No

# Moisture added or removed — add or remove moisture in the form of water vapour or water
Vapor | Liquid

Details

Select whether the source adds or removes moisture as water vapour or water:

Vapor - the enthalpy of added or removed moisture corresponds to the enthalpy of water vapour, which is greater than the enthalpy of water.
Liquid - the enthalpy of added or removed moisture corresponds to the enthalpy of water, which is less than the enthalpy of water vapour.

Values	`Vapor` \| `Liquid`
Default value	`Vapor`
Program usage name	`moisture_source_phase`
Evaluatable	No

# Rate of added moisture — constant mass flow rate through the source
kg/s | N*s/m | N/(m/s) | lbf/(ft/s) | lbf/(in/s)

Details

Mass flow rate of moisture through the source.

A positive value adds moisture to the connected humid air volume. A negative value removes moisture from this volume.

Dependencies

To use this parameter, uncheck Controlled source.

Units	`kg/s` \| `N*s/m` \| `N/(m/s)` \| `lbf/(ft/s)` \| `lbf/(in/s)`
Default value	`0.0 kg/s`
Program usage name	`moisture_mass_flow`
Evaluatable	Yes

# Added moisture temperature specification — Moisture temperature setting method
Atmospheric temperature | Specified temperature

Details

Selects the method for setting the moisture temperature:

Atmospheric temperature - the atmospheric temperature set by the unit Moist Air Properties (MA), connected to the circuit, is used.
Specified temperature - the value is set with the parameters Temperature of added moisture.

Dependencies

To use this parameter, uncheck Controlled source.

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

Details

Moisture Temperature. This temperature remains constant during the simulation. The unit uses this value only to estimate the specific enthalpy of added moisture. The specific enthalpy of removed moisture is determined based on the temperature of the connected humid air volume.

Dependencies

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

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

Examples

Modelling of artificial ventilation system