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Moisture Source (MA)

Inject or extract moisture at a constant or time-varying rate

  • Moisture Source (MA) block

Libraries:
Simscape / Foundation Library / Moist Air / Sources / Moisture & Trace Gas Sources

Description

The Moisture Source (MA) block represents a constant or time-varying source or sink of moisture for the connected moist air volume. A positive or negative moisture mass flow rate results in moisture being added or removed, respectively.

For a time-varying source, two physical signal input ports, M and T, supply the mass flow rate and temperature values, respectively. Alternatively, you can specify constant mass flow rate and temperature as block parameters.

You can add moisture as water vapor or liquid water. For water vapor, the energy associated with the added or removed moisture is

Φs={m˙specifiedhw(Tspecified),if m˙specified0m˙specifiedhw(Ts),if m˙specified<0 

where:

  • m˙specified is the water vapor mass flow rate specified by the input physical signal at port M or by the Moisture mass flow rate parameter.

  • hw is the water vapor specific enthalpy.

  • Tspecified is the temperature of added moisture, as specified by the input physical signal at port T or by the block parameters. The block uses this value to evaluate the specific enthalpy of the added moisture only. The specific enthalpy of removed moisture is based on the temperature of the connected moist air volume.

  • Ts is the temperature at port S, which is the same as the temperature of the connected moist air volume.

For liquid water, the energy associated with the added or removed moisture is

Φs={m˙specified(hw(Tspecified)Δhvap(Tspecified)),if m˙specified0m˙specified(hw(Ts)Δhvap(Ts)),if m˙specified<0 

where Δhvap is the water specific enthalpy of vaporization.

Port S is a moist air source conserving port. Connect this port to port S of a block with finite moist air volume to add or remove moisture through that block. For more information, see Using Moisture and Trace Gas Sources.

Ports

Input

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Input physical signal that specifies the water vapor mass flow rate through the source.

Dependencies

To enable this port, set the Source type parameter to Controlled.

Input physical signal that specifies the temperature of added moisture. The block uses this value to evaluate the specific enthalpy of the added moisture only. The specific enthalpy of removed moisture is based on the temperature of the connected moist air volume.

Dependencies

To enable this port, set the Source type parameter to Controlled.

Conserving

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Connect this port to port S of a block with finite moist air volume to add or remove moisture through that block.

Parameters

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Select whether the moisture mass flow rate and temperature can change during simulation:

  • Controlled — The moisture mass flow rate and temperature are variable, controlled by input physical signals. Selecting this option exposes the input ports M and T.

  • Constant — The moisture mass flow rate and temperature are constant during simulation, specified by block parameters. Selecting this option enables these parameters.

Select whether the source adds or removes moisture as water vapor or liquid water:

  • Vapor — The enthalpy of the added or removed moisture corresponds to the enthalpy of water vapor, which is greater than that of liquid water.

  • Liquid — The enthalpy of the added or removed moisture corresponds to the enthalpy of liquid water, which is less than that of water vapor.

Water vapor mass flow rate through the source. A positive value adds moisture to the connected moist air volume. A negative value extracts moisture from that volume.

Dependencies

To enable this parameter, set Source type to Constant.

Select a specification method for the moisture temperature:

  • Atmospheric temperature — Use the atmospheric temperature, specified by the Moist Air Properties (MA) block connected to the circuit.

  • Specified temperature — Specify a value by using the Temperature of added moisture parameter.

Dependencies

To enable this parameter, set Source type to Constant.

Enter the desired temperature of added moisture. This temperature remains constant during simulation. The block uses this value to evaluate the specific enthalpy of the added moisture only. The specific enthalpy of removed moisture is based on the temperature of the connected moist air volume.

Dependencies

To enable this parameter, set Added moisture temperature specification to Specified temperature.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018a

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