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Moisture Source (MA)

Inject or extract moisture at a constant rate

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

  • Moisture Source (MA) block

Description

The Moisture Source (MA) block represents a constant 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.

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 Moisture mass flow rate parameter.

  • hw is the water vapor specific enthalpy.

  • Tspecified is the temperature of added moisture, as specified 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

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 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.

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.

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

Enabled when the Added moisture temperature specification parameter is set to Specified temperature.

Extended Capabilities

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

Introduced in R2018a