# Moisture Source (MA)

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

**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

$${\Phi}_{s}=\{\begin{array}{ll}{\dot{m}}_{specified}\cdot {h}_{w}\left({T}_{specified}\right),\hfill & \text{if}{\dot{m}}_{specified}\ge 0\hfill \\ {\dot{m}}_{specified}\cdot {h}_{w}\left({T}_{s}\right),\hfill & \text{if}{\dot{m}}_{specified}0\text{}\hfill \end{array}$$

where:

$${\dot{m}}_{specified}$$ is the water vapor mass flow rate specified by the input physical signal at port

**M**or by the**Moisture mass flow rate**parameter.*h*_{w}is the water vapor specific enthalpy.*T*_{specified}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.*T*_{s}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

$${\Phi}_{s}=\{\begin{array}{ll}{\dot{m}}_{specified}\cdot \left({h}_{w}\left({T}_{specified}\right)-\Delta {h}_{vap}\left({T}_{specified}\right)\right),\hfill & \text{if}{\dot{m}}_{specified}\ge 0\hfill \\ {\dot{m}}_{specified}\cdot \left({h}_{w}\left({T}_{s}\right)-\Delta {h}_{vap}\left({T}_{s}\right)\right),\hfill & \text{if}{\dot{m}}_{specified}0\text{}\hfill \end{array}$$

where *Δh*_{vap} 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

### Conserving

## Parameters

## Extended Capabilities

## Version History

**Introduced in R2018a**