Moisture & Trace Gas Sensor (MA)

Measure humidity, water droplets, and trace gas levels in moist air network

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Libraries:
Simscape / Foundation Library / Moist Air / Sensors

Description

The Moisture & Trace Gas Sensor (MA) block measures the amount of humidity, water droplets, and trace gas in a moist air network. There is no mass or energy flow through the sensor.

The physical signal ports W, Tw, D, and G report the humidity, wet-bulb temperature, water droplet mass ratio, and trace gas level, respectively, measured at port A. Use the block parameters to control the port visibility and select the quantities to measure. Connect these ports to PS-Simulink Converter blocks to transform the output physical signals into Simulink^® signals, for example, for plotting or additional data processing.

The sensor measurements correspond to the moisture and trace gas level upstream of the measured node. For example, if port A of the Moisture & Trace Gas Sensor (MA) is connected to a node between pipe 1 and pipe 2 and the moist air flows from pipe 1 to pipe 2, then the moisture and trace gas level measured at port A are those of the moist air volume in pipe 1. If the air flow then switches direction and flows from pipe 2 to pipe 1, then the moisture and trace gas level measured at port A are those of the moist air volume in pipe 2. If the moisture and trace gas levels of the two moist air volumes are different, then the measured values change when the flow direction switches. If there are two or more upstream flow paths merging at the node, then the moisture and trace gas level measurement at the node represents the weighted average based on the ideal mixing of the merging flow.

Examples

Aircraft Environmental Control System

Models an aircraft environmental control system (ECS) that regulates pressure, temperature, humidity, and ozone (O3) to maintain a comfortable and safe cabin environment. Cooling and dehumidification are provided by the air cycle machine (ACM), which operates as an inverse Brayton cycle to remove heat from pressurized hot engine bleed air. Some hot bleed air is mixed directly with the output of the ACM to adjust the temperature. Pressurization is maintained by the outflow valve in the cabin. This model simulates the ECS operating from a hot ground condition to a cold cruise condition and back to a cold ground condition.

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Medical Ventilator with Lung Model

Models a positive-pressure medical ventilator system. A preset flow rate is supplied to the patient. The lungs are modeled with the Translational Mechanical Converter (MA), which converts moist air pressure into translational motion. By setting the Interface cross-sectional area to unity, displacement in the mechanical translational network becomes a proxy for volume, force becomes a proxy for pressure, spring constant becomes a proxy for respiratory elastance, and damping coefficient becomes a proxy for respiratory resistance.

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Ports

Output

W — Humidity measurement, unitless

physical signal

Physical signal output port for humidity measurement. To select the quantity you want to measure, use the Measured humidity specification parameter.

Dependencies

To enable this port, select the Humidity check box and set the Measured humidity specification parameter to

• Relative humidity

• Specific humidity

• Mole fraction

• Humidity ratio

Tw — Wet-bulb temperature measurement, K

physical signal

Physical signal output port for wet-bulb temperature measurement.

Dependencies

To enable this port, select the Humidity check box and set the Measured humidity specification parameter to Wet-bulb temperature.

G — Trace gas level measurement, unitless

physical signal

Physical signal output port for trace gas level measurement. To select the quantity you want to measure, use the Measured trace gas specification parameter.

Dependencies

To enable this port, select the Trace gas check box.

D — Mass ratio of water droplets to moist air, unitless

physical signal

Physical signal output port for the mass ratio of water droplets to moist air.

Dependencies

To enable this port, select the Water droplets check box.

Conserving

A — Sensor inlet

moist air

Moist air conserving port. Connect this port to the node in the moist air network where you want to measure the moisture and trace gas level.

Parameters

Humidity — Control output port visibility for measuring humidity

On (default) | Off

Selecting this check box exposes the output port W or Tw, which lets you measure the quantity specified by the Measured humidity specification parameter value.

Measured humidity specification — Select the humidity property to measure

Relative humidity (default) | Specific humidity | Mole fraction | Humidity ratio | Wet-bulb temperature

Select the property to measure:

• Relative humidity ― Physical signal port W reports the relative humidity.

• Specific humidity ― Physical signal port W reports the specific humidity.

• Mole fraction ― Physical signal port W reports the water vapor mole fraction.

• Humidity ratio ― Physical signal port W reports the humidity ratio.

• Wet-bulb temperature ― Physical signal port Tw reports the wet-bulb temperature.

Trace gas — Control output port visibility for measuring trace gas

On (default) | Off

Selecting this check box exposes the output port G, which lets you measure the quantity specified by the Measured trace gas specification parameter value.

Measured trace gas specification — Select the trace gas property to measure

Mass fraction (default) | Mole fraction

Select the property to measure:

• Mass fraction ― Physical signal port G reports the trace gas mass fraction.

• Mole fraction ― Physical signal port G reports the trace gas mole fraction.

Water droplets — Control output port visibility for measuring water droplets

Off (default) | On

Selecting this check box exposes the output port D, which lets you measure the mass ratio of water droplets to moist air.

Extended Capabilities

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

Version History

Introduced in R2018a

R2024b: Renamed from Humidity & Trace Gas Sensor (MA)

The Humidity & Trace Gas Sensor (MA) block is now the Moisture & Trace Gas Sensor (MA) block.

R2024b: Model water droplets suspended in moist air flow

Blocks in the moist air domain can now model water droplets suspended in a moist air flow. To model water droplets, select Enable entrained water droplets in the Moist Air Properties (MA) block connected to your moist air network.

R2023a: Use wet-bulb temperature to measure humidity

The block now has an option to measure humidity by using the wet-bulb temperature. Wet-bulb temperature is a method of measuring humidity that involves wrapping a wet cloth around a thermometer, so that you can measure the temperature including energy loss due to evaporation. Traditional psychrometers output data in the form of wet-bulb temperature.

Additionally, moist air sensor blocks with multiple output ports now have conditional port visibility on the block icon. You can use the block parameters to expose only the ports that you need for measurements in a particular model.

These changes have no compatibility impact.