Trace Gas Source (MA)

Inject or extract trace gas at a constant or time-varying rate

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

Description

The Trace Gas Source (MA) block represents a constant or time-varying source or sink of trace gas for the connected moist air volume. A positive or negative trace gas mass flow rate causes trace gas levels to increase or decrease, 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.

The energy associated with the added or removed trace gas is

$${\Phi }_s=\{\begin{array}{ll}{\dot{m}}_{specified}\cdot h_g\left(T_{specified}\right),\hfill & \text{if }{\dot{m}}_{specified}\ge 0\hfill \\ {\dot{m}}_{specified}\cdot h_g\left(T_s\right),\hfill & \text{if }{\dot{m}}_{specified}<0\hfill \end{array}$$

where:

• $${\dot{m}}_{specified}$$ is the trace gas mass flow rate specified by the input physical signal at port M or by the Trace gas mass flow rate parameter.

• h_g is the trace gas specific enthalpy.

• T_specified is the temperature of added trace gas, 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 trace gas only. The specific enthalpy of removed trace gas 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.

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 trace gas through that block. For more information, see Using Moisture and Trace Gas Sources.

Examples

Vehicle HVAC System

Models moist air flow in a vehicle heating, ventilation, and air conditioning (HVAC) system. The vehicle cabin is represented as a volume of moist air exchanging heat with the external environment. The moist air flows through a recirculation flap, a blower, an evaporator, a blend door, and a heater before returning to the cabin. The recirculation flap selects flow intake from the cabin or from the external environment. The blender door diverts flow around the heater to control the temperature.

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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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Ports

Input

M — Mass flow rate control signal, kg/s

physical signal

Input physical signal that specifies the trace gas mass flow rate through the source.

Dependencies

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

T — Temperature of added trace gas, K

physical signal

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

Dependencies

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

Conserving

S — Inject or extract trace gas

moist air source

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

Parameters

Source type — Select whether trace gas mass flow rate and temperature can change during simulation

Controlled (default) | Constant

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

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

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

Rate of added trace gas — Constant mass flow rate through the source

0 kg/s (default)

Trace gas mass flow rate through the source. A positive value adds trace gas to the connected moist air volume. A negative value extracts trace gas from that volume.

Dependencies

To enable this parameter, set Source type to Constant.

Added trace gas temperature specification — Select specification method for the temperature of added trace gas

Atmospheric temperature (default) | Specified temperature

Select a specification method for the trace gas 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 trace gas parameter.

Dependencies

To enable this parameter, set Source type to Constant.

Temperature of added trace gas — Trace gas temperature

293.15 K (default)

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

Dependencies

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

Extended Capabilities

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

Version History

Introduced in R2018a

R2023b: Usability enhancement for moist air sources

In R2023b, separate Trace Gas Source (MA) and Controlled Trace Gas Source (MA) blocks have been combined into a single Trace Gas Source (MA) block that lets you select between constant or time-varying source or sink of trace gas.

This change has no compatibility impact when you use these Foundation library blocks in your models. When you open an existing model, the Controlled Trace Gas Source (MA) blocks are automatically replaced by Trace Gas Source (MA) blocks with exposed input ports.

However, if you use these blocks in your custom composite components, you need to update the composite component code.

Source Block to Update	Old Syntax	New Syntax
Controlled Trace Gas Source (MA)	source = foundation.moist_air.sources.moisture_trace_gas.trace_gas_source_controlled;	source = foundation.moist_air.sources.moisture_trace_gas.trace_gas_source;
Trace Gas Source (MA)	source = foundation.moist_air.sources.moisture_trace_gas.trace_gas_source;	source = foundation.moist_air.sources.moisture_trace_gas.trace_gas_source(source_type=foundation.enum.constant_controlled.constant);