Flow Rate Source (TL)

Generate constant or time-varying mass flow rate or volumetric flow rate in thermal liquid network

Since R2023b

Libraries:
Simscape / Foundation Library / Thermal Liquid / Sources

Description

The Flow Rate Source (TL) block represents an ideal mechanical energy source in a thermal liquid network. The source can maintain the specified mass flow rate or volumetric flow rate regardless of the pressure differential. There is no flow resistance and no heat exchange with the environment. You specify the flow rate type by using the Flow rate type parameter.

The block icon changes depending on the values of the Source type and Flow rate type parameters.

Ports A and B represent the source inlet and outlet. The input physical signal at port M or V, depending on the flow rate type, specifies the flow rate. Alternatively, you can specify a fixed flow rate as a block parameter. A positive flow rate causes gas to flow from port A to port B.

The volumetric flow rate and mass flow rate are related through the expression

$\dot{m} = {\begin{array}{l} ρ_{B} \dot{V} & for \dot{V} \geq 0 \\ ρ_{A} \dot{V} & for \dot{V} < 0 \end{array}$

where:

$\dot{m}$ is the mass flow rate from port A to port B.
ρ_A and ρ_B are densities at ports A and B, respectively.
$\dot{V}$ is the volumetric flow rate.

The energy balance at the source is a function of the energy flow rates through ports A and B and the work done on the fluid:

$ϕ_{A} + ϕ_{B} + ϕ_{w o r k} = 0,$

where:

ϕ_A is the energy flow rate into the source through port A.
ϕ_B is the energy flow rate into the source through port B.
ϕ_work is the isentropic work done on the fluid.

The isentropic work term is

$ϕ_{w o r k} = \frac{\dot{m} (p_{B} - p_{A})}{ρ_{a v g}},$

where:

ϕ_work is the isentropic work done on the thermal liquid.
p_A is the pressure at port A.
p_B is the pressure at port B.
ρ_avg is the average liquid density,

$ρ_{a v g} = \frac{ρ_{A} + ρ_{B}}{2} .$

Assumptions and Limitations

There are no irreversible losses.
There is no heat exchange with the environment.

Ports

Input

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M — Mass flow rate control signal, kg/s
physical signal

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

Dependencies

To enable this port, set the Source type parameter to Controlled and Flow rate type to Mass flow rate.

V — Volumetric flow rate control signal, m^3/s
physical signal

Input physical signal that specifies the volumetric flow rate through the source.

Dependencies

To enable this port, set the Source type parameter to Controlled and Flow rate type to Volumetric flow rate.

Conserving

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A — Source inlet
thermal liquid

Thermal liquid conserving port. A positive flow rate causes the fluid to flow from port A to port B.

B — Source outlet
thermal liquid

Thermal liquid conserving port. A positive flow rate causes the fluid to flow from port A to port B.

Parameters

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Source type — Select whether flow rate can change during simulation
`Controlled` (default) | `Constant`

Select whether the flow rate generated by the source can change during simulation:

Controlled — The flow rate is variable, controlled by an input physical signal. Selecting this option exposes the input port M or V, depending on the value of the Flow rate type parameter.
Constant — The flow rate is constant during simulation, specified by a block parameter. Selecting this option enables the Mass flow rate or Volumetric flow rate parameter, depending on the value of the Flow rate type parameter.

Flow rate type — Select whether source generates mass or volumetric flow rate
`Mass flow rate` (default) | `Volumetric flow rate`

Select the type of flow rate, Mass flow rate or Volumetric flow rate.

Mass flow rate — Constant mass flow rate through the source
`0 kg/s` (default)

Desired mass flow rate of the fluid through the source.

Dependencies

To enable this parameter, set Source type to Constant and Flow rate type to Mass flow rate.

Volumetric flow rate — Constant volumetric flow rate through the source
`0 m^3/s` (default)

Desired volumetric flow rate of the fluid through the source.

Dependencies

To enable this parameter, set Source type to Constant and Flow rate type to Volumetric flow rate.

Power added — Select whether the source performs work
`Isentropic` (default) | `None`

Select whether the source performs work on the fluid flow:

Isentropic — The source performs isentropic work on the fluid to maintain the specified mass flow rate. Use this option to represent an idealized pump or compressor and properly account for the energy input and output, especially in closed-loop systems.
None — The source performs no work on the flow, neither adding nor removing power, regardless of the mass flow rate produced by the source. Use this option to set up the desired flow condition upstream of the system, without affecting the temperature of the flow.

Cross-sectional area at ports A and B — Area normal to flow path at inlet and outlet
`0.01 m^2` (default)

Area normal to flow path at the source inlet and outlet. The two cross-sectional areas are assumed identical.

Extended Capabilities

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

Version History

Introduced in R2023b

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R2023b: Usability enhancement for thermal liquid sources

In R2023b, separate Mass Flow Rate Source (TL), Controlled Mass Flow Rate Source (TL), Volumetric Flow Rate Source (TL), and Controlled Volumetric Flow Rate Source (TL) blocks have been combined into a single Flow Rate Source (TL) block that lets you select between generating constant or time-varying mass flow rate or volumetric flow rate. The new block lets you use the block parameters to configure the block and expose only the input ports that you need in a particular model, which helps reduce clutter and improve the block diagram layout.

This change has no compatibility impact when you use these Foundation library blocks in your models. When you open an existing model, the old blocks are automatically replaced by Flow Rate Source (TL) blocks with the appropriate configuration.

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 Mass Flow Rate Source (TL)	`source = foundation.thermal_liquid.sources.controlled_mass_flow_source;`	`source = foundation.thermal_liquid.sources.flow_source;`
Mass Flow Rate Source (TL)	`source = foundation.thermal_liquid.sources.mass_flow_source;`	`source = foundation.thermal_liquid.sources.flow_source(source_type=foundation.enum.constant_controlled.constant);`
Controlled Volumetric Flow Rate Source (TL)	`source = foundation.thermal_liquid.sources.controlled_volumetric_flow_source;`	`source = foundation.thermal_liquid.sources.flow_source(flow_type=foundation.enum.mass_volumetric_flow.volumetric);`
Volumetric Flow Rate Source (TL)	`source = foundation.thermal_liquid.sources.volumetric_flow_source;`	`source = foundation.thermal_liquid.sources.flow_source(source_type=foundation.enum.constant_controlled.constant,flow_type=foundation.enum.mass_volumetric_flow.volumetric);`

R2023a: Configure flow conditions without affecting temperature

The block includes the Power added parameter, which lets you specify whether the source performs work on the fluid flow. The default option, Isentropic power, is equivalent to the block behavior in previous releases. Use the new None option to set up the desired flow condition upstream of the system, without affecting the temperature of the flow.

Flow Rate Source (TL)