Flow Rate Source (2P)

Generate constant or time-varying mass flow rate or volumetric flow rate in two-phase fluid network

Since R2023b

Libraries:
Simscape / Foundation Library / Two-Phase Fluid / Sources

Description

The Flow Rate Source (2P) block represents an ideal mechanical energy source in a two-phase fluid 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.

Mass Balance

The volume of fluid in the source is considered negligible and is ignored in a model. There is no fluid accumulation between the ports and the sum of all mass flow rates into the source must therefore equal zero:

${\dot{m}}_{A} + {\dot{m}}_{B} = 0,$

where $\dot{m}$ denotes the mass flow rate into the source through a port.

When you set the Flow rate type parameter to Volumetric flow rate, the mass flow rate at port A is calculated from the volumetric flow rate:

$\dot{m_{A}} = {\begin{array}{l} \frac{\dot{V}}{v_{B}}, & if \dot{V} \geq 0 \\ \frac{\dot{V}}{v_{A}}, & otherwise \end{array},$

where $\dot{V}$ is volumetric flow rate and v is specific volume.

Energy Balance

By default, the source maintains the specified flow rate by performing isentropic work on the incoming fluid, though the block provides the option to ignore this term. The rate at which the source does work, if considered in the model, must equal the sum of the energy flow rates through the ports:

$ϕ_{A} + ϕ_{B} + ϕ_{Work} = 0,$

where ϕ denotes the energy flow rate into the source through a port or by means of work. The energy flow rate due to work is equal to the power generated by the source. Its value is calculated from the specific total enthalpies at the ports:

$ϕ_{Work} = {\dot{m}}_{A} (h_{A} - h_{B}) .$

The specific total enthalpy h is defined as:

$h_{*} = u_{*} + p_{*} v_{*} + \frac{1}{2} {(\frac{{\dot{m}}_{*} v_{*}}{S})}^{2},$

where the asterisk denotes a port (A or B) and:

u is specific internal energy.
p is pressure.
S is flow area.

The specific internal energy in the equation is obtained from the tabulated data of the Two-Phase Fluid Properties (2P) block. Its value is uniquely determined from the constraint that the work done by the source is isentropic. The specific entropy, a function of specific internal energy, must then have the same value at ports A and B:

$s_{A} (p_{A}, u_{A}) = s_{B} (p_{B}, u_{B}),$

where s is specific entropy. If the Power added parameter is set to None, the specific total enthalpies at the ports have the same value ( $h_{A} = h_{B}$ ) and the work done by the source reduces to zero ( $ϕ_{Work} = 0$ ).

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
two-phase fluid

Two-phase fluid conserving port. A positive flow rate causes fluid to flow from port A to port B.

B — Source outlet
two-phase fluid

Two-phase fluid conserving port. A positive flow rate causes 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 port A — Area normal to flow path at port A
`0.01 m^2` (default)

Area normal to flow path at port A.

Cross-sectional area at port B — Area normal to flow path at port B
`0.01 m^2` (default)

Area normal to flow path at port B.

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 two-phase fluid sources

In R2023b, separate Mass Flow Rate Source (2P), Controlled Mass Flow Rate Source (2P), Volumetric Flow Rate Source (2P), and Controlled Volumetric Flow Rate Source (2P) blocks have been combined into a single Flow Rate Source (2P) 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 (2P) 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 (2P)	`source = foundation.two_phase_fluid.sources.controlled_mass_flow_source;`	`source = foundation.two_phase_fluid.sources.flow_source;`
Mass Flow Rate Source (2P)	`source = foundation.two_phase_fluid.sources.mass_flow_source;`	`source = foundation.two_phase_fluid.sources.flow_source(source_type=foundation.enum.constant_controlled.constant);`
Controlled Volumetric Flow Rate Source (2P)	`source = foundation.two_phase_fluid.sources.controlled_volumetric_flow_source;`	`source = foundation.two_phase_fluid.sources.flow_source(flow_type=foundation.enum.mass_volumetric_flow.volumetric);`
Volumetric Flow Rate Source (2P)	`source = foundation.two_phase_fluid.sources.volumetric_flow_source;`	`source = foundation.two_phase_fluid.sources.flow_source(source_type=foundation.enum.constant_controlled.constant,flow_type=foundation.enum.mass_volumetric_flow.volumetric);`

Flow Rate Source (2P)

Description

Mass Balance

Energy Balance

Assumptions and Limitations

Ports

Input

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

Dependencies

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

Dependencies

Conserving

A — Source inlet two-phase fluid

B — Source outlet two-phase fluid

Parameters

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

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

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

Dependencies

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

Dependencies

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

Cross-sectional area at port A — Area normal to flow path at port A 0.01 m^2 (default)

Cross-sectional area at port B — Area normal to flow path at port B 0.01 m^2 (default)

Extended Capabilities

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

Version History

R2023b: Usability enhancement for two-phase fluid sources

See Also

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

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

A — Source inlet
two-phase fluid

B — Source outlet
two-phase fluid

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

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

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

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

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

Cross-sectional area at port A — Area normal to flow path at port A
`0.01 m^2` (default)

Cross-sectional area at port B — Area normal to flow path at port B
`0.01 m^2` (default)

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