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Volumetric Flow Rate Source (G)

Generate constant volumetric flow rate

  • Library:
  • Simscape / Foundation Library / Gas / Sources

  • Volumetric Flow Rate Source (G) block

Description

The Volumetric Flow Rate Source (G) block represents an ideal mechanical energy source in a gas network. The source can maintain a constant volumetric flow rate regardless of the pressure differential. There is no flow resistance and no heat exchange with the environment. A positive volumetric 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

m˙={ρBV˙for V˙0ρAV˙for V˙<0

where:

  • m˙ is the mass flow rate from port A to port B.

  • ρA and ρB are densities at ports A and B, respectively.

  • V˙ is the volumetric flow rate.

You can choose whether the source performs work on the gas flow:

  • If the source is isentropic (Power added parameter is set to Isentropic power), then the isentropic relation depends on the gas property model.

    Gas ModelEquations
    Perfect gas(pA)ZR/cpTA=(pB)ZR/cpTB
    Semiperfect gas0TAcp(T)TdTZRln(pA)=0TBcp(T)TdTZRln(pB)
    Real gass(TA,pA)=s(TB,pB)

    The power delivered to the gas flow is based on the specific total enthalpy associated with the isentropic process.

    Φwork=m˙A(hA+wA22)m˙B(hB+wB22)

  • If the source performs no work (Power added parameter is set to None), then the defining equation states that the specific total enthalpy is equal on both sides of the source. It is the same for all three gas property models.

    hA+wA22=hB+wB22

    The power delivered to the gas flow Φwork = 0.

The equations use these symbols:

cpSpecific heat at constant pressure
hSpecific enthalpy
m˙Mass flow rate (flow rate associated with a port is positive when it flows into the block)
pPressure
RSpecific gas constant
sSpecific entropy
TTemperature
wFlow velocity
ZCompressibility factor
ΦworkPower delivered to the gas flow through the source

Subscripts A and B indicate the appropriate port.

Assumptions and Limitations

  • There are no irreversible losses.

  • There is no heat exchange with the environment.

Ports

Conserving

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Gas conserving port. A positive mass flow rate causes gas to flow from port A to port B.

Gas conserving port. A positive mass flow rate causes gas to flow from port A to port B.

Parameters

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Select whether the source performs work on the gas flow:

  • Isentropic power — The source performs isentropic work on the gas to maintain the specified mass flow rate, regardless of the pressure differential. 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.

Desired volumetric flow rate of gas through the source.

Area normal to flow path at port A.

Area normal to flow path at port B.

Extended Capabilities

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

Introduced in R2019a