Mass Flow Rate Source (G)

Generate constant mass flow rate

Libraries:
Simscape / Foundation Library / Gas / Sources

Description

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

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 Model Equations
Perfect gas $\frac{{(p_{A})}^{Z \cdot R / c_{p}}}{T_{A}} = \frac{{(p_{B})}^{Z \cdot R / c_{p}}}{T_{B}}$
Semiperfect gas $\int_{0}^{T_{A}} \frac{c_{p} (T)}{T} d T - Z \cdot R \cdot \ln (p_{A}) = \int_{0}^{T_{B}} \frac{c_{p} (T)}{T} d T - Z \cdot R \cdot \ln (p_{B})$
Real gas $s (T_{A}, p_{A}) = s (T_{B}, p_{B})$
The power delivered to the gas flow is based on the specific total enthalpy associated with the isentropic process.
$Φ_{w o r k} = - {\dot{m}}_{A} (h_{A} + \frac{w_{A}^{2}}{2}) - {\dot{m}}_{B} (h_{B} + \frac{w_{B}^{2}}{2})$
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.
$h_{A} + \frac{w_{A}^{2}}{2} = h_{B} + \frac{w_{B}^{2}}{2}$
The power delivered to the gas flow Φ_work = 0.

Gas Model	Equations
Perfect gas	$\frac{{(p_{A})}^{Z \cdot R / c_{p}}}{T_{A}} = \frac{{(p_{B})}^{Z \cdot R / c_{p}}}{T_{B}}$
Semiperfect gas	$\int_{0}^{T_{A}} \frac{c_{p} (T)}{T} d T - Z \cdot R \cdot \ln (p_{A}) = \int_{0}^{T_{B}} \frac{c_{p} (T)}{T} d T - Z \cdot R \cdot \ln (p_{B})$
Real gas	$s (T_{A}, p_{A}) = s (T_{B}, p_{B})$

The equations use these symbols:

c_p	Specific heat at constant pressure
h	Specific enthalpy
$\dot{m}$	Mass flow rate (flow rate associated with a port is positive when it flows into the block)
p	Pressure
R	Specific gas constant
s	Specific entropy
T	Temperature
w	Flow velocity
Z	Compressibility factor
Φ_work	Power 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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A — Source inlet
gas

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

B — Source outlet
gas

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

Parameters

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

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. 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.

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

Desired mass flow rate of the gas through the source.

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.

Mass Flow Rate Source (G)