Controlled Mass Flow Rate Source (G)
A source of mass or volumetric flow.
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Description
The Flow Rate Source (G) unit is an ideal source of mechanical energy in a gas network. The source can maintain a given mass or volume flow rate regardless of pressure drop. There is no flow resistance and no heat exchange with the environment.
A positive flow rate causes gas to flow from port A to port B. If Controlled source type is enabled, the mass or volume flow rate is controlled by the input signal at ports M or V respectively. If Controlled source type is disabled, the mass or volumetric flow rate will be constant and set by Mass flow rate or Volumetric flow rate respectively.
Volumetric flow rate and mass flow rate are related by the expression
,
where:
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- is the mass flow rate from port A to port B, kg/s;
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and - densities at ports A and B respectively, kg/m³;
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- volume flow rate, m³/s.
Flow type switching is performed by parameter Flow type, which by default has the value Mass, which corresponds to mass flow. To switch to volumetric flow rate it is necessary to select the value Volumetric.
You can select whether the source performs gas flow operation:
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If the source is isentropic (the parameter Isentropic power added is enabled), the isentropic ratio depends on the gas property model.
Gas model Equation Ideal gas
Semi-ideal gas
Real gas
The power given to the gas flow is based on the specific total enthalpy associated with an isoentropic process.
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If the source does no work (the Isentropic power added parameter is off), the basic equation is written assuming that the specific total enthalpy is the same on both sides of the source. This is equally true for all three gas property models.
Power applied to the gas flow .
The following notations are used in the equations:
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- specific heat capacity at constant pressure, J/(kg∙K);
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- specific enthalpy, J;
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- mass flow rate, kg/s (the flow rate associated with a port is positive when gas enters the unit through that port);
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- pressure, Pa;
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- specific gas constant, J/(mol∙K);
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- specific entropy, J/(kg∙K);
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- temperature, K;
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- flow velocity, m/s;
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- compressibility coefficient;
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- power supplied to the gas flow through the source, W.
The indices A and B indicate the corresponding port.
Ports
Input
M - mass flow control signal, kg/sec
scalar
Input port that determines the mass flow rate of gas through the source.
Dependencies
To use this port, select the Controlled source type checkbox and set the Flow type parameter to Mass.
V - volumetric flow rate reference signal, m³/sec
scalar
Input port that defines the volumetric flow rate of gas through the source.
Dependencies
To use this port, select the Controlled source type checkbox and set the Flow type parameter to `Volumetric'.
Parameters
Controlled source type - whether the flow rate is set by the input signal
On (by default) | Off
Defines how the flow rate will be set:
-
on- mass or volume flow rate is set by M or V input signals respectively. -
Disabled - mass or volumetric flow rate is constant and set by Mass flow rate, kg/s or Volumetric flow rate, m³/s respectively.
Flow type - mass or volumetric flow rate is set
Mass (By default) | Volumetric.
Specifies which flow type is set:
-
Mass- mass flow rate is set. -
Volumetric' - sets the volumetric flow rate.
Mass flow rate, kg/s - constant mass flow rate through the source
0.0 (by default).
Constant mass flow rate of gas through the source.
Dependencies
Used when Controlled source type is disabled and Flow type is set to Mass.
Volumetric flow rate, m³/s - constant volumetric flow rate through the source
0.0 (By default).
Constant volumetric flow rate of gas through the source.
Dependencies
Used when Controlled source type is disabled and Flow type is set to `Volumetric'.
Specified flow rate conditions - whether to calculate the volumetric flow rate under standard or actual operating conditions
Actual conditions (By default) | Standard conditions.
Select whether the source calculates flow rate under actual operating conditions or under standard pressure and temperature:
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`Actual conditions' - the source calculates the volumetric flow rate using the gas density under actual system conditions.
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`Standard conditions' - the source calculates the volumetric flow rate using the gas density at standard conditions. When this option is selected, additional parameters are available to set the standard pressure and temperature.
Dependencies
To enable this option, set the Flow type parameter to `Volumetric'.
Standard pressure - gas pressure at standard conditions
`0.101325 MPa (by default).
Gas pressure at standard conditions.
Dependencies
To enable this parameter, set Specified flow rate conditions to `Standard conditions'.
Standard temperature is the gas temperature under standard conditions
`20.0 °C (by default).
Gas temperature at standard conditions.
Dependencies
To enable this parameter, set Specified flow rate conditions to `Standard conditions'.
Isentropic power added - whether the source is performing work
On (By default) | Off
Sets whether the source performs work on the gas flow:
-
on- the source performs isoentropic gas work to maintain a given mass flow rate regardless of pressure drop. Use this parameter to represent an ideal pump or compressor and to properly account for energy input and output, especially in closed loop systems. -
`Disabled' - the source does not perform any work on the flow, either adding or taking away power, regardless of the mass flow rate generated by the source. Use this option to set the desired flow regime at the system inlet without affecting the flow temperature.
Cross-sectional area at port A, m² - cross-sectional area normal to the flow path at port A
0.01 m² (by default).
Cross-sectional area normal to the flow path at port A.
Cross-sectional area at port B, m² - cross-sectional area normal to the flow path at port B.
0.01 m² (By default).
Cross-sectional area normal to the flow path at port B.