Engee documentation

Controlled Mass Flow Rate Source (G)

A source of mass or volumetric flow.

blockType: AcausalFoundation.Gas.Sources.FlowRate

controlled mass flow rate source (g)

Controlled Mass Flow Rate Source (G)

Path in the library:

/Physical Modeling/Fundamental/Gas/Sources/Controlled Mass Flow Rate Source (G)

controlled volumetric flow rate source (g)

Controlled Volumetric Flow Rate Source (G)

Path in the library:

/Physical Modeling/Fundamental/Gas/Sources/Controlled Volumetric Flow Rate Source (G)

mass flow rate source (g)

Mass Flow Rate Source (G)

Path in the library:

/Physical Modeling/Fundamental/Gas/Sources/Mass Flow Rate Source (G)

volumetric flow rate source (g)

Volumetric Flow Rate Source (G)

Path in the library:

/Physical Modeling/Fundamental/Gas/Sources/Volumetric Flow Rate Source (G)

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 the Controlled source type parameters are 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 the parameters Mass flow rate or Volumetric flow rate respectively.

Volumetric flow rate and mass flow rate are related by the expression

ρдляρдля ,

where:

  • - is the mass flow rate from port A to port B, kg/s;

  • ρ and ρ - densities at ports A and B respectively, kg/m³;

  • - volume flow rate, m³/s.

Switching the flow type is performed by parameters 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:

  • If the source is isentropic (parameters 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 the isoentropic process.

  • If the source does no work (the Isentropic power added parameters are 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:

  • - specific heat capacity at constant pressure, J/(kg∙K);

  • - specific enthalpy, J;

  • - mass flow rate, kg/s (the flow rate associated with a port is positive when gas enters the unit through that port);

  • - pressure, Pa;

  • - specific gas constant, J/(mol∙K);

  • - specific entropy, J/(kg∙K);

  • - temperature, K;

  • - flow velocity, m/s;

  • - compressibility coefficient;

  • - power supplied to the gas flow through the source, W.

The indices A and B indicate the corresponding port.

Assumptions and limitations

  • No irreversible losses.

  • No heat exchange with the environment.

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 parameters to Mass.

V - volumetric flow rate reference signal, m³/s
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 parameters to `Volumetric'.

Non-directional

A - source input
gas

Gas inlet port. Positive mass flow rate causes gas to flow from port A to port B.

B is the source outlet port
gas

Gas outlet port. Positive mass flow rate causes gas to flow from port A to port B.

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 parameters 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 the Controlled source type parameter is disabled and the Flow type parameter 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 the Controlled source type parameter is disabled and the Flow type parameter 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:

  • `Actual conditions' - the source calculates the volumetric flow rate using the gas density under actual system conditions.

  • `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 parameters 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 the Specified flow rate conditions parameter 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 the Specified flow rate conditions parameter 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.