Engee documentation

Controlled Pressure Difference Source (G)

The source of the pressure drop.

blockType: AcausalFoundation.Gas.Sources.PressureDifference

controlled pressure difference source (g)

Controlled Pressure Difference Source (G)

Path in the library:

/Physical Modeling/Fundamental/Gas/Sources/Controlled Pressure Difference Source (G)

pressure difference source (g)

Pressure Difference Source (G)

Path in the library:

/Physical Modeling/Fundamental/Gas/Sources/Pressure Difference Source (G)

Description

Block Controlled Pressure Difference Source (G) It is an ideal source of mechanical energy in the gas network. The source can maintain a constant pressure drop at its ports regardless of the mass flow through the source. There is no gas resistance and no heat exchange with the environment. A positive differential pressure value means that the pressure at port B is greater than the pressure at port A.

If the Controlled source type parameter is enabled, the pressure drop is controlled by the input scalar signal on the P port. If the Controlled source type parameter is disabled, the pressure drop is constant and is set by the Pressure difference, Pa parameter.

You can choose whether the source does work with the gas flow.:

  • If the source is isentropic (the Isentropic power added parameter is enabled), then the isentropic ratio depends on the model of gas properties.

    The gas model The equation

    The ideal gas

    Semi-ideal gas

    Real gas

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

  • If the source does not perform any work (the Isentropic power added parameter is turned off), then the basic equation is written based on the fact that the specific total enthalpy is the same on both sides of the source. This is equally true for all three models of gas properties.

    Power supplied to the gas stream .

The following notation is 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 the port is positive when gas enters the unit through this port);

  • — pressure, Pa;

  • — universal gas constant, J/(mol*K);

  • — specific entropy, J/(kg*K);

  • — temperature, K;

  • — flow rate, m/s;

  • — the coefficient of compressibility;

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

The A and B indexes indicate the corresponding port.

Assumptions and limitations

  • There are no irreversible losses.

  • There is no heat exchange with the environment.

Ports

Entrances

P — differential pressure setting signal, Pa
scalar

The input scalar signal that determines the pressure drop of the gas in the source. A positive signal on port P causes the pressure on port B to be greater than the pressure on port A.

Dependencies

Used if the Controlled source type parameter is enabled.

Non-directional

A — input of the pass source:q[<br>] gas

The gas port. A positive pressure drop causes the pressure at port B to be greater than the pressure at port A.

B — input of the pass source:q[<br>] gas

The gas port. A positive pressure drop causes the pressure at port B to be greater than the pressure at port A.

Parameters

Controlled source type — is the pressure drop set by the input signal
Enabled (by default) | Turned off

Determines how the pressure drop will be set:

  • Enabled — the pressure drop is set by the input signal P.

  • Turned off — the constant pressure drop is set by the parameter Pressure difference, Pa.

Isentropic power added — is the source doing the work of
Enabled (by default) | Turned off

Sets whether the source is working with the gas flow.:

  • Enabled — the source performs isentropic work with the gas to maintain a given mass flow rate regardless of the pressure drop. Use this parameter to represent the ideal pump or compressor and to properly account for energy consumption and output, especially in closed-loop systems.

  • Turned off — the source does not perform any work with the flow, neither adding nor subtracting power, regardless of the mass flow rate generated by the source. Use this option to set the desired flow mode at the system entrance without affecting the flow temperature.

Cross-sectional area at port A, m2 — the cross-sectional area normal to the flow path at port A
0.01 m2 (default)

The cross-sectional area normal to the flow path at port A.

Cross-sectional area at port B, m2 — the cross-sectional area normal to the flow path at port B
0.01 m2 (default)

The cross-sectional area normal to the flow path at port B.

Pressure difference, Pa — constant pressure drop
0 (default)

The pressure drop of the gas at the source ports.

Dependencies

Used if the Controlled source type parameter is disabled.

Examples