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Reservoir (G)

Boundary conditions for gas network at constant pressure and temperature

  • Reservoir (G) block

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The Reservoir (G) block represents an infinite reservoir at fixed pressure and temperature. The reservoir and its inlet can be at atmospheric pressure or at a specified pressure. Port A, a gas conserving port, represents the reservoir inlet.

The volume of gas inside the reservoir is assumed infinite. Therefore, the flow is assumed quasi-steady.

Gas enters and leaves the reservoir at the reservoir pressure, but its temperature is determined by the direction of gas flow. If gas flows into the reservoir, its temperature is determined by the gas network upstream. The reservoir acts as a heat sink. If gas flows out of the reservoir, its temperature equals that of the reservoir. The reservoir acts as a heat source.

This block also functions as a reference point for pressure and temperature measurements in a gas network. These measurements are relative to the reservoir pressure and temperature, respectively. Connect the reservoir to port B of a Pressure and Temperature Sensor (G) block to measure relative pressure and temperature of a node connected to the A port of the sensor.

Assumptions and Limitations

  • Reservoir pressure and temperature are constant.

  • Gas in the reservoir is quasi-steady.



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Gas conserving port associated with the reservoir inlet.


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Select a specification method for the reservoir pressure:

  • Atmospheric pressure — Use the atmospheric pressure, specified by the Gas Properties (G) block connected to the circuit.

  • Specified pressure — Specify a value by using the Reservoir pressure parameter.

Enter the desired pressure in the reservoir. This pressure remains constant during simulation.


Enabled when the Reservoir pressure specification parameter is set to Specified pressure.

Enter the desired temperature in the reservoir. This temperature remains constant during simulation.

The cross-sectional area of the reservoir inlet, in the direction normal to gas flow path.

Extended Capabilities

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

Version History

Introduced in R2016b