Controlled Reservoir (2P)

Two-phase fluid reservoir at variable pressure and temperature

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Libraries:
Simscape / Foundation Library / Two-Phase Fluid / Elements

Description

The Reservoir (2P) block sets boundary conditions in a two-phase fluid network. The reservoir is assumed infinite in size.

Port A represents the reservoir inlet. The flow resistance between port A and the reservoir interior is assumed negligible. The pressure at port A is therefore equal to the pressure inside the reservoir.

The specific enthalpy and specific internal energy at the reservoir inlet depend on the direction of flow. Fluid leaves the reservoir at the reservoir pressure and specific internal energy. Fluid enters the reservoir at the reservoir pressure, but the specific internal energy is determined by the two-phase fluid network upstream.

The block provides independent selection of pressure specification and energy specification, by using the Reservoir pressure specification and Reservoir energy specification parameters. Depending on the selected options, the block exposes the relevant input ports to provide the control signals for the selected quantities.

For certain option combinations, the pressure inside the reservoir must be less than the critical pressure because the saturation curves are not defined above the critical point. If you select such a combination, the Reservoir pressure above critical parameter lets you decide what happens when the fluid pressure exceeds the critical pressure.

This block also serves as a reference connection for the Pressure & Internal Energy Sensor (2P) block. In this case, the measured pressure and specific internal energy are relative to the reservoir pressure and specific internal energy.

Ports

Input

P — Pressure control signal, MPa

physical signal

Physical signal port that provides the reservoir pressure control signal.

Dependencies

To enable this port, set Reservoir pressure specification to Specified pressure.

Tc — Reservoir condensing temperature control signal, K

physical signal

Physical signal port that provides the reservoir condensing temperature control signal.

Dependencies

To enable this port, set Reservoir pressure specification to Saturation pressure at specified condensing temperature.

Te — Reservoir evaporating temperature control signal, K

physical signal

Physical signal port that provides the reservoir evaporating temperature control signal.

Dependencies

To enable this port, set Reservoir pressure specification to Saturation pressure at specified evaporating temperature.

T — Temperature control signal, K

physical signal

Physical signal port that provides either the subcooled liquid temperature or the superheated vapor temperature control signal, based on the Reservoir energy specification parameter setting.

Dependencies

To enable this port, set Reservoir energy specification to either Subcooled liquid temperature or Superheated vapor temperature.

X — Mass fraction of vapor control signal, unitless

physical signal

Physical signal port that specifies the mass fraction of vapor in the reservoir.

Dependencies

To enable this port, set Reservoir energy specification to Vapor quality.

a — Volume fraction of vapor control signal, unitless

physical signal

Physical signal port that specifies the volume fraction of vapor in the reservoir.

Dependencies

To enable this port, set Reservoir energy specification to Vapor void fraction.

H — Specific enthalpy of the fluid control signal, kJ/kg

physical signal

Physical signal port that specifies the specific enthalpy of the fluid in the reservoir.

Dependencies

To enable this port, set Reservoir energy specification to Specific enthalpy.

U — Specific internal energy of the fluid control signal, kJ/kg

physical signal

Physical signal port that specifies the specific internal energy of the fluid in the reservoir.

Dependencies

To enable this port, set Reservoir energy specification to Specific internal energy.

SC — Degree of subcooling of the fluid control signal, deltaK

physical signal

Physical signal port that specifies the degree of subcooling of the fluid in the reservoir, that is, the difference between the liquid saturation temperature and the fluid temperature.

This input signal specifies a temperature difference, in units of deltaK, rather than an absolute temperature. Therefore, if you connect a Simulink-PS Converter block directly to this port, do not select the Apply affine conversion check box.

Dependencies

To enable this port, set Reservoir energy specification to Degree of subcooling.

SH — Degree of superheating of the fluid control signal, deltaK

physical signal

Physical signal port that specifies the degree of superheating of the fluid in the reservoir, that is, the difference between the fluid temperature and the vapor saturation temperature.

This input signal specifies a temperature difference, in units of deltaK, rather than an absolute temperature. Therefore, if you connect a Simulink-PS Converter block directly to this port, do not select the Apply affine conversion check box.

Dependencies

To enable this port, set Reservoir energy specification to Degree of superheating.

Conserving

A — Reservoir inlet

two-phase fluid

Two-phase fluid conserving port associated with the reservoir inlet.

Parameters

Reservoir pressure specification — Specification method for reservoir pressure

Specified pressure (default) | Saturation pressure at specified condensing temperature | Saturation pressure at specified evaporating temperature

Specification method for the reservoir pressure:

• Specified pressure — Specify a value by using the control signal at port P.

• Saturation pressure at specified condensing temperature — Use the pressure along the liquid saturation curve that corresponds to the temperature specified by the control signal at port Tc. When you select this option, the block limits the pressure to be less than or equal to critical pressure.

• Saturation pressure at specified evaporating temperature — Use the pressure along the vapor saturation curve that corresponds to the temperature specified by the control signal at port Te. When you select this option, the block limits the pressure to be less than or equal to critical pressure.

Reservoir energy specification — Thermodynamic variable to use to define reservoir conditions

Subcooled liquid temperature (default) | Superheated vapor temperature | Vapor quality | Vapor void fraction | Specific enthalpy | Specific internal energy | Degree of subcooling | Degree of superheating

Thermodynamic variable to use for energy specification:

• Subcooled liquid temperature — Specify the subcooled liquid temperature inside the reservoir by using the control signal at port T. When you select this option, the block limits the pressure to be less than or equal to the critical pressure. The block also limits the input at port T to the range between the minimum temperature and the liquid saturation temperature to avoid the discontinuity in the corresponding specific internal energy or specific enthalpy when the input temperature varies across the saturation temperature.

• Superheated vapor temperature — Specify the superheated vapor temperature inside the reservoir by using the control signal at port T. When you select this option, the block limits the pressure to be less than or equal to the critical pressure. The block also limits the input at port T to the range between the vapor saturation temperature and the maximum temperature to avoid the discontinuity in the corresponding specific internal energy or specific enthalpy when the input temperature varies across the saturation temperature.

• Vapor quality — Specify the mass fraction of vapor in the reservoir by using the control signal at port X. When you select this option, the block limits the pressure to be less than or equal to critical pressure. You can specify a state that is a liquid-vapor mixture. You cannot specify a subcooled liquid or a superheated vapor because the vapor quality is 0 and 1, respectively, across the whole region. Additionally, the block limits the pressure to below the critical pressure.

• Vapor void fraction — Specify the volume fraction of vapor in the reservoir by using the control signal at port a. When you select this option, the block limits the pressure to be less than or equal to critical pressure. You can specify a state that is a liquid-vapor mixture. You cannot specify a subcooled liquid or a superheated vapor because the vapor quality is 0 and 1, respectively, across the whole region. Additionally, the block limits the pressure to below the critical pressure.

• Specific enthalpy — Specify the specific enthalpy of the fluid in the reservoir by using the control signal at port H. This option does not limit the fluid state.

• Specific internal energy — Specify the specific internal energy of the fluid in the reservoir by using the control signal at port U. This option does not limit the fluid state.

• Degree of subcooling — Specify the degree of subcooling of the fluid in the reservoir by using the control signal at port SC. The degree of subcooling is the difference between the liquid saturation temperature and the fluid temperature. When you select this option, the block limits the pressure to be less than or equal to critical pressure.

• Degree of superheating — Specify the degree of superheating of the fluid in the reservoir by using the control signal at port SH. The degree of superheating is the difference between the fluid temperature and the vapor saturation temperature. When you select this option, the block limits the pressure to be less than or equal to critical pressure.

Cross-sectional area at port A — Area normal to flow path at reservoir inlet

0.01 m^2 (default) | positive scalar

Flow area of the reservoir inlet, represented by port A.

Reservoir pressure above critical — Define action for when reservoir pressure exceeds critical pressure

Warn and limit to critical pressure (default) | Limit to critical pressure | Error

Define action for when reservoir pressure exceeds critical pressure:

• Warn and limit to critical pressure — The block issues a warning and limits the pressure to critical pressure.

• Limit to critical pressure — The block limits the pressure to critical pressure, but the simulation continues without a warning.

• Error — Simulation stops with an error.

Dependencies

This parameter is automatically exposed when you select a combination of pressure specification and energy specification options that requires the pressure inside the reservoir to be less than the critical pressure.

Extended Capabilities

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

Version History

Introduced in R2015b