Reservoir (2P)

A tank with a two-phase liquid at constant temperature and pressure.

blockType: AcausalFoundation.TwoPhaseFluid.Elements.Reservoir

Path in the library:

/Physical Modeling/Fundamental/Two Phase Fluid/Elements/Reservoir (2P)

Description

Block Reservoir (2P) sets the boundary conditions for pressure and temperature in a two-phase liquid network. It is assumed that the reservoir is considered infinitely large, so the pressure and specific internal energy in it are constant.

Port A represents the entrance to the tank. The flow resistance between port A and the inside of the tank is considered negligible. Therefore, the pressure in port A is equal to the pressure inside the tank.

The specific enthalpy and specific internal energy at the tank inlet depend on the flow direction. The liquid leaves the tank at a pressure and specific internal energy that are equal to the pressure and specific internal energy of the tank. The liquid enters the tank at a pressure that is equal to the pressure in the tank, but the specific internal energy is determined by the network of the two-phase liquid located upstream.

The unit provides independent selection of pressure and energy parameters using the parameters Reservoir pressure specification and Reservoir energy specification. Depending on the selected parameters, the block provides additional parameters for setting the values of the selected values.

This unit also serves as a reference connection for Pressure, Temperature & Internal Energy Difference Sensor (2P) units and Absolute Pressure, Temperature & Internal Energy Sensor (2P). In this case, the measured pressure and specific internal energy are relative to the pressure and specific internal energy in the tank.

Assumptions and limitations

It is assumed that the pressure and specific internal energy of the liquid in the tank are constant.
The flow resistance between port A and the inside of the tank is negligible. The pressure is the same in port A and inside the tank.

Ports

Conserving

# A — entrance to the reservoir
two-phase liquid

Details

The port of the two-phase liquid corresponds to the entrance to the tank.

Program usage name

port

Parameters

# Reservoir pressure specification — the method of setting the pressure in the tank
Atmospheric pressure | Specified pressure | Saturation pressure at specified condensing temperature | Saturation pressure at specified evaporating temperature

Details

The method of setting the pressure in the tank:

Atmospheric pressure — use the atmospheric pressure set in the two-phase liquid network;
Specified pressure — specify the pressure value using the parameter Reservoir pressure;
Saturation pressure at specified condensing temperature — use the pressure along the saturation curve of the liquid corresponding to the temperature set by the parameter Reservoir condensing temperature;
Saturation pressure at specified evaporating temperature — use the pressure along the vapor saturation curve corresponding to the temperature set by the parameter Reservoir evaporating temperature.

Values	`Atmospheric pressure` \| `Specified pressure` \| `Saturation pressure at specified condensing temperature` \| `Saturation pressure at specified evaporating temperature`
Default value	`Atmospheric pressure`
Program usage name	`pressure_type`
Evaluatable	No

Details

A thermodynamic variable used to set energy:

Temperature — specify the absolute temperature inside the tank using the parameter Reservoir temperature. You can specify the state of supercooled liquid or superheated steam. You cannot specify a mixture of liquid and steam, because the temperature is constant in the region of the mixture of liquid and steam.
Vapor quality — specify the mass fraction of steam in the tank using the parameter Reservoir vapor quality. You can use this parameter only when the pressure is less than the critical pressure, because there is no value above the critical point. You can specify the state of the liquid and steam mixture. You cannot specify supercooled liquid or superheated steam, because the degree of dryness is 0 and 1 accordingly, in the entire region. In addition, the unit limits the pressure to a value below the critical value.
Vapor void fraction — specify the volume fraction of steam in the tank using the Reservoir void fraction parameter. You can use this parameter only when the pressure is less than the critical pressure, since this value is absent above the critical point. You can specify the state of the liquid and steam mixture. You cannot specify supercooled liquid or superheated steam, because the degree of dryness is 0 and 1 accordingly, in the entire region. In addition, the unit limits the pressure to a value below the critical value.
Specific enthalpy — specify the specific enthalpy of the liquid in the tank using the parameter Reservoir specific enthalpy. This parameter does not limit the state of the liquid.
Specific internal energy — specify the specific internal energy of the liquid in the tank using the parameter Reservoir specific internal energy. This parameter does not limit the state of the liquid.
Degree of subcooling — specify the degree of supercooling of the liquid in the tank using the parameter Reservoir subcooling. You can use this parameter only when the pressure is below the critical point, because saturation curves are not defined above the critical point.
Degree of superheating — specify the degree of overheating of the liquid in the tank using the parameter Reservoir superheating. This option can only be used when the pressure is below the critical point, since saturation curves are not defined above the critical point.

Values	`Temperature` \| `Vapor quality` \| `Vapor void fraction` \| `Specific enthalpy` \| `Specific internal energy` \| `Degree of subcooling` \| `Degree of superheating`
Default value	`Temperature`
Program usage name	`energy_type`
Evaluatable	No

Details

The absolute temperature inside the tank. This temperature remains constant during the simulation. The set temperature corresponds to a certain enthalpy either in the region of supercooled liquid or in the region of superheated steam. For most liquids, the temperature in the region of the liquid-vapor mixture in the P-H diagram is constant, so the temperature value does not directly correspond to the enthalpy value in the region of the liquid-vapor mixture.

Dependencies

To use this parameter, set for the parameter Reservoir energy specification meaning Temperature.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`293.15 K`
Program usage name	`T_const`
Evaluatable	Yes

# Cross-sectional area at port A — the area normal to the flow direction at the reservoir inlet
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The cross-sectional area of the inlet A to the tank.

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`0.01 m^2`
Program usage name	`port_area`
Evaluatable	Yes

# Reservoir vapor quality — mass fraction of steam in the tank

Details

The mass fraction of steam in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set for the parameter Reservoir energy specification meaning Vapor quality.

Default value	`0.5`
Program usage name	`x_const`
Evaluatable	Yes

# Reservoir vapor void fraction — volume fraction of steam in the tank

Details

The volume fraction of steam in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set for the parameter Reservoir energy specification meaning Vapor void fraction.

Default value	`0.5`
Program usage name	`alpha_const`
Evaluatable	Yes

# Reservoir specific enthalpy — specific enthalpy of the liquid in the tank
J/kg | kJ/kg | cal/kg | kcal/kg | mm^2/s^2 | cm^2/s^2 | m^2/s^2 | km^2/s^2 | km^2/hr^2 | in^2/s^2 | ft^2/s^2 | ft^2/min^2 | mi^2/s^2 | mi^2/hr^2 | Pa/(kg/m^3) | psi/(lbm/ft^3) | bar/(kg/m^3)

Details

The specific enthalpy of the liquid in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set for the parameter Reservoir energy specification meaning Specific enthalpy.

Units	`J/kg` \| `kJ/kg` \| `cal/kg` \| `kcal/kg` \| `mm^2/s^2` \| `cm^2/s^2` \| `m^2/s^2` \| `km^2/s^2` \| `km^2/hr^2` \| `in^2/s^2` \| `ft^2/s^2` \| `ft^2/min^2` \| `mi^2/s^2` \| `mi^2/hr^2` \| `Pa/(kg/m^3)` \| `psi/(lbm/ft^3)` \| `bar/(kg/m^3)`
Default value	`1500.0 kJ/kg`
Program usage name	`h_const`
Evaluatable	Yes

# Reservoir specific internal energy — specific internal energy of the liquid in the tank
J/kg | kJ/kg | cal/kg | kcal/kg | mm^2/s^2 | cm^2/s^2 | m^2/s^2 | km^2/s^2 | km^2/hr^2 | in^2/s^2 | ft^2/s^2 | ft^2/min^2 | mi^2/s^2 | mi^2/hr^2 | Pa/(kg/m^3) | psi/(lbm/ft^3) | bar/(kg/m^3)

Details

The specific internal energy of the liquid in the tank. This value remains constant during the simulation.

Dependencies

To use this parameter, set for the parameter Reservoir energy specification meaning Specific internal energy.

Units	`J/kg` \| `kJ/kg` \| `cal/kg` \| `kcal/kg` \| `mm^2/s^2` \| `cm^2/s^2` \| `m^2/s^2` \| `km^2/s^2` \| `km^2/hr^2` \| `in^2/s^2` \| `ft^2/s^2` \| `ft^2/min^2` \| `mi^2/s^2` \| `mi^2/hr^2` \| `Pa/(kg/m^3)` \| `psi/(lbm/ft^3)` \| `bar/(kg/m^3)`
Default value	`1500.0 kJ/kg`
Program usage name	`u_const`
Evaluatable	Yes

Details

The degree of supercooling of the liquid in the tank, that is, the difference between the saturation temperature of the liquid and the temperature of the liquid. This value remains constant during the simulation.

Dependencies

To use this parameter, set for the parameter Reservoir energy specification meaning Degree of subcooling.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`5.0 deltaK`
Program usage name	`delta_T_subcooling_const`
Evaluatable	Yes

Details

The degree of overheating of the liquid in the tank, that is, the difference between the temperature of the liquid and the saturation temperature of the steam. This value remains constant during the simulation.

Dependencies

To use this parameter, set for the parameter Reservoir energy specification meaning Degree of superheating.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`5.0 deltaK`
Program usage name	`delta_T_superheating_const`
Evaluatable	Yes

# Reservoir pressure — pressure in the tank
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The absolute pressure inside the tank. This pressure remains constant during the simulation. The default value corresponds to atmospheric pressure at mean sea level.

Dependencies

To use this parameter, set for the parameter Reservoir pressure specification meaning Specified pressure.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.101325 MPa`
Program usage name	`p_const`
Evaluatable	Yes

Details

The pressure of the liquid inside the tank is equal to the saturation pressure along the saturation curve of the liquid corresponding to the given condensation temperature. The condensation temperature must be below the critical temperature, since saturation curves are not defined above the critical point.

Dependencies

To use this parameter, set for the parameter Reservoir pressure specification meaning Saturation pressure at specified condensing temperature.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`373.15 K`
Program usage name	`T_condensing_const`
Evaluatable	Yes

Details

The pressure of the liquid inside the tank is equal to the saturation pressure along the vapor saturation curve corresponding to the given evaporation temperature. The evaporation temperature must be below the critical temperature, since saturation curves are not defined above the critical point.

Dependencies

To use this parameter, set for the parameter Reservoir pressure specification meaning Saturation pressure at specified evaporating temperature.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`373.15 K`
Program usage name	`T_evaporating_const`
Evaluatable	Yes