Engee documentation

Constant Volume Chamber (TL)

A chamber with a fixed volume of coolant and a variable number of ports.

blockType: AcausalFoundation.ThermalLiquid.Elements.ConstantVolumeChamber

constant volume chamber (tl)

Path in the library:

/Physical Modeling/Fundamental/Thermal Liquid/Elements/Constant Volume Chamber (TL)

Description

Block Constant Volume Chamber (TL) simulates the accumulation of mass and energy of a coolant in a chamber of a fixed volume. The chamber can have from one to four ports, designated A, B, C, D, through which liquid can flow. The volume of liquid can exchange heat with a thermal network, for example, with a network representing the surrounding space of the chamber, through the thermal port H.

The mass of the liquid in the chamber varies depending on the density, which in a thermally conductive liquid usually depends on pressure and temperature. The liquid enters the chamber when the pressure in front of the port rises above the pressure in the chamber, and flows out when the pressure gradient reverses. The effect in the model is often to smooth out sudden pressure changes, similar to how an electric capacitor smooths out the voltage.

The flow resistance between the port and the inside of the chamber is considered negligible. Therefore, the pressure inside the chamber is equal to the pressure at the inlet.

Similarly, the thermal resistance between the thermal port and the interior of the chamber is considered negligible. The temperature inside the chamber is equal to the temperature at the heat port.

Conservation of mass

Liquid can flow in and out of the chamber through ports A, B, C and D. The volume of the chamber is fixed, but due to the compressibility of the liquid, its mass may vary depending on pressure and temperature.

The mass accumulation rate in the chamber must be exactly equal to the mass flow rate through ports A, B, C and D:

where

  • — pressure inside the container;

  • — temperature;

  • — isothermal modulus of volumetric elasticity;

  • — coefficient of isobaric thermal expansion;

  • — mass flow rate of the liquid.

Energy conservation

Energy can enter and leave the chamber in two ways: by liquid flow through ports A, B, C and D and by heat flow through port H. No work is done on the liquid inside the chamber. Therefore, the rate of energy accumulation in the internal volume of the liquid should be equal to the sum of the energy flows through ports A, B, C, D and H:

where

  • — enthalpy;

  • — density;

  • — specific heat;

  • — camera volume;

  • — energy flow;

  • — heat flow.

Conservation of momentum

The pressure drop due to viscous friction between the individual openings and the interior of the chamber is considered negligible. Gravity and other volumetric forces can be ignored. Therefore, the pressure in the internal volume of the liquid must be equal to the pressure at ports A, B, C and D:

Assumptions and limitations

  • There is a fixed volume of liquid in the chamber.

  • The flow resistance between the inlet and the inside of the chamber is negligible.

  • The thermal resistance between the thermal port and the interior of the chamber is negligible.

  • The kinetic energy of the liquid in the chamber is negligible.

Variables

Use the parameter group Initial Targets to set the priority and initial target values for the block parameter variables before modeling. For more information, see Configuring physical blocks using target values.

Ports

Conserving

# A — thermal liquid port
thermal liquid

Details

The thermal liquid port corresponds to the entrance to the chamber.

Program usage name

port_a

# H — thermal port
heat

Details

Through this port, the liquid in the chamber exchanges heat with the thermal network.

Program usage name

thermal_port

# B — thermal liquid port
thermal liquid

Details

The thermal liquid port corresponds to the second entrance to the chamber.

Dependencies

To use this port, set the parameter Number of ports value 2, 3 or 4.

Program usage name

port_b

# C — thermal liquid port
thermal liquid

Details

The thermal liquid port corresponds to the third entrance to the chamber.

Dependencies

To use this port, set the parameter Number of ports value 3 or 4.

Program usage name

port_c

# D — thermal liquid port
thermal liquid

Details

The thermal liquid port corresponds to the fourth entrance to the chamber. If the chamber has four inlet openings, then it can be used as a joint in a cross connection.

Dependencies

To use this port, set the parameter Number of ports value 4.

Program usage name

port_d

Parameters

Parameters

# Chamber volume — volume of liquid inside the chamber
m^3 | um^3 | mm^3 | cm^3 | km^3 | ml | l | gal | igal | in^3 | ft^3 | yd^3 | mi^3

Details

The volume of liquid in the chamber. This volume is constant during the simulation.

Units

m^3 | um^3 | mm^3 | cm^3 | km^3 | ml | l | gal | igal | in^3 | ft^3 | yd^3 | mi^3
Default value

0.001 m^3
Program usage name

volume
Evaluatable

Yes

# Number of ports — number of input ports in the camera
1 | 2 | 3 | 4

Details

The number of input ports in the camera.

The camera can have from one to four ports, designated A, B, C, D.

When the parameter value is changed, the corresponding ports are opened or hidden in the block icon.

Values

1 | 2 | 3 | 4
Default value

1
Program usage name

port_count
Evaluatable

No

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

Details

The area of the input port A, normal to the flow direction.

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_a_area
Evaluatable

Yes

# Cross-sectional area at port B — the area of the input port B, normal to the flow direction
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The area of the input port B, normal to the flow direction.

Dependencies

To use this parameter, set for the parameter Number of ports meaning 2, 3 or 4.

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_b_area
Evaluatable

Yes

# Cross-sectional area at port C — the area of the input port C, normal to the flow direction
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The area of the input port C, normal to the flow direction.

Dependencies

To use this parameter, set for the parameter Number of ports meaning 3 or 4.

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_c_area
Evaluatable

Yes

# Cross-sectional area at port D — the area of the input port D, normal to the flow direction
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The area of the input port D, normal to the flow direction.

Dependencies

To use this parameter, set for the parameter Number of ports meaning 4.

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_d_area
Evaluatable

Yes