Gas-Charged Accumulator (TL)
A battery with a chamber for gas in a heat-conducting liquid network.
blockType: EngeeFluids.ThermalLiquid.Volumes.GasChargedAccumulator
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Description
Block Gas-Charged Accumulator (TL) It is a battery with a chamber for gas in a heat-conducting liquid network. The battery consists of a chamber pre-filled with gas and a chamber for a heat-conducting liquid. The chambers are separated by a diaphragm, piston, or any other separator.
Battery diagram
When the pressure of the liquid at the battery inlet becomes greater than the pressure in the pre-filled gas chamber, the liquid enters the battery and compresses the gas. A decrease in liquid pressure leads to decompression of the gas and the release of accumulated liquid into the system.
The movement of the separator is limited by a rigid limiter when the volume of the liquid is zero or when the volume of the liquid is equal to the capacity of the liquid chamber. If the set spring stiffness is too low, the liquid volume may briefly drop below zero or rise above the volume of the container. Use the parameter Hard-stop stiffness coefficient to fix it.
Conservation of mass
The equation of conservation of mass in a liquid chamber has the form:
where
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— the density of the heat-conducting liquid;
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— isothermal modulus of elasticity;
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— coefficient of isobaric thermal expansion;
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— pressure of the heat-conducting liquid;
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— temperature of the heat-conducting liquid;
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— the mass flow rate of the heat-conducting liquid entering the battery through the A port.
The unit calculates the change in volume of the liquid chamber over time using the equations:
where
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— limiter stiffness coefficient, parameter value Hard-stop stiffness coefficient;
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— the damping coefficient of the limiter, the value of the parameter Hard-stop damping coefficient;
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— mass flow of liquid in the chamber when the battery separator comes into contact with the upper rigid limiter:
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— mass flow of liquid in the chamber when the battery separator comes into contact with the lower rigid limiter:
Conservation of momentum
Conservation of momentum is represented by the following equation:
where — contact pressure of the rigid limiter:
Energy conservation
The energy conservation equation in the liquid chamber has the form:
where
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— specific internal energy of a heat-conducting liquid;
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— energy flow into the liquid chamber through the battery inlet;
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— energy flow into the liquid chamber through the battery wall.
Camera volumes
The volume of liquid in the battery is the difference between the total volume of the battery and the volume of gas.:
where
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— total battery capacity;
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— the volume of liquid in the battery;
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— the amount of gas in the battery;
_ Camera volumes_
The working volume of the liquid chamber is the difference between the total volume of the battery and the minimum volume of the gas chamber when the liquid chamber is full.:
where
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— volume of the liquid chamber;
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— the minimum volume of the gas chamber, the small part of the chamber that remains filled with gas when the liquid chamber is full.
The dependence of gas pressure and volume between the current state and the pre-charging state is polytropic:
where
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— pressure in the gas chamber at a given time step;
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— the volume of gas in the battery at a given time step;
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— pressure in the gas chamber when the liquid chamber is empty;
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— total volume of the liquid chamber;
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— polytropy indicator.
Assumptions and limitations
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Gas compression is considered as a polytropic process.
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The load on the separator is not taken into account.
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The influence of fluid inertia is not taken into account.
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
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A
—
thermal liquid inlet port
thermal liquid
Details
Thermal liquid port, corresponds to the inlet to the accumulator. The flow rate is positive if the fluid enters the accumulator.
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H
—
heat port
heat
Details
A heat port related to the heat capacity of a volume of fluid.
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Parameters
Parameters
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Total accumulator volume —
total battery capacity
m^3 | um^3 | mm^3 | cm^3 | km^3 | ml | l | gal | igal | in^3 | ft^3 | yd^3 | mi^3
Details
The total volume of the accumulator, including the liquid chamber and the gas chamber, it is equal to the sum of the volume of the liquid chamber and the minimum volume of the gas chamber.
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| Evaluatable |
Yes |
#
Minimum gas volume —
minimum gas chamber volume
m^3 | um^3 | mm^3 | cm^3 | km^3 | ml | l | gal | igal | in^3 | ft^3 | yd^3 | mi^3
Details
Minimum gas chamber volume, the small portion of the chamber that remains filled with gas when the liquid chamber is full.
The value of this parameters must be non-zero to avoid dividing by zero when the liquid chamber is full.
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| Evaluatable |
Yes |
#
Precharge pressure (gauge) —
gas chamber pressure
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 initial overpressure in the empty accumulator chamber. Fluid enters the accumulator when the inlet pressure is equal to or greater than the pressure in the pre-filled gas chamber.
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| Evaluatable |
Yes |
# Specific heat ratio — specific heat capacity coefficient
Details
Specific heat capacity coefficient (adiabatic value).
Parameters are necessary to account for heat transfer, usually its value is between 1 and 2, depending on the properties of the gas in the chamber.
For dry air at 20°C, the value of the adiabatic exponent for an isothermal process is 1, and for an adiabatic (and isoentropic) process it is 1.4.
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| Evaluatable |
Yes |
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Cross-sectional area at port A —
cross-sectional area of the hole
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac
Details
Cross-sectional area of the opening at the inlet to the accumulator.
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| Evaluatable |
Yes |
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Hard-stop stiffness coefficient —
stiffness factor
Pa/m^3 | MPa/m^3
Details
The stiffness coefficient of the upper and lower rigid accumulator limiters. Stiffeners are used to limit the fluid volume between zero and the fluid chamber volume.
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| Evaluatable |
Yes |
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Hard-stop damping coefficient —
damping factor
MPa*s/m^6
Details
The damping coefficients of the upper and lower rigid accumulator limiters. The rigid stops are used to limit the fluid volume between zero and the fluid chamber volume. The damping coefficients account for the dissipative part of the contact forces of the rigid stops.
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |