Shuttle Valve (IL)
Single line switching valve in isothermal liquid network.
blockType: EngeeFluids.IsothermalLiquid.Valves.DirectionalControl.Shuttle
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Description
Block Shuttle Valve (IL) simulates a single-line pressure control valve or switching component in an isothermal liquid network. Flow through the valve is from port A or port A1 to port B. When the pressure drop between A and A1, , exceeds a predetermined threshold pressure, the channel between ports A and B opens to flow and port A1 closes. The channel is fully switched when the pressure reaches Pressure at which A-B is fully open and A1-B is fully closed. When falls below the threshold pressure, the flow inlet switches to port A1.
Mass flow equation
Mass conservation equation for mass flow through the valve:
There is no flow between ports A and A1.
The mass flow rate through the valve is calculated as follows:
where
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- is the flow coefficient, the value of the parameters Discharge coefficient;
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- valve opening area, either between ports A and B or between ports A1 and B;
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- the value of the parameter Cross-sectional area at ports A and B;
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- average density of the liquid;
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- the pressure difference across the valve. Depending on the open channel through the valve, this is or , or the normalised switching pressure between the two inlet ports , defined below;
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- the critical pressure drop, which depends on the critical Reynolds number and on the open channel through the valve:
The critical Reynolds number is the point of regime transition between laminar and turbulent flow.
The pressure loss describes the pressure drop in the valve due to a reduction in valve area, can vary if different valve channels have different areas:
Pressure recovery describes a positive change in valve pressure due to an increase in area. To disregard the pressure recovery, uncheck the box Pressure recovery. In this case the pressure loss .
The block calculates , using the opening parameterization and the valve opening dynamics.
Valve opening parameterization
The linear parameterization of the valve opening area depends on the channel through the valve. The dynamic area is defined on the normally open channel between ports A and B:
If the value is between the parameters Pressure at which A-B is fully closed and A1-B fully open and Pressure at which A-B is fully open and A1-B is fully closed, the normalised pressure is defined as:
If the value of is below Pressure at which A-B is fully closed and A1-B fully open, then .
If is higher than Pressure at which A-B is fully open and A1-B is fully closed, then .
When the valve input is switched from port A to port A1, the valve opening area is:
When the valve is in the nearly open or nearly closed position in the linear parameterization, it is possible to maintain numerical stability in the simulation by adjusting the parameter Smoothing factor. If the parameter Smoothing factor is non-zero, the block smoothly maintains the normalised control pressure between 0 and 1.
Opening dynamics
If Opening dynamics is checked, a delay is introduced into the flow response to the modelled control pressure. The pressure becomes the dynamic control pressure . The instantaneous change in the dynamic control pressure is calculated from the time constant Opening time constant :
By default, the check box Opening dynamics is unchecked.
Ports
Conserving
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A1
—
isothermal liquid port
isothermal liquid
Details
Valve inlet port.
| Program usage name |
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A
—
isothermal liquid port
isothermal liquid
Details
Valve inlet port.
| Program usage name |
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B
—
isothermal liquid port
isothermal liquid
Details
Valve outlet port.
| Program usage name |
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Parameters
Parameters
#
Pressure at which A-B is fully closed and A1-B fully open —
threshold pressure for fully open inlet A1
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar
Details
Threshold pressure between ports A and A1 below which the channel between ports A1 and B is fully open and the channel between ports A and B is fully closed.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Pressure at which A-B is fully open and A1-B is fully closed —
threshold pressure for fully open inlet A
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar
Details
Threshold pressure between ports A and A1 above which the channel between ports A and B is fully open and the channel between ports A1 and B is fully closed.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Maximum opening area —
fully open valve area
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2
Details
Maximum open area of the valve. This value is used to determine the normalised valve pressure and the valve opening area during operation.
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Leakage area —
valve clearance area in fully closed position
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2
Details
The sum of all clearances when the valve is in the fully closed position. Any area less than this value equates to the specified leakage area. This parameter contributes to the stability of the numerical solution by maintaining flow continuity.
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| Evaluatable |
Yes |
#
Cross-sectional area at ports A and B —
area at the inlet or outlet of the valve
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2
Details
The cross-sectional area at the inlet and outlet ports A, A1 and B. This area is used when calculating the mass flow rate through the valve.
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Discharge coefficient — flow coefficient
Details
Correction factor that takes into account the rarefaction losses in theoretical flows.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Critical Reynolds number — upper limit of Reynolds number for laminar flow
Details
Upper Reynolds number limit for laminar flow through the valve.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Smoothing factor — numerical smoothing factor
Details
A continuous smoothing factor that introduces a level of gradual change based on the flow characteristic when the valve is in the nearly open and nearly closed positions. Set a non-zero value less than one to increase the stability of the simulation in these modes.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Pressure recovery — whether to take into account the increase in pressure when expanding the area
Details
Whether to take into account the pressure increase when the fluid flows from a region with a smaller cross-sectional area to a region with a larger cross-sectional area.
| Default value |
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| Program usage name |
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| Evaluatable |
No |
# Opening dynamics — whether to take into account the flow response to valve opening
Details
Whether to account for transient effects in the fluid system caused by valve opening. Checking Opening dynamics approximates the opening conditions by introducing a first order lag in the flow response. Parameters Opening time constant also affects the modelled opening dynamics.
| Default value |
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| Program usage name |
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| Evaluatable |
No |
#
Opening time constant —
valve opening time constant
d | s | hr | ms | ns | us | min
Details
A constant that determines the time required for the fluid to reach steady state when opening or closing the valve from one position to another. This parameters affects the modelling of the opening dynamics.
Dependencies
To use this parameter, select the checkbox Opening dynamics.
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| Evaluatable |
Yes |