Local Restriction (TL)
Local narrowing of the flow in the heat-conducting liquid network.
blockType: AcausalFoundation.ThermalLiquid.Elements.LocalRestriction
|
Local Restriction (TL) Path in the library: |
|
Variable Local Restriction (TL) Path in the library: |
.svg)
.svg)
Description
Block Local Restriction (TL) simulates a pressure drop due to a local narrowing of the flow, for example, due to the presence of a valve or a hole in the network of a heat-conducting liquid.
Ports A and B represent the input and output of the unit Local Restriction (TL). Depending on the Restriction type parameter, the area of the constriction can be fixed or controlled. In the case of a controlled input signal on the AR port specifies the narrowing cross-sectional area.
The block icon changes depending on the value of the Restriction type parameter.
In the local constriction, there is no heat exchange with the environment, the process is diabetic.
Local Restriction (TL) It consists of a sudden contraction followed by a sudden expansion. At the point of constriction, the liquid accelerates, causing a pressure drop. In the expansion zone, if the Pressure recovery parameter is turned off, the momentum of the accelerated fluid is lost. If the Pressure recovery option is enabled, the sudden expansion restores some of the momentum and allows the pressure to rise slightly after narrowing.
The figure shows a schematic representation of the local constriction.
Conservation of mass
The equation of conservation of mass for Local Restriction (TL) it looks like this
where:
-
— mass flow through port A;
-
— mass flow through port B.
Momentum Balance
The pressure difference between ports A and B follows from the pulse balance:
where:
-
— pressure drop;
-
— density of the liquid;
-
— dynamic viscosity of the liquid;
-
— cross-sectional area of ports A and B;
-
— the cross-sectional area of the constriction;
-
— the velocity of the liquid in the constriction;
-
— critical fluid velocity;
-
— critical Reynolds number;
-
— expense ratio.
If the Pressure recovery parameter is disabled, then
where:
-
— pressure in port A.
-
— pressure in port B.
If the Pressure recovery parameter is enabled, then
Ports
Entrance
AR is the value of the narrowing cross—sectional area, m2
scalar
An input signal specifying the value of the narrowing cross-sectional area. The value is limited by the minimum and maximum limits set by the block parameters.
Dependencies
This port is used only if the Restriction type parameter is set to Variable.
Non-directional
A — inlet or outlet
heat-conducting liquid
The port of the heat-conducting liquid corresponds to the inlet or outlet of the local restriction. This block has no internal orientation.
B — inlet or outlet
heat-conducting liquid
The port of the heat-conducting liquid corresponds to the inlet or outlet of the local restriction. This block has no internal orientation.
Parameters
Restriction type — the ability to change the cross-sectional area of the narrowing
Variable (by default) | Fixed
Select whether the cross-sectional area of the constriction can change during the simulation.:
-
Variable— The input signal on the AR port defines the cross-sectional area, which can change during the simulation. The Minimum restriction area and Maximum restriction area parameters set the lower and upper boundaries of the cross-sectional area. -
Fixed— the narrowing cross-sectional area, set by the value of the Restriction area parameter, remains constant during simulation. At the same time, the AR port is hidden.
Minimum restriction area — the lower limit of the value of the cross-sectional area of the narrowing
1e-10 m2 (default)
The lower boundary of the narrowing cross-sectional area. You can use this parameter to set the leakage area. The input signal AR is limited to this value to prevent further reduction of the cross-sectional area.
Dependencies
To use this parameter, set the Restriction type parameter to Variable.
Maximum restriction area — the upper limit of the value of the cross-sectional area of the narrowing
0.005 m2 (default)
The upper limit of the cross-sectional area. The input signal AR reaches the upper limit at this value to prevent further increase in the cross-sectional area.
Dependencies
To use this parameter, set the Restriction type parameter to Variable.
Restriction area — the cross-sectional area of the narrowing of the
1e−3 m2 (default)
The cross-sectional area of the constriction is normal to the flow direction.
Dependencies
To use this parameter, set the Restriction type parameter to Fixed.
Cross-sectional area at ports A and B — cross-sectional area of ports A and B
0.01 m2 (default)
The cross-sectional area of the flow at ports A and B. It is assumed that this area is the same for the two ports.
Discharge coefficient — the ratio of the actual mass flow to the theoretical mass flow through the narrowing of the
0.64 (default)
The flow coefficient is a semi–empirical parameter defined as the ratio of the actual mass flow to the theoretical mass flow through a restriction.
Critical Reynolds number — critical Reynolds number
150 (default)
The Reynolds number, at which the transition from the laminar to the turbulent regime occurs.
Pressure recovery — accounting for pressure recovery
enabled (by default) | turned off
Determines whether the pressure recovery at the outlet of the local constriction will be taken into account.